大气氮湿沉降对青山湖富营养化的影响

Wet deposition of atmospheric nitrogen and its eutrophic effect on Qingshan Lake

针对大气湿沉降氮的区域通量问题,通过2008年春、夏季对临安青山湖区湿沉降中氮素化学形态的分析,揭示了大气氮湿沉降的时间分布特征,通过估算大气氮湿沉降的输入通量,研究湿沉降对湖区水体富营养化的贡献.结果表明,春季青山湖降水总氮浓度范围为(1.30±0.02)—(9.80±0.85)mg.L-1,其中铵态氮占总氮比例最高,为40.7%,硝态氮和有机氮的比例分别为33.5%和25.8%;雨水氮浓度随着降雨强度的增大呈显著下降趋势,铵态氮和硝态氮所占的比例随着降雨的进行会逐渐升高,而有机氮的比例却有不断降低的趋势;青山湖春季大气氮沉降负荷为6.64 kg.hm-2,雨水中平均的氮浓度为(4.86±0.65)mg.L-1,严重超过了水体富营养化0.2 mg.L-1的阈值,对青山湖水生生态系统造成潜在的威胁.

This paper focused on the contribution of atmospheric nitrogen wet deposition to the eutrophication of regional lakes.The nitrogen species composition of rainfall in Qingshan Lake was analyzed to explore the seasonal pattern and spatial distribution of various nitrogen species.The results indicated that mean DTN concentration at all sites ranged between（1.30±0.02）—（9.80±0.85）mg·L-1 in the spring.Ammonium accounted for 40.7% of DTN,being the highest ratio.Nitrate and dissolved organic N accounted for 33.5% and 25.8% of DTN,respectively.N concentration decreased with precipitation intensity as a result of dilution,and the species composition changed significantly during continuous rainfall.The spring wet deposition of atmospheric nitrogen flux amounted to 6.64 kg·hm-2,and the average DTN concentration was（4.86±0.65）mg·L-1,which far outweighed the threshold value of eutrophication（0.2 mg·L-1）,and may cause potential threat to the ecosystem of Qingshan Lake.