喀斯特
地下水
碳酸盐
δ18O
硝酸盐
碳酸盐岩
地质学
地球化学
水文学(农业)
中国
环境科学
稳定同位素比值
地球科学
沉积岩
化学
地理
古生物学
考古
量子力学
物理
有机化学
岩土工程
作者
Boyang Xu,Yi-Hsiu Lin,Yazun Wu,Yiyang Wang
标识
DOI:10.1016/j.scitotenv.2023.169300
摘要
Karst water as the vital water supply source is an increasingly serious problem suffering from NO3− pollution. Identifying sources and transformations is the key to effectively controlling diffuse NO3− pollution. In this study, 25 karst groundwater samples were collected from the Xujiagou karst groundwater system in June 2023, and chemical variables and stable isotopes (δ15N, δ18O, 87Sr/86Sr) were determined in different occurrence environments of carbonate rocks (exposed, covered, and buried carbonate rock areas). The results showed that the karst groundwater is dominated by nitrification. Human activities have affected the water quality of karst groundwater. The nitrate concentration ranged from 5.69 to 124.22 mg/L, and 4 % exceeds the quality indexes of class III water in China's standard for groundwater quality (20 mg/L as NO3−-N). NH4+ in fertilizer, manure and septic waste, and soil N were the main sources of nitrate pollution in the karst groundwater system. The distribution of NO3− sources is closely related to land-use types. Soil N (72.2 %) became the dominant nitrate source in the exposed area due to the small amount of urban land and the large distribution of forest and grassland. There were more cultivated land and large agricultural activities in the covered area, NH4+ in fertilizer (59.1 %) contributes the most to NO3− sources. The buried area dominated by urban land, the influence of human activities (densely population and agricultural production activities) caused the highest concentration and coefficient of variation of nitrate in this area, and manure and septic waste (64.2 %) were the most to NO3− sources. This study can provide an important scientific basis for the protection of karst groundwater, and provide theoretical support for the treatment of karst groundwater pollution sources in the “monoclinic paraclinal” strata in northern China.
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