Evidence from experiments, modeling, and field observations for effects of increased salinization on re-distribution of sediment base cations in Taihu Lake, China

Taihu Lake, the third largest freshwater lake in China, has experienced rapid salinization in the past decades; however, little is known about the impact of sodium (Na) on ion exchange in the lake environment. To explore the potential effect of increased Na on the migration of base cations (Ca and Mg) and resulting redistribution between the water and sediment, we used the adsorption-exchange experiment, MINTEQ modeling to explore the cation exchange induced by high Na input, and its impact on the redistribution of Ca and Mg in Taihu different media. The results indicated that exchanged quantity of Ca and Mg increased with time, and the exchange process reached 90% during 0-4 h and reached equilibrium after 24 h under 100 mg/L Na (the maximum Na concentration in Taihu sediment pore water). Our MINTEQ modeled result indicated that the exchanged quantity of Ca and Mg increased with the increasing Na concentration, with Ca being preferably exchanged over Mg at the same Na concentration. The MINTEQ model further predicted that, in the Taihu lake environment, the exchange adsorption would reach the equilibrium at the concentration of 6000 mg/L Na, with exchanged Ca2+ and Mg2+ accounting for 47% and 55% of the total exchangeable Ca and Mg in the sediment, respectively. Although current Na-induced exchange in the Taihu lake has been far from the equilibrium, the MINTEQ result confirmed the existence of this reaction and predicted the potential redistribution of base cations or Ca/Mg ratio in the lake sediment and water phase with further Na increase. Furthermore, our field observations not only confirmed the existence of Na-induced cation exchange in this lake environment but also were generally in agreement with our experimental and modeled results. The increased salinization-induced ion exchange would alter the re-distribution of base cations and the resulting potential ecosystem consequences should be given close attention in this large freshwater lake.

Trend of PFAS concentrations and prediction of potential risks in Taihu Lake of China by AQUATOX

Per- and polyfluoroalkyl substances (PFAS) are recognized as emerging environmental pollutants due to their high persistence and toxicities to humans and animals. Understanding the temporal trend of PFAS in the environment is important for their pollution control and making appropriate policies. Many studies have reported the PFAS concentrations in Taihu Lake, the third largest lake in China, while their temporal trend during the years was seldom investigated. This study summarizes the PFAS concentrations in the water, sediment and organisms in Taihu Lake from 2009 to 2020 to depict their temporal trends. Meanwhile, the ecological model of AQUATOX was applied to evaluate and predict the potential risks of PFAS from 2012 to 2030. The results showed that the total PFAS concentrations varied but without distinct increase or decrease in both water and sediment during the years, while PFAS concentrations in organisms significantly decreased. The yearly mean concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in the water were 21.7-25.4 ng/L and 9.7-26.5 ng/L respectively, lower than the Standards for Drinking Water Quality of China and the suggested water quality criteria to protect the aquatic organisms. In sediment, PFOA and PFOS concentrations were 0.16-0.69 ng/g and 0.15-0.82 ng/g respectively, much lower than the recommended sediment quality guideline values. Based on the AQUATOX prediction, there will be no major threats caused by PFAS to the growth of biota in Taihu Lake in the near future, while the biomass of some species (e.g. carp) will be affected under the perturbation of PFAS. Both field investigation and AQUATOX simulation showed that PFOS concentrations in invertebrates and fish descend steadily, while no remarkable decrease in PFOA concentrations was expected. This study suggests a decreasing ecological risk of PFAS in Taihu Lake, while highlights the necessity of continuous monitoring of PFAS contamination.

Derivation and application of a parameter for denitrification rates in the Taihu Lake model based on an isotope-labeled denitrification experiment

In recent years, the total nitrogen concentration in Taihu Lake has decreased significantly. Denitrification, as the main nitrogen removal process, is the key reason for the decrease. Here, the denitrification parameter values in the Environmental Fluid Dynamic Code (EFDC) model were calculated based on isotope-labeled denitrification experiment instead of selecting the recommended values directly. This study further focused on EFDC denitrification parameter derivation with an experimental denitrification rate (Dtot) to reduce simulation errors. According to the EFDC nitrate deposition flux mechanism, the conversion equation between the denitrification rate of the first sediment layer ([Formula: see text]) in EFDC and Dtot was successfully derived. The results revealed a linear correlation between [Formula: see text] and (Dtot)1/2. The [Formula: see text] values of sampling points ranged from 0.25 to 0.27 m·day-1, within the range of model parameters. After substituting [Formula: see text] into the Taihu Lake EFDC model, the average percentage bias and determination coefficient of total nitrogen were 16.25% and 0.87, respectively. The average total nitrogen concentration reduction caused by denitrification at water quality calibration points ranged from 0.027 to 0.305 mg·L-1.

[Spatiotemporal Occurrence of Organophosphate Esters in the Surface Water and Sediment of Taihu Lake and Relevant Risk Assessment]

Aiming to explore the spatiotemporal occurrence of organophosphate esters (OPEs) in the aquatic environment of Taihu Lake and to assess the relevant ecological risk, monomeric and oligomeric OPEs in the surface water and sediment of Taihu Lake were determined using solid phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry. The target monomeric OPEs included chlorinated OPEs, alkyl OPEs, and aryl OPEs. There was no significant difference in the spatial distribution of OPEs in water and sediment between the pollutant-impacted and less-impacted zones. The average concentrations of OPEs in summer and winter were, respectively, 752.7 and 498.5 ng·L-1 in water and 124.0 and 54.5 ng·g-1 in sediment, indicating an obvious seasonal difference, especially for the monomeric OPEs. The OPEs levels in both the water and sediment were ranked in the order of chlorinated OPEs > alkyl OPEs > aryl OPEs≈oligomeric OPEs. The pseudo-partitioning coefficients (Kd) of OPEs between the sediment and surface water of Taihu Lake were much higher in summer (0.05-4.17 L·g-1) compared to those in winter (0.02-3.47 L·g-1) and were significantly positively correlated with the lg Kow values of OPEs. Based on the median concentrations of OPEs in the water of Taihu Lake, the ecological risk of OPEs was assessed by risk quotient (RQ) values, which indicated a medium risk at an RQ level of 0.34 during winter and 0.35 during summer. The assessment results showed that the risk ranking of OPEs was consistent with that of their concentrations, and the monomeric OPEs posed a higher ecological risk in summer compared to that in winter. Although the ecological risk of oligomeric OPEs in this study was not serious and was lower than that of monomeric OPEs, it is an urgent requirement to conduct ecotoxicology studies on oligomeric OPEs in the future since available data is highly limited at present.

Estimating the temporal and spatial distribution and threats of bisphenol A in temperate lakes using machine learning models

Bisphenol A (BPA) is easily enriched in many human-disturbed watersheds, particularly lakes with poor water mobility, which is posing a threat to aquatic biota. While previous studies have focused on the concentration of BPA in water and its toxicity to aquatic organisms, a small amount of measured data is not enough to reveal the temporal and spatial distribution and threats of BPA, and estimate the ecological risk in watersheds. Therefore, we collected 164 measured BPA data points from Taihu Lake to develop machine learning models using random forest (RF), support vector machine (SVM) and least square regression (LSR) and created month-by-month watershed prediction maps in temperate lakes to estimate the spatiotemporal distribution and threats of BPA. Due to RF's superior robustness to noisy data, the RF model exhibits the best performance among the three algorithms. The RF model showed acceptable predictive performance on the modeling dataset (coefficients of determination and root-mean-square error for the training set were 0.927 and 17.499, respectively, and 0.607, 39.645 for the validation set, respectively). The maps indicated that areas susceptible to anthropogenic activities were more severely polluted by BPA, and rainy climate may favor the migration of BPA to aquatic ecosystems. The model was also applied to predict 42 data points of BPA collected from Dianchi Lake, and the results showed that most predicted data were within a factor of 10 of the measured data, but the prediction accuracy of the model has declined. The ecological risks in the two lakes were evaluated and attention should be paid to the regions with higher risks. Our study provided a novel idea for comprehensive monitoring of an unconventional trace pollutant with endocrine disrupting effects in aquatic ecosystems and analyzing their spatiotemporal distribution, which will contribute to the scientific assessment of the ecological risk of BPA.

The Effects and Mechanisms of pH and Dissolved Oxygen Conditions on the Release of Arsenic at the Sediment-Water Interface in Taihu Lake

The pH and dissolved oxygen (DO) conditions are important environmental factors that control the migration of arsenic (As) at the sediment-water interface. This study investigates the distribution differences of reactive iron, manganese, and arsenic at the sediment-water interface under anaerobic and aerobic conditions at different pH levels. The strong buffering capacity of sediment to water pH results in a shift towards neutral pH values in the overlying water under different initial pH conditions. The level of DO becomes a key factor in the release of As from sediment, with lower DO environments exhibiting higher release quantities and rates of As compared to high DO environments. Under low DO conditions, the combined effects of ion exchange and anaerobic reduction lead to the most significant release of As, particularly under pH 9.5 conditions. The formation of amorphous ferrous sulfide compounds under low DO conditions is a significant factor contributing to increased arsenic concentration in the interstitial water. Therefore, the re-migration of endogenous arsenic in shallow lake sediments should consider the combined effects of multiple driving forces.

