Spatio-temporal variations and ecological risks of organochlorine pesticides in surface waters of a plateau lake in China.

Qilu Lake is one of the 9 plateau lakes in Yunnan, China, with a lake surface altitude of 1796.62 m above sea level. In spite of the importance and agriculturally-intensive phenomenon in Qilu Lake Basin, few studies have provided a modern evaluation of pesticide residues and potential effects to local aquatic organisms. The primary goal of this study was to determine the spatio-temporal variations of organochlorine pesticides (OCPs) in this area, and to further assess the related ecological risks. Of the 25 OCPs analyzed, 14 were detected, and the concentrations of ∑25OCPs were highest in the upstream of rivers, followed by regions close to the lake shore, and the lowest concentrations were found in Qilu Lake in every season except winter. The concentrations of ∑25OCPs were the highest in summer, and the lowest in winter. OCP concentrations in spring and in autumn were similar. 4,4'-DDD, γ-HCH, HCB, trans-chlordane, and cis-chlordane were 5 OCPs with relatively high risk in Qilu Lake Basin. Interestingly, higher OCP concentrations do not necessarily correspond to higher ecological risk levels. Low predicted no-effect concentration (PNEC) values and relatively high toxicity of these OCPs led to their high risk quotient (RQ) values. This work further illustrated that although OCPs have been banned for many years, they were still frequently detected in surface waters, and caused risks to aquatic animals.

Polycyclic aromatic hydrocarbons in surface waters from the seven main river basins of China: Spatial distribution, source apportionment, and potential risk assessment.

In this study, we report long-term measurements of Polycyclic Aromatic Hydrocarbons (PAHs) collected from the surface waters of seven river basins across China. The spatial distribution, source apportionment, and potential risk assessment of 16 USEPA designated PAHs were reviewed. Water samples were collected from the Songhua River Basin (SRB), Yangtze River Basin (YtRB), Yellow River Basin (YRB), Pearl River Basin (PRB), Huai River Basin (HuRB), Liao River Basin (LRB), and Hai River Basin (HRB). Our results show that the total PAH concentration in the surface waters from primary river basins ranged from 99.60 to 3805.00 ng/L in the dry season with a geometric mean value of 797.96 ng/L, and from 235.84 to 11,812.20 ng/L in the wet season with a geometric mean value of 820.75 ng/L. In the river basins examined, the geometric concentration of Σ16PAHs ranged from 215.50 ng/L to 1969.91 ng/L, with a median value of 837.73 ng/L. In the decreasing order across seven river basins, the geometric mean Σ16PAHs content varied as: SRB (1969.91 ng/L) > LRB (1155.87 ng/L) > YRB (884.06 ng/L) > PRB (837.73 ng/L) > HuRB (559.10 ng/L) > HRB (261.84 ng/L) > YtRB (215.50 ng/L). Moreover, the total PAH concentration was slightly lower in the dry season than in the wet season. The pollution level of PAHs in North China was higher than in South China. No discernible temporal trend was observed in Σ16PAHs observed in China during the past decade. Overall, PAHs designated for priority control measures were Nap, Phe, and Flu; as 2- and 3-ring PAHs were the dominant compounds in the river basins, accounting for 33.7% and 36.9% of the total PAHs, respectively. Source analysis revealed that coal and biomass combustion were the main contributors to PAHs in the river basins, accounting for about 40% of the total. The geometric mean concentrations of individual PAH, including BaP, BaA, BbF, BkF, Ind, and DaA in some water samples exceeded the environmental quality standards of both China and the United States. According to metrics describing eco-toxicity from water contamination, the river basin was at moderate risk in YtRB, YRB, PRB, HuRB, and HRB, but at high risk in SRB and LRB, suggesting that targeted control measures or remedial actions should be undertaken to decrease PAH contamination in China.

Assessment of the spatial distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in urban soil of China.

Long-term (2004-2018) persistent organic pollutants (POPs) data were collected for urban soils of China. The dataset included concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in soils, comprising a range of different compounds. Understanding the source of OCP and PCB pollution is an important step in controlling and reducing pollution levels in the environment. This study aimed to analyze the spatio-temporal distribution, pollution sources, and potential health risks of OCPs and PCBs in urban soils in different regions of China. It was found that the total OCP concentrations ranged from 7.6 to 37331 µg/kg with a mean value of 2861 µg/kg, and PCBs concentrations ranged from 0.3 to 123467 µg/kg with a mean value of 4984 µg/kg. The highest OCP concentrations were observed in Beijing and Hebei, whereas the highest PCB concentrations were found in the Zhejiang province. The geographical distribution showed that the total mean concentration of POPs of urban soil was much higher in East China than in West China. According to the isomer ratios, about 64% of provinces and cities showed new sources of dichlorodiphenyltrichloroethane (DDT) input and dicofol input was found in 30% of China. Hexachlorocyclohexane (HCH) in urban soils was mainly derived from fresh usage of lindane (γ-HCH) in most regions of China. Lifetime carcinogenic and non-carcinogenic risks of OCPs and PCBs through ingestion, inhalation, and dermal contact indicated that PCBs in urban soils of China often exceeded safe levels. The total lifetime carcinogenic risk values of PCBs were higher than the individual lifetime acceptable risk level (10-4) in 64% of the studied regions and the non-carcinogenic risk values exceeded the target risk level (10-1) in 53% of the regions. The improved knowledge of the distribution and main pollution sources of POPs in urban soil of China as a result of this study can contribute to better decision-making support for soil pollution control and monitoring.