[Characteristics of Water Environment and Its Influencing Factors in Zhari Namco Basin, Xizang].

Zhari Namco is situated in the alpine grassland belt of northwestern Xizang with a fragile ecological environment. As the third-largest lake in Xizang, there has been a long-term lack of research data concerning its basin water environment. In an effort to elucidate the surface water environment characteristics of the basin and the factors influencing them, an extensive investigation was conducted from August 2021 to June 2022, encompassing periods of high flow, low flow, and base flow. Further, the study also involved comprehensive assessments of the water chemistry characteristics and spatial-temporal variation in lake sampling sites of the basin that were not significant by using mathematical statistics, hydrochemical analysis, correlation analysis, and principal component analysis. The findings revealed the following： ① The water in the Zhari Namco Basin exhibited an alkaline nature, with dominant ionic compositions in the lake comprising Na+, SO42-, and Cl-, whereas the rivers were primarily characterized by Ca2+, HCO3-, and SO42-. ② The main pollutants exceeding established standards included sulfates, arsenic, chlorides, and total phosphorus. The study identified significant spatiotemporal variations in water quality. Temporally, the exceedance of sulfates, arsenic, and total phosphorus was most pronounced during high-flow periods, followed by that during low-flow and base flow periods, with chloride levels showing less temporal variation. Spatially, river water quality surpassed that of the lakes, with arsenic, total phosphorus, TDS, sulfate, chloride, K+, and Na+ concentrations in lakes 1 to 2 orders of magnitude higher than those in rivers. Water qualities exceeding the established standard were primarily found in the lake, with less spatial variations within the lake itself. ③ Hydrochemical processes within the basin were found to be primarily influenced by natural phenomena, including evaporation-concentration and rock weathering. Various elements entered the lakes via surface runoff, where they continuously accumulated under the influence of evaporation-concentration processes, ultimately leading to exceedances. ④ Temporal variations in water quality were primarily attributed to increased elemental loss and intensified evaporation during high-flow periods. The spatial discrepancies in water quality were predominantly a consequence of the differing hydrodynamic conditions between flowing water bodies and enclosed water bodies.

[Spatial Characteristics and Ecological Risks of Perfluoroalkyl Substances in Coastal Urbanized Areas of China and South Korea].

This study concentrated on the 15 perfluoroalkyl substances (PFASs) in the coastal areas of China and South Korea, an urbanized area with intensive human activities. In total, 126 water samples and 125 sediment samples were collected and determined by HPLC-MS/MS. Fifteen PFASs were detected at least once in all the sites. The total concentrations of PFASs in water and sediment samples ranged from 6.75 ng·L-1 to 20982 ng·L-1 and from 0.229 ng·g-1 to 53.8 ng·g-1 (dw), respectively. The concentrations of PFASs in waters and sediments were relatively high in China, and PFOA was the predominant PFAS. In contrast, short chain compounds such as PFBA and PFPeA played a major role in water, and PFOS, PFBA, and PFOA dominated the sediment samples in South Korea. The partition coefficients of PFASs were closely related to the fraction of organic carbon in the sediment and the carbon chain length of PFASs. Among the 15 compounds, the partition coefficients of 9 were significantly correlated with the fraction of organic carbon (r>0.21, P<0.05), and the partition coefficient steadily increased with the increase of the carbon chain length. The results of ecological risk assessment suggested that the coastal urbanized areas of China and South Korea are still at a low risk. However, some specific areas also showed PFAS pollution. More attention should be paid to the potential health risks.

[Spatio-temporal Variations in the Characteristics of Water Eutrophication and Sediment Pollution in Baiyangdian Lake].

