The Fluctuation of Arsenic Levels in Lake Taihu

This study was conducted to investigate the arsenic levels in the waters of lake Taihu, a huge, shallow, and very important lake which has been suffered with serious eutrophication in China. Unexpected great difference was detected for arsenic levels between the collected water samples of three successive surveys in Taihu in May 2009, Fall 2009, and May 2010, with arsenic levels in May 2009 being more than tenfold of those in Fall 2009 and May 2010. Such difference in arsenic levels do not routinely happen like seasonal changes as reported in many other lakes of the world. Considering arsenic contents as well as some basic aquatic monitoring data of the lake, such great arsenic fluctuations were probably due to the effects of strong hydraulic turbulence in Taihu for its very shallow depth. The spatial distribution of arsenic in Taihu were similar, despite great difference of arsenic levels in the three successive surveys, indicating such differences did not come from arsenic external input around the lake. The sudden increase of arsenic levels in Taihu highlights the importance of stabilization or removing of arsenic in lake sediments so as to keep arsenic lower than the national hygiene standard of China.