太湖湖滨带春季悬浮物沉降特征与水体营养盐响应

为研究湖滨带悬浮物沉降过程中水体营养盐时空分布状况,在太湖西岸湖滨带典型区域进行原位沉降实验,计算了沉降量和沉降通量,并对沉降过程中TP、TN、NH+4-N、NO-3-N测定分析.结果表明,太湖西岸湖滨带沉降通量表现为人工芦苇区近岸无植被区自然芦苇区远岸无植被区,平均沉降通量分别为(1 383.40±925.60)、(1 208.67±743.50)、(278.72±142.53)、(245.58±154.25)g·(m2·d)-1,沉降第6 d以后沉降量稳定上升,沉降速率大于分解速率;经过持续15 d野外沉降实验观测,沉降过程中近岸带的TP含量是远岸带的2~3倍,且沉积物捕获器内NH+4-N和NO-3-N含量出现显著的差异(P0.01);沉降量与水体TN和NH+4-N含量呈显著相关(P0.01,n=42),表明沉降量的增加会导致上覆水体TN与NH+4-N含量增加;TN与NH+4-N相关系数为0.84,显示沉降量的增加可能加速氮素不同形态间相互转化,这一现象在当前太湖湖泛治理中应当予以重视.

Deposition Characteristics of Suspended Solids and the Response of Dissolved Nutrients in Spring in the Western Lakeside of Taihu Lake

To reveal the spatiotemporal characteristics of nutrients in the deposition process of suspended solids in lakeside zone,in situ deposition tests were performed in the western lakeside of Taihu Lake,and the contents of TP,TN,NH₄⁺-N and NO₃^--N were measured and analyzed.The results showed that the deposition fluxes in the western lakeside of Taihu Lake ranked as follows:artificial reed areas >non-vegetation nearshore areas >natural reed areas >non-vegetation offshore areas,with their average values of (1383.40±925.60),(1208.67±743.50),(278.72±142.53),(245.58±154.25) g·(m²·d)^-1,respectively.From the 6th day,the deposition volume steadily increased,with the deposition rate larger than the decomposition rate.Through the 15-day continuous in situ observation,the content of TP in nearshore zone was 2-3 folds larger than that of offshore zone,and the content of NH₄⁺-N was significantly different from that of NO₃^--N in the settlement bottle (P<0.01).The deposition volume was significantly and positively correlated to both TN and NH₄⁺-N contents in the water column (P<0.01,n=42),suggesting that the TN and NH₄⁺-N contents in the overlying water increased with the deposition fluxes.The correlation coefficient between TN and NH₄⁺-N was 0.84,implicating that the increase of deposition flux may accelerate the mutual transformation between different forms of nitrogen.These findings should be taken into account in the current control of black blooms and nutrient management in Taihu Lake.