Industrial effluents and N-nitrosamines in karst aquatic systems: a study on distribution and ecological implications.

The discharge of electroplating wastewater, containing high concentrations of N-nitrosamines, poses significant risks to human health and aquatic ecosystems. Karst aquatic environment is easily impacted by N-nitrosamines due to the fragile surface ecosystem. However, it's still unclear in understanding N-nitrosamine transformation in karst water systems. To explore the response and transport of nine N-nitrosamines in electroplating effluent within both karst surface water and groundwater, different river and groundwater samples were collected from both the upper and lower reaches of the effluent discharge areas in a typical karst industrial catchment in Southwest China. Results showed that the total average concentrations of N-nitrosamines (∑NAs) in electroplating effluent (1800 ng/L) was significantly higher than that in the receiving river water (130 ng/L) and groundwater (70 ng/L). The dynamic nature of karst aquifers resulted in comparable average concentrations of ∑NAs in groundwater (70 ng/L) and river water (79 ng/L) at this catchment. Based on the principal component analysis and multiple linear regression analysis, the electroplating effluent contributed 89% and 53% of N-nitrosamines to the river water and groundwater, respectively. The results based on the species sensitivity distribution model revealed N-nitrosodibutylamine as a particularly toxic compound to aquatic organisms. Furthermore, the average N-nitrosamine carcinogenic risk was significantly higher in lower groundwater reaches compared to upper reaches. This study represents a pioneering effort in considering specific N-nitrosamine properties in evaluating their toxicity and constructing species sensitivity curves. It underscores the significance of electroplating effluent as a primary N-nitrosamine source in aquatic environments, emphasizing their swift dissemination and significant accumulation in karst groundwater.

Analysing N-nitrosamine occurrence and sources in karst reservoirs, Southwest China.

N-nitrosamines in reservoir water have drawn significant attention because of their carcinogenic properties. Karst reservoirs containing dissolved organic matter (DOM) are important drinking water sources and are susceptible to contamination because of the fast flow of various contaminants. However, it remains unclear whether N-nitrosamines and their precursor, DOM, spread in karst reservoirs. Therefore, this study quantitatively investigated the occurrence and sources of N-nitrosamines based on DOM properties in three typical karst reservoirs and their corresponding tap water. The results showed that N-nitrosamines were widely spread, with detection frequencies > 85%. Similar dominant compounds, including N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosopyrrolidine, and N-nitrosodibutylamine, were observed in reservoirs and tap water, with average concentrations of 4.7-8.9 and 2.8-6.7 ng/L, respectively. The average carcinogenic risks caused by these N-nitrosamines were higher than the risk level of 10-6. Three-dimensional fluorescence excitation-emission matrix modeling revealed that DOM was composed of humus-like component 1 (C1) and protein-like component 2 (C2). Fluorescence indicators showed that DOM in reservoir water was mainly affected by exogenous pollution and algal growth, whereas in tap water, DOM was mainly affected by microbial growth with strong autopoietic properties. In the reservoir water, N-nitrosodiethylamine and N-nitrosopiperidine were significantly correlated with C2 and biological indicators, indicating their endogenously generated sources. Based on the principal component analysis and multiple linear regression methods, five sources of N-nitrosamines were identified: agricultural pollution, microbial sources, humus sources, degradation processes, and other factors, accounting for 46.8%, 36.1%, 7.82%, 8.26%, and 0.96%, respectively. For tap water, two sources, biological reaction processes, and water distribution systems, were identified, accounting for 75.7% and 24.3%, respectively. Overall, this study presents quantitative information on N-nitrosamines' sources based on DOM properties in typical karst reservoirs and tap water, providing a basis for the safety of drinking water for consumers.

Background levels of OCPs, PCBs, and PAHs in soils from the eastern Pamirs, China, an alpine region influenced by westerly atmospheric transport.

