National investigation of semi-volatile organic compounds (PAHs, OCPs, and PCBs) in lake sediments of China: Occurrence, spatial variation and risk assessment

The effects of population and regional economy on the levels and distribution of hexabromocyclododecanes in soils from Jiangsu, Southeast China

China used to be the major producer and consumer of hexabromocyclododecanes (HBCDs). Although HBCDs are restricted under the Stockholm Convention, emissions from the flame-retarded materials will continue for several decades and be potentially long-term sources of HBCDs leaching to the environment, and their adverse effects on human health and the environment will continue to raise concerns globally. The levels and distribution of HBCDs in soils of different land use types in the prosperous and densely populated Yangtze River Delta region, China were investigated. The total HBCD concentrations (ΣHBCDs) ranged between 0.17 and 6.28 ng g-1 dw (dry weight) with a mean value of 1.20 ng g-1 dw, which was at a low level worldwide. The three HBCD stereoisomers, α-HBCD, β-HBCD and γ-HBCD contributed 37%, 11% and 52% on average, respectively. The spatial distribution of HBCDs showed that northern and southern Jiangsu regions had higher HBCD levels than those in central region. HBCD contamination differed considerably among three type of lands, industrial land > urban and commercial land > agricultural and suburban land, suggesting that anthropogenic activities such as industrial production, urbanization and commercial activities etc. are the major sources of HBCDs, especially the influence of industries. No relationships were found between HBCD concentrations and per capita GDP (gross domestic product) in northern Jiangsu, while they were significantly positively correlated in southern Jiangsu. Mass inventory of HBCDs in the surface soils of Jiangsu was 38.6 tons. The estimated daily intakes (EDIs) of HBCDs for human via soil ingestion were 0.75, 1.68-3.77, 7.83-12.9 pg kg-1 bw d-1 for ages > 21, 6 to 21 years and under 6 years, respectively. The mean EDIs for children under 6 years old was approximately 13 times greater than that of adult.

Environmental DNA-based assessment of multitrophic biodiversity in a typical river located in the Loess Plateau, China: Influence of PAHs and suspended sediments

Polycyclic aromatic hydrocarbon (PAH) pollution and high suspended sediment (SS) contents are significant anthropogenic and natural stressors that threaten aquatic biodiversity. However, the characteristics of multitrophic biological communities and their co-occurrence patterns in response to PAHs in sediment-laden rivers remain unclear. This study investigated the spatial distribution of species across three trophic levels, including algae, metazoan, and fish, in the Beiluo River on the Loess Plateau, China, using environmental DNA metabarcoding. Biodiversity was assessed in relation to 16 PAHs, SS, and environmental variables. The PAH in the dissolved phase ranged from 19.70 to 1613.30 ng/L dominated by low molecular weight (LMW) PAHs. Partial least squares path modeling (PLS-PM) revealed a negative correlation between PAH distribution and SS in the river. In terms of biodiversity, the richness and Shannon index of algae (Chlorophyta and Dinophyceae) were positively associated with acenaphthene (ACE) levels. Conversely, the Shannon index and richness of metazoans (Rotifera and Arthropoda) appeared to decline in response to Benzo[a]anthracene (BaA) and pyrene (PYR). Fishes (Cypriniformes and Clupeiformes) demonstrated greater tolerance to PAH contamination than algae and metazoans, and their reduced richness and Shannon index were linked to the high SS loads (> 0.45 μm). The co-occurrence patterns highlighted a stronger association connection between algae and metazoan communities than fish. This study provides valuable insights into how PAHs could reshape the structure of riverine multitrophic communities under conditions of elevated SS loads.

Polychlorinated biphenyls in aquatic products from Shandong, China

PCBs were analysed in 110 samples, including marine fish, freshwater fish and marine bivalves. The levels of ∑7PCBs in marine fish ranged from 0.18 to 5.59 ng g-1 wet weight (ww), in freshwater fish from 0.10 to 1.19 ng g-1 ww and in marine bivalves from 0.07 to 5.59 ng g-1 ww. The highest level of PCBs was found in Scomberomorus niphonius. In marine fish, freshwater fish and marine bivalves, the most abundant compounds were Hexa-CBs, Tri-CBs and Hexa-CBs, respectively. PCBs were distributed in a species-specific manner in aquatic products. None of the aquatic product samples analysed exceeded the limit for ∑7PCBs set by China or the limit established by the European Union.

Assessment of recent lake sediment conditions in the conterminous U.S

This study provides the largest sediment quality assessment of lakes in the conterminous United States (U.S.). A variety of lakes (n = 1005) were selected based on the randomized, probabilistic sampling design of the broader 2017 National Lakes Assessment study. Surficial sediment samples (0-5 cm) were collected at one representative site (generally the deepest point) for each lake (n = 969). The samples were analyzed for 16 metal(loid)s, 25 polycyclic aromatic hydrocarbons (PAHs), 53 polychlorinated biphenyl (PCB) congeners, 27 legacy pesticides and metabolites, total organic carbon, and grain size. Metal(loid)s and PAHs were widely distributed due to natural and potential anthropogenic sources, with regional variations observed for lakes in the nine ecoregions encompassing the U.S. Most sites did not have detectable PCB congeners or legacy pesticides. An integrative chemical index of mean probable effect concentration quotients, composed of seven metal(loid)s and ƩPAH13, was used to assess sediment quality for the estimated population of 224,916 lakes in the conterminous U.S. Nationally, 26.5% (CI of 20-33%) of lakes were in good condition (corresponding to predicted low incidences of toxicity to benthic organisms), 69.3% (CI of 63-76%) of lakes were in fair condition, and 1.8% (CI of 0.6-3%) of lakes were in poor condition (corresponding to predicted high incidences of sediment toxicity). Unweighted metal(loid) and ƩPAH13 concentrations were compared to lake, watershed, and land use data. Deeper lakes were significantly more contaminated (or naturally enriched) with As, Cd, Cu, Pb, Hg, Zn, and ƩPAH13 than shallow lakes. Lakes at lower elevation were also associated with more contamination (or natural enrichment) of As, Cr, Pb, Hg, Ni, Zn, and ƩPAH13 than higher elevation lakes. Greater contamination was associated with watersheds containing larger percentages of developed land. This study demonstrates an approach which can be used by others to assess sediment quality in their jurisdictions.

Spatial patterns, source apportionment, and risk assessment of polychlorinated biphenyls (PCBs) in the surface sediments of eastern China lakes along a latitudinal gradient: Insights guided by full-congener analysis

Understanding the occurrence, sources, and ecological risks of polychlorinated biphenyls (PCBs), which are universal persistent organic pollutants, is critical for improving the sustainability and ecological safety of lake systems. Herein, to determine PCB contamination levels and formulate control strategies in lake sediments, 210 sediment samples were collected from 21 lakes along a latitudinal gradient (18-45°N, ∼3000 km) across eastern China and were analyzed for all 209 PCB congeners. The results showed that the total PCB concentration varied greatly from 0.26 to 163.82 ng/g dry weight and exhibited a latitudinal trend of central > north/south. Spatial variations were affected mainly by the organic carbon fraction and local population density. Most lakes had similar PCB profiles, with lower chlorinated PCBs dominating. Notably, non-Aroclor PCB 11 was the most abundant congener. Moreover, unintentionally produced PCBs (UP-PCBs) accounted for ∼31 % of all PCBs. These findings highlight that the significance of UP-PCBs has been overlooked in past studies and that full-congener analysis is necessary for future monitoring. According to the ecological risk assessment of PCBs, zero to moderate risk existed in lake sediments. Therefore, effective strategies are needed to mitigate the impact of PCBs (especially UP-PCBs) from multiple sources on lakes.

Organochlorine pesticides and polychlorinated biphenyls in sediments of the Lanzhou reach of Yellow River (China): Spatial distribution, sources and risk assessment

Knowledge about sediment levels and sources of persistent organic pollutants (POPs) in Lanzhou section Yellow River remains limited. Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in 12 sediment samples from this region were measured by GC/MS. OCPs concentrations ranged from 85.6 to 202 ng/g, while PCBs levels varied between 3.08 and 32.3 ng/g. Our findings demonstrated a significant correlation between these pollutants and total organic matter (TOC), highlighting TOC's role in pollutants distribution. Notably, OCPs and PCBs levels were higher in the eastern section, following the water flow direction. The primary OCPs components were hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), whereas PCBs were dominated by perchlorinated compound. Source identification indicated that OCPs primarily originated from historical residues and recent applications, while industrial activities as significant PCBs sources. Sediment quality guidelines and health risk assessments indicated negligible environmental risk. This study providing valuable insights on sediment pollution control and management strategies.

