MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(LIA-1117-689968) Natural occurrence of Microcystin and its relative environmental factors in Dianshan Lake, China.

LIAN, M¹, YU, S², DIXON, K¹, ¹ Institute of Environmental and Human Health, Texas Tech University / TTU Health Sciences Center, Lubbock, TX, USA² Fudan University School of Public Health, Shanghai, Shanghai, P.R.China

ABSTRACT- Freshwater eutrophication is an important environmental issue worldwide. As one of its secondary outcomes, waterblooms of cyanobacteria and its hepatotoxic metabolite, microcystin, are becoming threats to the safety of drinking water. Dianshan Lake is the biggest freshwater lake in the Shanghai area of China, and the source of Huangpu River that is the source of drinking water in Shanghai City. To evaluate the safety of drinking water, we investigated the natural occurrence of microcystin in Dianshan Lake. Results of the seasonal study showed that microcystin occurred mainly in summer, and the microcystin concentration was positively related to the water temperature and total phosphorus, and negatively related to water pH value, visual degree of water body, and the ratio of nitrogen-phosphorus, but not correlated with total nitrogen because of the high concentration of nitrogen throughout the year. In the second study during summer, sampling was expanded to 11 locations, 4 depths, and once every 6 hours in a day. The result showed that microcystin concentration ranged from 0 to 4817ng/L. The distribution of microcystin was significantly different between day and night, and among locations. No difference, however, was found among different depths because depth of the lake was only 2 meters. Microcystin content was highest in the morning and afternoon. It was the lowest in the southwest of the lake because of the algal movement following the southwestward wind direction. Stepwise regression analysis showed that microcystin distribution was mainly related to total phosphorus and visual degree of water body. An investigation of seven waterworks around the lake showed that microcystin concentration of source water ranged from 132 to 1865ng/L. Microcystin was detected in one waterworks in four seasons, and in two waterworks, microcystin was detected in tap water in August.

Key words: Cyanobacteria, Waterbloom, Microcystin