[Distribution, Sources, and Ecological Risk Evaluation of Heavy Metals in Surface Sediments of Taihu Lake]

For the surface sediment samples of Taihu Lake in 2010, the eight physicochemical indices of pH, temperature, Eh, water content, porosity, grain size, total phosphorus, and Loss-on-ignition were measured and analyzed, along with the contents of nine heavy metals:Cu, Zn, Ni, Cr, Pb, Ba, Mn, Co, and V. The order of magnitudes of heavy metal content of surface sediments in Taihu Lake was:Mn>Ba>Zn>Cr>V>Ni>Pb>Cu>Co. This suggested that the contents of the nine heavy metals were beyond the background value, which had a close connection to the geology of the Taihu Lake Basin and were influenced by human activity to varying degrees. The clustering analysis and the spatial distribution of the heavy metals revealed that the concentrations of heavy metals in the North and South Taihu Lake sections decreased from the lake shore to the lake center, the concentrations of heavy metals in the West Taihu Lake section increased from the lake shore to the lake center, and the distribution of heavy metals in the center of the lake remained relatively uniform. According to the correlation study, the metal elements were positively correlated with one another to varying degrees, indicating that they originate from the same source of pollution. According to the PCA and PMF analyses, there were some different sources of heavy metals in Taihu Lake, in which the transportation and industrial complex source were the most important sources, the diagenesis was the second major source, and agriculture was the third major source. Furthermore, the heavy metal pollution was evaluated using the geoaccumulation and the potential ecological risk indices. This offers a solid theoretical backing for the future management of heavy metal pollution in Taihu Lake.

Distribution and changes in microplastics in Taihu Lake and cyanobacterial blooms formed by the aggregation of Microcystis colonies

As a new type of pollutant, microplastics have attracted much attention. As the third largest freshwater lake in China, Taihu Lake is characterized by severe eutrophication caused by external pollution and frequent occurrence of cyanobacterial blooms. Although there have been previous investigations into the spatial distribution of microplastics in Taihu Lake, research on the relationships among microplastics, pollutants, and cyanobacterial blooms, as well as the spatiotemporal distribution and changing characteristics of microplastics, is deficient. This study investigated the characteristics of microplastics, pollutants, and cyanobacterial blooms in the surface water and sediments of Taihu Lake. The abundances of microplastics were 0-3.7 items/L in the surface water and 44.42-417.56 items/kg (dry weight) in the sediments. Microplastics are most abundant in the western, southern, and northern lake areas. The northern and western lake areas are severely polluted, and cyanobacterial blooms are prone to occur in these areas. This study found that microplastics exist in the surface water of the southeastern lake area, which is a source of drinking water, and the microplastics may thus have adverse effects on drinking water quality. As the main organisms in the cyanobacterial blooms, Microcystis and microplastics have similar spatial distributions in Taihu Lake and are both affected by wind. Based on a combination of the investigations of this paper with the existing research on the microplastics in Taihu Lake, the spatiotemporal distribution of microplastics was obtained: the abundance of microplastics in surface water has continuously decreased, there are no obvious spatial distribution differences, and the spatial distribution of microplastics in the sediments is the same as that in the surface water.

[Spectral Characteristics and Source Analysis of Chromophoric Dissolved Organic Matter in Surface Water of Taihu Lake Before Cyanobacterial Blooming]

Chromophoric dissolved organic matter (CDOM) is an important part of the nutrient biogeochemical cycle in aquatic ecosystems. To explore the characteristics and sources of CDOM components in the surface water of Taihu Lake, UV-visible spectroscopy and excitation emission matrix fluorescence spectroscopy-parallel factor analysis were used to analyze CDOM components in surface water. Combined with CDOM optical parameters (a355, SUVA254, a250/a365, FI, BIX, and HIX), the spatial differences and pollution sources were identified, and a preliminary comparison was made between this study and the historical data of CDOM components in Taihu Lake. According to the results, a355, SUVA254, and a250/a365 showed the characteristics of high concentration, high aromatic ability, and low relative molecular weight of CDOM in the surface water of the eastern part of Taihu Lake; however, the northern part showed the opposite characteristics. Four components were isolated from CDOM using parallel factor analysis:one tyrosine-like (C1), two types of tryptophan (C2 and C4), and one fulionic acid (C3). The main component C1 had a strong linear relationship with the C2 and C3 components, suggesting that different components originated from similar pollution sources. The fluorescence index showed that CDOM in different areas of Taihu Lake were differently affected by endogenous and terrestrial inputs; however, the overall humification degree was low. This indicated that the CDOM components in Taihu Lake were primarily protein-like (C1, C2, and C4) (>85%) and autogenous, with good biochemical availability.

Characteristics of fish community structure and environmental driving factors in Taihu Lake during the first year of fishing ban

Taihu Lake has officially implemented the full fishing ban policy since October 1, 2020. We investigated fish community of Taihu Lake in the four seasons of 2020. A total of 42 fish species were collected, belonging to 6 orders, 7 families, and 33 genera. The first five dominant species ranked by the index of relative importance were Coilia nasus, Toxabramis swinhonis, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, and Salangichthys tangkahkeii. The number of C. nasus accounted for 85.1% of the total number of catches. According to the distributional characteristics of cyanobacterial blooms and aquatic plants, Taihu Lake could be divided into the northern, central, and eastern regions. There was no significant difference in catch per unit effort (CPUE) among different lake regions, but Shannon diversity index and Pielou evenness index in the eastern region was greater than in the other two regions. The CPUE, Shannon diversity index, and Pielou evenness index were significantly different among the four seasons, with the lowest CPUE in autumn and higher diversity in autumn and winter than in spring and summer. Electrical conductivity, water depth, chloride, and transparency were the main environmental factors driving the seasonal variations of fish community in Taihu Lake, while electrical conductivity, dissolved oxygen, total alkalinity, and transparency were key variables driving the spatial patterns. The results could be used as the baseline data for fish community studies in Taihu Lake after the fishing ban.

Vertical distribution of dissimilatory iron reducing communities in the sediments of Taihu Lake

The reduction of Fe(III) coupled with the oxidation of organic matter, primarily stimulated by dissimilatory iron-reducing bacteria (DIRB) under anoxic conditions, is a critical biogeochemical process in lacustrine sediments. Many single strains have been recovered and investigated, however, the changes in the diversity of culturable DIRB communities with sedimentary depth have not been fully revealed. In this study, 41 DIRB strains affiliated to ten genera of phylum Firmicutes, Actinobacteria, and Proteobacteria were isolated from the sediments of Taihu Lake at three depths (0-2 cm, 9-12 cm, and 40-42 cm), referring to distinct nutrient conditions. Fermentative metabolisms were identified in nine genera (except genus Stenotrophomonas). The DIRB community diversity and the microbial iron reduction (MIR) patterns vary in vertical profiles. The community abundance varied with the TOC contents in vertical profiles. The DIRB communities, containing 17 strains of 8 genera, were most diverse in the surface sediments (0-2 cm), where organic matter was most abundant among the three depths. 11 DIRB strains of five genera were identified in the 9-12 cm sediments with the lowest content of organic matter, while 13 strains of seven genera were identified in deep sediments (40-42 cm). Among the isolated strains, phylum Firmicutes dominated the DIRB communities at three depths, while its relative abundance increased with depth. Fe²⁺ ion was recognized as the dominant microbial ferrihydrite-reducing product of DIRB from 0 to 12 cm sediments. Instead, lepidocrocite and magnetite were the main MIR products of DIRB retrieved from 40 to 42 cm. The results indicate that the MIR driven by fermentative DIRB is crucial in lacustrine sediments and that the distribution of nutrients and iron (minerals) likely influences the diversity of DIRB communities in the lacustrine sediments.

Effects of nutrient reduction and habitat heterogeneity on benthic macroinvertebrate assemblages in a large shallow eutrophic lake

The Taihu Lake ecosystem has been subjected to numerous anthropogenic stressors during the past decades, leading to substantial changes in nutrient dynamics and habitat quality. For instance, the northwestern lake bays receive large amounts of nutrient-rich wastewater and have frequently experienced algal blooms, while the eastern lake region is still dominated by submersed macrophytes. Such changes in environmental characteristics can greatly impact benthic macroinvertebrate communities. We used a 15-year monitoring data series collected by the Taihu Laboratory for Lake Ecosystem Research to examine the spatial and temporal variations of the benthic invertebrate fauna and evaluate its status and trends. We found that three major communities could be distinguished based on taxonomic group composition and abundance, and these corresponded well with three lake habitat types: algal-dominated, macrophyte-dominated, and open-lake zone. An analysis of temporal trends showed major changes in the macroinvertebrates during the study period, largely driven by a lake-wide and significant decline in the abundance of pollution-tolerant taxa. The spatial and temporal variations of macroinvertebrate communities were mainly explained by nutrients (e.g., total nitrogen and ammonium concentrations) and habitat factors (e.g., sediment substrates and macrophyte biomass) as indicated by Random Forests regression, but the major drivers of macroinvertebrate density differed among the three lake zones at the temporal scale. Moreover, our findings suggest that benthic invertebrates were more sensitive to the improvement of the lake's environmental conditions than the pelagic community was. This study provides insights into the responses of macroinvertebrates to ecological dynamics in lakes and highlights the importance of continued monitoring for tracking long-term changes.