Decoupling Sources of Anthropogenic Influences on Sediments of the Visovac Lake (Krka National Park, Croatia) Using Multiparametric Approach

Historical changes of sediment characteristics and levels of inorganic and organic contaminants were studied in dated sediment cores from the Visovac Lake, situated in the Krka National Park, Croatia, to identify the main sources of anthropogenic pressures on this highly protected system. Depth distributions of lithogenic elements showed a steady decrease of terrigenous inputs due to the reduction in agricultural activities in the area, which was particularly pronounced during the 1991-1995 war in Croatia. Vertical and longitudinal distributions of Cd and Zn indicated that they are predominately of anthropogenic origin. The historical profiles of these toxic metals coincide well with the recorded production of metal industry in the upper reach of the Krka River with a sharp decrease reflecting the interruption by the war and slow recovery afterwards. By contrast, the recovery of the tourist industry in Krka NP after the war was accompanied by increasing contamination by elements characteristic of boat and car traffic (Sn, Cu, Pb) as well as oil pollution. The contamination with polycyclic aromatic hydrocarbons and polychlorinated biphenyls was only moderate. Although levels of metallic and organic contamination can be considered relatively low, the observed shift from industrial to tourism-related sources indicated that touristic activities should also be regarded as a possible threat for this vulnerable karst aquatic ecosystem.

Combining chemical analysis and toxicological methods to access the ecological risk of complex contamination in Daye Lake

As one of the nine primary non-ferrous metal smelting bases in China, Daye Lake basin was polluted due to diverse human activities. But so far the pollution status and related ecological risks of this region have not been detailly investigated. In current study, pollutants including heavy metals, polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in eight sediment samples from Daye Lake were quantified. 18S rRNA gene sequencing was employed to profile the nematode community structure within these sediments. Model organism Caenorhabditis elegans (C. elegans) were further applied for a comprehensive ecological risk assessment of Daye Lake. Notably, Cadmium (Cd) was identified as a key driver of ecological risk, reaching an index of 1287.35. At sample point S4, OCPs particularly p,p'-DDT, displayed an extreme ecological risk with a value of 23.19. Cephalobidae and Mononchida showed strong sensitivity to pollutant levels, reinforcing their suitability as robust bioindicators. The composite pollutants in sampled sediments caused oxidative stress in C. elegans, with gene Vit-2 and Mtl-1 as sensitive biomarkers. By employing the multiple analysis methods, our data can offer valuable contributions to environmental monitoring and health risk assessment for composite polluted areas.

Fluorescence and Photophysical Properties of Anthracene and Phenanthrene in Water

Polyaromatic hydrocarbons (PAHs) are widely spread pollutants in the environment, including soil and water. Anthracene (anth) and phenanthrene (phen) pose severe health impacts on human lives due to their carcinogenic nature by increasing cancer risk to the skin, lungs, and bladder. Fluorescence spectroscopy is a promising , efficient and straightforward tool for characterizing these trace PAHs in water. Therefore, the current work provides a detailed insight into the fluorescence properties of anth and phen in water. The fluorescence EEMs (excitation-emission matrices) of anth showed emissions at 380 nm, 400 nm, and 425 nm with single excitation at 250 nm, whereas phen showed two emissions < 380 nm, at 350 nm and 365 with single excitation at 250 nm. Then the theoretical EX/EM wavelengths were calculated by DFT and CIS-B3LYP for these compounds in water. The environmental effect of pH variation on fluorescence EEM shows a significant difference in fluorescence intensity without changing in peak locations, with highest fluorescence intensity at neutral pH than acidic and alkaline. Furthermore, the theoretical pH effect was described for the first time by simulating the protonated (+ 1), deprotonated (-1) and neutral molecules in water at the DFT level of theory. The variation in simulated oscillator strengths was similar in trend with the experimental fluorescence intensity of these compounds. The HOMO-LUMO were calculated to obtain the energy gap, molecular softness, molecular hardness, electronic potential and electrophilicity of anth and phen. To find the fluorophore contribution, the fluorescence of homogeneous mixture of both isomers was analyzed, which showed an enhanced fluorescence intensity of anth by 12-20%, whereas a decrease of 9-14% was observed in phen. This study describes that the fluorescence technique could be a fast and easy method to distinguish and identify PAHs isomers (anth and phen) in water.

Differentiated cognition of the effects of human activities on typical persistent organic pollutants and bacterioplankton community in drinking water source

Accelerated urbanization in developing countries led to a typical gradient of human activities (low, moderate and high human activities), which affected the pollution characteristics and ecological functions of aquatic environment. However, the occurrence characteristics of typical persistent organic pollutants, including organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), and bacterioplankton associated with the gradient of human activities in drinking water sources is still lacking. Our study focused on a representative case - the upper reaches of the Dongjiang River (Pearl River Basin, China), a drinking water source characterized by a gradient of human activities. A comprehensive analysis of PAHs, OCPs and bacterioplankton in the water phase was performed using gas chromatography-mass spectrometry (GC-MS) and the Illumina platform. Moderate human activity could increase the pollution of OCPs and PAHs due to local agricultural activities. The gradient of human activities obviously influenced the bacterioplankton community composition and interaction dynamics, and low human activity resulted in low bacterioplankton diversity. Co-occurrence network analysis indicated that moderate human activity could promote a more modular organization of the bacterioplankton community. Structural equation models showed that nutrients could exert a negative influence on the composition of bacterioplankton, and this phenomenon did not change with the gradient of human activities. OCPs played a negative role in shaping bacterioplankton composition under the low and high human activities, but had a positive effect under the moderate human activity. In contrast, PAHs showed a strong positive effect on bacterioplankton composition under low and high human activities and a weak negative effect under moderate human activity. Overall, these results shed light on the occurrence characteristics of OCPs, PAHs and their ecological effects on bacterioplankton in drinking water sources along the gradient of human activities.

Ecotoxicological risk assessments and components of persistent organic pollutants and metals in the historical settlement area (Iznik (Nicea) lake) large water resource sediments

The main objectives of this study are to measure permanent organic and inorganic pollutants in detail in an area that hosts historical structures underneath and feeds the huge ecosystem with water, to reveal risk values. Total PAH concentrations in the samples ranged from 43.41 to 202.7 ng/g. Total OCP concentration ranged from 5.15 to 17.98 ng/g, while total PCB concentration ranged from 0.179 to 0.921 ng/g. PCB 28/31, 138, and 153 are the highest detected PCBs. It was found that the lake sediment reached toxic equivalent quotient (TEQ) values of 29.21 for total PAHs and 28.90 for carcinogenic PAHs. Negligible concentration risk quotient had a low to moderate ecological and toxicological risk between 12.91 and 64.42. Highest pollution index value was found 3.81 and the risk index value reached 417.4. It has been revealed that toxicologically risky components accumulate over many years even in the best-protected water resources.

Recent advances in clay minerals for groundwater pollution control and remediation

Clay minerals are abundant on Earth and have been crucial to the advancement of human civilization. The ability of clay minerals to absorb chemicals is frequently utilized to remove hazardous compounds from aquatic environments. Moreover, clay-based adsorbent products are both environmentally acceptable and affordable. This study provides an overview of advances in clay minerals in the field of groundwater remediation and related predictions. The existing literature was examined using data and information aggregation approaches. Keyword clustering analysis of the relevant literature revealed that clay minerals are associated with groundwater utilization and soil pollution remediation. Principal component analysis was used to assess the relationships among clay mineral modification methods, pollutant properties, and the Langmuir adsorption capacity (Qmax). The results demonstrated that pollutant properties affect the Qmax of pollutants adsorbed by clay minerals. Systematic cluster analysis was utilized to classify the collected data and investigate the relationships. The pollution adsorption mechanism of the unique structure of clay minerals was investigated based on the characterization results. Modified clay minerals exhibited changes in surface functional groups, internal structure, and pHpzc. This review provides a summary of recent clay-based materials and their applications in groundwater remediation, as well as discussions of their challenges and future prospects.

Ecological risk of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the sediment of a protected karst plateau lake (Caohai) wetland in China

Understanding PAH and OCP distributions and sources in lakes is necessary for developing pollutant control policies. Here, we assessed the occurrence, risk, and sources of PAHs and OCPs in the sediment of Caohai Lake. The PAHs were predominantly high-molecular-weight compounds (mean 57.5 %), and the diagnostic ratios revealed that coal, biomass burning, and traffic were the sources of PAHs. HCHs (6.53 ± 7.22 ng g-1) and DDTs (10.86 ± 12.16 ng g-1) were the dominant OCPs and were primarily sourced from fresh exogenous inputs. RDA showed that sediment properties explained 74.12 % and 65.44 % of the variation in PAH and OCP concentrations, respectively. Incremental lifetime cancer risk (ILCR) assessment indicated that hazardous PAHs in Caohai Lake sediment posed moderate risks to children and adults (ILCR>1.0 × 10-4), while the risk from OCPs was low; however, the recent influx of HCHs and DDTs requires additional attention.

Distribution and ecological risk assessment of priority water pollutants in surface river sediments with emphasis on industrially affected areas

Priority water pollutants comprising six plasticizers, 18 volatile organic compounds (VOCs), total petroleum hydrocarbon (TPH), 1,4-dioxane, epichlorohydrin, formaldehyde, acrylamide, and cyanides were determined in surface river sediments to assess their distribution patterns and ecological risks. Among these, di (2-ethylhexyl) phthalate (DEHP), toluene, TPH, and acrylamide were frequently found in sediments. The industrial sites had higher concentrations of ∑plasticizers (median 628 ng/g dry weight (dw)), ∑VOCs (median 3.35 ng/g dw), acrylamide (median 0.966 ng/g dw), and TPH (median 152 μg/g dw) in sediments than the mixed and non-industrial areas. The other pollutants did not show the significant differences in levels according to site types because of their relatively low detection frequencies. Volatile and soluble substances as well as hydrophobic pollutants were predominantly detected in surface sediments from industrial areas. Sediment contamination patterns were affected by the size and composition of the industrial zones around the sampling sites. The ecological risks determined using the sediment quality guidelines (DEHP, VOCs, and TPH) and the mean probable effect level quotients (DEHP) were mostly acceptable. However, the two most representative industrial regions (the largest industrial area and the first industrial city) showed risks of concern for DEHP and TPH.