Long-range atmospheric transport (LRAT) plays a crucial role in the occurrence of persistent organic pollutants (POPs) in remote regions. When studying the LRAT of POPs on the Tibetan Plateau, westerly-controlled regions have received insufficient attention compared with regions influenced by the Indian monsoon or air flow from East Asia. We investigated the residual levels of POPs in soils from the eastern Pamirs and used air backward trajectory analysis to elucidate the influence of potential source regions via LRAT. Organochlorine pesticides (OCPs, mainly comprising DDTs, HCHs, and HCB), polychlorinated biphenyls (PCBs, mainly comprising penta- and hexa-CBs), and polycyclic aromatic hydrocarbons (PAHs, mainly comprising three- and four-ring) were detected at low concentrations of 40-1000,

Occurrence of N-nitrosamines and their precursors in the middle and lower reaches of Yangtze River water.

The presence of some types of N-nitrosamines in water bodies is of great concern worldwide due to their carcinogenic risks and harmful mutagenic effects on human health. In the present study, eight N-nitrosamines and their formation potentials (FPs) were primarily investigated in Yangtze River surface water to evaluate their spatial distribution, mass loads, and ecological risks. The results showed that of the eight N-nitrosamines investigated, NDMA (<1.5-17 ng/L), NDEA (<1.4-9.5 ng/L), NDPA (1.0 ng/L), NMOR (<1.0-1.3 ng/L), NPIP (<2.1-3.7 ng/L), and NDBA (<3.6-30 ng/L) were detected. The FPs of NDMA (<27-130 ng/L), NDEA (<0.9-2.3 ng/L), NDPA (<1.2-1.9 ng/L), NPYR (<1.4-2.9 ng/L), NMOR (<1.0 ng/L), and NDBA (<1.1-14 ng/L) were significantly identified. NDBA was predominantly observed in surface water, while NDMA was noticeably detected in chloraminated water samples. It was estimated that approximately 5.4 t/y of N-nitrosamines were carried by the Yangtze River to the East China Sea, whereas the input flux of N-nitrosamine precursors was estimated to be approximately 69.5 t/y. Spatial variations were observed due to the input of N-nitrosamines from the upstream dams and lakes. The origin of N-nitrosamine precursors was not associated with the presence of sediment in river water. NDEA could be introduced into river water by the discharge of wastewater. NDBA and its precursors could originate from industrial and aquaculture activities. NDMA and its precursors could result from both of the aforementioned sources. Moreover, the wastewater discharge from small cities, pH value, wastewater treatment ratio, and dilution could be the key factors that influence the occurrence of N-nitrosamines along the Yangtze River. More attention should be paid to the cancer risks posed by N-nitrosamines. The ecological risks posed by N-nitrosamines in the Yangtze River can be ignored.

Trace metals in aquatic environments of a mangrove ecosystem in Nansha, Guangzhou, South China: pollution status, sources, and ecological risk assessment.

Mangrove forests are widely located along coastlines. They have been identified to be inimitable and dynamic ecosystems. This study investigated the trace metals in mangrove water and surface sediments of Nansha, Guangzhou, China. Zn (148.42 ± 247.47 µg L-1) was the most abundant metal in waters, followed by As (82.34 ± 118.95 µg L-1), Pb (22.96 ± 120.50 µg L-1), and Ni (19.42 ± 47.84 µg L-1). In sediments, the most abundant metal was Fe (27.04 ± 1.91 g kg-1), followed by Mn (1049.04 ± 364.11 mg kg-1), Zn (566.33 ± 244.37 mg kg-1), and Cr (106.9 ± 28.51 mg kg-1). Higher contents of trace metals were detected in vicinity areas of the river mouth. The results of pollution indexes, including contamination factor, enrichment factor, and geo-accumulation index, indicated the pollution of Cd, Cu, Pb, and Zn in sediments. The Spearman correlation and cluster analysis were used to evaluate the metal sources. In water, the significant correlations among Zn and water chemical parameters (Na, Mg, K, Ca, conductivity, pH, and Cl) might indicate the natural source of Zn from the seawater. Water sampling sites in estuaries and coastal areas were clustered separately, which might indicate the influences of upstream water and the seawater, respectively. In sediments, the significant relationships among Cd, Pb, and Zn concentrations were likely to imply the emissions from industries and exploitation of the Pb-Zn mine. The occurrence of Cr and Cu in sediments can be attributed to the spills of lubricants or oil. Cd in sediments could cause serious ecological risk.

