Dynamics and ecological risk assessment of chromophoric dissolved organic matter in the Yinma River Watershed: Rivers, reservoirs, and urban waters

Preliminary analysis on the characteristics of light absorption coefficients in typical rivers of different river basins across China

As a vital constituent of water's optical properties, the absorption coefficients influence the distribution of underwater light field, consequently impacting the structures and functional patterns of riverine ecosystems. In this study, the light absorption of non-algal particulates (ad(λ), m-1), phytoplankton (aph(λ), m-1) and CDOM (ag(λ), m-1) of 380 water samples collected from 133 rivers in eight external river basins across China from 2013 to 2023 were examined to determine the optical absorption characteristics. Results showed significant differences in ad(λ), aph(λ) and ag(λ) across different basins. ① The water bodies of eight basins can be categorized into 5 dominant types of absorption coefficients. ② In eastern China, ag(440) exhibited a northeast-high and southwest-low spatial distribution pattern. The Songliao River Basin had the highest ag(440) than other basins. The higher slope S of ag(λ) in rivers compared to lakes and reservoirs confirm river water primarily derive CDOM from external sources, distinguishing them from lakes and reservoirs. ③ The Huaihe and Haihe River Basins had higher ad(440) and aph(440) values, primarily due to lower terrain and human activities, leading to the accumulation of suspended particles and nutrients. And soil erosion from the Loess Plateau caused significant differences in ad(440) between the upper and middle reaches of the Yellow River Basin. These findings hold significant implications for understanding the optical characteristics of rivers in China.

Water quality assessment for organic matter load in urban rivers considering land cover dynamics

The strategy of considering a model that is comparable to the Soil Conservation Service Curve-Number (SCS-CN) method that employs land use maps to estimate the effects of land use on the water quality has considerable potential for application. This paper presents the LUPC (Land Use Pollutant Contribution) Model to estimate water pollution from the watershed land use obtained by satellite image classification (Sentinel-2). It defines that each land use produces a specific pollutant load per unit area, called Pollutant Standard Index (PSI), which undergoes degradation and/or retention until it reaches the river. This decay estimate is based on a Kernel Function. Organic matter (OM) was the pollutant chosen for the definition of the LUPC model and fractions of labile and refractory organic matter (LOM, ROM). The model was applied to the Barigüi River basin, and five samples were collected at 12 points along the river. Water quality parameters such as dissolved organic carbon (DOC) and UV-Visible absorbance in addition to chemical and biological oxygen demand (COD and BOD), dissolved oxygen (DO), and nitrogen and phosphorus fractions were the reference for modeling purposes. The results indicate that organic loads can be estimated from watershed characteristics, despite influence from seasonal influences captured by the PSI values and the basin shape parameter. Considering its versatile response, the LUPC model can be used for integrated water resources and land use planning and management and be indicator of the potential pollution of rivers by OM.

Residues, potential source and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface water of the East Liao River, Jilin Province, China

The environmental risks posed by polycyclic aromatic hydrocarbons (PAHs) and the diversity of their anthropogenic origins make them a global issue. Therefore, it is of utmost significance for protecting the aquatic environment and the growth of neighboring populations to identify their possible origins and ecological risk. Here, we detail the contamination profiles of 15 PAHs found in the East Liao River's surface waters in Jilin Province and use the receptor model Absolute Principal Component Analysis - Multiple Linear Regression (APCS-MLR) and diagnostic ratios method to identify the primary potential sources of pollution. Based on the natural hazard risk formation theory (NHRFT), an ecological risk assessment (ERA) model for PAHs in the East Liao River was developed. The method assesses the ecological risk status of PAHs by integrating the risk quotient (RQ) approach and the DPSIRM (driving force, pressure, state, impact, response, management) conceptual framework. Total concentrations in the surface water body were between 396.42 and 624.06 ng/L, with an average of 436.99 ng/L. The source research revealed that coal, biomass, and traffic emission sources are the most likely PAH contributors to the East Liao River. The ERA found that the majority of the sites' locations of the study were at low risk for PAHs in surface water bodies (30.7 % and 32.2 %, respectively), while only a tiny percentage of sites were at high or very high risk (1.8 % and 13.6 %). The study results provide theoretical support for the East Liao River's ecological, environmental protection, and policy formulation.

