洱海大气氮磷湿沉降特征及入湖负荷估算

Characteristics of atmospheric nitrogen and phosphorus wet deposition in Erhai Lake and estimation on load into lake

为了揭示洱海湖区大气氮磷湿沉降特征,于2019年6月至2020年5月期间,以总氮(TN)、总磷(TP)为主要水化学指标,对湖区布设的4个站点进行雨水监测;结合同期降水数据和湖区水质监测资料分析,阐释了洱海湿沉降污染物浓度和沉降通量的时空分布特征,估算了湿沉降直接入湖污染负荷量,并评估了其入湖负荷对湖区水环境的潜在影响。研究结果表明:①洱海流域年降水量由南向北、自西向东递减,降水主要集中在6~10月份,约占年降水量的79%~96%;②降水中总氮浓度均值为(1.180±0.682)mg/L,总磷浓度均值为(0.072±0.021)mg/L,降水总氮、总磷浓度呈现明显的季节性差异,浓度与降水量呈显著负相关;③总氮、总磷湿沉降通量7月份最大、5月份最小,沉降通量与降水量呈极显著正相关;④洱海湖面湿沉降总氮输入量约为183.32 t,总磷约为11.19 t,湖面湿沉降总氮直接入湖负荷占入湖河道年输入的20.01%,总磷占15.22%。

In order to reveal the characteristics of atmospheric nitrogen and phosphorus wet deposition in Erhai Lake area,we analyzed the total nitrogen(TN)and total phosphorus(TP)in rainwater of 4 stations located in the lake area from June 2019 to May 2020.Combined with the analysis of precipitation data and lake water quality monitoring data in the same period,we explained the temporal and spatial distribution characteristics of wet deposition pollutant concentration and deposition flux in Erhai Lake,estimated the wet deposition load into the lake,and evaluated the influence of pollution load into the lake on the water quality of the lake area.The results showed that:①The annual precipitation in Erhai Lake Basin decreased from south to north and from west to east.The rainfall was mainly concentrated in June to October,accounting for 79%~96%of the annual rainfall.②The average concentration of total nitrogen in precipitation was(1.180±0.682)mg/L,and the average total phosphorus concentration was(0.072±0.021)mg/L.The concentrations of total nitrogen and total phosphorus in rainwater showed obvious seasonal differences,and concentration was significantly negatively correlated with rainfall.③The deposition flux of total nitrogen and total phosphorus was the largest in July and the smallest in May,and the deposition flux was significantly positively correlated with rainfall.④The total nitrogen input to Erhai Lake by wet deposition was about 183.32 t,which accounted for 20.01%of nitrogen load by river inputs,and the corresponding total phosphorus was about 11.19 t,which accounted for 15.22%of phosphorus load by river inputs.