Disclosing the bioaccumulation and biomagnification behaviors of emerging per/polyfluoroalkyl substances in aquatic food web based on field investigation and model simulation

Emerging poly/perfluoroalkyl substances (PFASs) have been widely detected in the environment, but their bioaccumulation and biomagnification behaviors are not well understood. We collected surface water, sediment, and various aquatic organisms from Lake Taihu, China. Several emerging PFASs, such as fluorotelomer sulfonates (FTSs), hexafluoropropylene oxides (HFPOs), and chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) were frequently detected in water and sediment samples. The concentrations of HFPO trimer acid (HFPO-TA), 4,8-dioxa-3 H-per-fluorononanoate, and FTSs were remarkably higher than those reported previously, indicating that their application is increasing in Taihu Basin. These emerging PFASs displayed higher sediment/water partitioning coefficients (log K_oc) than the corresponding perfluoroalkyl acids (PFAAs) with the same perfluorinated carbon chain length. HFPOs and Cl-PFESAs were more labile to deposit in fish livers than perfluorooctanoic and perfluorooctane sulfonic acids, respectively. Both field investigations and model simulations indicated that HFPO-TA and Cl-PFESAs, as well as the hydrogen-substituted analogs of 6:2 Cl-PFESA (6:2 H-PFESA), were biomagnified along the aquatic food chain. The bioaccumulation model simulation revealed that the accumulation of these emerging PFASs in fish was mainly through dietary intake, whereas gill respiration and fecal excretion facilitated their elimination. Metabolic transformation might also contribute to their elimination relative to the legacy ones.

Estimating the contribution of environmental variables to water quality in the postrestoration littoral zones of Taihu Lake using the APCS-MLR model

Water quality monitoring is one of the most important aspects of postrestoration assessments because it affects water pollution control and the development of sustainable management strategies. However, a comprehensive understanding of potential water pollution and source apportionment in restoration projects is still lacking. In this study, the water quality variables of three restored national wetland parks with different cofferdam systems (i.e., an eco-layered cofferdam, a fully enclosed cofferdam, and open water) in the littoral zone of Taihu Lake were monitored monthly for three years (2019-2021). Hydrochemical and meteorological variables were used as auxiliary parameters for multivariate statistics, including principal component analysis (PCA) and absolute principal component score-multiple linear regression (APCS-MLR), to accurately estimate the source apportionment of the potential factors influencing the water environment. PCA extracted three or four potential sources, accounting for 64.71 %, 65.40 %, and 63.85 % of the total variance. The APCS-MLR results showed that wind direction and volatile suspended solids were the primary sources affecting water quality in open water, with a sum of the mean source contributions of 40.7 %. In fully enclosed cofferdam systems, the dire state of endogenous pollution was the greatest potential source affecting water quality, with a mean contribution of 41.2 %. The eco-layered cofferdam alleviated the contributions of suspended solids (mean contribution of 23.7 %) and nutrients in the water column (mean contribution of 30.8 %); however, the contribution of organic matter in the cofferdam was relatively high (mean contribution of 13.4 %). Based on these results, eco-layered cofferdams play a positive role in eutrophication control and ecological restoration in the littoral zone of large shallow lakes. Meanwhile, adding meteorological variables to assist hydrochemical variables in multivariate statistics may improve the accuracy and certainty of pollution source apportionment and support decision-makers in developing water quality protection and management strategies for postrestoration projects in littoral zones.

Differences in Carbon and Nitrogen Migration and Transformation Driven by Cyanobacteria and Macrophyte Activities in Taihu Lake

The metabolic activities of primary producers play an important role in the migration and transformation of carbon (C) and nitrogen (N) in aquatic environments. This study selected two typical areas in Taihu Lake, a cyanobacteria-dominant area (Meiliang Bay) and a macrophyte-dominant area (in the east area of the lake), to study the effects of cyanobacteria and macrophyte activities on C and N migration and transformation in aquatic environments. The results showed that total N and total particulate N concentrations in the water of the cyanobacteria-dominant area were much higher than those in the macrophyte-dominant area, which was mainly due to the assimilated intracellular N in cyanobacteria. Macrophyte activity drove a significantly higher release of dissolved organic C (DOC) in the water than that driven by cyanobacteria activity, and the DOC contents in the water of the macrophyte-dominant area were 2.4~4.6 times the DOC contents in the cyanobacteria-dominant area. In terms of the sediments, organic matter (OM), sediment total N and N species had positive correlations and their contents were higher in the macrophyte-dominant area than in the cyanobacteria-dominant area. Sediment OM contents in the macrophyte-dominant area increased from 4.19% to 9.33% as the sediment deepened (0~10 cm), while the opposite trend was presented in the sediments of the cyanobacteria-dominant area. Sediment OM in the macrophyte-dominant area may contain a relatively high proportion of recalcitrant OC species, while sediment OM in the cyanobacteria-dominant area may contain a relatively high proportion of labile OC species. Compared with the macrophyte-dominant area, there was a relatively high richness and diversity observed in the bacterial community in the sediments in the cyanobacteria-dominant area, which may be related to the high proportion of labile OC in the OM composition in its sediments. The relative abundances of most OC-decomposing bacteria, denitrifying bacteria, Nitrosomonas and Nitrospira were higher in the sediments of the cyanobacteria-dominant area than in the macrophyte-dominant area. These bacteria in the sediments of the cyanobacteria-dominant area potentially accelerated the migration and transformation of C and N, which may supply nutrients to overlying water for the demands of cyanobacteria growth. This study enhances the understanding of the migration and transformation of C and N and the potential effects of bacterial community structures under the different primary producer habitats.

Occurrence and distribution of triclosan and its transformation products in Taihu Lake, China

The transformation products of triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) may be more persistent and toxic than their parent compound, yet their occurrence in aquatic environments is poorly understood. In this study, we identified three transformation products in sediment samples from Taihu Lake and compared their concentrations with the parent compound triclosan. Triclosan in Taihu Lake was at low level, ranging from 0.086 to 1.1 ng/L in surface water and 0.0058-8.3 ng/g in sediments. The three detected transformation products included methyl triclosan, chlorinated triclosan derivatives, and methyl chlorinated triclosan derivatives. Those transformation products constituted 0.73-87.5% of the total triclosan (total triclosan is the sum of triclosan, methyl triclosan, chlorinated triclosan derivatives, and methyl chlorinated triclosan derivatives on a molar basis), indicating that the ecological risk of transformation products should be considered in addition to the parent compound. Different transformation products had distinct spatial distributions. Chlorinated triclosan derivatives had the highest concentration in samples from the northwest region (0.016-0.21 ng/g) of the lake and were positively correlated with triclosan, which may indicate the possible transformation from triclosan to chlorinated triclosan derivatives. Methyl triclosan and methyl chlorinated triclosan derivatives were generally higher in samples from the center of the lake (0.22-0.28 ng/g for methyl triclosan and 0.017-0.021 ng/g for methyl chlorinated triclosan derivatives, respectively), indicating the possible occurrence of in situ microbial methylation of triclosan and chlorinated triclosan derivatives and the accumulation of those methylated analogues in Taihu Lake.

Characterizing spatiotemporal variations of polycyclic aromatic hydrocarbons in Taihu Lake, China

In this study, we analyzed the concentration distributions of 20 polycyclic aromatic hydrocarbons (PAHs) in 41 water samples which were collected from the northern part of Taihu Lake during 4 field campaigns (201511, 201606, 201702 and 201709). The concentrations were determined with GC-MS, and their spatial and seasonal distribution characteristics were interpreted. The results show that 2-ring PAHs present considerably higher concentrations in warm seasons than cold seasons, but the concentrations of the other higher-ring PAHs are rather stable in warm and cold seasons. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. Meanwhile, the spatial distributions of the PAH concentrations in cold seasons were rather various in the sampling area, while the distributions in the warm seasons were homogeneous. The different distributions could result from the water recharge from the Yangtze River during cold seasons, which diluted PAH concentrations in the northeastern part of the lake. Furthermore, via literature review on PAH concentrations in water body, PAHs are in a wide range of levels and their patterns are different among the studies, which should be more effected by local factors instead of general PAH properties. The results from this study also present special characteristics of PAHs in Taihu Lake, which exhibit more insight on PAHs existence in water bodies.

Spatial-Temporal Variations of Water Quality in Urban Rivers after Small Sluices Construction: A Case in Typical Regions of the Taihu Lake Basin

Urban river pollution is considered a 'necessary evil' consequence of disproportionate developmental expansion in metropolises. Unprecedented expansion and anthropic activities lead to the deterioration of urban rivers with municipal and industrial sewage. The construction of sluices is one of the irrefutable parts of the process. In order to prevent floods and drought, many cities build sluices and dams in rivers to balance water quantity in different seasons. To explore the change characteristics of the water quality in urban rivers after the construction of sluices and dams, the change in the total phosphorus (TP) and total nitrogen (TN) concentrations upstream and downstream of rivers was investigated under the condition of sluices closure in Wuxi. According to the results, when the sluices were closed, the pollutants of TP and TN would accumulate upstream in rivers, which caused the water quality in the upper reaches to be worse than that in the lower reaches. Specifically, the TN and TP concentrations downstream of urban rivers in Wuxi were approximately 14.42% and 13.80% lower than those upstream when the sluices were closed. Additionally, the water quality in urban rivers was usually better in summer and autumn than in the other seasons, showing obvious seasonality after the construction of the sluices. The research will provide a theoretical basis for future sluice operation and the water resources management of urban rivers.

