Eutrophication causes analysis under the influencing of anthropogenic activities in China's largest fresh water lake (Poyang Lake): Evidence from hydrogeochemistry and reverse simulation methods

Abstract

Human activities have become one of the vital influence factors resulting in eutrophication in the large fresh water lake. However, few studies have been conducted in a large fresh water lake basin to research the influence of industrial and agricultural activities on lake eutrophication through a systematic hydrogeochemical perspective. In this study, 36 samplings were collected in dry and wet season from 2017 to 2018 in China’s largest fresh water lake (Poyang Lake). Hydrogeochemical methods (comprehensive trophic level index, entropy-weighted water quality index, ion ratio coefficient, land use/cover change analysis) and hydrogeochemical reverse simulation were used to investigate the anthropogenic causes of lake eutrophication. The results showed that the trophic level index of Poyang Lake increased from 46.08 to 56.38 and achieved the light eutropher level. Ion ratio coefficient analysis revealed the influence of industrial sewage, manure input and agricultural input on the lake. Reverse simulation results showed the urea increased 5.244e-5 mmol/l and the calcium superphosphate decreased 1.554e-8 mmol/l in dry season. While the urea decreased 3.719e-5 mmol/l and the calcium superphosphate decreased 5.381e-7 mmol/l in wet season. Additionally, the cultivated land and construction land area increased 74.4 km2 and 46.31 km2 from 2017 to 2018, which aggravated the eutrophication. TN/TP also affected water quality in Poyang Lake. These results will be helpful to reveal the anthropogenic influence on eutrophication in large fresh water lakes so that put forward targeted treatment measures. Providing the reference for water resources utilization and pollution control in the similar large fresh water lakes.