闽西北农田生态系统中大气氮湿沉降研究

在福建省三明市将乐县连续3年定位收集湿沉降,研究闽西北地区农田生态系统大气氮素湿沉降的浓度、沉降量以及时间变化规律。结果表明:降水中TN、TIN、DON、NH4+-N和NO3--N的平均浓度分别为1.22,0.83,0.38,0.53,0.30mg/L,无机氮与有机氮的比例达到2.18,且在每次降雨中总氮的浓度均超过水体富营养化阈值(0.2mg/L)。该地区湿沉降氮输入量有明显的季节性变化,春、夏季高,秋、冬季低。在湿沉降输入氮中NH4+-N、NO3--N和DON占总氮的比例分别为43.77%,24.78%和31.45%,湿沉降以无机氮(TIN)为主,平均年无机氮(TIN)沉降量为8.71kg/hm2,占总氮(TN)沉降量的68.55%。总氮(TN)年输入量为4.17～18.00kg/hm2,平均值为12.71kg/hm2。大气中氮素湿沉降对生态环境有一定的风险。

Nitrogen Wet-deposition in Agro-ecosystem of Northwestern Fujian Province

The nitrogen(N) concentration and deposition amount in wet deposition in agro-ecosystem at the northwest of Fujian province were studied from December 2008 to November 2011.The results showed that concentration of TN,TIN,DON,NH+4-N and NO-3-N in rainwater were 1.22,0.83,0.38,0.53,0.30 mg/L,the ratio of TIN to DON was 2.18.The amount of nitrogen wet-deposition in this area had a strong seasonal pattern,with higher values in spring and summer,low values in autumn and winter,about 80% of nitrogen wet-deposition occurred in spring and summer.Proportions of NH+4-N,NO-3-N and DON to TN inputted by wet deposition were 43.77%,24.78% and 31.45%,respectively.TIN was the dominant species in nitrogen wet-deposition,averaged value of TIN deposition in the northwest of Fujian province was 8.71 kg/(hm2·a),accounting for 68.55% of the whole N wet deposition.Annual TN input from wet deposition varied from 4.17 kg/(hm2·a) to 18.00 kg/(hm2·a) and was 12.71 kg/(hm2·a) on average.The nitrogen wet deposition in northwest of Fujian province will have significant risk on nitrogen balance within the agro-ecosystem.