Enrichment, bioaccumulation and human health assessment of organochlorine pesticides in sediments and edible fish of a plateau lake

The organochlorine pesticides (OCPs) are with features of persistence, high toxicity, bioaccumulation and adverse impact on ecosystems and human beings. Although OCPs pollutions have been observed in the plateau lakes, comprehensive understandings in the distribution characteristics and human health risks of OCPs in these valuable but fragile ecosystems are limited. We here investigated the distribution, bioaccumulation process and health risks of OCPs in the Jianhu lake, a representative plateau lake in China. The endrin ketone, endrin aldehyde and heptachlor were the most dominant species in surface and columnar sediments. Their total contents ranged between 0 ~ 1.92 × 103 ng·g-1. The distribution of OCPs in sediment cores combined with chronology information indicated that the fast accumulation of OCPs happened during the last decades. Combining the distribution features of OCPs in different sources with mixing model results of carbon isotope (δ13C), farming area was identified as the main source (46%), and the OCPs were transported to lake by inflow-rivers (37%). The enrichment of OCPs in sediments caused considerable bioaccumulation of OCPs in local fish (∑OCPs 0-3199.93 ng·g-1, dw) with the bio-sediment accumulation factor (BSAF) ranging from ND to 9.41. Moreover, growing time was another key factor governing the accumulation in specific species (Carassius auratus and Cyprinus carpio). Eventually, the carcinogenic risk index (CRI) and exposure risk index (ERI) of the endrin category and aldrin exceeded the reference value, indicating relatively high health risks through consumption of fish. Overall, this study systematically illustrated the bioaccumulation process and health risks of OCPs in the typical plateau lake, providing theoretical support for the better protection of this kind of lakes.

Assessing the potential risks, sources and the relationship between the dissolved and particulate polycyclic aromatic hydrocarbons (PAHs) in the typical semi-enclosed bay, Bohai Bay of China

This study aimed to investigate the spatial and temporal distribution as well as the partitioning behavior of dissolved and particulate polycyclic aromatic hydrocarbons (PAHs) during the summer and autumn seasons of 2020. It was found that the average concentration of PAHs in surface seawater was significantly higher in autumn (58.16 ng L-1) than in summer (40.47 ng L-1) due to a large amount of input in autumn and more photodegradation and biodegradation affected by higher temperatures in summer. The spatial distribution indicated that the river had a significant dilution effect on PAHs in summer and became a significant input source in autumn. In addition, a large number of oil and gas development platforms were distributed throughout the Bohai Bay, and the discharge of production and domestic sewage contributed to the PAHs pollution level. As a semi-enclosed bay, the water exchange capacity of Bohai Bay was poor, leading to a greater accumulation of PAHs in the marine environment. The diagnostic ratios and PCA-MLR indicated that petroleum was the most important source of PAHs with a contribution of 45%, followed by fuel combustion (39%) such as coal and oil. Photooxidation in seawater resulted in a reduction of BaP/BeP, indicating that seasonal variations in photooxidation had a significant impact on the composition of PAHs (summer: 1.49, autumn: 2.96). The concentration of particulate PAHs was correlated with the concentration of dissolved PAHs and SPM, and the proportion of 3-rings (43.8%) and 4-rings (49.8%) PAHs was significantly higher on SPM. The distribution coefficients Log Kd and φspm-water showed a trend of increasing and then decreasing as the number of rings increased, with the 4-rings Pyr exhibiting the highest value. According to the ecological risk assessment, the ecological risk of total PAHs was low (RQNCs < 800, RQMECs < 1), but the ecological risk of individual PAHs and the carcinogenicity of high-ring PAHs could not be ignored (＞96.5%). This study is significant for investigating the "sources and sinks" of PAHs in the complex marine environment by analyzing the partitioning behavior of PAHs in different phases.

Sediment core records and impact factors of polycyclic aromatic hydrocarbons in Chinese lakes

Lake sediment is a natural sink for polycyclic aromatic hydrocarbons (PAHs). PAH sedimentation characteristics and their impact factors of Chinese lakes have mainly been qualitative assessed. However, quantitative impacts of PAH sedimentation from different factors have not been well analyzed. To fill this gap, we screened PAH sedimentation records from the literature, for 51 lakes in China and other regions of the world, to identify historical concentration variation and the impact factors of PAHs in different regions, in lake sediment. The results show that PAH concentrations in the sediment core in the selected Chinese lakes (478 ± 812 ng/g dry weight (dw)) were significantly lower than those in North America (5518 ± 6572 ng/g dw) and Europe (3817 ± 4033 ng/g dw). From 1900 to 2015, most of the lakes in China showed an increasing trend of PAH sedimentation concentrations, with the lakes in Southeastern China showed a decreasing trend of PAH concentration in the period of 2001-2015, which was later than the peak times shown in Western countries (1941-1970). The 2-3-ring PAHs were the main components in the sediment core of Chinese lakes, but the proportion to the total PAHs decreased from 72% in 1900-1940 to 55% in 2001-2015. Generalized additive modeling (GAM) was adopted to simulate the associations between PAH sedimentation records and the impact factors. There are large regional variations of economic and industrial development in China. The impact factors of PAH accumulation in the lake sediments differ in different regions. However, population and the consumption of coal, pesticides, and fertilizer were identified to be the most important impact factors influencing PAH sedimentation. The Chinese government needs to strengthen control measures on pollutant discharge to reduce the anthropogenic impact of PAH sedimentation in lakes.

Polychlorinated biphenyls and organochlorine pesticides in surface sediments from river networks, South Korea: Spatial distribution, source identification, and ecological risks

In this study, the nationwide monitoring of 65 polychlorinated biphenyls (PCBs) and 23 organochlorine pesticides (OCPs) in surface sediments was conducted at 77 sites in river networks in South Korea. The concentrations of ∑PCBs were relatively high in industrial sites (0.0297-138 ng/g dry weight (dw); mean 15.1 ng/g dw; median 5.44 ng/g dw), followed by industrial and agricultural (not detected (ND)-15.2 ng/g dw; mean 1.23 ng/g dw; median 0.513 ng/g dw), other sites (0.0369-0.209 ng/g dw; mean 0.116 ng/g dw; median 0.101 ng/g dw), and agricultural (0.0119-0.359 ng/g dw; mean 0.117 ng/g dw; median 0.0476 ng/g dw). The distribution and composition of PCBs in sediments are affected by past use of commercial products, atmospheric deposition, wastewater effluents, and manufacturing processes. The concentrations of ∑OCPs in industrial sites ranged from 0.0587 to 8.70 ng/g dw (mean 1.85 ng/g dw; median 0.989 ng/g dw), followed by industrial and agricultural (ND-8.54 ng/g dw; mean 0.739 ng/g dw; median 0.343 ng/g dw), other sites (0.0247-0.143 ng/g dw; mean 0.0939 ng/g dw; median 0.114 ng/g dw), and agricultural (0.00838-0.931 ng/g dw; mean 0.232 ng/g dw; median 0.0752 ng/g dw). Hexachlorobenzene and pentachlorobenzene are unintentionally generated in industries and combustion processes. Dichlorodiphenyltrichloroethanes and chlordane were dominantly distributed by historical use, whereas recent inputs (i.e., long-range transport and atmospheric deposition) were related to aldrin, heptachlor, and hexachlorocyclohexanes. The ecological risks determined by the sediment quality guidelines and mean probable effect level quotients were acceptable, except at two sites.

Organochlorine Compounds in the Amur (Heilong) River Basin (2000-2020): A Review

Persistent organic pollutants (POPs) are well-known contaminants that raise serious concerns, even more than 20 years after they were banned. Their worldwide distribution and persistence necessitate continuous monitoring in all components of the environment. The most challenging issues of POP regulation are associated with international water resources because their solutions require international cooperation in environment protection. This review provides data on various POPs (DDT, HCH, endrin, dieldrin, and PCBs) and their concentrations in aquatic organisms inhabiting the Amur River basin, one of the most poorly explored regions of Northeast Asia. Most studies have been conducted in the Songhua River (China), a tributary of the Amur River, which indicates that large inland bodies of water, especially those of international importance, require more extensive research.