Progress in urban resilience research and hotspot analysis: a global scientometric visualization analysis using CiteSpace

Increasing global climate change has led to increasingly sudden, abnormal, and complex natural disasters. Global disaster governance is facing complex and severe challenges. Urban resilience research (URR) can help cities withstand disasters and quickly recover from adversities through the rational allocation of resources. Consequently, URR has attracted considerable attention from urban ecology researchers. Over the past decade, despite an increasing number of articles reported on URR, there has been no systematic theoretical framework, no comprehensive review of the research, and no clarity on how different perspectives have evolved. This research selects 1647 articles related to global urban resilience from the Web of Science Core Collection and performs a global scientometric visualization analysis using CiteSpace and ArcGIS software. In this study, we visually display the most productive institutions, authors, and sources in URR. Additionally, we explain how research topics have changed over time and analyze research frontiers. The results show that (1) URR has accelerated globally in the last decade; (2) research hotspots are mainly concentrated in environmental science and ecology, science and technology, and water resources; and (3) URR is gradually becoming a multidisciplinary research field. Our research reveals the status and future trends of URR through quantitative visualization methods, helping to address some emerging and unexpected risks and vulnerabilities.

Variations in the light absorption coefficients of phytoplankton, non-algal particles and dissolved organic matter in reservoirs across China

Reservoirs were critical sources of drinking water for many large cities around the world, but progress in the development of large-scale monitoring protocols to obtain timely information about water quality had been hampered by the complex nature of inland waters and the various optical conditions exhibited by these aquatic ecosystems. In this study, we systematically investigated the absorption coefficient of different optically-active constituents (OACs) in 120 reservoirs of different trophic states across five eco-regions in China. The relationships were found between phytoplankton absorption coefficient at 675 nm (a_ph (675)) and Chlorophyll a (Chla) concentration in different regions (R²:0.60-0.82). The non-algal particle (NAP) absorption coefficient (a_NAP) showed an increasing trend for reservoirs with trophic states. Significant correlation (p < 0.05) was observed between chromophoric dissolved organic matter (CDOM) absorption and water chemical parameters. The influencing factors for contributing the relative proportion of OACs absorption including the hydrological factors and water quality factors were analyzed. The non-water absorption budget from our data showed the variations of the dominant absorption types which underscored the need to develop and parameterize region-specific bio-optical models for large-scale assessment in water reservoirs.

Response of aquatic macroinvertebrates communities to multiple anthropogenic stressors in a lowland tributary river

In the current study the response of aquatic macroinvertebrate communities to multiple anthropogenic stressors in a typical lowland river that crosses pristine sectors situated toward headwaters, as well as densely populated urban areas was assessed. We wished to develop an effective bioassay procedure for assessing water and sediment quality in lotic ecosystems from Romania with the aid of macroinvertebrate organisms correlated with physico-chemical parameters and pollutants in both dissolved fractions and material bonded to sediment. A fast scanning approach of the river, from springs to the mouth, was employed. We found significant changes in physico-chemical parameters along a longitudinal gradient, the highest values being registered within the urban area and heavily agriculturally developed areas. The macroinvertebrates showed affinities for certain abiotic factors, emphasising their potential use for future studies as reliable ecological indicators, shaped by a synergic combination of urban effects and magnitude of type of land use.

Extended CPT-TODIM method for interval-valued intuitionistic fuzzy MAGDM and its application to urban ecological risk assessment

The urban ecological risk assessment is a new research field, which has been rising and developing with the change of environment management objectives and environment conception. The urban ecological risk assessment could be regarded as a classical multi-attribute group decision making (MAGDM) issue. The interval-valued intuitionistic fuzzy set (IVIFS) can fully describe the uncertain information for the urban ecological risk assessment. Furthermore, the classical TODIM (an acronym in Portuguese for Interactive Multi-Criteria Decision Making) is built on cumulative prospect theory (CPT), which is a selectable method in reflecting the DMs’ psychological behavior. Thus, in this paper, the TODIM method based on the CPT is proposed for MAGDM issue under IVIFS. At the same time, it is enhancing rationality to get the weight information of attributes by using the interval-valued intuitionistic fuzzy entropy weight method. And focusing on hot issues in contemporary society, this article applies the discussed method to urban ecological risk assessment, and demonstrates urban ecological risk assessment model based on the proposed method. Finally, through comparing the outcome of comparative analysis, we conclude that this improved approach is acceptable.

