洞庭湖氮磷时空分布与水体营养状态特征

为揭示通江湖泊洞庭湖水体、沉积物营养盐的时空分布特征,分别于2012年1月和6月在入湖河道、湖区和出湖口共采集了13个具有代表性的水样和沉积物样品,分析了样品中氮、磷的含量及洞庭湖的营养水平. 结果表明,洞庭湖水体中ρ(TN)、ρ(TP)、ρ(NH₄+-N)和ρ(NO₃--N)全湖平均值分别为2.34、0.06、0.27和0.54mg/L,沉积物中w(TN)、w(TP)、w(NH₄+-N)、w(NO₃--N)全湖平均值分别为1220.47、678.97、28.94、4.41mg/kg. 氮、磷含量总体表现为入湖河口大于湖体和出湖口,并且入湖河流中以湘江支流较高,湖体以东洞庭湖区较高. 不同季节间的对比表明,水和沉积物样品中氮、磷含量均表现为6月高于1月,尤其水体中ρ(TN),6月显著高于1月(P<0.01). 洞庭湖全湖TLI(∑)(综合营养状态指数)平均值为45.93,分布规律与ρ(TN)、ρ(TP)一致. 与其他富营养化湖泊相比,洞庭湖ρ(TN)、ρ(TP)较高,但没有发生大面积水华,主要是因为其换水周期短、流速较大所致. 

Spatial and Temporal Distribution of Nitrogen and Phosphorus and Nutritional Characteristics of Water in Dongting Lake

In order to explore the spatial and temporal nutrient distribution characteristics of the overlying water and sediment in Dongting Lake, samples of overlying water and sediment from 13typical sites including inflow river, lake region and outflow river were collected and analyzed in January and June, 2012. The content of nitrogen and phosphorus and the trophic levels were analyzed. The results show that the average concentrations of total nitrogen (TN), total phosphorus (TP), ammonia (NH₄+-N) and nitrate (NO₃--N) in the overlying water were 2.34,0.06,0.27and 0.54mg/L, respectively. The average contents of TN, TP, NH₄+-N and NO₃--N in the sediment were 1220.47, 678.97,8.94and 4.41mg/kg, respectively. The highest concentration of phosphorus and nitrogen occurred in the estuary of the inflowing river, especially the Xiangjiang River. The average concentrations of phosphorus and nitrogen in the eastern part of Dongting Lake were higher compared with other regions of the lake. The concentrations of nitrogen and phosphorus in June part of generally higher than those in January, especially for TN in the overlying water (P<0.01). The average value of the comprehensive nutrition state index was 45.93, and its spatial and temporal distribution characteristics were similar to those of TN and TP. Compared with other eutrophic lakes, alga blooms at a large scale did not happen with relatively higher concentrations of TN and TP in the overlying water and the sediment in Dongting Lake, which could be explained by the shorter hydraulic retention time and larger water flow rate.