First evidence and potential sources of novel brominated flame retardants and BDE 209 in the deepest ocean

Organic anthropogenic pollutants reach even the deepest parts of the oceans, i.e., the hadal trenches. We here presented the concentrations, influencing factors, and potential sources of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in hadal sediments and amphipods from the Mariana, Mussau and New Britain trenches. Results showed that BDE 209 was the dominant PBDEs congener and DBDPE was the dominant NBFRs. No significant correlation was found between TOC contents and PBDEs or NBFRs levels in sediment. Lipid content and body length were the potential important factors affecting variation in pollutant concentrations in the carapace & muscle of amphipods, while the pollution levels of viscera were mainly affected by the sex and lipid content. PBDEs and NBFRs might reach trench surface seawater through long-range atmospheric transport and oceans currents but with little contribution from the Great Pacific Garbage Patch. Determination of carbon and nitrogen isotopes indicated that the pollutants were transported and accumulated in amphipods and sediment via different pathways. PBDEs and NBFRs in the hadal sediments were generally transported via the settling of sediment particles of either marine or terrigenous origin whereas in amphipods they accumulated via feeding on animal carrion through the food web. This is the first study reporting on BDE 209 and NBFR contaminations in hadal settings and provide new insight on influencing factors and sources of PBDEs and NBFRs in the deepest oceans.

Chlorinated organic pollutants in global flooded soil and sediments: Pollution status and potential risk

Chlorinated organic pollutants (COPs) were widely detected in anaerobic environments while there is limited understanding of their pollution status and potential environmental risks. Here, we applied meta-analysis to identify the occurrence status, pollution sources, and environmental risk of COPs from 246 peer-published literature, including 25 kinds of COPs from 977 sites. The results showed that the median concentrations of COPs were at the ng g^-1 level. By the combination of principal component analysis (PCA) and positive matrix factorization (PMF), we established 7 pollution sources for COPs. Environmental risk assessment found 73.3% of selected sites were at a security level but the rest were not, especially for the wetlands. The environmental risk of COPs was usually underestimated by the existing evaluation methods, such as without the consideration of the non-extractable residues (NER) and the multi-process coupling effect. Especially, the synergetic coupling associations between dechlorination and methanogenesis might increase the risk of methane emission that has barely been previously considered in previous risk assessment approaches. Our results expanded the knowledge for the pollution control and remediation of COPs in anaerobic environments.

Occurrence of OCPs & PCBs and their effects on multitrophic biological communities in riparian groundwater of the Beiluo River, China

Persistent Organic Pollutants (POPs) may exert adverse effects on human and ecosystem health. However, as an ecologically fragile zone with strong interaction between river and groundwater, the POPs pollution in the riparian zone has received little attention. The goal of this research is to examine the concentrations, spatial distribution, potential ecological risks, and biological effects of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the riparian groundwater of the Beiluo River, China. The results showed that the pollution level and ecological risk of OCPs in riparian groundwater of the Beiluo River were higher than PCBs. The presence of PCBs (Penta-CBs, Hexa-CBs) and CHLs, respectively, may have reduced the richness of bacteria (Firmicutes) and fungi (Ascomycota). Furthermore, the richness and Shannon's diversity index of algae (Chrysophyceae and Bacillariophyta) decreased, which could be linked to the presence of OCPs (DDTs, CHLs, DRINs), and PCBs (Penta-CBs, Hepta-CBs), while for metazoans (Arthropoda) the tendency was reversed, presumably as a result of SULPHs pollution. In the network analysis, core species belonging to bacteria (Proteobacteria), fungi (Ascomycota), and algae (Bacillariophyta) played essential roles in maintaining community function. Burkholderiaceae and Bradyrhizobium can be considered biological indicators of PCBs pollution in the Beiluo River. Note that the core species of interaction network, playing a fundamental role in community interactions, are strongly affected by POPs pollutants. This work provides insights into the functions of multitrophic biological communities in maintaining the stability of riparian ecosystems through the response of core species to riparian groundwater POPs contamination.

Occurrence, spatial distribution, and risk assessment of short- and medium-chain chlorinated paraffins in sediment from black-odorous rivers across China

Chlorinated paraffins (CPs) were massively produced for varied industrial purposes, of which improper handling and consequent environmental release resulted in worldwide contamination. The present study investigated the occurrence and spatial distribution of short- and medium-chain chlorinated paraffins (SCCP/MCCPs) in 171 sediment samples from black-odorous urban rivers across China. Total SCCP and MCCP concentrations ranged from 8.3 to 9.4 × 10⁴ (median: 1.1 × 10³) ng/g dw, and from not-detected-value to 1.0 × 10⁶ (median: 1.3 × 10⁴) ng/g dw, respectively. No clear spatial distribution of SCCPs and MCCPs was observed since black-odorous urban rivers were polluted by point-sources of the SCCP/MCCPs. Significant positive correlations were identified between SCCP/MCCPs and total organic carbon, and between SCCP/MCCPs and other persistent organic matter, including polybrominated diethyl ethers, polychlorinated biphenyls, antibiotics, and plasticizers. The average ratios of MCCPs to SCCPs in most samples were divided into 11 and 16, implying the manufacturing and use of at least two types of CP technical mixtures in China. The composition of SCCP/MCCPs were similar to that in their commercial products. Ecological risk assessments by two approaches, including the Federal Environmental Quality Guidelines and Risk Quotient, both revealed that SCCP/MCCP in surface sediments confer an ecological risk. ENVIRONMENTAL IMPLICATION: SCCPs and MCCPs can be considered "hazardous materials" because of their massive production and their potential persistence, long-distance transfer, bioaccumulation potential, and toxicity. This research conducted a comprehensive study on SCCP/MCCP in black-odorous urban river sediments across China and revealed their environmental risk, which may improve understanding of SCCP/MCCP contamination characteristics.

The characteristics of polycyclic aromatic hydrocarbons and heavy metals in water and sediment of dajiuhu subalpine wetland, shennongjia, central China, 2018-2020: Insights for sources, sediment-water exchange, and ecological risk

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) are persistent environmental issues. Secondary emissions are produced as a result of climate change and human activity. To observe spatio-temporal variations of PAHs and HMs and to discuss the sources as well as the source or sink of PAHs for sediment and peat, twelve surface sediment and surface water sites were chosen along the direction of the flow to down hole in the Dajiuhu area, simultaneously, surface peat and water samples were collected in peatland. Samples were continuously taken for three years (Sep. 2018, Sep. 2019, and Sep. 2020, respectively). The results showed that PAHs and HMs are common in sediment and peat. PAHs concentration is generally higher in peat and water, while HMs concentration is relatively higher in water and relatively low in sediment and peat, and the ecological risk of sediment was low. HMs in sediment are mainly affected by rock weathering, while PAHs are mainly affected by atmospheric deposition, biomass and coal combustion and vehicle emission. HMs and PAHs can be used as an indicator of rock weathering and human activity in Dajiuhu area, respectively. A water-sediment fugacity analysis revealed that peat is a sink for PAHs, confirming that it has a high capacity for adsorbing organic contaminants, and that sediments are secondary sources of PAHs that can release them into water. Attention should be paid to the increased fugacity fraction (ff) value in peatland, indicating that peat might be converted from a sink to a source of PAHs.

Deriving freshwater sediment quality guidelines of polycyclic aromatic hydrocarbons using method of species sensitivity distribution and application for risk assessment

Contamination of polycyclic aromatic hydrocarbons (PAHs) in sediment has long been of great concern because of their toxic effects to benthic organisms. Sediment quality guidelines (SQGs) are the basis to evaluate the potential ecological risks of PAHs in sediments. Species sensitivity distribution (SSD) has been widely applied in deriving water quality criteria, but seldom employed in SQGs. In this study, SSD was used to derive the freshwater SQGs for four representative PAHs (naphthalene, phenanthrene, pyrene and benzo[a]pyrene) based on the sediment toxicity results. A linear relationship between the SQGs and octanol-water partition coefficient (log K_OW) was developed, and applied to predict the SQGs of other twelve PAHs. The obtained SQGs were in the range of 0.46 - 1.79 mg/kg with a geometric mean of 0.97 mg/kg, which was proposed as the SQGs for total PAHs. Based on these SQGs, the risk quotients of PAHs in the sediments collected from Haihe River of China were calculated, and the toxic effects were also tested using three representative benthic organisms. As the risk quotients of the PAHs and heavy metals in the sediments were summed up, good correlations were found (p = 0.074 and 0.018) between them and the observed toxicities of the sediments. The SQGs developed for PAHs was promising in ecological risk assessment for contaminated freshwater sediments.

Concentrations and source identification of priority polycyclic aromatic hydrocarbons in sediment cores from south and northeast Thailand

In this study, the environmental fate of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in tropical lake sediments and their potential sources have been discussed. 15 PAHs (i.e. ΣPAH) have been investigated in two lakes, namely Songkhla Lake (SKL) and Nong Han Kumphawapi Lake (NHL), which are located at the southern and north-eastern parts of Thailand, respectively. Since these two lakes are registered as important wetlands under the Ramsar convention (United Nations Educational, Scientific and Cultural Organization: UNESCO), the quantitative identification of potential contributors of PAHs is an inevitable analytical tool for launching an evidence-based policy. The ΣPAH concentrations observed in SKL and NHL sediments (n = 135) were in the range of 19.4–1,218 ng g⁻¹ and 94.5–1,112 ng g⁻¹, respectively. While the exponential decline of ΣPAH contents were detected in SKL sediments, NHL showed a trend of enhancing PAH contents with depth. The averaged benzo [a]pyrene (B [a]P) contents of surface sediments in both lakes were much below the value stipulated by the United States Environmental Protection Agency (US-EPA) guidelines for carcinogen risk assessment. Based on numerous multivariate statistical techniques coupled with source apportionment analysis, “biomass burning” and “anthropogenic activities” are two potential contributors of the PAHs detected in the study areas. To achieve the long-term conservation of nature with related ecosystem services and cultural values, it is therefore important to promote decision-making based on ecotoxicological studies of carcinogenic substances.