Spatial distribution, risk assessment, and source identification of heavy metals in water from the Xiangxi River, Three Gorges Reservoir Region, China

Heavy metals (HMs) contamination in rivers has attracted wide concern due to its persistence and potential risks to the natural environment and human health. In this study, eight HMs (As, Hg, Cu, Pb, Ca, Zn, Mn, and Ni) were measured by inductively coupled plasma mass spectrometry in 24 water samples to investigate HMs contamination levels in the Xiangxi River of the Yangtze River basin. A geographic information systems kriging interpolation method was used to reveal the spatial distribution of HMs contamination. The results indicate that most HMs occurred at acceptable levels below the Surface Water Quality Standard (GB 3838-2002), with the highest concentration (23.23 mg kg^-1) of Mn being observed at sampling site X20. The values of the potential ecological risk index (RI) suggest that high potential ecological risks were present at sampling sites X1, X3, X4, X14, X16, X17, and X24, which reached moderate risk level. The highest value of RI (279.56) was observed at site X17. HM spatial distributions show that upstream pollution is more severe than downstream. The hazard index was below 1 for all HMs except for Mn, indicating that HMs in Xiangxi River pose a low risk to human health. HM source identification was accomplished using principal component analysis and Pearson's correlation. Cu, Cd, Ni, and Hg originate primarily from agriculture, while Pb, Zn, and As originate primarily from transportation and mining. This research provides a reference on the risks posed by HMs in Xiangxi River and will support efforts to protect and improve water quality in Xiangxi River.

Application of an Interval Two-Stage Robust (ITSR) Optimization Model for Optimization of Water Resource Distribution in the Yinma River Basin, Jilin Province, China

The present study is based on the application of an interval two-stage stochastic programming (ITSP) model in the Yinma River Basin. A robust method based on interval two-stage robust (ITSR) optimization is introduced to construct an optimization model of water resource distribution in order to solve the problems of water shortage in low-income and high-income areas caused by the unreasonable distribution of water resources. The model would help in reducing the system risk in the Yinma River Basin caused by an excessive pursuit of economic benefits. The model simulations show that the amount of water required for the water resource distribution is significantly reduced after balancing the risks and the water resource distribution of the water use departments is reduced by up to 20%. In addition, the situation of water scarcity of various water use departments shows a decreasing trend. There is no scarcity of water use in Panshi, Yongji, Shuangyang and Jiutai areas. The water shortage of water use departments in other areas is reduced by up to 97%. The allocation of reused water to ecological and environmental departments with higher water demand further solved the water shortage problem in low-income departments in the interval-two-stage planning model. In this study, after the introduction of the robust optimization method in the Yinma River Basin, the stability of the water resources distribution system is significantly improved. In addition, the risk of water use system in the interval-two-stage stochastic model can be avoided.

Integrated valuation of alternative land use scenarios in the agricultural ecosystem of a watershed with limited available data, in the Pampas region of Argentina

Historically, Argentina has been among the world leaders in the production and export of agricultural products. The country is increasingly confronted with severe conflicts that originate from trade-offs between actors involved in the agricultural sector. This work presents an integrated valuation of alternative land use scenarios in the Carcarañá River Lower Basin, offering a way to link the various value domains by involving a broad set of multidimensional indicators and stakeholder concerns. Twenty-one indicators that address all three pillars of sustainability, environmental, economic and social, are selected and quantified. Three scenarios are analyzed: the Actual scenario, dominated by industrial-scale agriculture that primarily yields soybeans, maize and wheat; a Conservation Agriculture scenario, promoting permanent soil cover by crop rotation and the implementation of untreated buffer zones around the cities; and a Short Sighted Exploitation scenario, contributing to short-term profits for agribusiness but increasing pressure on the natural resources. A decision support system is implemented in the Driver, Pressure, State, and Ecosystem Services indicator framework. The Conservation Agriculture scenario is identified as the best option by stakeholders grouped into Regulatory State, Civil Society and Consensus perspectives. A ranking change occurs when the valuation is carried out from the Private Sector point of view and the Actual scenario comes in first position. We dare to say that the methodology presented in this work is a socio-technical innovation that can contribute to the process needed to achieve broad consensus among the agribusiness actors in Argentina.

