Cross-sectional observations of algal MCYST pollution and source water pollution index changes in Dianshan Lake, Shanghai

Abstract

Abstract Background: Dianshan Lake is the largest freshwater lake in Shanghai and is the major water source for the Upper Huangpu River, which supplies raw water for the Jinze reservoir. In this continuously monitored study, we tested the water quality in Dianshan Lake to understand the main water pollution indicators and the status of algal toxins, and to evaluate the water quality of Dianshan Lake. Methods: We collected water samples from each 5 monitoring points in Dianshan Lake every month in 2021. Test methods followed the national standards of China , detection of MCRR and MCCR by high performance liquid chromatography combined with mass spectrometry. calculating the Carlson index to assess eutrophication. Also, we collected 10 kinds of aquatic organisms and examined them for the algal toxins once a month. We selected healthy human volunteers for experiment in which we sampled fasting venous blood from each individual in both observation and control groups to measure impaired renal function. Results: All seasonal conditions, including the high water, flat water, and dry periods, were represented in the 600 water samples taken from Dianshan Lake in 2021. The permanganate index (CODMn) fell within the Chinese national surface water quality standard III, while total nitrogen and total phosphorus did not meet surface water standards. According to the Carlson index, Dianshan Lake exhibited moderate eutrophication. MC-LR was the dominant toxin in the high temperature season while algal toxins. In June through August, MC-RR was extremely abundant while MC-LR dominated in July through October. In the aquatic organisms, both MC-LR and MC-RR were detected in every month’s samples. The levels of toxins in the human study differed significantly between the observation group and the control group. Individuals in the observation group exhibited renal function injury。 Conclusion: Dianshan Lake water exhibits eutrophication. We found both MC-LR and MC-RR in aquatic organisms. In our experiment, indicating that long-term exposure to the polluted water may cause a health risk.