The association between phenanthrene and nutrients uptake in lotus cultivar 'Zhongguo Hong Beijing'

It has been well documented that polycyclic aromatic hydrocarbon (PAHs) can be taken up from the environment by the plants and translocated into the shoots. However, the mechanisms underlying this process are poorly understood. Nelumbo nucifera L. (lotus) is a highly ornamental aquatic plant known to possess strong phytoremediation capability. In the present study, the association between phenanthrene (Phe) and nutrients, including nitrogen (N) and phosphorus (P), in lotus was investigated. Over 2 years, all eight lotus cultivars tested accumulated Phe to various degrees when grown in PAH-polluted sediment (0.46 mg/kg Phe). Cluster analysis showed N. nucifera 'Zhongguo Hong Beijing (ZHB)' was the one with the highest Phe levels in the leaves and petals in 2 years. The Phe concentrations in the tissues of 'ZHB' were 3.14 mg/kg and 1.63 mg/kg on average in the first and second year, respectively. Interestingly, 'ZHB' was also the cultivar with the lowest N and P levels considering 2 years and tissues. Hydroponic studies further revealed a negative association between the concentrations of Phe and those of N and P in the aerial tissues under 0.5 and 1.0 mg/L Phe treatments in 'ZHB'. Furthermore, the significant reductions of the roots number (72.6%), longest root length (75.8%), and petiolar height (34.6%) in 'ZHB' seedlings exposed to 1.0 mg/L Phe were observed, indicating that Phe retarded the growth of lotus. These results provide a new understanding of the accumulation of Phe in plants and the association with nutrients and enrich the basis of phytoremediation to the contaminated environment.

Integrated estrogenic effects and semi-volatile organic pollutants profile in secondary and tertiary wastewater treatment effluents in North China

Endocrine-disrupting effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to remove estrogenic activity in effluents and the association with organic micropollutants was not well known. We evaluated the estrogenic activity using a well-characterized in vivo bioassay featuring the Chinese rare minnows (Gobiocypris rarus) and analyzed 886 semi-volatile organic compounds (SVOCs) in effluents from four secondary wastewater treatment plants (SWTP A-D) and a tertiary wastewater treatment plant (TTP E) that utilized various common treatment processes in northern China. The final effluents from SWTPs and TTP E all exhibited estrogenic effects, increasing male fish plasma vitellogenin (VTG) contents and estradiol/testosterone (E₂/T) ratios. Key regulating genes in the male fish liver including vtg1, vtg3, era, erβ, and cyp19a were upregulated. TTP E demonstrated high performance in reducing estrogenic activity in the effluents, with a reduction of 64% in integrative biomarkers of estrogenic response (IBR). UV disinfection at SWTPs removed IBR by 14%- 33%, while ozone disinfection at TTP E did not reduce IBR. Several SVOCs including alkanes, chlorobenzenes, and phthalates, detected at ng/L to µg/L level, significantly correlated with effluent estrogenic activity. Our findings suggest the necessity and the potential means to improve the efficiency of current wastewater treatment approaches to achieve better protection for aquatic organisms against the joint effects of mixtures of various categories of micropollutants in effluents.

Organophosphate pesticides in South African eutrophic estuaries: Spatial distribution, seasonal variation, and ecological risk assessment

The seasonal variation, spatial distribution, and ecological risks of thirteen organophosphate pesticides (OPPs) were studied in the Sundays and Swartkops estuaries in South Africa. Ten pesticides were detected in surface water samples from both estuaries, while all OPPs were detected in sediments. The highest concentration of OPPs (18.8 μg pyrazophos L^-1) was detected in surface water samples from Swartkops Estuary, while 48.7 μg phosalone kg^-1 dw was the highest in sediments collected from Sundays Estuary. There was no clear seasonal pattern in OPPs occurrence in surface water from both systems. However, their occurrence in sediments was in the following order: winter > autumn > summer > spring, perhaps indicating major pesticide input in the winter seasons. Results from ecological risk assessment showed that pyraclofos and chlorpyrifos (CHL) in surface water from both systems are respectively likely to cause high acute and chronic toxicity to fish (risk quotient - RQ > 1). For sediments of both estuaries, the highest acute and chronic RQs for fish were calculated for isazophos and CHL respectively. The majority of the detected OPPs in sediments posed potential high risks to Daphnia magna from both systems. These results suggest that these aquatic organisms (fish, and Daphnia), if present in the studied estuaries, can develop certain forms of abnormalities due to OPP exposure. To this end, proper measures should be taken to reduce OPP input into the estuarine systems.

Organochlorine pesticides and polychlorinated biphenyls in high mountain lakes, Mexico

Pollution levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the El Sol and the La Luna alpine lakes. The lakes are located in central Mexico, in the crater of the Nevado de Toluca volcano. The El Sol and the La Luna lakes are extremely relevant in Mexico and in the world because they are recognized as pristine regions and environmental reservoirs. Samples of atmospheric aerosol, sediment, plankton, and Tubifex tubifex (sludge worm) were collected at three different sample locations for three years (2017, 2018, and 2019) at three different times of year, meaning that the weather conditions at the time of sampling were different. Pollutants were analysed by gas chromatography-mass spectrometry with negative chemical ionisation (GC-MS/NCI). Endosulfan was the most frequent and abundant pollutant, showing the highest peaks of all. Atmospheric aerosol revealed Σ₂ = 45 pg/m³, including α and β, while sediment lakes displayed α, β and endosulfan sulfate as Σ₃ = 1963 pg/g, whereas plankton and Tubifex tubifex showed Σ₂ = 576 pg/g and 540 pg/g for α and β respectively. Results of endosulfan ratios (α/β) and (α-β/endosulfan sulfate) suggest that both fresh and old discharges continue to arrive at the lakes. This study shows for the first time the pollution levels of OCP and PCB in high mountain lakes in Mexico. These results that must be considered by policy makers to mitigate their use in the various productive activities of the region.

North-south geographic heterogeneity and control strategies for polycyclic aromatic hydrocarbons (PAHs) in Chinese lake sediments illustrated by forward and backward source apportionments

As universal and supervirulent pollutants, understanding the potential sources of polycyclic aromatic hydrocarbons (PAHs) in lakes is critical for formulating pollutant control policies that will ensure the ecological safety of aquatic environments. Geographic heterogeneity of PAHs in lake sediments from China nationwide was investigated to indicate north-south dissimilarities in PAH levels and sources and propose specific PAH control strategies. Geographic PAH patterns showed that higher concentrations were found in the south compared to the north due to higher energy consumption and more intense industrial activities. Furthermore, the primary contributors in the south were high molecular weight (HMW) PAHs, whereas low molecular weight (LMW) PAHs were dominant in the north. The results of forward source apportionment based on the PAH emission method (EM) were consistent with the backward method using the positive matrix factorization (PMF) model, which verified the feasibility of the combined methods. Petroleum from transport was the dominant PAH source in the south, and purifying gasoline and diesel, promoting new energy vehicles and direct injection engines might effectively reduce PAH emission. Domestic coal was the main PAH source in the north, thereby adding active substance in coal and using cleaner energy could reduce PAH release.

PAHs Source Identification in Sediments and Surrounding Soils of Poyang Lake in China Using Non-Negative Matrix Factorization Analysis

Identifying sources of soil and sediment PAHs and apportioning their contributions are key in building effective pollution abatement strategies, especially for Poyang Lake—the largest freshwater lake in China. PAHs were detected in all the monitored soil and sediment samples under three land use types, with the concentrations varying by area, ranging from moderate to relatively high. The order of PAHs content in different the land use types was as follows: industrial soil > grassland soil > agricultural soil. Although agricultural soil was dominated by LMW PAHs, industrial grassland soils were dominated by HMW PAHs. Based on factor analysis, non-negative matrix factorization analysis was effective in non-negative constrained skew rotation, especially for clear and interpretable source analysis of PAHs.

Bioaccumulation of organochlorine pesticides in Antarctic krill (Euphausia superba): Profile, influencing factors, and mechanisms

Accumulation of organochlorine pesticides (OCPs) in Antarctic krill (Euphausia superba), a keystone species in the Southern Ocean, is potentially harmful to the Antarctic ecosystem and human health. In the current study, we collected E. superba specimens (including muscle and carapace tissues) from Bransfield Strait in northern Antarctic Peninsula and South Georgia to analyze the profile, influencing factors and mechanisms of OCPs bioaccumulation in them. Results indicated that the biological traits (δ¹³C, δ¹⁵N and lipid contents) of krill were significantly affected by habitat. There may exist growth dilution of OCPs in Antarctic krill and no fresh OCPs input in Antarctica, except for endosulfan I. Based on lipid-normalized concentrations, no significant differences were observed between the two regions at most sampling sites. However, OCP levels showed tissue and sex dependence. Boosted regression trees (BRTs) and partial least squares structural equation models (PLS-SEMs) were built to better investigate the main factors affecting the bioaccumulation of OCPs. Lipid content, negatively correlated with OCP levels, was the main factor. In vitro silicon modeling indicated that CYP3A4 metabolism capacity in krill contributed to the OCP residues except for endosulfan I. The results of this study expand current knowledge of OCPs in Antarctic marine biota, as well as their influencing factors and potential mechanisms.