The origin of high hydrocarbon groundwater in shallow Triassic aquifer in Northwest Guizhou, China.

Original high hydrocarbon groundwater represents a kind of groundwater in which hydrocarbon concentration exceeds 0.05 mg/L. The original high hydrocarbon will significantly reduce the environment capacity of hydrocarbon and lead environmental problems. For the past 5 years, we have carried out for a long-term monitoring of groundwater in shallow Triassic aquifer in Northwest Guizhou, China. We found the concentration of petroleum hydrocarbon was always above 0.05 mg/L. The low-level anthropogenic contamination cannot produce high hydrocarbon groundwater in the area. By using hydrocarbon potential, geochemistry and biomarker characteristic in rocks and shallow groundwater, we carried out a comprehensive study in Dalongjing (DLJ) groundwater system to determine the hydrocarbon source. We found a simplex hydrogeology setting, high-level water-rock-hydrocarbon interaction and obviously original hydrocarbon groundwater in DLJ system. The concentration of petroleum hydrocarbon in shallow aquifer was found to increase with the strong water-rock interaction. Higher hydrocarbon potential was found in the upper of Guanling formation (T2g3) and upper of Yongningzhen formation (T1yn4). Heavily saturated carbon was observed from shallow groundwater, which presented similar distribution to those from rocks, especially from the deeper groundwater. These results indicated that the high concentrations of original hydrocarbon in groundwater could be due to the hydrocarbon release from corrosion and extraction out of strata over time.

Polycyclic aromatic hydrocarbons (PAHs) in multimedia environment of Heshan coal district, Guangxi: distribution, source diagnosis and health risk assessment.

Mining activities are among the major culprits of the wide occurrences of soil and water pollution by PAHs in coal district, which have resulted in ecological fragilities and health risk for local residents. Sixteen PAHs in multimedia environment from the Heshan coal district of Guangxi, South China, were measured, aiming to investigate the contamination level, distribution and possible sources and to estimate the potential health risks of PAHs. The average concentrations of 16 PAHs in the coal, coal gangue, soil, surface water and groundwater were 5114.56, 4551.10, 1280.12 ng g(-1), 426.98 and 381.20 ng L(-1), respectively. Additionally, higher soil and water PAH concentrations were detected in the vicinities of coal or coal gangue dump. Composition analysis, isomeric ratio, Pearson correlation analysis and principal component analysis were performed to diagnose the potential sources of PAHs in different environmental matrices, suggesting the dominant inputs of PAHs from coal/coal combustion and coal gangue in the soil and water. Soil and water guidelines and the incremental lifetime risk (ICLR) were used to assess the health risk, showing that soil and water were heavily contaminated by PAHs, and mean ICLRcoal/coal-gangue and mean ICLRsoil were both significantly higher than the acceptable levels (1 × 10(-4)), posing high potential carcinogenic risk to residents, especially coal workers. This study highlights the environmental pollution problems and public health concerns of coal mining, particularly the potential occupational health hazards of coal miners exposed in Heshan.

Distribution Characteristics, Concentrations, and Sources of Cd and Pb in Laoxiawan Channel Sediments from Zhuzhou, China.

Twenty sediment cores encompassing surface (0-20 cm) and deeper (50-60 cm) sediment layers were retrieved from the 3000 m-long Laoxiawan Channel, which receives industrial effluents from Zhuzhou City (China). Analytical results showed that cadmium (Cd) concentrations ranged between 115.7-1126.7 and 108.8-2059.3 mg/kg while lead (Pb) values ranged between 234-3000 and 145-4292 mg/kg in the surface and bottom sediments, respectively. The results also indicated that high levels of Cd and Pb were present in the vicinity of the channel mouth and confluence area. Indices for potential ecological risk and geo-accumulation were used to evaluate the environmental effects and intensity of heavy metal pollution over time. High concentrations of Cd and Pb in the bottom sediments of Laoxiawan Channel were mainly associated with wastewater discharge (10(6) m(3)/year). Thus, the Laoxiawan Channel may be an important metal contaminant source for the Xiang River.

Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications.

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), the sum of dicofol and 4,4'-dichlorobenzophenone (p,p'-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, ß-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and ß-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p'-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p'-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p'-DDNU→p,p'-DBP, whereas the amount of p,p'-DDMU converted from p,p'-DDD and p,p'-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

[Occurrence and Risk Assessment of N-nitrosamines and Their Precursors in Qingjiang River Basin].

N-nitrosamines are a type of nitrogen-containing organic pollutant with high carcinogenicity and mutagenicity. In the main drinking water sources of small and medium-sized towns in China, the contamination levels of N-nitrosamines remain unclear. In addition, there is still lack of research on the concentration of N-nitrosamines and their precursors in tributary rivers. In this study, eight N-nitrosamines and their formation potentials （FPs） were investigated in the Qingjiang River, which is a primary tributary of the Yangtze River. The sewage discharge sites were also monitored, and the environmental influencing factors, carcinogenic and ecological risks caused by N-nitrosamines, and their precursors were evaluated. The results showed that six N-nitrosamines were detected in water samples of the Qingjiang River, among which NDMA [（10 ±15） ng·L-1], NDEA [（9.3 ±9.3） ng·L-1], and NDBA [（14 ±7.8） ng·L-1] were the dominant N-nitrosamines, whereas seven N-nitrosamines were detected in chloraminated water samples, among which NDMA-FP [（46 ±21） ng·L-1], NDEA-FP [（26 ±8.3） ng·L-1], and NDBA-FP [（22 ±13） ng·L-1] were the dominant N-nitrosamine FPs. The concentrations of N-nitrosamines in the middle reaches of the Qingjiang River were higher than those in the upper and lower reaches. Furthermore, the concentrations of N-nitrosamines in the sample sites of sewage discharge and tributaries were significantly higher than those in other sampling sites. The monitoring results at the direct sewage discharge points indicated that the main source of N-nitrosamines in river water was the sewage carrying N-nitrosamines and their precursors. In addition, the concentrations of the three dominant N-nitrosamines including NDMA, NDBA, and NDEA were positively correlated with each other, mainly because of their similar sewage sources. The average carcinogenic risk to residents due to N-nitrosamine in drinking water sources was 2.4×10-5, indicating a potential carcinogenic risk. Moreover, due to the high concentrations of N-nitrosamine formation potentials in the Qingjiang River, the carcinogenic risk of drinking water may be even higher. The ecological risk assessment showed that the ecological risk quotient values of N-nitrosamines in the Qingjiang River watershed were lower than 0.002, which was negligible.

Impact of agricultural activities on the occurrence of N-nitrosamines in an aquatic environment.

N-Nitrosamines, nitroso compounds with strong carcinogenic effects on humans, have been frequently detected in natural waters. In agricultural areas, there is typically a lack of drinking water treatment processes and distribution systems. As a result, residents often consume groundwater as drinking water which may contain N-nitrosamines, necessitating the investigation of the occurrence, sources, and carcinogenic risk of N-nitrosamines within the groundwater of agricultural areas. This study identified eight N-nitrosamines in groundwater and river water in the Jianghan Plain, a famous agricultural region in central China. N-Nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosomorpholine (NMOR), N-nitrosopyrrolidine (NPYR), and N-nitrosodi-n-butylamine (NDBA) were detected in groundwater, with NDMA being the main compound detected (up to 52 ng L-1). Comparable concentrations of these N-nitrosamines were also found in river water. From laboratory experiments, we found a tremendous potential for the formation of N-nitrosamines in groundwater. Principal component analysis and multiple linear regression analysis results showed that the primary sources of N-nitrosamines in groundwater were the uses of nitrogen fertilizers and pesticides carrying specific N-nitrosamines such as NPYR. The average total carcinogenic risk values of detected N-nitrosamines were higher than the acceptable risk level (10-5), suggesting a potential carcinogenic risk of groundwater. Further research is urgently needed to minimize N-nitrosamine levels in the groundwater of agricultural areas, particularly in those where pesticides and fertilizers are heavily used.

