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

Abstract

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.