Abstract: In order to understand the effects of acid rain on the nitrogen (N) content in the water body of Wenzhou Sanyang wetland,this paper measured the concentrations of different N forms in the wetland,of which,NH₄⁺-N was 2.90～10.75 mg·L^-1,average in 5.38 mg·L^-1; NO₃^--N was 0.16～0.44 mg·L^-1, average in 0.31 mg·L^-1;and total was 34.04～63.20 mg·L^-1,average in 55.75 mg·L^-1.The pH value was 6.1～6.5,average in 6.4.The measurement of the N input from precipitation in the past two years and its proportion to the existed N in the water body of the wetland showed that the input of NH₄⁺-N,NO₃^--N and total N was 2.48×10⁴～2.86×10⁴ kg,2.87～4.96×10⁴ kg and 5.35×10⁴～7.82×10⁴ kg,and its proportion was 56～64%,11.21～19.38 times and 12%～17%,respectively.The N amount directly to the wetland water body was 0.72×10⁴～0.84×10⁴ kg,0.83×10⁴～1.44×10⁴ kg and 1.55×10⁴～2.27×10⁴,and its proportion was 16%～19%，3.24～5.63 times and 3%～5%.The results indicated that acid rain was one of the main sources of pollutant nitrogen which aggravated the water pollution of the Sanyang wetland.

Key words: Phytoplankton, Red tide, Abundance, Water dynamics, Changjiang River estuary