滇池水体和沉积物中营养盐的分布特征

Study on Nutrient Distribution of Lake Water and Sediments in Dianchi Lake

在滇池外海不同方位选取6个采样点,研究了水质现状,沉积物Eh,pH,总氮,总磷以及间隙水重金属的剖面分布特征。结果表明,滇池水体仍属富营养化状态。在氧化表层下,Eh随沉积深度的增加迅速降低,沉积物深层为还原状态。pH在沉积物剖面变化不大,为7 0～8 5。滇池沉积物含有丰富的营养物质,总氮和总磷最高质量分数分别为8 67和3 46g kg。剖面分布表明,沉积物表层总氮和总磷含量远高于底层,在表层0～10cm含量随深度增加而迅速降低。重金属元素在水-土界面的浓度梯度为沉积物向水体的扩散提供了条件。不同采样点相比,位于昆明市附近的S6点沉积物内负荷较大。在外源减少的情况下,沉积物内负荷可能在一定时间内成为控制滇池水质的主导因子。

Six sites were selected for sampling in Wai-hai of Dianchi Lake to observe water quality,vertical distribution of redox potential (E_h),pH,total N(TN) and total P(TP) in sediments and heavy metal contents in porewater.It was shown that Dianchi Lake still suffered from eutrophication.Below the oxdic surface layer E_h declined rapidly with sediment depth and it was under anoxic condition in deeper sediment.The pH value changed slightly in the profile,which ranged from 7.0 to 8.5.TN and TP concentrations of sediment in Dianchi Lake were high,and the maximum reached 8.67 g/kg and 3.46 g/kg respectively.Vertical profiles showed that concentrations of TN and TP in surface sediments were much higher than that in deeper layers and decreased steeply with the depth on top 10 cm sediment layers.There was a gradient of heavy metals at the sediment-water interface indicating that heavy metals could diffuse from sediment into the overlaying water.Compared among six sampling sites,sediment load was much higher at S6 than that at other sites.Sediment internal load would be a dominant factor controlling water quality when external load was reduced in Dianchi Lake.