Seasonal variation and ecological risk assessment of dissolved organic matter in a peri-urban critical zone observatory watershed

Peri-urban ecosystems are among the most intensive areas in terms of competition between different ecosystem components. Dissolved organic matter (DOM) plays a significant role in aquatic carbon cycling. The chemical composition of DOM and associated potential ecological risks in peri-urban aquatic ecosystems are poorly understood. Herein, we used fluorescence excitation-emission matrix and parallel factor analysis (EEM-PARAFAC) to characterize DOM in a peri-urban critical zone observatory watershed in Eastern China. According to the theory of natural disaster risk formation, we calculated the ecological risk of DOM in the peri-urban watershed. Seasonal variation in DOM concentrations was observed, whereas fluorescent DOM concentrations were site-specific across four sub-watersheds. The analysis of DOM absorption properties revealed the presence of DOM components with high aromatic content and large molecular weight in the watershed. Four fluorescent components (two humic-like and two protein-like substances) were identified using the PARAFAC model. Spatial distribution analysis showed that DOM quality was mainly influenced by human activities, and the proportion of protein-like substance (C3) was strongly correlated with anthropogenic parameters. The distribution of optical indices indicated diverse sources of DOM in the watershed. Ecological risk related to DOM was greater in the dry season than the wet season. There was a slight risk in most areas, with an extreme risk in areas experiencing the most intensive human disturbance, which were also extremely or heavily vulnerable. The results emphasize the strong influence of human disturbance on the ecological risk of DOM in peri-urban aquatic ecosystems. Our study provides useful information for ecological risk assessment of DOM that is difficult to obtain using traditional chemical analysis.

Absorption characteristics of CDOM in treated and non-treated urban lakes in Changchun, China

In urban settings, one may find (i) lakes that are non-treated (NT) and impacted by recurrent discharges of pollutants and nutrients, and (ii) lakes that, through restoration measures and active management, are treated (T) from external inputs. The optical properties of chromophoric dissolved organic matter (CDOM) have been used to assess the anthropogenic impact on lakes ecology, but their application in comparative assessments of urban lakes has not been attempted. For 2 years, we measured nutrients and CDOM properties in water samples collected from NT and T lakes in the city of Changchun, China. Significant differences in CDOM properties were found between the two types of lakes, and these results were supported by redundancy analysis. The NT lakes were eutrophic while the T lakes were mesotrophic, with mean trophic status index (TSI) of 74.2 and 50.3, respectively. The CDOM absorption coefficient at 350 nm, a(350), was 2-fold higher in NT than in T lakes (6.59 vs 3.21 m^-1). In the NT lakes, CDOM components predominantly comprised large molecular weight (MW > 1000-Da) humus-like substances of allochthonous origin, whereas in the T lakes CDOM was dominated by low MW (<1000-Da) substances from autochthonous production. Seasonal fluctuation has a great influence on the CDOM concentration, but a little influence on its molecular composition. The CDOM concentration were higher in summer than in other seasons. Weather conditions (rainfall, temperature) and biophysical processes (biodegradation, photo-bleaching) likely contributed to these variations. We found the water quality of the treated lakes was getting better from 2016 to 2018. In summary, the study results, not only revealed seasonal effects, but most importantly documented the impact of human activities on the characteristics of CDOM in urban lakes. Most specifically, the sharp difference between the lakes in regard to a(350) (2-fold lower in T than in NT lakes) demonstrated the suitability CDOM absorption coefficient as an early indicator of the impact of treatment measures on the hydrochemistry of DOM in urban lakes.