Spatiotemporal Patterns in pCO2 and Nutrient Concentration: Implications for the CO2 Variations in a Eutrophic Lake

Lakes are considered sentinels of terrestrial environmental change. Nevertheless, our understanding of the impact of catchment anthropogenic activities on nutrients and the partial pressure of carbon dioxide (pCO2, an important parameter in evaluating CO2 levels in water) is still restrained by the scarcity of long-term observations. In this study, spatiotemporal variations in nutrient concentrations (total nitrogen: TN, total phosphorus: TP, nitrate: NO3--N, and ammonium: NH4+-N) pCO2 in Taihu Lake were analyzed from 1992 to 2006, along with the gross domestic product (GDP) and wastewater discharge (WD) of its catchment. The study area was divided into three zones to characterize spatial heterogeneity in water quality: the inflow river mouth zone (Liangxi River and Zhihugang River), transition zone (Meiliang Bay), and central Taihu Lake, respectively. It is abundantly obvious that external nutrient inputs from the catchment have a notable impact on the water parameters in Taihu Lake, because nutrient concentrations and pCO2 were substantially higher in the inflow river mouth zone than in the open water of Meiliang Bay and central Taihu Lake. The GDP and WD of Taihu Lake's catchment were significantly and positively correlated with the temporal variation in nutrient concentrations and pCO2, indicating that catchment development activities had an impact on Taihu Lake's water quality. In addition, pCO2 was negatively correlated with chlorophyll a and the saturation of dissolved oxygen, but positively correlated with nutrient concentrations (e.g., TN, TP, and NH4+-N) in inflow river mouth zone of Taihu Lake. The findings of this study reveal that the anthropogenic activities of the catchment not only affect the water quality of Taihu Lake but also the CO2 concentrations. Consequently, catchment effects require consideration when modeling and estimating CO2 emissions from the extensively human-impacted eutrophic lakes.

Simulation modelling the structure related bioaccumulation and biomagnification of per- and polyfluoroalkyl substances in aquatic food web

Until now, there is no bioaccumulation model to predict bioaccumulation of polyfluoroalkyl substances (PFASs) in aquatic organisms due to their unique amphiphilic properties. For the first time, protein contents instead of lipid contents of organisms were used in bioaccumulation models to predict the concentrations and reveal the accumulation mechanisms of PFASs in various aquatic organisms, based on the available data. Comparison between the modeled and measured results indicated the models were promising to predict the PFAS concentrations in the fishes at different trophic levels very well, as well as their bioaccumulation factors (BAF) and trophic magnification factors (TMF) of PFASs in fish. Both water and sediment are important exposure sources of PFASs in aquatic organisms. As the two main uptake pathways, the contribution of gill respiratory decreases while that of dietary intake increases with the chain length of PFASs increasing. Fecal excretion and gill respiration are the main pathways for fish to eliminate PFASs, and their relative contributions increase and decrease respectively with chain length. The short-chain (C6-C8) perfluoroalkyl acids (PFAAs) are greatly eliminated via gill respiratory quickly, leading to their very low BAFs. As the carbon chain length increases, dietary intake becomes dominant in the uptake, while elimination is mainly through fecal excretion with relatively low rates, especially in the fishes with high protein contents. For the very long chain (C12-C16) PFASs, they are very difficult to excrete with a low total elimination rate constant (k_e = 0.463-0.743 d^-1), thus leading to their high BAFs and TMFs. The high intake rate but low elimination rate, as well as the high water and sediment concentrations together contribute to the highest accumulated concentration perfluorooctane sulfonic acid in the fish of Taihu Lake.

[Comparison of Health Risk from Sources of Perfluoroalkyl Substances in Taihu Lake for Different Years]

Pollution characteristics and spatial distributions of perfluoroalkyl substances (PFASs) in surface water samples were investigated in Taihu Lake in 2010 and 2019, respectively. A hybrid model based on the positive matrix factorization (PMF) and the health risk assessment model were employed for quantifying the contributions of sources to PFASs concentrations and the source risks. The method contained two stages:1 the sources of PFASs were apportioned using the PMF model, and 2 the contribution of health risks from each source was quantitively estimated. Three factors (source categories) were extracted using PMF, including:coating industry sources, textile and electroplating sources, and fluoride-processing industry sources. Their contributions to PFASs concentration were 29.59%, 25.68%, and 44.72% for 2010 and 67.69%, 10.26%, 22.05%, for 2019, respectively. The health risk of PFASs in the water assessed by the health risk assessment (HRA) model was 4.56E-07 for 2010 and 2.69E-07 for 2019, which was lower than 1E-06. The source contributions to health risks estimated by the PMF-HRA hybrid model were:64.86% (2010) and 92.48% (2019) for textile and electroplating sources, 31.30% (2010) and 5.04% (2019) for coating industry sources, and 3.84% (2010) and 2.48% (2019) for fluoride-processing industry sources. For the two years, the concentrations of PFOA and PFOS were reduced significantly, indicating the effective control of their emissions during the past ten years in Taihu Lake. However, it was also shown that the concentrations of PFBS and PFHxS were increased. These findings suggest that the above short chain-PFCs species should be the focus for further control and management, and their health risks should be studied in future research.

Spatiotemporal correlations between water quality and microbial community of typical inflow river into Taihu Lake, China

Changxing River, which is a typical inflow river into Taihu Lake and occurs severe algae invasion, is selected to study the effect of different pollution sources on the water quality and ecological system. Four types of pollution sources, including the estuary of Taihu Lake, discharge outlets of urban wastewater treatment plants, stormwater outlets, and nonpoint source agricultural drainage areas, were chosen, and next-generation sequencing and multivariate statistical analyses were used to characterize the microbial communities and reveal their relationship with water physicochemical properties. The results showed that ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were the main pollutants in Changxing River, especially at stormwater outlets. At the same time, the diversity of microbial communities was the highest in the summer, and dominant microbes included Proteobacteria (40.9%), Bacteroidetes (21.0%), and Euryarchaeota (6.1%). The results of BIOENV analysis showed that the major seasonal differences in the diversity of microbial community of Changxing river were explained by the combination of water temperature (T), air pressure (P), TP, and COD_Mn. From the perspective of different pollution types, relative abundances of Microcystis and Nostocaceae at the estuary of Taihu Lake were correlated positively with dissolved oxygen (DO) and pH, and relative abundances of Pseudomonas and Arcobacter were correlated positively with concentrations of TN and nitrate nitrogen (NO₃^--N) at stormwater outlets. This study provided a reference for the impact of pollution types on river microbial ecosystem under complex hydrological conditions and guidance for the selection of restoration techniques for polluted rivers entering the important lake.

[Influence of Different Hydraulic Disturbance Intensities on the Migration of Aged PSMPs Between Sediment and Water]

Taking Taihu Lake as the research object, for the aged polystyrene microplastics (PSMPs), the influence of hydraulic disturbance intensity on the migration process of PSMPs between mud and water phases was discussed, and the morphology and elements of PSMPs were analyzed using microscopic characterization methods including FTIR and SEM-EDS, as was done for characterization. The results showed that under disturbance conditions (55 r·min^-1 and 120 r·min^-1), the suspended solids (SS) and PSMPs in the overlying water were higher than those in the control experiment. This was due to the fact that the PSMPs were affected by buoyancy and reunited on the water surface under undisturbed conditions. Under low-intensity (55 r·min^-1) disturbances, SS and PSMPs in the overlying water were (264.67±16.01) mg·L^-1 and (239.67±6.51) n·mL^-1, respectively, and (120 r·min^-1) under high intensity. Under disturbance, the SS and PSMPs in the overlying water were (264.67±16.01) mg·L^-1 and (239.67±6.51) n·mL^-1, respectively. In the bottom mud, PSMPs were (491.00±23.46) mg·L^-1 and 2.00 n·mL^-1, respectively. Additionally, according to the SEM-EDS analysis, the surface of PSMPs had sediment elements (Si, etc.), which showed that it was easier to promote the adsorption of PSMPs by suspended solids under high strength. The abundance of PSMPs in the sediments also confirmed that the greater the intensity of the disturbance, the easier it was to promote the migration of PSMPs to the sediments.

A modified cyanobacteria prediction model based on cellular automata model using N and P concentration reverse data: a case study in Taihu Lake

The problem of algal bloom caused by eutrophication has attracted global attention. Many scholars have studied the problem associated with algae bloom, but few have carried out dynamic monitoring, instead focusing on the formation mechanism of cyanobacteria. For our study of the Taihu Lake in China, we used Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat remote sensing image data from 2017 to establish a prediction model. First, we used MODIS data to retrieve the concentration of N, P, and chlorophyll a in water. Then, we applied the analytic hierarchy process (AHP) model to the inversion results to construct the diffusion potential index. Finally, we used C# to compile the cellular automata (CA) model. We found that the distribution of cyanobacteria predicted by our method was consistent with the algal bloom situation of Taihu Lake in 2017. The results showed that the method effectively predicts the dynamic transfer of cyanobacteria from outbreak to diffusion in a short period of time, which can help decision-makers monitor lake health.

Validation and Assessment of Diffusive Gradients in Thin-Films (DGT) Technique for Measuring Nutrients in Taihu Lake Water with Algae Bloom

DGT (diffusive gradients in thin films) technique has been developed for measuring nitrogen in freshwaters and applied to assess the bioavailability of phosphorus in soils/sediments. These two elements are the main nutrients causing algae bloom, but DGT has never been used in the field water conditions with algae bloom. In our study, a pair of DGT devices were used in comparison with grab sampling to characterize the performance of this technique to measure labile NO₃-N, NH₄-N, and PO₄-P concentrations in algae-cultivated Taihu Lake water. The results showed that DGT measurement was highly affected by algae bloom and the environmental conditions using the current assemblies, especially for NH₄-N measurement. For in situ measurement of nutrients in the real environment, an improvement to the DGT technique is required. The comprehensive assessment of the level of eutrophication needs to consider a variety of environmental factors rather than just the concentration of nutrients.