Current and Future Trends of Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons in Surface Water and Sediments of China: Insights from Their Long-Term Relationships between Concentrations and Emissions

In this study, we analyzed the temporal trend of polycyclic aromatic hydrocarbons (PAHs) in China using data reported over the past 20 years. We found that the total concentrations of low molecular weight PAHs (C_ΣLPAHs) in surface water and sediments were positively correlated with their total emissions (E_ΣLPAHs), which increased between 2000 and 2008, then decreased until 2017. Additionally, the total concentrations of high molecular weight PAHs (C_∑HPAHs) in surface water and sediments were positively correlated with their total emissions (E_ΣHPAHs), which increased significantly from 2000 to 2014 and then plateaued. Two future scenarios were assessed to explore C_∑LPAHs and C_∑HPAHs in surface water and sediments. PAH emissions were reduced by technological improvement in 2030 for coal consumption in Scenario 1 and for control of biomass burning in Scenario 2. Scenario 1 was more efficient than Scenario 2 in reducing C_∑HPAHs in the surface water and sediments of China for the areas where C_ΣHPAHs in surface water exceeded the annual average standard (i.e., 30 ng L^-1), with reductions of 38 and 24% in Scenarios 1 and 2, respectively. The observed relationships in this study can provide tools for emission reduction policies in the future.

What is the spatial-temporal behavior of a low, medium and high adsorptive compound in two contrasting natural sediments in OECD 218/219 test systems?

Artificial sediment used in studies according to OECD 218/219 (Sediment Water Chironomid Toxicity Test Using Spiked Sediment/Water) does not necessarily mirror the characteristics of natural sediments. To investigate the influence of sediment characteristics on the spatial-temporal behaviors of bixafen (KfOM = 2244 mL/g), fluopyram (KfOM = 162 mL/g) and N,N-dimethylsulfamide (KfOM ≈ 0 mL/g), experiments according to OECD 218/219 with two contrasting natural sediments were conducted. The silt loam sediment provided a high content of organic matter (OM) (13.1%), while the OM (0.45%) of the sandy sediment was low. Diffusion into (OECD 219) or out (OECD 218) of the sediment was dependent on the extent of adsorption, which is linked to the model compounds ́ adsorption affinities and the sediments ́ OM. Consequently, N,N-dimethylsulfamide showed unhindered mobility in each experimental set up, while the high adsorption affinities of fluopyram and bixafen limited the diffusion in the respective sediments. Therefore, in experiments with the silt loam sediment, both compounds revealed a limited mobility and either accumulated in the top 5 mm of the sediment (OECD 219) or remained homogenously distributed over the sediment depth (OECD 218). A greater mobility was observed within the sandy sediment.The influence of OM as found in a study using artificial sediment could be confirmed. Moreover, the applicability of a TOXSWA model was reassured to predict the measured concentrations at different sediment depths. TOXSWA is used in the regulatory exposure assessment to simulate the behavior of pesticides in surface waters. Calibration of three driving input parameters by inverse modelling (diffusion-, adsorption coefficient and OM) revealed no potential for improvement. The core sampling technique used and the model may contribute to a more realistic determination of concentration to which the Chironomid larvae are exposed to. This applies to water sediment test systems where the test organisms do not evenly inhabit the sediment.

Spatiotemporal distribution of polycyclic aromatic hydrocarbons in sediments of a typical river located in the Loess Plateau, China: Influence of human activities and land-use changes

The Loess Plateau, as the key energy base of China, has sensitive responses to the global changes, and receives polycyclic aromatic hydrocarbons (PAHs) from anthropogenic activities. However, understanding how anthropogenic and climate factors affect synergistically the PAHs distribution in this vulnerable ecological environment is deficient. Here the spatiotemporal distribution of PAHs in sediments from a typical river of the Loess Plateau were investigated. The PAHs were mainly from coal combustion in the range of 194-514 ng g^-1, and their concentrations were generally higher in normal season than wet season as the dilution effect of high river discharge and strong precipitation. The interactive effects of land-use and precipitation showed PAHs enriched in forest-grass land were transferred into rivers through surface and subsurface runoff during light rainfall, resulting in the increase of the PAHs concentrations in river sediments. In contrast, large precipitation in wet season would obscure any spatial variations. In addition, human activities, especially energy production, directly enhanced PAHs accumulation in river sediments due to the emission from the production processing of oil and coal, and indirectly influenced the PAHs by impacting the per capita GDP. These findings had important implications for the management and prediction of PAH accumulation.

Vertical distribution and effect of historical residual organochlorine pesticides on microbial community structure in sediment cores from an abandoned oxidation pond after dredging for 15 years

The vertical distribution pattern of 19 organochlorine pesticides (OCPs), together with microbial ester-linked fatty acid methyl ester (EL-FAME) profiles were investigated in sediments from an abandoned oxidation pond of Ya-Er lake, China, which had been heavily polluted by hexachlorocyclohexanes (HCHs) and chlorobenzenes in 1980s. Subsurface sediment samples were taken from five sediment cores along the transect running from the lakeshore (0.5~2.7 m in depth) to lakebed (0.1~0.4 m). The total OCP concentration ranged from 29.8 to 941.8 ng g^-1 dw. Hexachlorobenzene (HCB), HCHs, and dichlorodiphenyl-trichloroethanes (DDTs) were the three dominant OCP classes, accounting for 26.5-97.4%, 1.8-33.2%, and 0.4-15.5% of the total OCP concentration, respectively. Hot spots of HCB, HCHs, and DDTs were detected at 0.9~2.7 m deep layers of the lakeshore, where was once the main dredged sediment backfill site for in-situ remediation of the oxidation pond in 2002-2004. HCHs and HCB still showed high potential ecological risks. The sources of OCPs were identified and quantified using principal component analysis with absolute principal component scores-multiple linear regression model. The first three major sources were persistent residues, recent agricultural input, and historical industrial input, contributing on average 28.2%, 17.9%, and 17.1% of total OCPs, respectively. Redundancy analysis of microbial EL-FAME profiles and nine dominant OCPs revealed that the spatial variation in microbial community structure was significantly corresponded with the OCP composition. This is the first study highlighting the concern on historical industrial inputs of OCPs in subsurface sediments of the lakeshore disposal zone. The findings could help to distinguish the artificial backfill sediments from undisturbed polluted sediments for optimization of further dredging plans.

Spatial distribution, source identification and ecological risk assessment of POPs and heavy metals in lake sediments of Istanbul, Turkey

Istanbul needs to be protected and constantly monitored water resources due to its increasing population and the decrease in precipitation. This study aims to comprehensively reveal surface sediments collected from reservoirs that supply water to Istanbul concerning POPs (PAHs, PCBs, and OCPs) and heavy metals; to identify possible sources of PAHs, and conduct their ecological risk assessment. Pollution indices in this study were used as contamination degree (CD) contamination factor (CF), geoaccumulation index (I_geo), pollution load index (PLI) and Sediment Quality Guidelines (SQGs). Total PAH concentrations of surface sediments at the sampling points ranged from 46.29 ng/g (A7) to 403.9 ng/g (A15). Benzo(b)fluoranthene (5.647-59.42 ng/g), Pyrene (3.625-83.10 ng/g), Fluoranthene (3.363-66.48 ng/g), Phenanthrene (3.115-52.48 ng/g), Chrysene (3.532-43.98 ng/g), Naphthalene (6.606-36.20 ng/g), Benzo(g,h,i)perylene (3.316-41.73 ng/g) and Indeno(1,2,3-c,d)pyrene (3.453-38.84 ng/g) are the dominant PAH compounds. PAH pollution may be caused by the village-town settlements near the dam and the O7-D020 highway. Total OCP concentration ranged from 2.233 ng/g (A12) to 7.337 ng/g (A1), while total PCB concentration ranged from 0.246 ng/g (A13) to 3.708 ng/g (A1). The lowest total OCP and PCB concentrations were found in surface sediments taken from Kazandere, Papuçdere and Alibey Dam lakes. DDT p,p (0.072-5.177 ng/g) has the highest concentration among all sediment samples. While the most dominant OCP compounds in the samples were DDT p,p, DDE p,p and DDD p,p, HCH alpha, HCH beta, respectively, PCB 153, 138 and 180 were the highest detected PCB congeners in the same samples. Total heavy metal concentration varied from 77,812 mg/kg to 267,072 mg/kg. According to PAH diagnostic analysis, the surface sediments of Terkos, Büyükçekmece, Elmalı, Darlık, Sazlıdere, Alibey and Ömerli Dams were polluted by petrogenic sources, while the surface sediments of Kazandere and Papuçdere Dams were affected by pyrogenic sources. None of the levels of POPs in the samples exceeded the ERM values. Slight and moderate contamination of heavy metals, such as Pb and Zn, were present in most of the sampling points according to CD, CF, PLI and I_geo values. The quality criteria of heavy metals showed that almost all of the sampling points had Cd, Pb and Hg concentrations below the ERL values. The Ni concentrations at most of the sampling points significantly exceeded the ERM values. The concentrations of As, Cr, Cu and especially Ni and Zn exhibit a significant toxic risk to aquatic organisms to sediment quality criteria.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