Since the establishment of Xiong'an New District, a series of comprehensive pollution control measures have been implemented in Baiyangdian Lake. To evaluate the pollution status and identify the main sources of pollution of Baiyangdian Lake, 30 water samples and 29 sediment samples were collected in the lake. Five water quality indexes (i.e., concentrations of chemical oxygen demand, total phosphorus (TP), total nitrogen (TN), NH4+-N, and chlorophyll-a) and three sediment quality indexes (i.e., concentrations of TN, TP, and heavy metals) were measured. Along with historical monitoring data, the spatio-temporal pollution characteristics and their influencing factors in Baiyangdian Lake were analyzed. The results show that the Baiyangdian Lake water is eutrophicated. Of the 30 sampling sites, 8 are "mildly eutrophicated" (accounting for 26.7%), 16 are "moderately eutrophicated" (accounting for 53.3%), and 6 are "severely eutrophicated" (accounting for 20%). Compared with the periods between 1991 and 2017, the water quality of most sampling sites, especially in the northern parts, has improved a lot. This shows that the pollution control measures have basically curbed the gradually increasing trend of pollution in the waterbody. The nutritive pollution in sediment is severe. The concentrations of TN are between 1483.7 and 14234.1 mg·kg-1, with a mean value of 5054.9 mg·kg-1, and the concentration coefficient variation in different sites is as high as 46.5%. The concentrations of TP are between 360.3 and 1964.4 mg·kg-1, with a mean value of 925.4 mg·kg-1, and the concentration coefficient variation in different sites is 25.7%. Geoaccumulation index calculation shows that the mean Igeo value of heavy metals in sediments is less than 1, which indicates cleanness or slight pollution. The main contributions to heavy metal pollution are Cd, Zn, and Cu. Regarding ecological risk of heavy metals, only some sites (i.e., L3, L21, L28, and L29) are at high and very high risk level, while the remaining sites are at moderate risk level. Overall, the pollution of Baiyangdian Lake changes from the northern part to the southern part, and the main influencing factors also change from external pollution to endogenous pollution caused by the discharge of villages in the lake and the sediments.

[Spatial Distribution and Risk Assessment of Heavy Metals in Soils from a Typical Urbanized Area].

With the rapid urbanization in China, soil environments are facing high risks. Taking a typical urbanized area as a case study, a total of 106 surface soil samples (0-20 cm) and 96 subsurface soil samples (20-40 cm) were collected to determine the concentrations of heavy metals, and then, the Nemerow index and Hankson index methods were used to evaluate their degrees of ecological risk. The spatial distributions of ecological risks were also explored. Experimental results showed that the concentrations of Cr, Ni, Cu, Zn, As, Cd, Pb, and Hg in surface soil samples were 2.87-84.64, 1.40-56.00, 2.75-125.05, 15.05-201.39, 1.46-89.92, 0.001-0.92, 15.29-160.07, and 0.006-0.52 mg·kg-1, respectively, and those in subsurface soil samples were 3.56-75.14, 1.65-71.58, 3.28-290.04, 17.99-296.94, 3.07-65.67, 0.02-1.00, 11.10-97.59, and 0.01-0.41 mg·kg-1, respectively. According to the risk control standards for soil contamination of agricultural land, approximately 71.70%, 40.57%, 4.72%, 3.77%, and 0.94% of Cd, Cu, Pb, As, and Zn, respectively, in the surface soil samples exceeded the standards, while 72.92%, 39.58%, 6.25%, 3.13%, 3.13%, and 1.04% of Cd, Cu, As, Zn, Pb, and Ni, respectively, in the subsurface soil samples exceeded the standards. Obviously, the pollution by Cd and Cu was the most severe in the research area, and the main contaminated areas were distributed in the northern part of the land. The soil environmental quality pollution assessment illustrated that high risk areas were distributed in the northern part of the research area too. The risk assessment results indicated that the main pollution factor was Cd, which is accordance with the serious pollution findings for Cd. In response to these results, effective management and remediation methods should be taken to control the soil environment pollution in this typical urbanized area.

[Risk Assessment and Risk Management of Chemicals in China].

Risk assessment and risk management have been increasingly approved as an effective approach for appropriate disposal and scientific management of chemicals. This study systematically analyzed the risk assessment methods of chemicals from three aspects including health risk, ecological risk and regional risk. Based on the current situation of classification and management towards chemicals in China, a specific framework of risk management on chemicals was proposed by selecting target chemicals, predominant industries and related stakeholders as the objects. The results of the present study will provide scientific support for improving risk assessment and reasonable management of chemicals in China.