Occurrence and driving forces of different nitrogen forms in the sediments of the grass and algae-type zones of Taihu Lake

Excessive nitrogen (N) load in sediments is at risk of release resulting in the degradation of grass-type lake ecosystems. At present, the occurrence characteristics of N forms and the driving forces of organic N (ON) hydrolysis in the sediments of Taihu Lake were still unclear. Here, 52 sampling sites in 7 lake areas in Taihu Lake were investigated to compare the spatial occurrence characteristics of the sedimentary free N (FN), exchangeable N (EN), acid hydrolyzable N (HN), and residual N (RN) and their associated driving forces. The results showed that the total N contents in the dry sediment ranged from 1811.56 to 5594.06 mg kg^-1, and the contribution was in the order of RN > HN > EN > FN. Spatially, RN and total organic carbon were significantly consistently influenced by dam construction and deposition algal residue. The HN concentration was high in the estuaries affected by N inputs from the rivers. The coupling relationship of spatial distribution between ON and N forms was revealed. The factors, i.e., algal residue deposition and terrigenous N inputs, were considered as the main driving forces stimulating the ON hydrolysis in the algae-type lake zones. It can be deduced that controlling terrigenous N inputs and sediment suspension may be the key to inhibiting the transformation from grass-type to algae-type lake ecosystem.

Polycyclic aromatic hydrocarbons (PAHs) in the upstream rivers of Taihu Lake Basin, China: spatial distribution, sources and environmental risk

The polycyclic aromatic hydrocarbon (PAH) pollution in Taihu Lake Basin has caused widespread concern. However, the spatial temporal distribution of PAHs in the upstream rivers of Taihu Lake Basin remains largely unknown. Thus, this study aims to investigate the level, spatial distribution, sources, and environment risk caused by PAHs in upstream rivers of Taihu Lake Basin. The concentrations of total 16 PAHs (∑16PAHs) ranged from 188.64 to 1060.39 ng/g, with an average of 472.62 ng/g. High-molecular-weight (HMW) PAHs were the predominant compounds in most sample sites. The results of source analysis demonstrated that the PAH pollution was mainly sourced from mixture of combustion and direct petroleum spillage. The ecological risk assessment showed that moderate ecological risk caused by the PAH contaminants might occur in most sample sites. The incremental lifetime cancer risks (ILCRs) ranged from 2.07 ×10-4 - 2.66 × 10-3 for children and 9.66 ×10-5 - 1.24 × 10-3 for adult, indicating moderate cancer risk of PAH-contaminated sediments.

Occurrence of titanium dioxide nanoparticle in Taihu Lake (China) and its removal at a full-scale drinking water treatment plant

The occurrence of titanium dioxide nanoparticle (TNP), an emerging contaminant, in Taihu Lake of China was investigated. Ti was present at a concentration of 224 ± 59 μg/L in the water samples collected from a water source in east Taihu Lake. Approximately 0.19% of the Ti-containing matter was at the nano-scale. Scanning Electron Microscope analysis verified the existence of Ti-containing components, such as TiOx and FeTiOx. Furthermore, Ti K-edge X-ray absorption near-edge structure spectroscopy was used to detect the phase composition of nano-scaled Ti-containing matter. The spectra showed the three characteristic peaks of TiO2 in the samples, suggesting the occurrence of TNP in Taihu Lake. A least-squares linear combination fitting analysis indicated that the TNP concentration in the water source was ~0.77 μg/L in water and ~0.85 μg/g-dry in sediment. The removal performance of the TNP at a full-scale conventional drinking water treatment plant indicated that ~61% of TNP was removed via coagulation/sediment, sand filtration, and disinfection/clear water reservoir. The coagulation/sediment process accounted for approximately 70% of the total removed TNP. The finished water contained ~ 0.30 μg/L TNP. This study is the first that reported the presence and transport of TNP in a full-scale drinking water treatment system.

A deep learning method for cyanobacterial harmful algae blooms prediction in Taihu Lake, China

Cyanobacterial Harmful Algae Blooms (CyanoHABs) in the eutrophic lakes have become a global environmental and ecological problem. In this study, a CNN-LSTM integrated model for predicting the CyanoHABs area was proposed and applied to the prediction of the CyanoHABs area in Taihu Lake. Firstly, the time-series data of the CyanoHABs area in Taihu Lake for 20 years were accurately obtained using MODIS images from 2000 to 2019 based on the FAI method. Then, a principal component analysis was performed on the daily meteorological data for the month before the outbreak of CyanoHABs in Taihu Lake from 2000 to 2019 to determine the meteorological factors closely related to the outbreak of CyanoHABs. Finally, the features of CyanoHABs area and meteorological data were extracted by Convolutional Neural Networks (CNN) model and used as the input of Long Short Term Memory Network (LSTM). An integrated CNN-LSTM model approach was constructed for predicting the CyanoHABs area. The results show that high R² (0.91) and low mean relative error (17.42%) verified the validity of the FAI index to extract the CyanoHABs area in Taihu Lake; the meteorological factors closely related to the CyanoHABs outbreak in Taihu Lake are mainly temperature, relative humidity, wind speed, and precipitation; the CNN-LSTM integrated model has better prediction effect for both training and test sets compared with the CNN and LSTM models. This study provides an effective method for predicting temporal changes in the CyanoHABs area and offers new ideas for scientific and effective regulation of inland water safety.

Evaluation and prediction of water quality in the dammed estuaries and rivers of Taihu Lake

Proper evaluation of water quality is pertinent to estuarine habitat restoration. Identifying the degrading factors of the water environment and predicting the trend of eutrophication are key to restore the habitat. Through trophic level index (TLI), water quality index (WQI), modified Nemerow pollution index (NPI), and the Random Forest (RF) model, water samples collected from various estuaries of Taihu Lake from 2017 to 2019 were evaluated. To predict the water quality development, four scenarios were set viz. S1: add or remove an ecological buffer, S2: increase or reduce the external nutrients, S3: open or close the dam/gate, and S4: increase or decrease the internal release. In Wuli Lake, the nutrient concentrations in the river regions were higher than in the lake regions, while a contrary trend was observed in Gonghu Bay. The estuarine water quality in the dry season (WQI = 40.91, NPI = 1.73) was merely worse than that in the wet season (WQI = 47.27, NPI = 1.67). On the other hand, the eutrophic status in the wet season (TLI_Wet = 57.93) was worse than that in the dry season (TLI_Dry = 57.23). The estuarine water quality of Taihu Lake has improved from 2017 to 2019 but still belongs to medium level. The principal component analysis (PCA) revealed that dam construction, land use types, unstable hydrodynamic conditions, and trumpet-shaped estuary were the main factors that aggravated the water quality degradation. The RF model has strong forecasting capabilities for estuarine water quality. When the estuaries are close to residential and industrial districts, controlling the surface runoff and improving sewage treatment efficiency are the most effective measures to improve the water quality. In the estuaries, the sediments are usually disturbed by the wind-waves. Conclusively, reducing sediment disturbance and internal contamination accumulation via biological and engineering measures is the key to estuarine restoration.

Drinking water elements constituent profiles and health risk assessment in Wuxi, China

Water elements pollution has attracted public attention globally. Wuxi is located in East China, and its water source, Taihu Lake, has been severely polluted since 2007. Studies of elemental pollution profiles have yet to be conducted in this area. In this study, 56 water samples were collected in 2018, and 33 elements were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that the levels of 33 elements ranged from 1.35 × 10^-3 μg/L(Tl) to 101 mg/L(Ca), with Sr, Al, Fe, B, Ti, Ba, and Zn levels being relatively higher. A comprehensive literature review showed spatial distribution of conspicuous elements in drinking water worldwide. Meanwhile, Monte Carlo simulations were applied to evaluate exposure health risks. The total hazard index(HI) for 14 non-carcinogens and the average incremental lifetime cancer risk (ILCR) of As and Pb exposure through drinking water were found acceptable. Sensitivity analyses suggested that Sb and As in the drinking water represent an increasing risk to human health. The results of this study provide key data on local metal pollution characteristics, help identify potential risk factors, and contribute to the development of effective environmental management policies for Taihu Lake.

Tris(1,3-dichloro-2-propyl)phosphate Induces Mass Mortality of Crucian Carp (Carassius carassius) Embryos in Taihu Lake

Global fishery resources have been declining for decades, leading some fisheries to collapse. Although the decline is partly due to man-made chemical contamination, causal chemicals have been identified in only a few cases. We conducted consecutive 3-year investigations of embryonic mortality in Taihu Lake, China, including heavily contaminated northern areas, including Zhushan (ZS), Meiliang (ML), and Gonghu (GH), and the less polluted southeastern Suzhou (SZ). In 2016, 65.8% of crucian carp (Carassius carassius) embryos collected from ZS died before hatching, a substantially higher mortality rate than those observed in ML (21.7%), GH (15.2%), and SZ (2.2%). In 2017, the embryonic mortality rates were 38.8% in ZS, 1.3% in ML, 6.9% in GH, and 3.5% in SZ, and these rates strongly correlated with the concentrations of tris(1,3-dichloro-2-propyl)phosphate (TDCIPP): 104.2, 1.8, 4.6, and 4.1 ng/g lipid weight (lw) in embryos from ZS, ML, GH, and SZ, respectively. In 2018, embryonic mortality decreased to 4.0% in ZS and 1.2% in GH, consistent with decreases in embryonic TDCIPP concentrations to 17.1 and 1.5 ng/g lw, respectively. Moreover, the TDCIPP concentrations in dead embryos (70.5-216.8 ng/g lw) were much higher than those in live embryos (1.2-10.5 ng/g lw). Embryonic mortality was also observed in well-controlled laboratory experiments in which wild crucian carp were exposed to TDCIPP at concentrations similar to those measured in embryos collected from Taihu Lake, thus confirming TDCIPP as a causal factor in mass crucian carp embryo mortality in Taihu Lake. TDCIPP thus poses a threat to the sustainability of fisheries worldwide, given the high worldwide production volume of this chemical and its embryonic lethal toxicity.