Intensive Livestock Production Causing Antibiotic Pollution in the Yinma River of Northeast China

Antibiotics are increasingly used in livestock production in rural China, raising concerns over pollution and health risk in countryside waterways. The Yinma River Basin in China’s far northeast is an agriculture-dominated area mixed with a densely populated province capitol city, providing a suitable area for investigating the influence of a typical land use mix in Northeast China on riverine antibiotic levels and transport. In this study, we sampled water along the Yinma River from upstream to downstream in a wet and a dry season and analyzed the samples for two popularly used antibiotics, ciprofloxacin (CIP) and norfloxacin (NOR). The goal of the study was to determine the spatiotemporal distribution of the antibiotics in Yinma’s two tributaries, Yitong and Yinma, which drain intensive livestock production land, and to elucidate which environmental and social factors influence the distribution of antibiotics in the cold and low mountainous areas. Water sample collection and instream measurements on dissolved oxygen and other ambient conditions were conducted at 17 locations along the Yinma and Yitong tributaries in August 2015 (wet season) and November 2015 (dry season). In addition to determining CIP and NOR levels, water samples were also analyzed for dissolved organic carbon (DOC), ammonia (NH3), and free chlorine. We found a significantly higher level of NOR when compared to CIP, indicating greater use of the first in livestock production. The level of both antibiotics was higher in the wet season (NOR: 61.063 ± 13.856 ng L−1; CIP: 3.453 ± 0.979 ng L−1) than in the dry season (57.435 ± 14.841 ng L−1; 3.091 ± 0.824 ng L−1), suggesting higher runoff of the antibiotics from the drainage area during the raining season. The level of antibiotics was higher in rural areas, especially forested and wetland areas where livestock typically graze, as well as in the lower river basin. However, the health risk of antibiotics is determined by the physical condition and lifestyle of the residents in the river basin, hence showing a higher vulnerability of the urban area than the rural area.

Occurrence and distribution of selected antibiotics in the surface waters and ecological risk assessment based on the theory of natural disaster

With increasing population growth and resource depletion, ecological health is a hotspot and urgent topic. Our study investigated the occurrence and distribution of five antibiotics, i.e., metronidazole (MET), sulfamethoxazole (SMZ), ciprofloxacin (CFX), norfloxacin (NFX), and enrofloxacin (EFX), in the surface water from Erlong Lake, China. With the seasonal and spatial variations of antibiotics, this study developed an interdisciplinary approach for the ecological risk of antibiotics considering the natural, human, and socioeconomic elements of watershed based on the risk theory of natural disaster. This approach integrates the geographic information system (GIS) spatial analysis tool, natural disaster theory, "driving force"-"pressure"-"state"-"impact"-"response" (DPSIR) model, and ordered weighted averaging (OWA) operators in terms of various environmental factors, representing a new ecological risk paradigm for environmental managers or decision-makers to identify environmental change. A total of 69 samples were collected in wet, dry, and normal seasons from 2017 to 2018, and laboratory analyses revealed that four antibiotics (MET, SMZ, CFX, and NFX) were widely detected in the lake. The mean concentrations decreased in the order of MET (1041.7 ng L^-1) > SMZ (771.4 ng L^-1) > CFX (646.4 ng L^-1) > NFX (179.0 ng L^-1) > EFX (15.3 ng L^-1), with their levels in natural surface waters higher than those in other studies. Antibiotic concentrations were higher in dry seasons than in other seasons, and the concentrations were strongly correlated with EC (electrical conductivity), pH, DOC (dissolved organic carbon), and TP (total phosphorus) according to redundancy analysis (RDA). Significant seasonal variations were found in CFX and EFX (ANOVA, p < 0.001). For the whole watershed, the ecological extremely and heavily vulnerable levels were concentrated in the central and northwest regions of the watershed, i.e., Changling county and Lishu county. Hence, the ecological distributions of extreme risk and heavy risk posed by the five selected antibiotics were assessed by using the mixture hazard quotient methods and DPSIR model which were also located in these counties in different seasons. The antibiotic results of ecosystem risk assessment can support decision-makers in identifying and prioritizing the necessary taking of specific measures and different risk attitudes to preserve the quality of ecological health for a city or multiple counties.