Comprehensive insights into the occurrence, source, distribution and risk assessment of polycyclic aromatic hydrocarbons in a large drinking reservoir system

The resource, environment, and ecological value of drinking reservoirs have received widespread concerns due to the pollution of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs). Therefore, we comprehensively studied the occurrence, source, distribution, and risk assessment of representative PAHs in Fengshuba Reservoir (FSBR) (large drinking reservoir, China). The total concentrations of 16 USEPA PAHs in the water phase, porewater phase, sediment phase, and soil phase were in ranges of 109.72-393.19 ng/L, 5.75-35.15 μg/L, 364.4-743.71 μg/kg, and 367.81-639.89 μg/kg, respectively. The naphthalene (Nap) was the dominant PAHs in the water phase, while it was Nap and phenanthrene (Phe) in porewater, sediment, and soil phase. The main sources of PAHs in FSBR were biomass combustion. Redundancy analysis indicated that the NTU, NO₂^-, NH₄⁺, Chl-α, and IC were the dominant factors influencing the PAH distribution in water phase, and the PAHs in sediment phase was affected by T and NO₃^-. Pseudo-partitioning coefficients indicated that the PAHs in the porewater phase were more likely to migrate to the sediment phase. Risk assessment indicated that the PAHs both in the water and sediment phases were generally in a low-risk state, while the PAHs in the soil phase were in a moderate-risk state, and the Nap was in a high-risk state, and exposure to the PAHs in FSBR through drinking and skin exposure had little impact on consumers' health. In summary, Nap could be used as a key indicator to evaluate the existence and potential risk of PAHs in FSBR.

Octanol-water partition coefficient (logKow) dependent movement and time lagging of polycyclic aromatic hydrocarbons (PAHs) from emission sources to lake sediments: A case study of Taihu Lake, China

Understanding the movement of polycyclic aromatic hydrocarbons (PAHs) from emission sources to sediments is important for achieving long-term pollution control of PAHs in sediments. In this study, by exploring the correlation of individual PAHs concentrations (C_PAHs) in Taihu Lake sediments reported in the past twenty years with their annual emissions (E_PAHs) in the lake region, it was observed that mean concentrations of PAHs with low logK_ow (i.e., logK_ow≤4.00) in Taihu Lake sediments were correlated best with their emissions without lagging between the sediment sampling time and the PAHs emitting time. However, for PAHs with middle logK_ow (i.e., 4.00<logK_ow≤4.57) or high logK_ow (i.e., logK_ow>4.57), their mean concentrations in sediments were correlated best with the emissions of PAHs emitted 1 or 2 years before the sediment sampling time. The longer lagging time of PAHs with middle or high logK_ow from emission sources to lake sediments could be attributed to their retardation in soils and river sediments around the lake. Moreover, the retardation in soils and river sediments is dependent on PAHs logK_ow and degradation half-life, indicating the dependence of PAHs concentration in sediments on their environmental behaviors, including sorption and degradation. K_ow dependent movement and the time lagging observed in Taihu Lake for PAHs from emission sources to sediments could be valuable for developing measures to control PAHs, especially for congeners with high logK_ow.

Recording and response of persistent toxic substances (PTSs) in urban lake sediments to anthropogenic activities

Owing to the intensification of human activities, urban lakes serving as important freshwater resources are becoming seriously deteriorated, especially due to persistent toxic substance (PTS) pollution. Therefore, the spatial distribution and sediment record of PTS in urban lake sediments in the middle Yangtze River Basin were investigated to indicate its response to anthropogenic emission and pollution reduction actions. Spatial distribution of typical PTSs (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) included) showed that pollutants were concentrated in the southeast and center of the urban lake due to riverine inputs suffering from both petrochemical and municipal wastewaters. The sedimentary record of PAH concentrations indicated an increase from the 1960s to a peak level in the 2000s, which was induced mainly by increased PAH emissions, with PAH levels decreasing subsequently due to craft improvement of wastewater treatment plants (WWTPs). Source apportionment results revealed that historical PAH emissions transferred from petrogenic sources to a mixture of energy combustion and petrochemical industry. Furthermore, OCP and PCB pollutions reached peak levels in 1980s, which is consistent with their historical usage for agricultural and industrial production. From the synthetic sediment quality index (SeQI) analysis, sediment quality in nearly half of sites was poor, while the sediment record suggested that sediment quality had turned better since 2000s maybe due to the WWTP improvement. Furthermore, significant correlations (p < 0.05) between PTS levels and the ratio of PAH emissions to the number of WWTPs documented the PTS levels in response to the surrounding anthropogenic pollution and WWTPs in urban lakes.

Occurrence, spatial distribution, source, and ecological risk assessment of organochlorine pesticides in Dongting Lake, China

The occurrence, distribution, sources, and ecological risks of organochlorine pesticides in Dongting Lake of China were investigated. The average concentrations of organochlorine pesticides (OCPs) in 22 surface water samples and 14 sediment samples were 90.07 ng/L and 80.65 ng/g dw, respectively. Sixteen types of OCPs, dominated by HCHs, DDTs and heptachlor, were detected in the Dongting Lake. The relationships of OCP residues between Dongting Lake and its tributary rivers have been discussed and the hydraulic connections with the Yangtze River and the Three Gorges Dam (TGD) were also considered. Results showed that the shortage of runoff, earlier dry season, and reduction of sediment deposition extremely deteriorated the hydraulic conditions, magnified the water cycle, and restrained the self-purification of OCPs. The ∑OCPs in surface water were concentrated in the inlets of Yangtze River, Lishui River, Zishui River, Yuanshui River, and Xiangjiang River. Moreover, the ∑OCPs in the outlet of the Yangtze River also maintained a high level, indicating that OCPs posed adverse effects on the Yangtze River. Risk assessments of OCPs in the surface water of Dongting Lake were estimated according to available water quality guidelines and health risk assessment models. The results indicated that OCPs in the surface water of Dongting Lake were safe for aquatic organisms and human health. In addition, sediment quality guidelines (SQGs) were also applied to evaluate the potential ecotoxicological risks of OCPs in sediments. The results presented that contaminants of γ-HCH; o,p'-DDD; and dieldrin in sediment had adverse effects on benthic organisms, indicating that fundamental solutions should be proposed to control OCP contamination in Dongting Lake.

Eutrophication-induced regime shifts reduced sediment burial ability for polycyclic aromatic hydrocarbons: Evidence from Lake Taihu in China

Regime shifts from a vegetated state with clear water to a turbid state with high contents of phytoplankton and suspended particles have been found in numerous waters worldwide. The fate and risks of hydrophobic organic contaminants (HOCs) in such waters may be altered, and the effects on burial ability of HOCs remain unknown. Influences of regime shifts on sediment burial ability for 16 polycyclic aromatic hydrocarbons (PAHs) (defined as burial/emission ratio) were investigated based on the evidence from the third largest freshwater lake (Lake Taihu) in China. The results of δ¹³C, δ¹⁵N, atomic ratio of C_org/N, and the content of total organic carbon testing and historical data suggested that the regime shifted abruptly from macrophytes to phytoplankton dominance in Lake Taihu in the late 1980s. The annual burial ability for the PAHs decreased gradually over time by 63.2%-98.9% in the period from 1980 to 2016. Meanwhile, the decrease rates of PAH burial ability varied from -1.65% y^-1 to -2.98% y^-1, depending on the hydrophobicity of the compound. The PAH burial ability varied with the dominant primary producers associated with the trophic level index of the water column. Regime shifts had a stronger influence on the burial ability of PAHs with higher hydrophobicity. This study helps to understand the fate and potential risks of HOCs in waters due to eutrophication-induced regime shifts.