Distribution and sedimentation of microplastics in Taihu Lake

Microplastics have been reported in environmental media for decades, but gaps in our knowledge about them still remain. We investigated the third biggest freshwater lake in China - Taihu Lake - and the 30 major rivers around it. Microplastics were detected in lake water and sediment, and in river water, at abundances varying from 1.7 to 8.5 items/L, 460 to 1380 items/kg and 1.8 to 18.2 items/L, respectively. Inflow rivers were more polluted with microplastics than outflow rivers. The most common shape was fragment. Microplastic sizes of <100 μm dominated in inflow rivers, 100-200 μm dominated in lake water and outflow rivers. The average size of microplastics in outflow rivers (200.4 μm) was larger than that in inflow rivers (166.2 μm). Microplastics of <100 μm only accounted for 28% in the lake surface water but were as high as 70% in the sediment, indicating that smaller microplastics may more easily settle in the lake. The main components of the microplastics were identified as being polyvinyl chloride and polyethylene. There were about 1.2E06 items/s microplastics entered Taihu Lake. Four main rivers located at northwestern lake accounted for 79% of the total inflow microplastic fluxes.

Impact of light quality on freshwater phytoplankton community in outdoor mesocosms

In shallow lakes, wind wave turbulence alters underwater spectral composition, but the influence of this phenomenon on phytoplankton community structure is poorly understood. We used 100L mesocosms to investigate the influence of light quality on a natural phytoplankton community collected from Taihu Lake in China. The communities in mesocosms were exposed to sunlight filtered for white, blue, green, and red light, while wave-making pumps simulated wind wave turbulence similar to Taihu Lake. Over the course of experiment, each filtered light reduced the total phytoplankton abundance compared to white light. The mean abundance of phytoplankton in controls was 1.72, 1.78, and 7.89 times of that in the red, blue, and green light treatments. Red, blue, and green light significantly promoted the growth of cyanobacteria, green algae, and diatoms, respectively, and induced successional change of the phytoplankton species under the tested conditions. The proportion of Microcystis to total phytoplankton abundance in controls and red light shifted from 87.09% at the beginning to 37.95% and 56.30% at the end of the experiment, respectively, and maintained its dominance, whereas Microcystis lost its dominance and was replaced by Scenedesmus (53.78%) and Synedra (53.18%) in the blue and green light, respectively. Given the process of how these phytoplankton compete in designated spectrum, exploring these influences could help provide new insights into the dominance formation of toxic cyanobacteria.

Risk assessment concerning the heavy metals in sediment around Taihu Lake, China

The present study sought to determine the systematic pollution status of the heavy metals (HMs) found in the sediment around Taihu Lake, China. The concentrations and speciations of the HMs in the sediment were measured. The Ni and Cr concentrations exceeded the probable effect level (PEL), while the concentrations of the other HMs (except Hg) were between the threshold effect level and the PEL. The enrichment factor values for all HMs indicated slight enrichment. The geoaccumulation index revealed that the HMs represented light pollution, while the average contaminant factor value of the HMs indicated moderate pollution. The ecological risk factor value indicated a medium ecological risk, with Cd and Hg being associated with a high and considerable potential ecological risk, respectively. The ecological risk index indicated that the ecological risk posed by the HMs was high. The contamination degree revealed a moderate level of metal pollution, while the pollution load index indicated a heavy pollution level. The extractable proportion of the HMs (except for Cr and As) exceeded 50%. In the case of Cd, the exchangeable proportion was 51.11%, which indicated it to be extremely unstable. PRACTITIONER POINTS: Heavy metals (except for Cr and As) have a high potential ecological risk. All selected heavy metals implying varying degrees of instability. Cd was the most serious pollutant based on the Igeo, Cf and EF analyses.

Derivation of water quality criteria of zinc to protect aquatic life in Taihu Lake and the associated risk assessment

Zinc is a widely distributed environmental pollutants and has been listed as priority heavy metal pollutant in China. Similar as other heavy metals, toxicity of zinc to aquatic organisms affects by environmental factors such as water hardness. It is necessary to develop regional water quality criteria (WQC) to protect native aquatic life against zinc due to the diversity of aquatic organisms' variability across different water systems, as a concretization and supplement for national zinc WQC. This study derived WQC for zinc by species sensitivity distribution (SSD) curve method. The zinc toxicity data of the aquatic organisms in Taihu Lake used in SSD curve was collected based on published toxicity data for zinc with hardness values and supplemented with acute toxicity tests conducted in this study. Six aquatic organism natives to Taihu Lake were selected to conduct zinc acute toxicity test in a range of hardness conditions. The relationship between water hardness and zinc toxicity was constructed. The criterion maximum concentration (CMC) and criterion continuous concentration (CCC) for zinc in Taihu Lake were then derived, which considered the water quality and taxonomic groups in Taihu Lake. The CMC and CCC were 100.69 μg/L and 30.79 μg/L, respectively. The environmental risk of zinc to Taihu Lake are acceptable, at moderate to low levels. This study has provided a basis for regional water quality criterion derivation and risk assessment in China.

Occurrence, spatiotemporal distribution, and risk assessment of current-use pesticides in surface water: A case study near Taihu Lake, China

This study involved the monitoring and risk assessment of current-use pesticides in surface water from the northwestern section of the Taihu Lake Basin (China) in 2019. In particular, 114 current-use pesticides were measured in samples collected during four campaigns spread across the wet, dry, and normal seasons. Pesticide concentrations were measured by means of a novel analytical method involving online solid-phase extraction coupled to LC-MS/MS. In total, 1 plant growth regulator, 34 herbicides, 23 insecticides, and 25 fungicides were detected. Detection frequencies greater than 90% were recorded for 26 pesticides; furthermore, acetamiprid, azoxystrobin, bentazone, carbendazim, isoprothiolane, metolachlor, paclobutrazol, and triadimenol were present in every sample. The measured pesticide concentrations varied widely, from below the detection limit to 10,600 ng/L (tricyclazole). The highest median concentrations for the fungicide, herbicide, and insecticide families were observed for carbendazim (135 ng/L), metolachlor (40 ng/L), and imidacloprid (31 ng/L), respectively. Twenty-two pesticides were quantitatively reported in Chinese surface water for the first time. The number and concentration of detected pesticides were significantly higher in June and September (wet season) compared to March and December (dry season). Agricultural areas of the study area were more contaminated than the residential and industrial sections. Imidacloprid was the only pesticide that exhibited high risk to sensitive ecological species (RQ_median > 1) in all four seasons. Isoproturon, isoprothiolane, and pretilachlor were identified as high risk in March (RQ_median = 4.5), September (1.3), and June (1.1), respectively; moreover, another eight pesticides posed a high ecological risk at specific sites. Seven pesticides recorded moderate risks (i.e., RQ_median = 0.1-1.0). Of the 18 pesticides with cases of high risk, a novel risk index, which accounted for frequency of PNEC exceedance, ranged from 6.7 (imidacloprid) to 7.1 × 10^-5 (propiconazole). The integrated consideration of ecological risk and frequency of risk inform priorities for regional pesticide management and control.

Hourly remote sensing monitoring of harmful algal blooms (HABs) in Taihu Lake based on GOCI images

The increasingly serious harmful algal blooms (HABs) in Taihu Lake has brought huge losses to the local economy and people's life in Taihu Lake. Satellite remote sensing technology has become one of the most important monitoring methods for HAB disasters due to its large-scale and long-term advantages. GOCI image has become the new data source of HAB monitoring because of its large size and high time resolution. Due to the low spatial resolution (500 m) and the existence of mixed pixels, the error of HAB area obtained by the NDVI method is large. In this paper, the linear mixing model (LMM) and the normalized difference vegetation index (NDVI) threshold method are combined to extract the HAB area from GOCI images with 500-m spatial resolution. Compared with the results of the HAB area extracted by Landsat8 OLI and MODIS data, three small areas in the study area were selected to verify the accuracy of the HAB area extracted from the GOCI image on October 2, 2015. The results show that when the NDVI threshold is 0.1, the area error of HABs is the smallest when the extracted HAB pixels mask the decomposition results of mixed pixels; besides, the area error of HABs extracted from the GOCI image is smaller than that from MODIS image; finally, GOCI image can extract the spatial dynamic distribution of HABs in Taihu Lake within 8 h a day, which has higher temporal resolution than the MODIS image. Compared with the NDVI threshold method and LMM method, the inversion accuracy is greatly improved, and the accuracy is stable in different regions. It can provide technical support for the decision-making and assessment of HAB ecological disasters.

Seasonal distribution and ecological risks of phthalic acid esters in surface water of Taihu Lake, China

Phthalic acid esters (PAEs) are endocrine-disrupting compounds that are ubiquitous in surface water. However, early studies on PAEs only focused on six species on the priority contaminant list, and the seasonal variation in the PAE distribution in Taihu Lake, China is unclear. The present study investigated the occurrence, spatial distribution, and ecological risks of 16 PAEs in Taihu Lake during the dry, normal, and wet seasons. The results showed that dibutyl phthalate, diethylhexyl phthalate (DEHP), and diisobutyl phthalate (DIBP) were the major species detected in the surface water of Taihu Lake. The summed concentration of the six priority PAEs accounted for less than 50% of the total, indicating that the contamination of the other PAE congeners was non-negligible. Significant seasonal effects were observed that the total PAE concentration was higher in the wet season than in the dry season, and there were significant positive correlations between the total PAE concentration and rainfall, the water reserve, and the water level. In the dry season, a relatively high PAE level was detected in the area close to the inflow river estuary and the tourist island in the lake. The concentrations of PAEs in the lakeshore area were higher than those in the lake center in the normal season, and were generally high in the wet season. DEHP posed high risks for fish regardless of the season, while butyl benzyl phthalate, DIBP, dihexyl phthalate, and diphenyl phthalate also showed high risks in the normal and wet seasons. These results suggest that the contamination and risks of congeners other than the priority PAEs are also of necessary concern, and seasonal variation should be considered for a comprehensive understanding of PAE contamination in surface water.