N-nitrosamines in electroplating and printing/dyeing industrial wastewater treatment plants: Removal efficiency, environmental emission, and the influence on drinking water.

The discharge of industrial wastewater containing high concentrations of N-nitrosamines to the aquatic environment can impair downstream source waters and pose potential risks to human health. However, the transport and fate of N-nitrosamines in typical industrial wastewater treatment plants (IWWTPs) and the influence of these effluents on source water and drinking water are still unclear. This study investigated nine N-nitrosamines in four full-scale electroplating (E-) and printing/dyeing (PD-) IWWTPs, two drinking water treatment plants (DWTPs) in the lower reaches of these IWWTPs, and the corresponding tap water in South China. The total concentrations of N-nitrosamines (∑NAs) were 382-10,600, 480-1920, 494-789, and 27.9-427 ng/L in influents, effluents, source water, and tap water, respectively. The compositions of N-nitrosamine species in different influents varied a lot, while N-nitrosodi-n-butylamine (NDBA) and N-nitrosodimethylamine (NDMA) dominated in most of the effluents, source water, and tap water. More than 70 % N-nitrosamines were removed by wastewater treatment processes used in E-IWWTPs such as ferric-carbon micro-electrolysis (Fe/C-ME), while only about 50 % of N-nitrosamines were removed in PD-IWWTPs due to the use of chlorine reagent or other inefficient conventional processes such as flocculation by cationic amine-based polymers or bio-contact oxidation. Therefore, the mass fluxes of N-nitrosamines discharged from these industrial wastewaters to the environment in the selected two industrial towns were up to 14,700 mg/day. The results based on correlation and principal component analysis significantly demonstrated correlations between E-and PD-effluents and source water and tap water, suggesting that these effluents can serve as sources of N-nitrosamines to local drinking water systems. This study suggests that N-nitrosamines are prevalent in typical IWWTPs, which may infect drinking water systems. The findings of this study provide a basis data for the scientific evaluation of environmental processes of N-nitrosamines.

Occurrence and fate of N-nitrosamines in full-scale domestic wastewater treatment plants and their impact on receiving waters along the Lijiang River, China.

Domestic wastewaters contaminated with N-nitrosamines pose a significant threat to river ecosystems worldwide, particularly in urban areas with riparian cities. Despite widespread concern, the precise impact of these contaminants on receiving river waters remains uncertain. This study investigated eight N-nitrosamines in wastewater treatment plants (WWTPs) and their adjacent receiving river, the Lijiang River in Guilin City, Southwest China. By analyzing thirty wastewater samples from five full-scale WWTPs and twenty-three river water samples from Guilin, we quantified the mass loads of N-nitrosamines discharged into the surrounding watershed via domestic effluents. The results revealed that N-nitrosodimethylamine (10-60 ng/L), N-nitrosodiethylamine (3.4-22 ng/L), and N-nitrosopyrrolidine (not detected-4.5 ng/g) were predominant in influents, effluents, and sludge, respectively, with the overall removal efficiencies ranging from 17.7 to 65.6% during wastewater treatment. Cyclic activated sludge system and ultraviolet disinfection were effective in removing N-nitrosamines (rates of 59.6% and 24.3%), while chlorine dioxide disinfection promoted their formation. A total of 30.4 g/day of N-nitrosamine mass loads were observed in the Lijiang River water, with domestic effluents contributing about 31.3% (19.4 g/day), followed by livestock breeding wastewater (34.5%, 12.0 g/day), and unknown sources (24.7%, 7.5 g/day). These findings highlight the critical role of WWTPs in transporting N-nitrosamines to watersheds and emphasize the urgent need for further investigation into other potential sources of N-nitrosamine pollution within watersheds.

