太湖地区氮素湿沉降动态及生态学意义：以常熟生态站为例

在常熟生态站2001年6月至2003年5月连续两年定位收集湿沉降，对太湖地区氮素湿沉降动态进行研究．结果表明，湿沉降氮输入量季节变化显著，夏、春季高，秋、冬季低．在湿沉降输入氮中NH4^+-N、NO3^--N和DON的比例分别为47．6％、35．1％和17．4％．湿沉降中NH4^+-N主要来自当地农田的氨挥发，湿沉降NH4^+-N月输入量随月降雨量增加而增加(R0=0．3178^**)．该地区空气中NO3^--N浓度相对比较稳定，湿沉降中NO3^--N浓度与降雨量呈负相关(R^2=0．4205^***)．湿沉降NO33^--N月输入量与月降雨次数呈直线正相关(R^2=0．6757***)，而与月降雨量相关性较差(R^2=0．1985^*)．湿沉降TN年输入量为27．0kg·hm^-2，并在所有降雨中，氮浓度均超过水体富营养化阈值(0．2mg·L^-1)．

Dynamics and ecological significance of nitrogen wet-deposition in Taihu Lake region-Taking Changshu Agro-ecological 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.