Spatial distribution, historical trend, and ecological risk assessment of phthalate esters in sediment from Taihu Lake, China

In this study, the distribution of phthalate esters (PAEs) in twenty surface sediment and five core sediment samples in Taihu Lake, China, was investigated, and their ecological risks were assessed. Of the 10 PAE congeners, five PAEs including diethyl phthalate (DEP), dimethyl phthalate (DMP), di-n-butyl phthalate (DBP), di-iso-butyl phthalate (DIBP), and bis(2-ethylhexyl) phthalate (DEHP) were identified and quantified, and the rest 5 PAEs were below the limits of quantification. The concentrations of the total PAEs (ΣPAEs) in surface sediments and core sediments varied from 1.12 × 10³ to 18.71 × 10³ ng/g and 0.23 × 10³ to 5.22 × 10³ ng/g, respectively. The dominant PAEs were DBP and DIBP, contributing 85.90% to the ΣPAEs. Overall, the highest concentrations of ΣPAEs occurred in northern lake, followed by eastern lake and western lake, and southern lake was the least polluted area. The spatial distribution of ΣPAEs in sediments showed that the PAE distribution pattern was influenced by the riverside environment. The historical trend of the past 100 years was reconstructed in the core sediment via a ²¹⁰Pb dating technique. The vertical profile of the PAE congeners indicated that concentrations of PAEs started to increase since the 1990s in northern core sediments. It was estimated that the inventories of ΣPAEs in Taihu Lake was 4868.01 t. The potential ecological risk assessment by hazard quotient (HQ) method revealed that DBP posed a moderate risk due to its relatively high concentrations, with DIBP posed a low risk, while DEP, DMP, and DEHP exhibited no risk to the aquatic system.

[Pollution Characteristics and Risk Assessment of Organophosphate Esters in Rivers and Water Body Around Taihu Lake]

To explore the pollution characteristics, potential sources, and ecological and health risk of organophosphate eaters (OPEs) in the surface water of Taihu Lake, water samples from 18 surrounding rivers were collected, as well as 11 water samples from Taihu Lake. The concentrations of 13 OPEs in the water were determined using UPLC-MS/MS, and the spatial distribution of the OPEs in surface water of Taihu Lake basin was further analyzed. The results indicate that, in addition to tripropyl phosphate (TPrP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tricresyl phosphate (TCrP), ten OPEs were detected in all the water samples, the total concentration (ΣOPEs) ranged from 152.5 ng·L^-1 to 2524 ng·L^-1, and the concentration median value was 519.2 ng·L^-1. Tri(chloropropyl) phosphate (TCPP) and tri(2-chloroethyl) phosphate (TCEP) were the dominant OPEs, with the concentration ranges of 73.7-1753.9 ng·L^-1 (medium value:204.6 ng·L^-1) and 43.9-313.5 ng·L^-1 (medium value:131.3 ng·L^-1), respectively. The ΣOPEs decreased from the northwest region to the southeast, which corresponds to the economic and industrial development. The results of the source identification reveal that the wastewater discharge from electronics and textile enterprises, construction materials, and vehicular and marine traffic emissions may be the principal sources of the OPEs in Taihu Lake. The ecological risk assessment results indicate that only TCPP, tri(dichloropropyl) phosphate (TDCP), and triphenyl phosphate (TPhP) in some sites had a low risk. The health risk assessment reveals that there were no risks based on water intake, but the long-term risk of OPEs to the aquatic ecosystem and surrounding residents still need attention.

[Spatiotemporal Distributions and Ecological Risk Assessments of Typical Antibiotics in Surface Water of Taihu Lake]

Using solid phase extraction-high performance liquid chromatography tandem mass spectrometry, antibiotics belonging to four classes (i.e. sulfonamides, quinolones, tetracycline, and macrolides) in the surface water of Taihu Lake were monitored monthly for a year. Moreover, the potential ecological risks of antibiotics in Taihu Lake were assessed. During the one-year monitoring, all the eighteen target antibiotics were detected to some extent in the surface water. The detection rates of five sulfonamides (sulfamethoxazole, sulfathiazole, sulfadiazine, sulfadimethazine, and trimethoprim) were higher than 50%. The concentrations of quinolones in the surface water were relatively higher. The average and medium concentrations of ciprofloxacin were 13.0 ng·L^-1 and 13.5 ng·L^-1, respectively. There were significant differences in the antibiotic pollution during the different months, with the average concentrations of the target antibiotics ranging from 7.3 to 33.5 ng·L^-1. The concentration levels were lower from June to October, while higher concentrations were observed from February to May and in November. In the surface water of Taihu Lake, the spatial variations of antibiotics among the 20 sampling sites were not significant, with the average concentrations ranging from 13.0 to 14.3 ng·L^-1. During the one-year monitoring, the rates of medium and high risks that the antibiotics posed to algae reached 57.5%. The ecological risks of antibiotics were more severe in April and November, and the quinolones may be the dominant risk factor. This issue should be carefully considered by management authorities.

Using sediment resuspension to immobilize sedimentary phosphorus

The response of the transformation of internal phosphorus (P) to resuspended sediment was investigated in the sediment-water system under different disturbance intensity. The sediments and overlying water were collected from Taihu Lake, a typical shallow lake. The concentrations of particulate P (PP) and dissolved inorganic P (DIP) in the water phase and algal available P (AAP) and P fractions in the sediments and suspended particle characteristics were evaluated in laboratory-simulated experiments. The results show that dissolved oxygen (DO) in the overlying water increased continuously and pH decreased slightly under sediment resuspension. The concentration of ammonia nitrogen (NH₄⁺-N) showed a distinct decline, indicating that sediment resuspension promotes the penetration of DO into the sediments. It was also favor of the formation of metal oxides and hydroxides, inducing soluble amorphous metal compounds oxidized to insoluble crystalline metal compounds under disturbance condition. This resulted in the increase of refractory P in sediment compared with the static conditions. Sediment resuspension is beneficial to long-term P retention. This can be confirmed by the increase of maximum P adsorption amount (Q_max) and the decrease of the degree of P saturation (DPS) and equilibrium P concentration (EPC₀). This is the main explanation of DIP decrease in the overlying water. It is indicating that sediment resuspension not only improves the redox environment in the sediment-water system but also enhances P retention capacity.

[Surface water change characteristics of Taihu Lake from 1984-2018 based on Google Earth Engine]

Lakes are important fresh water resources. Accurate understanding of lake dynamic changes benefits the sustainable development of water resources and socio-economic development. Based on the Google Earth Engine (GEE), we analyzed the dynamics of Taihu Lake from 1984 to 2018 by adopting the dataset of Joint Research Centre's Global Surface Water and Landsat imagery. The modified normalized difference water index (MNDWI) was used to explore the changes in the area of Taihu Lake in recent 35 years. The results showed that the area of Taihu Lake increased during 1984-2018, with a total increase of 45.31 km². The area in spring and winter was larger than that in summer. Eastern Taihu Lake was the main part of Taihu Lake showing area change. Compared with 1984, 88.9% of the water area of Taihu Lake in 2018 did not change, and 0.3% of the water area disappeared permanently. Lake area changes were affected by both natural and anthropogenic factors. Agricultural irrigation, fish farming, reclamation of surrounding lakes, water conservancy engineering facilities, and the transformation of land-use types caused the reduction in lake area. Increased annual precipitation and the implementation of environmental protection policies were the main factors for the increases in lake area. The results provide reference for effective sustainable water resource management and verify the feasibility of monitoring long-term surface water change based on the GEE platform.

Rufibacter hautae sp. nov., a red-pigmented bacterium from freshwater lake sediment, and proposal of Rufibacter quisquiliarum as a latter heterotypic synonym of Rufibacter ruber

A taxonomic identification using a polyphasic approach was performed on strain NBS58-1^T, which was isolated from the interfacial sediment of Taihu Lake in China. Strain NBS58-1^T was Gram-stain-negative, aerobic, non-spore-forming and catalase-positive. Phylogenetic analyses based on 16S rRNA gene and three housekeeping genes (rpoB, gyrB and dnaK) sequences supported the position that strain NBS58-1^T should be classified within the genus Rufibacter. The 16S rRNA gene sequence of strain NBS58-1^T possessed the highest similarity to Rufibacter sediminis H-1^T (96.60 %), followed by Rufibacter glacialis MDT1-10-3^T (96.17 %). And the ANI value between strain NBS58-1^T and R. glacialis MDT1-10-3^T was 79.3 %. The respiratory quinone was menaquinone 7 (MK-7). The major cellular fatty acids comprised iso-C_15 : 0 and summed feature 3. Phosphatidylethanolamine, two unidentified phospholipids and four unidentified lipids were the main polar lipids. The genomic DNA G+C content was 51.3 mol%. Based on phenotypic features and phylogenetic position, a novel species with the name Rufibacter hautae sp. nov. is proposed. The type strain is NBS58-1^T=(KACC 21309^T=MCCC 1K04037^T). We also proposed Rufibacter quisquiliarum as a latter heterotypic synonym of Rufibacter ruber.

