Phosphorus pollution still not under control in Lake Taihu
In local folklore, the shimmering and crystal clear Lake Taihu came into being after a silver basin was dropped from the heavenly palace. However, since China’s start of the reform and opening up, the view was not longer that enticing as intensive farming and rapid urbanization in its basin quickly deteriorates its water quality.
Although efforts to clean up the lake has never stopped in the recent past, eutrophication keeps haunting the Lake. As surface runoffs usually carry in large amounts of excessive nutrients, they would make lakes eutrophic, which would be a favorable condition for algae and other plankton. The rapid and massive reproduction of plankton and degradation of the algae after their death, also known as algae blooms, could deplete oxygen in the water, making it hypoxic, which in turn causes the death of other organisms and the deterioration of water quality. Phosphorus is the most important element in this process, so controlling its concentration in lakes is the key to solving eutrophication issues. The phosphorus concentration of Taihu Lake is dependent on the phosphorus entering and leaving the Lake, the phosphorus exchange between lake water and sediments, and the absorption and decomposition of phosphorus by aquatic organisms. At present stage, controlling and reducing external-sourced phosphorus is one of the keys.
Li et al (2021) estimated the total phosphorus loading in rivers entering and leaving the Lake between 2012 and 2018, and calculated its annual average concentration by weighing flow volumes. By looking at changes in flow volumes and pollutants in different parts of the Lake, the study wants to explore the relationship between total phosphorus loading, volumes of inflows, and phosphorus concentrations. The results of the study find that: (1) In recent years, total phosphorus concentration and loading in rivers draining into the Lake are significantly higher than those discharging from it, indicating poor water quality of inflows. (2) By concentration of phosphorus, water quality in the southwest and northwest parts of the Lake is significantly worse than that in the east and southeast. Total phosphorus concentration in the west part of the lake accounts the largest proportion, which could be as high as 67%. (3) The concentration of phosphorus entering the lake from its west, which has the largest total phosphorus loading, was not effectively controlled in the past 7 years.
- Li Qiongfang, Xu Shuhong, Chen Qihui, Jia Xiaowang, Yan Fangjia, Zhu Yuting, Lin Peng, Gao Yun. Analysis of changes in total phosphorus concentration and load of rivers entering and exiting the lake in various water resources subregions around Taihu Lake[J/OL]. Lake Science :1-17[2021-10-29]. http://kns.cnki.net/kcms/detail/32.1331.P.20210901.1141.002.html (in Chinese).