[Dynamics and ecological significance of nitrogen wet-deposition in Taihu Lake region--taking Changshu Agroecological Experiment Station as an example].

Nitrogen wet deposition was monitored for two years (2001.6-2003.5) at the Changshu Ecological Station in Taihu Lake region. The results showed that the amount of nitrogen wet deposition had a strong seasonal pattern, with higher levels in summer and spring, and low values in autumn and winter. The proportions of NH4(+)-N, NO3(-)-N and DON (dissolved organic nitrogen) to TN (total nitrogen) inputted by wet deposition were 47.6%, 35.1% and 17.4%, respectively. Ammonia volatilization from farmland was the most important source of NH4(+)-N in wet deposition. The monthly NH4(+)-N input from wet deposition increased with monthly rainfall (R2 = 0.3178**), while the monthly NO3(-)-N input from wet deposition had a lower correlation (R2 = 0.1985*) with monthly rainfall but positively related with the time of rainfall (R2 = 0.6757***). The NO3(-)-N concentration in the air was relatively steady in a period of time. Its concentration in wet deposition had a negative correlation with rainfall (R2 = 0.4205***). The annual TN input from wet deposition was 27.0 kg x hm(-2), but its concentration in each rainfall was higher than 0.2 mg x L(-1) (the threshold N concentration for inland water eutrophication). The nitrogen inputted by wet deposition had an ecological significance on both nitrogen balance in agroecosystem and eutrophication.