Screening and optimization of interpolation methods for mapping soil-borne polychlorinated biphenyls.

There is yet no scientific consensus, and for now, on how to choose the optimal interpolation method and its parameters for mapping soil-borne organic pollutants. Take the polychlorinated biphenyls (PCBs) for instance, we present the comparison of some classic interpolation methods using a high-resolution soil monitoring database. The results showed that empirical Bayesian kriging (EBK) has the highest accuracy for predicting the total PCB concentration, while root mean squared error (RMSE) in inverse distance weighting (IDW) is among the highest in these interpolation methods. The logarithmic transformation of non-normally distributed data contributed to enhance considerably the semivariogram for modeling in kriging interpolation. The increasing of search neighborhood reduced IDW's RMSE, but slightly affected in ordinary kriging (OK), while both of them resulted in over smooth of prediction map. The existence of outliers made the difference between two points increase sharply, and thereby weakening spatial autocorrelation and decreasing the accuracy. As predicted error increased continuously, the prediction accuracy of different interpolation methods reached unanimity gradually. The attempt of the assisted interpolation algorithm did not significantly improve the prediction accuracy of the IDW method. This study constructed a standardized workflow for interpolation, which could reduce human error to reach higher interpolation accuracy for mapping soil-borne PCBs.

Occurrence and mass loads of N-nitrosamines discharged from different anthropogenic activities in Desheng River, South China.

N-nitrosamines are widespread in various bodies of water, which is of great concern due to their carcinogenic risks and harmful mutagenic effects. Livestock rearing, domestic, agricultural, and industrial wastewaters are the main sources of N-nitrosamines in environmental water. However, information on the amount of N-nitrosamines these different wastewaters contribute to environmental water is scarce. Here, we investigated eight N-nitrosamines and assessed their mass loadings in the Desheng River to quantify the contributions discharged from different anthropogenic activities. N-nitrosodimethylamine (NDMA) (< 1.6-18 ng/L), N-nitrosomethylethylamine (NMEA) (< 2.2 ng/L), N-nitrosodiethylamine (NDEA) (< 1.7-2.4 ng/L), N-nitrosopyrrolidine (NPYR) (< 1.8-18 ng/L), N-nitrosomorpholine (NMOR) (< 2.0-3.5 ng/L), N-nitrosopiperidine (NPIP) (< 2.2-2.5 ng/L), and N-nitrosodi-n-butylamine (NDBA) (< 3.3-16 ng/L) were detected. NDMA and NDBA were the dominant compounds contributing 89% and 92% to the total N-nitrosamine concentrations. The mean cumulative concentrations of N-nitrosamines in the livestock rearing area (26 ± 11 ng/L) and industrial area (24 ± 4.8 ng/L) were higher than those in the residential area (16 ± 6.3 ng/L) and farmland area (15 ± 5.1 ng/L). The mean concentration of N-nitrosamines in the tributaries (22 ng/L) was slightly higher than that in the mainstem (17 ng/L), probably due to the dilution effect of the mainstem. However, the mass loading assessment based on the river's flow and water concentrations suggested the negligible mass emission of N-nitrosamines into the mainstem from tributaries, which could be due to the small water flow of tributaries. The average mass loads of N-nitrosamines discharged into the mainstem were ranked as the livestock rearing area (742.7 g/d), industrial area (558.6 g/d), farmland area (93.9 g/d), and residential areas (83.2 g/d). In the livestock rearing, residential, and industrial area, NDMA (60.9%, 53.6%, and 46.7%) and NDBA (34.6%, 33.3%, and 44.9%) contributed the most mass loads; NDMA (23.4%), NDEA (15.8%), NPYR (10.1%), NPIP (12.8%), and NDBA (37.8%) contributed almost all the mass loads in the farmland area. Photodegradation amounts of NDMA (0.65 ~ 5.25 µg/(m3·day)), NDBA (0.37 ~ 0.91 µg/(m3·day)), and NDEA (0 ~ 0.66 µg/(m3·day)) were also calculated according to the mass loading. Quantifying the contribution of different anthropogenic activities to the river will provide important information for regional river water quality protection. Risk quotient (RQ) values showed the negligible ecological risks for fish, daphnid, and green algae.