Suspended particulate matter (SPM)-bound polycyclic aromatic hydrocarbons (PAHs) in lakes and reservoirs across a large geographical scale

Suspended particulate matter (SPM) plays a key role in the environmental fate of polycyclic aromatic hydrocarbons (PAHs) in lake environment. However, less is known about the occurrence, compositions and sources of SPM-bound PAHs as well as the correlations between SPM-bound PAHs and different suspended particulate organic matter (SPOM) on large geographical scale. In this study, we focused on the SPM-bound PAHs in 46 lakes and reservoirs across China to fill this gap. Our results showed that the concentrations of Σ₂₀ PAHs ranged from 334 to 38427 ng·g^-1 with a geometric mean (GM) of 3915 ng·g^-1. The occurrence of SPM-bound PAHs in this study was at a moderate level with large variations, which was associated with location and water depth according to linear discriminant analysis (LDA). Phenanthrene (Phe) was investigated as the overwhelming species with a GM of 1777 ng·g^-1, and was followed by fluoranthene (Fla), fluorene (Flu) and pyrene (Pyr) with GMs of 499 ng·g^-1, 276 ng·g^-1 and 184 ng·g^-1, respectively. The profiles of SPM-bound PAHs were primarily dominated by low-ring PAHs ranging from 56.0% to 97.1% (85.5% ± 7.7%, mean ± standard deviation). Four diagnostic ratios were applied for preliminary diagnoses, but inconsistent results were obtained in most samples. Ridge regression was applied to ascertain the potential influences of different SPOM on SPM-bound PAHs. The results revealed that the presence of SPM-bound PAHs was not only influenced by anthropogenic emissions, but also associated with biogenic organic matter. Our results provided a higher explanation than those just preliminarily estimated by total organic carbon (TOC). Nevertheless, there still exist over 50% of variance unexplained for most PAHs, and further study could focus more on the information of SPOM structures and potential local effects.

Spatiotemporal toxicity assessment of suspended particulate matter (SPM)-bound polycyclic aromatic hydrocarbons (PAHs) in Lake Chaohu, China: Application of a source-based quantitative method

The spatiotemporal associations between the emissions and environmental toxicities of polycyclic aromatic hydrocarbons (PAHs) in lake still remain an issue. Here, we focused on the suspended particulate matter (SPM)-bound PAHs in Lake Chaohu, China to quantitatively estimate their spatiotemporal toxicities from different sources. A source-based quantitative method, positive matrix factorization (PMF)-benzo[a]pyrene-based toxic equivalency (TEQ_BaP) model, was applied. Firstly, we investigated the spatiotemporal characteristics of SPM-bound PAHs. The concentrations of Σ₂₁ PAHs ranged from 1646 to 19267 ng·g^-1. Low-ring PAHs were found to have the highest fractions. T-distributed stochastic neighbor embedding (t-SNE)-partitioning around medoid (PAM) technic revealed significantly spatiotemporal variation characteristics of SPM-bound PAHs in Lake Chaohu. Season, location (west or east lake zone), and sample classification (estuary or lake) together governed the patterns. Then, their potential sources were apportioned. Our results found that diagnostic ratios did not work perfectly. However, 3 factors were separated by PMF model. Unburned petroleum (F1), biomass, coal and gasoline combustion (F2), and diesel, straw combustion (F3) were the main sources of PAHs, accounting for 36.16%, 48.96% and 14.88%, respectively. The patterns of the source profiles were season-dependent. Finally, the toxicity of SPM-bound PAHs from different sources were predicted by PMF-TEQ_BaP model, and the model predictions were satisfactorily acceptable. Overall, predicted Σ₁₉ TEQ_BaP of SPM-bound PAHs in Lake Chaohu ranged from 20.8 to 947.9 ng·g^-1. Benzo[e]pyrene (BeP), benzo[a]pyrene (BaP) and benzo[b]fluoranthene (BbF) were the main toxic species. Temporally, PAH toxicity posed significantly seasonal differences. F3 had primary contributions to Σ₁₉ TEQ_BaP. Cutting the diesel consumption and using cleaner energy substitutes were suggested to reduce the PAH toxicity in Lake Chaohu. Overall, we expected this study could give new insights into the spatiotemporal associations between the sources and toxicities of SPM-bound PAHs in lake ecosystem.

Nationwide health risk assessment of juvenile exposure to polycyclic aromatic hydrocarbons (PAHs) in the water body of Chinese lakes

The high emissions of polycyclic aromatic hydrocarbons (PAHs) pose a serious threat to the lake ecosystem and human health, and the human health risk assessment of PAH exposure is expected as an urgent project in China. This paper focused on 44 Chinese lakes in 6 lake zones to investigate the occurrence, composition and source of 19 PAHs in water body and estimate the human health risk under PAH exposure. The "List of PAH Priority Lakes" in China was generated based on the combination of incremental lifetime cancer risk (ILCR) model and Monte Carlo simulation. Our results showed that the Σ₁₇ PAHs ranged from 3.75 ng·L^-1 to 368.68 ng·L^-1 with a median of 55.88 ng·L^-1. Low-ring PAHs were the predominant compounds. PAH profiles varied significantly at lake zone level. Diagnostic ratios showed that PAHs might derive from petroleum and coal or biomass combustion. Benzo[a]pyrene-equivalent toxic concentrations (BaPeq) of the Σ₁₇ PAHs ranged from 0.07 ng·L^-1 to 2.26 ng·L^-1 (0.62 ± 0.52 ng·L^-1, mean ± standard deviation) with a median of 0.47 ng·L^-1. Benzo[a]anthracene (BaA), benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) were the main toxic isomers. Juvenile exposure to PAHs via oral ingestion (drinking) and dermal contact (showering) had negligible and potential health risks, respectively. Juveniles were the sensitive population for PAH exposure. 15 lakes were screened into the "List of PAH Priority Lakes" in three priority levels: first priority (Level A), moderate priority (Level B) and general priority (Level C). Lake Taihu, Lake Chaohu and Lake Hongze were the extreme priority lakes. Optimizing the economic structures and reducing the combustion emissions in these areas should be implemented to reduce the population under potential health risk of PAHs.

Distribution, sources, and behavior of PAHs in estuarine water systems exemplified by Salt River, Taiwan

Water, suspended particulate matter (SPM), and sediment samples were collected from Salt River in Taiwan and analyzed the concentrations of 16 types of polycyclic aromatic hydrocarbons (PAHs). The analysis results were used to examine the distribution, source, partition behavior, and potential ecological risks of PAHs in the estuarine water systems. The mean concentration of total PAHs in water, SPM, and sediment samples was 0.485-10.2 μg/L, 26.7-169 mg/kg dw, and 0.343-29.4 mg/kg dw, respectively. The highest concentration was found at the river mouth and decreased toward the river and sea with the tide. The distribution of the diagnostic ratios of PAHs showed that the combustion of coal and petroleum products are the main sources of PAHs in Salt River. The in site organic carbon normalized partition coefficients for SPM-water (K'_oc(SPMW)) and sediment-water (K'_oc(SedW)) were 2.8-4.5 and 4.6-6.0 (log units), respectively, increasing with the number of rings in PAHs. The values log K'_oc(SedW) and log K'_oc(SPM-W) showed a significant linear correlation with their octanol-water partition coefficients (p < 0.01), and their slopes were 0.427 and 0.316, respectively. The fugacity fraction was used to evaluate the exchange of PAHs in water-SPM-sediment systems. Results showed that in SPM, 2-4-ring PAHs tend to be released into water, whereas 5-6-ring PAHs in water tend to be adsorbed onto SPM. The exchange of PAHs between water and sediment occurs in the direction of adsorption onto sediment from water. The assessment of the mean risk quotient, total toxicity equivalence, and mean effect range-median quotient of PAHs showed that the PAHs in the water and SPM of Salt River may have moderate to high ecological risk. In sediment, PAHs in the lower reaches and estuary may pose moderate to high ecological risk, whereas PAHs in the middle and upper reaches show low to moderate ecological risk.

Distribution, sources and ecological risks of organochlorine compounds (DDTs, HCHs and PCBs) in surface sediments from the Pearl River Estuary, China

The Pearl River Estuary is an important sink of organochlorine compounds (OCs), and OC pollution levels in surface sediments remain largely unknown at present. We collected and analysed residual DDTs, HCHs and PCBs of 45 surface sediments from the Pearl River Estuary in 2017. The values of DDTs (1.83 to 6.98 ng·g^-1) and HCHs (0.43 to 2.14 ng·g^-1) were higher in the Humen outlet, and the values of PCBs (4.6 to 187.4 ng·g^-1) were higher in the coastal areas of Shenzhen. The DDTs and HCHs have generally decreased while the PCBs have been rapidly increasing in recent decades. The DDTs might originate from technical DDT and dicofol. The major source of HCHs was lindane. The main potential sources of PCBs were increased industrial products, ship painting, E-waste disassembly, maricultural and agricultural pollution. The total PCBs and DDTs had medium ecological risks according to the sediment quality guidelines.

Climate change has weakened the ability of Chinese lakes to bury polycyclic aromatic hydrocarbons

Burial in sediments is a crucial way to reduce mobilization and risks of hydrophobic organic contaminants (HOCs), but ability of sediments to bury HOCs may be altered if the environment is changed. Whether the ability of sediments to bury HOCs has been affected by climate change remains largely unclear. We excluded the impacts of anthropogenic emissions and eutrophication from that of climate change, and for the first time found that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation had weakened the ability of Chinese lakes to bury 16 polycyclic aromatic hydrocarbon (PAHs) by 69.2% ± 9.4%-85.7% ± 3.6% from 1951 to 2017. The relative contributions of the climatic variables to the reduced burial ability depended on the properties of the PAHs, and lakes. Burial ability of the PAHs responded differently to climate change, and was correlated to their volatilization and aqueous solubility, and lake area, catchment area/lake area ratio, and water depth. Our study suggests that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation can undermine global efforts to reduce environmental and human exposure to PAHs.