Aquatic organic matter: Classification and interaction with organic microcontaminants

Organic matter (OM) in aquatic system is originated from autochthonous and allochthonous natural sources as well as anthropogenic inputs, and can be found in dissolved, particulate or colloidal form. According to the type/composition, OM can be divided in non-humic substances (NHS) or humic substances (HS). The present review focuses on the main groups that constitute the NHS (carbohydrates, proteins, lipids, and lignin) and their role as chemical biomarkers, as well as the main characteristics of HS are presented. HS functions, properties and mechanisms are discussed, in addition to their association to the fate, bioavailability, and toxicity of organic microcontaminants in the aquatic systems. Despite the growing diversity and potential impacts of organic microcontaminants to the aquatic environment, limited information is available about their association with OM. A protective effect is, however, normally seen since the presence of OM (HS mainly) may reduce bioavailability and, consequently, the concentration of organic microcontaminants within the organism. It may also affect the toxicity by either absorbing ultraviolet radiation incidence and, then, reducing the formation of phototoxic compounds, or by increasing the oxygen reactive species and, thus, affecting the decomposition of natural and anthropogenic organic compounds. In addition, the outcome data is hard to compare since each study follows unique experimental protocols. The often use of commercial humic acid (Aldrich) as a generic source of OM in studies can also hinder comparisons since differences in composition makes this type of OM not representative of any aquatic environment. Thus, the current challenge is find out how this clear fragmentation can be overcome.

Terrestrial humic-like fluorescence peak of chromophoric dissolved organic matter as a new potential indicator tracing the antibiotics in typical polluted watershed

Natural surface waters are threatened globally by antibiotics pollution. In this study, we analyzed antibiotics and CDOM (Chromophoric dissolved organic matter) fluorescence in different water bodies using HPLC method and Excitation Emission Matrix- Parallel factor analysis, respectively. A combination of field studies in the Yinma River Watershed were conducted in rivers, reservoirs and urban rivers, and 65 CDOM and antibiotic samples were taken in April, May, July, and August 2016. EEM-PARAFAC analysis identified two components; a humic-like (C1) component and a tryptophan-like (C2) component. The redundancy analysis (RDA) demonstrated that CDOM could explain 38.2% (two axes) of the five antibiotics in reservoirs (N = 31), and 26.0% (two axes) of those in rivers and urban water (N = 30). Furthermore, the Pearson correlation coefficient between Sulfamethoxazole and C1 in reservoir water was 0.91 (t-test, 2-tailed, p < 0.01), and that between Sulfamethoxazole and C2 was 0.68 (t-test, 2-tailed, p < 0.01). This indicated that the humic-like component of CDOM PARAFAC fluorescence could detect Sulfamethoxazole contamination levels in the homogenized reservoir waters. Our results identified Sulfamethoxazole and Quinolones (Norfloxacin, 16.5 ng L^-1; Enrofloxacin, 0.3 ng L^-1; Ciprofloxacin, 30.9 ng L^-1) at mean concentrations of 369.5 ng L^-1 and 15.9 ng L^-1, respectively, which were the higher levels in natural surface waters. The FTIR spectroscopy of the mixture of humic acid and sulfamethoxazole showed that the absorbance at 3415 cm^-1 linked to OH stretching of OH groups and at 1386 cm^-1 because of OH bending and vibration of COOH groups became weaker, indicating that COOH groups of humic acid can adsorb and react with -NH₂ of sulfamethoxazole. The CDOM PARAFAC components can be adapted for online or in situ fluorescence measurements as an early warning of Sulfamethoxazole distribution and contamination in similar aquatic environments.