[Temporal and Spatial Occurrence of NSAIDs in Taihu Lake and Relevant Risk Assessment]

Non-steroidal anti-inflammatory drugs (NSAIDs) are a class of drug residues with a high frequency of detection in Taihu Lake. However, little information is available about the occurrence of typical NSAID mixtures in Taihu Lake as a whole across the four seasons. Therefore, for each season, the concentrations of five typical NSAIDs including diclofenac, ibuprofen, indomethacin, naproxen, and ketoprofen were monitored in the water of Taihu Lake by the method of high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) at 19 transects covering the entire lake. The temporal and spatial occurrence of NSAID mixtures in the water of Taihu Lake and their correlation with environmental factors were analyzed, and the mixture risk quotient (MRQ) model was also used to assess the ecological risk of the NSAID mixtures. The research results are as follows:① The concentrations of NSAIDs in the northern, western, and eastern waters of Taihu Lake are at a higher level compared to those in the central waters. Ketoprofen is the main contributor to the contamination of NSAID mixtures in all regions of Taihu Lake. ② The concentrations of NSAIDs in Taihu Lake are higher in summer (15.9-134.3 ng·L^-1) and autumn (16.4-144.6 ng·L^-1) but lower in spring (25.3-72.5 ng·L^-1) and winter (14.6-57.4 ng·L^-1), being significantly correlated with water conductivity and pH, respectively. ③ The MRQ model evaluation reveals that there are nine sections in Taihu Lake showing a high ecological risk (MRQ>1) from NSAID mixtures throughout the year. The ecological risk of the NSAID mixtures at a medium or high level (MRQ>0.1) lasts for a long time spanning the spring, summer, and autumn seasons, of which the risk is greatest in autumn. Overall, the pollution caused by the NSAID mixtures in the water of Taihu Lake should not be ignored, and especially great attention should be paid to the pollution in autumn.

Response of the nitrogen load and its driving forces in estuarine water to dam construction in Taihu Lake, China

To regulate the water level and minimize the occurrence of water eutrophication in shallow lakes, dams and gates are often constructed in rivers. However, this practice may result in a deterioration of water quality in some estuaries. In the present study, using the correction of Nemerow pollution index (CNPI) and a redundancy analysis (RDA), water samples from different dammed rivers around Taihu Lake were compared to assess the pollution risk and identify the factors responsible for water eutrophication. The average total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC) concentrations, and chemical oxygen demand (CODMn) were 2.45 ± 2.28, 0.08 ± 0.06, 43.01 ± 18.75, and 10.78 ± 4.86 mg L-1, respectively. The CNPI values indicated that approximately 76.47% of the estuarine water was moderately polluted (1 < CNPI < 7.28). A positive correlation was observed between dam construction and nutrient concentrations (e.g., rTN = 0.38, p < 0.05; rTP = 0.89, p < 0.01). Under the effects of dam construction, land use change, estuary shape, and meteorological conditions, there was a clear spatial variation of the TN concentrations. Dams that were closed all year round accelerated the TN accumulation in the water around them. The pollution risk in a trumpet-shaped estuary was higher than that in other regions (t = 2.92, p = 0.02). Endogenous release of pollutants was an important factor that may have a priming effect on algal blooms and should be given more attention. In Wuli Lake, exogenous pollution was the dominant pollutant source. A total of 74.49% of the nitrogen losses with the runoff into the estuarine water in 2018 were derived from urban domestic sewage and constructed land, with the load being 4.40 times higher than in 2000. The RDA results revealed that dam construction was the main factor (43.70%) affecting water quality, while meteorological conditions, land use types, estuary shape, and other factors contributed 56.30%. Scientific regulation and control of dam operation is important to protect the water environment of Taihu Lake.

Application of subfossil Bosmina and its δ13C values in tracing the long-term food web dynamics of shallow eutrophic lakes: A case in Taihu Lake, southeast China

Cladoceran subfossil assemblages have been used successfully to trace the signals of long-term changes in lake eutrophication. However, their potential for reconstructing food webs has not yet been explored extensively. Here, we assess whether the stable carbon isotope analysis (SCIA) of subfossil Bosmina can be used to reconstruct the eutrophication and food web history of a shallow lake in southeast China. Two ²¹⁰Pb-dated sediment cores were collected from the western and central parts of Taihu Lake, one of the largest eutrophic lakes in the region. Multiproxy analyses of the cores were performed, including of the subfossil Bosmina assemblages, stable carbon isotopes of subfossil Bosmina (δ¹³C_s-bos) and bulk sediment (δ¹³C_org), total organic carbon (TOC), loss on ignition (LOI), C/N, total nitrogen (TN), and total phosphorous (TP). Stable carbon isotopes of living algae (δ¹³C_alg) and Bosmina (δ¹³C_l-bos) were also measured at the same sampling locations. The δ¹³C_s-bos gradually declined over time with reciprocal increases in the assemblages of subfossil Bosmina and total cladocerans and in the TOC, LOI, TN and TP in both cores. The δ¹³C_alg and δ¹³C_l-bos values further revealed depleted ¹³C. The changes in the δ¹³C_s-bos in relation to the other proxies indicated rapid nutrient enrichment and a possible shift in the food web in Taihu Lake, providing new insight into the reconstruction of food webs and eutrophication in shallow lakes in southeast China.

[Environmental Significance of Phosphorus Fractions of Phytoplankton-and Macrophyte-Dominated Zones in Taihu Lake]

It is of great importance to study the environmental significance of phosphorus fractions in overlying water and sediments of typical phytoplankton-and macrophyte-dominated zones. It will help to clarify the process of phosphorus migration and transformation in the sediment-water interface, and has practical significance for understanding the eutrophication process and its treatment in different regions of Taihu Lake. The investigation was conducted within typical phytoplankton-and macrophyte-dominated zones of Taihu Lake over four seasons to analyze the spatial and temporal differences between phosphorus fractions in water and sediments, and reveal their environmental significance. The results showed that:① Total phosphorus (TP), total soluble phosphorus (DTP), dissolved inorganic phosphorus (DIP), and particulate phosphorus (PP) in the overlying water of phytoplankton-dominated zones were much higher than those in macrophyte-dominated zones. Most of them showed seasonal characteristics, which were higher in summer and autumn than in winter and spring. PP is the main component of TP, accounting for 71.8% to 89.6%. A similar distribution character was found in the content of chlorophyll (Chl-a) compared with phosphorus concentration in overlying water. ② The concentration of TP in the surface sediments of phytoplankton-dominated zones was 372.38-529.64 mg·kg^-1, and that in macrophyte-dominated zones was 304.29-454.27 mg·kg^-1. In surface sediments, concentrations of TP in phytoplankton-dominated zones were significantly higher than in phytoplankton-dominated zones. The highest TP concentrations appeared in winter, and the lowest in summer. These were owing to the input of exogenous pollution, and the migration and transformation of internal phosphorus between sediments and overlying water under different environmental conditions. ③ The order of the mass fraction of phosphorus in sediments was:NH₄Cl-P < Fe-P < Org-P < Res-P < Al-P < Ca-P. Mobile-P=NH₄Cl-P+Fe-P+Org-P, accounting for 9.10%-16.93% of TP in phytoplankton-dominated zones, and slightly higher in macrophyte-dominated zones, where it was 8.11%-13.50%. Res-P accounted for 10.06%-14.97% of TP in phytoplankton-dominated zones, and 11.02%-20.28% in macrophyte-dominated zones. The risk of internal phosphorus release in phytoplankton-dominated zones is high, which is not conducive to the fixation and burial of phosphorus. The eutrophication degree of different regions in Taihu Lake is obviously different, and different characteristics of phosphorus release and burial are showed. The phytoplankton-dominated zones deserve special attention because of their high internal phosphorus load and release potential.

[Effects of Exogenous Inputs on Phosphorus Recovery and Transport in Newborn Surface Layers from Sediment Dredging]

The effect of external pollution inputs on phosphorus recovery, transport, and transformation in newborn surface layers from sediment dredging remains unclear. Clarifying this issue is important for the control and management of external pollution loads at the watershed scale, particularly after the implementation of sediment dredging activities. In this study, sediments in Meiliang Bay of Lake Taihu were investigated. In-situ dredging simulation was used to study the transport and transformation of phosphorus at the sediment-water interface, before and after dredging, with either external or non-external particulate matter inputs, and to explore the effect of dredging on phosphorus release as part of internal loading. The results showed that limiting the inputs of external particulate matter and dredging had positive impacts on the control of TP and TN in the sediments. Dredging significantly reduced the content of potentially mobile phosphorus (Mobile-P) in surface sediments. Iron-bound phosphorus (Fe-P) was the first main component of the reduced Mobile-P and Organic phosphorus (Org-P) was the second. The content of Loose-bound phosphorus (Lb-P) was less than 1‰ of the total phosphorus. After 210 days of the experiment, the concentration of PO₄^3--P in the pore water of the dredged treatment was lower than that of the undredged treatment, and this difference was more pronounced without external particulate matter input. Furthermore, the concentration of PO₄^3--P in the pore water of the dredged treatment (without external particulate matter input) was maintained at a low level, while this first increased and then subsequently decreased for the other treatments. The concentrations of PO₄^3--P in pore water were positively correlated with Fe-P in the corresponding sediment layers. Source-sink transition took place between winter and spring, leading to the switch in sediment functioning as a sink to a source. The results indicated that dredging could reduce the release rate of internal phosphorus from sediments. Furthermore, limiting the input of external particulate matter plays an important role in facilitating the control of internal phosphorus loading by dredging.