Occurrence and transport of N-nitrosamines in the urban water systems of the Pearl River Delta, southern China.

The discharge of substantial amounts of N-nitrosamines-contained wastewater into receiving rivers can significantly deteriorate water quality, as these carcinogenic compounds can be easily transported into groundwater and drinking water systems. This study investigated the distribution of eight species of N-nitrosamines in river water, groundwater, and tap water located in the center of the Pearl River Delta (PRD), China. The results showed that three major N-nitrosamines, including N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosodibutylamine (NDBA), with concentrations of up to 64 ng/L, were observed in river water, groundwater, and tap water, whereas the other compounds occurred sporadically. In river water and groundwater, high concentrations of NDMA, NDEA, N-nitrosomorpholine (NMOR), and NDBA were found in industrial and residential lands as compared to agricultural lands owing to the influence of various human activities. The primary sources of N-nitrosamines in river water were industrial and domestic wastewater, and the infiltration of river water was responsible for the high levels of N-nitrosamines in groundwater. Among the target N-nitrosamines, NDEA and NMOR with long biodegradation half-lives (>4 days) and low LogKow values (<1) displayed the highest potential for groundwater. N-nitrosamines in groundwater and tap water pose significant potential cancer risks to residents, especially children, and juveniles, with lifetime cancer risks of over 10-4, necessitating advanced water treatments for drinking water and critical controls on primary industrial discharge in urban areas.

Occurrence of microplastics in the seawater and atmosphere of the South China Sea: Pollution patterns and interrelationship.

Microplastic (MP) pollution is a serious global environmental problem, particularly in marine ecosystems. However, the pollution patterns of MPs in the ocean and atmosphere, particularly the sea-air interrelationship, remain unclear. Therefore, the abundance, distribution patterns, and sources of MPs in the seawater and atmosphere of the South China Sea (SCS) were comparatively investigated. The results showed that MPs were prevalent in the SCS with an average abundance of 103.4 ± 98.3 items/m3 in the seawater and 4.62 ± 3.60 items/100 m3 in the atmosphere. The spatial analysis indicated that the pollution patterns of seawater MPs were mainly determined by land-based discharge and sea surface currents, whereas atmospheric MPs were predominantly determined by air parcel trajectory and wind conditions. The highest MP abundance of 490 items/m3 in seawater was found at a station near Vietnam with current vortices. However, the highest MP abundance of 14.6 items/100 m3 in the atmosphere was found in air parcels with low-speed southerly winds from Malaysia. Similar MP compositions (e.g., polyethylene terephthalate, polystyrene, and polyethylene) were observed in the two environmental compartments. Furthermore, similar MP characteristics (e.g., shape, color, and size) in the seawater and atmosphere of the same region suggested a close relationship between the MPs in the two compartments. For this purpose, cluster analysis and calculation of the MP diversity integrated index were performed. The results showed an obvious dispersion between the two compartment clusters and a higher diversity integrated index of MPs in seawater than in the atmosphere, thus implying higher compositional diversity and more complex sources of MPs in seawater relative to the atmosphere. These findings deepen our understanding of MP fate and patterns in the semi-enclosed marginal sea environment and highlight the potential interrelationship of MPs in the air-sea system.

Sedimentary records of persistent organic pollutants (OCPs and PCBs) in Ngoring Lake, the central Tibetan Plateau, China: Impacts of westerly atmospheric transport and cryospheric melting.

