Abstract:

Researches on  effects of wet deposition on water quality and primary productivity are meaningful to understand the mechanism of eutrophication and recovery of lake ecosystem.In June,2012,phytoplankton primary productivity is determined by means of dark and light bottle method (Winkler method) from six insitu enclosures in the Meiliang Bay of Lake Tai.Simultaneously,total nitrogen,total phosphorus,ammonium,nitrate and silicate were also measured.,The results show that. (1) N deposition gives the first place in the wet deposition,N deposition account for 99.12% and 98.93% in two wet deposition.And the concentration of ammonium is higher than nitrate,while P deposition as well as Si deposition are negligible;(2) high concentration of ammonium carried by the rain caused a higher concentration of ammonium in enclosures after wet deposition.Since stormy wave may promote the DSi to release from the sediment,this maybe the reason why the concentration of DSi also changed significantly in the enclosures which was not accepting the wet deposition before and after the wet deposition;(3)There was a remarkable change in primary productivity and daily variation of primary productivity in enclosures receiving wet deposition.The increase of primary productivity is obvious,in the first wet deposition,the primary productivity increases 191.30%,52.08% and 100.00% in three different time periods;while in the second wet deposition,the primary productivity increases105.42%,73.96% and 61.62%.But the primary productivity of the encloses not accepting wet deposition does not change significantly.Because of the wet deposition,the N:P in enclosures accepting wet deposition became more suitable for phytoplankton growth.The analysis results indicate that the wet deposition has obvious effects on the water quantify and primary productivity