Hai-Chao Zhao1, Sheng-Rui Wang, Ming Zhao, Li-Xin Jiao, Bin Liu, Xiang-Can Jin. 1. State Environmental Protection Key Laboratory for Lake Pollution Control, Research Center of Lake Eco-Environment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China. haichaozhao19@163.com
Abstract
The contents of DO and nitrogen (N), phosphorus (P), chlorophyll a in water from Lake Erhai were analysed by combining the nitrogen and phosphorus forms in sediment. The results indicated that the DO contents of the water from Lake Erhai varied from 6.61 to 7.42 mg/L from 1992 to 2009, which is generally decreased. The minimum mean value was 6.42 mg/L in September. The trend of the DO contents from north to south was decreasing, and also decreased with the increasing of the water depth in Lake Erhai, the DO content was 5.15 mg/L at the water bottom. The relationship between the contents of DO and N, P was negative, and the relativity of different months was greater than that of different years. The relationship between the contents of DO and the contents of labile-P, organic-P, NH4(+) -N in sediment was negative, which was positive with the contents of Fe/Al-P, inorganic P and NO3(-) -N. The relationship between the contents of DO and chlorophyll a in water was negative, which indicated that Lake Erhai is aerobic, and is approaching anaerobic gradually. With the increasing of released content of N and P, the increasing of alga biomass was accelerated and the worsening of water body eutrophication also can be promoted by the decreased DO content in water from Lake Erhai.
The contents of DO and pan class="Chemical">nitrogen (N), pan class="Chemical">phosphorus (P), chlorophyll a in water from Lake Erhai were analysed by combining the nitrogen and phosphorus forms in sediment. The results indicated that the DO contents of the water from Lake Erhai varied from 6.61 to 7.42 mg/L from 1992 to 2009, which is generally decreased. The minimum mean value was 6.42 mg/L in September. The trend of the DO contents from north to south was decreasing, and also decreased with the increasing of the water depth in Lake Erhai, the DO content was 5.15 mg/L at the water bottom. The relationship between the contents of DO and N, P was negative, and the relativity of different months was greater than that of different years. The relationship between the contents of DO and the contents of labile-P, organic-P, NH4(+) -N in sediment was negative, which was positive with the contents of Fe/Al-P, inorganic P and NO3(-) -N. The relationship between the contents of DO and chlorophyll a in water was negative, which indicated that Lake Erhai is aerobic, and is approaching anaerobic gradually. With the increasing of released content of N and P, the increasing of alga biomass was accelerated and the worsening of water body eutrophication also can be promoted by the decreased DO content in water from Lake Erhai.