Lake sediments in remote alpine regions are used to infer information on persistent organic pollutants (POPs) delivery via long-range atmospheric transport (LRAT) with limited influences from local sources. When studying the deposition history of POPs on the Tibetan Plateau, regions influenced by westerly air mass flow have received insufficient attention compared with regions governed by the monsoon. Herein, we collected and dated two sediment cores from Ngoring Lake to reconstruct the depositional time trends of 24 organochlorine pesticides (OCPs) and 40 polychlorinated biphenyls (PCBs) and assess the response to emission reductions and climate change. DDTs, HCHs, hexachlorobenzene (HCB), and PCBs were all detected in the sediment core at low concentrations of 110-600, 4.3-400, 8.1-60, and 3.3-71 pg/g, respectively. The composition of PCBs, DDTs, and HCHs was dominated by congeners with 3 and 4 chlorines (avg. 70 %), p,p'-DDT (avg. 90 %), and ß-HCH (avg. 70 %), respectively, indicating the influence of LRAT and the contribution of technical DDT and technical HCH from potential source regions. Temporal trends of PCB concentrations normalized by total organic carbon echoed the peak of global emissions of PCBs around 1970. The rising trend of concentrations of ß-HCH and DDTs after the 1960s in sediments was mainly explained by the input of contaminants with melting ice and snow from a cryosphere shrinking under global warming. This study verifies that westerly air mass flow brings fewer contaminants to the lacustrine environment on the Tibetan Plateau than the monsoon and demonstrates the impacts of climate change on the secondary emission of POPs from the cryosphere to the sediments.

Comparison of atmospheric polycyclic aromatic hydrocarbons (PAHs) over six years at a CAWNET background site in central China: Changes of seasonal variations and potential sources.

Total suspended particles (TSP) and gaseous samples were collected by using a high-volume sampler from March 2012 to March 2013 and January 2018 to January 2019 at a background site (Jinsha, JSH) in central China to study the chemical characteristics, seasonal variations, and potential sources of polycyclic aromatic hydrocarbons (PAHs). The average concentrations of ∑15PAHs were 24.55 ± 9.19 ng m-3 in 2012/2013 and 20.98 ± 9.77 ng m-3 in 2018/2019. Low-ring PAHs were more concentrated in gas phase while high-ring PAHs were prone into particle phase. The concentrations of PAHs in the two sampling years were high in winter but low in summer and autumn. The relationships between the gas concentrations of PAHs and temperature indicated that most PAHs were influenced by long-range atmospheric transport (LRAT) in 2012/2013 and in 2018/2019, excluding anthracene (Ant) and pyrene (Pyr) were partially affected by air-surface re-volatilization in 2012/2013. The source of atmospheric PAHs at JSH was similar in 2012/2013 and 2018/2019,which was mainly due to the LRAT of PAHs emitted from biomass/fossil fuel combustion in the northern area of JSH. From 2012/2013 to 2018/2019, there was no significant difference between the concentrations of PAHs in spring and winter, whereas the concentrations of PAHs decreased from 2012/2013 to 2018/2019 in summer. In all, the control of PAHs at the source region was partially effective from 2012/2013 to 2018/2019.

Organochlorine Pesticides in Karst Soil: Levels, Distribution, and Source Diagnosis.

Excessive reclamation and improper use of agrochemicals in karst areas leads to serious non-point source pollution, which is of great concern and needs to be controlled, since contaminants can easily pollute groundwater due to the thin patchy soil and developed karst structures. The occurrences of organochlorine pesticides (OCPs) in karst soil were investigated by analyzing 25 OCPs in the karst soils near the Three Gorges Dam, China. The total concentrations of OCPs ranged 161-43,100 (6410 ± 9620) pg/g, with the most abundant compounds being p,p'-DDT and mirex. The concentration differences between the orchard and vegetable field and between upstream and downstream presented the influences of land-use type and water transport on the OCP spatial distributions. Composition analysis indicated the possible fresh inputs of lindane, technical DDT, aldrin, endrin, mirex, and methoxychlor. Their illegal uses implied an insufficient agrochemical management system in undeveloped karst areas. Principal component analysis with multiple linear regression analysis characterized the dominant sources from current agricultural use and current veterinary use in the study area. OCPs in the soils might not pose significant cancer risk for the residents, but they need to be controlled due to their illegal uses and bioaccumulation effect via the food chain.