Distribution of Bioavailable Phosphorus (BAP) in lake sediments of the middle and lower reaches of the Yangtze River

Abstract

Bioavailable Phosphorus (BAP) in sediments of Lake Taihu (6 sites) , Lake Chaohu (4 sites) and Lake Longgan (3 sites) was analyzed by chemical extraction method. The mean BAP content in north Lake Taihu was 259.5 mg/kg, 114. 6 mg/kg in west of Lake Taihu, 40. 6 mg/kg in the middle of the lake and 50. 7 mg/kg in East Lake Taihu. It was very obvious that BAP contents were higher in the north of the lake and lower in the south. The mean BAP content in the west of Lake Chaohu was 254. 2 mg/kg while was 101. 9 mg/kg in the east of the lake. The content is 67. 8 mg/kg in Lake Longgan. All these data showed the more polluted lakes (lake zones) was with higher BAP contents in the sediments. The BAP contents in the sediment cores decreased exponentially that meant the BAP would transform to non-bioavailable form with sedimentation effect. Because of the higher bioactivity in summer, the BAP was more easily transformed to soluble phosphorus and resulted in lower content in the sediment. There was positive correlation between the BAP contents in sediments and soluble reactive phosphorus ( SRP) and the correlation was better in the lakes/lake zones with lower BAP contents than in the lakes/lake zones with higher contents.