Characterizing fluvial heavy metal pollutions under different rainfall conditions: Implication for aquatic environment protection

Globally, fluvial heavy metal (HM) pollution has recently become an increasingly severe problem. However, few studies have investigated the variational characteristics of fluvial HMs after rain over long periods (≥1 year). The Dakan River in Xili Reservoir watershed (China) was selected as a case study to investigate pollution levels, influencing factors, and sources of HMs under different rainfall conditions during 2015 and 2016. Fluvial HMs showed evident spatiotemporal variations attributable to the coupled effects of pollution generation and rainfall diffusion. Fluvial HM concentrations were significantly associated with rainfall characteristics (e.g., rainfall intensity, rainfall amount, and antecedent dry period) and river flow, which influenced the generation and the transmission of fluvial HMs in various ways. Moreover, this interrelationship depended considerably on the HM type and particle size distribution. Mn, Pb, Cr, and Ni were major contributors to high values of the comprehensive pollution index; therefore, they should be afforded special attention. Additionally, quantitative source apportionment of fluvial HMs was conducted by combining principal component analysis with multiple linear regression and chemical mass balance models to obtain comprehensive source profiles. Finally, an environment-friendly control strategy coupling "source elimination" and "transport barriers" was proposed for aquatic environment protection.

The Human Health Assessment to Phthalate Acid Esters (PAEs) and Potential Probability Prediction by Chromophoric Dissolved Organic Matter EEM-FRI Fluorescence in Erlong Lake

Phthalate acid esters (PAEs) are suspected to cause wide environmental pollution and have adverse effects on human health. Three priority control phthalates, namely dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP), were determined in 45 water samples from the largest drinking water source in Jilin Province. Chromophoric-dissolved organic matter (CDOM), which are composed of complex compounds and are a proxy for water quality, can be monitored using a fluorometer. This study attempted to understand the correlations of the CDOM fluorescence regional integration (FRI) components with PAEs and CDOM characteristics under seasonal and spatial variations in the Erlong Lake. The characteristics of the CDOM absorption parameters in different water samples showed a higher aromatic content and molecular weight in October because of increased terrestrial inputs. The Σ3PAEs concentrations ranged from 0.231 mg L⁻¹ to 0.435 mg L⁻¹ in water, and DEP contributed to more than 90% of the Σ3PAEs. The FRI method identified five fluorescence components: one tyrosine-like (R1), one tryptophan-like (R2), one fulvic-like (R3), one microbial protein-like (R4), and one humic-like (R5) component. However, significant relationships exist between DEP and R3 (R² = 0.78, p < 0.001), R4 (R² = 0.77, p < 0.001), and R5 (R² = 0.58, p < 0.001). Quantifying the relationship between CDOM and PAEs was highly significant, because the results will simplify the componential analysis of pollutants from a spatiotemporal perspective as compared to traditional chemical measurements. The human health risk assessment results revealed no human health risk (HQ < 1) in the Erlong Lake basin.

The relationship of chromophoric dissolved organic matter parallel factor analysis fluorescence and polycyclic aromatic hydrocarbons in natural surface waters

Polycyclic aromatic hydrocarbons (PAHs), a large group of persistent organic pollutants (POPs), have caused wide environmental pollution and ecological effects. Chromophoric dissolved organic matter (CDOM), which consists of complex compounds, was seen as a proxy of water quality. An attempt was made to understand the relationships of CDOM absorption parameters and parallel factor analysis (PARAFAC) components with PAHs under seasonal variation in the riverine, reservoir, and urban waters of the Yinma River watershed in 2016. These different types of water bodies provided wide CDOM and PAHs concentration ranges with CDOM absorption coefficients at a wavelength of 350 nm (a _CDOM(350)) of 1.17-20.74 m^-1 and total PAHs of 0-1829 ng/L. CDOM excitation-emission matrix (EEM) presented two fluorescent components, e.g., terrestrial humic-like (C1) and tryptophan-like (C2) were identified using PARAFAC. Tryptophan-like associated protein-like fluorescence often dominates the EEM signatures of sewage samples. Our finding is that seasonal CDOM EEM-PARAFAC and PAHs concentration showed consistent tendency indicated that PAHs were un-ignorable pollutants. However, the disparities in seasonal CDOM-PAH relationships relate to the similar sources of CDOM and PAHs, and the proportion of PAHs in CDOM. Overlooked and poorly appreciated, quantifying the relationship between CDOM and PAHs has important implications, because these results simplify ecological and health-based risk assessment of pollutants compared to the traditional chemical measurements.