洞庭湖近20年水质与富营养化状态变化

利用近20年水质监测资料,系统地分析了洞庭湖水质与营养状态的时空变化特征. 结果表明,受流域社会经济发展等因素的综合影响,洞庭湖水质整体呈下降趋势,水体富营养化日趋严重,东洞庭湖的富营养程度稍高于西洞庭湖和南洞庭湖. 洞庭湖水体主要污染物为TN和TP, ρ(TN)、ρ(TP)年均值分别为1.08~1.93和0.026~0.203 mg/L. 洞庭湖水体中ρ(Chla)与ρ(TN)呈显著正相关；浮游植物数量与ρ(TN)、ρ(TP)呈显著正相关,与最大流量呈显著负相关. 2007年洞庭湖流域造纸企业污染整治后,洞庭湖水体中ρ(COD_Cr)降低,但ρ(TN)、ρ(TP)仍呈上升之势,浮游植物数量显著增加. 洞庭湖水体富营养化治理应以控制面源污染为重点. 

Changes of Water Quality and Eutrophic State in Recent 20 Years of Dongting Lake

Temporal and spatial trends of water quality and eutrophic level in Dongting Lake were analyzed using monitoring data for recent 20 years. The results showed that, by the combined effects of the socioeconomic development, water quality deteriorated with eutrophication, and the eutrophic level in the east Dongting Lake was more serious than that in the west and the south Dongting Lake. Total nitrogen and total phosphorus were the major pollutants in the lake. The annual average contents of these two pollutants varied from 1.08 to 1.93 mg/L and from 0.026 to 0.203 mg/L, respectively. A significantly positive relationship between the concentration of chlorophyll a and the total nitrogen was found in the water phase. Phytoplankton quantity was positively related to the total nitrogen and the total phosphorus, and was negatively related to the maximum water flow. Although chemical oxygen demand in the water phase decreased after remediation of the paper-making enterprises in 2007, concentrations of the total nitrogen and the total phosphorus still showed an increasing trend, and phytoplankton abundance increased significantly. Our results suggest that eutrophication control in Dongting Lake should pay more attention to the non-point pollution.