基于WRF-CMAQ的中国典型湖泊大气氮沉降特征

Characteristics of Atmospheric Nitrogen Deposition in Typical Lakeacross China Based on the WRF-CMAQ model

采用WRF-CMAQ模型模拟了2018年中国4个典型湖泊的不同形态氮(总氮TN、氧化态氮OXN、还原态氮REDN、硝酸盐氮NO-3-N、铵盐氮NH+4-N)的大气沉降通量。2018年青海湖、乌梁素海、东湖与太湖全年氮沉降通量分别为3.02、4.38、64.25、21.67 kgN/hm 2,大气氮沉降贡献的氮负荷分别占乌梁素海、东湖与太湖总氮负荷的0.9%、22.3%、11.3%,东湖与太湖受大气氮沉降的影响程度显著高于青海湖和乌梁素海,表明大气氮沉降对发达地区湖泊的影响更应受到关注。通过敏感性试验分析大气氮沉降量的影响因子,结果显示含氮污染物的沉降速率对湖泊氮沉降通量的影响不明显,而含氮污染物排放速率降低20%,可使4个湖泊总氮沉降通量下降11%~22%,表明相对氮沉降速率、氮排放变化是影响氮沉降量的主要因素。本研究为进一步厘清大气氮沉降对湖泊总氮负荷的作用并制定有效控制措施提供了科学依据。

The WRF-CMAQ model is employed to estimate the atmospheric nitrogen deposition of different nitrogen forms in four major lakes of China in 2018.The nitrogen forms include total nitrogen(TN),oxidized nitrogen(OXN),reduced nitrogen(REDN),nitrate nitrogen(NO-3-N),and ammonium nitrogen(NH+4-N).The annual nitrogen deposition fluxes in 2018 for Lake Qinghaihu,Lake Ulansuhai,Lake Donghu,and Lake Taihu were 3.02,4.38,64.25,and 21.67 kgN/hm 2,respectively.Atmospheric nitrogen deposition contributed 0.9%,22.3%,and 11.3%of the total nitrogen load in Lake Ulansuhai,Lake Donghu,and Lake Taihu,respectively.Lake Donghu and Lake Taihu were significantly more affected by atmospheric nitrogen deposition than Lake Qinghaihu and Lake Ulansuhai,highlighting the need for increased concern regarding atmospheric nitrogen deposition in developed regions.Sensitivity analysis revealed that the deposition velocity of nitrogen pollutants had an insignificant impact on local nitrogen deposition fluxes.However,reducing the source emission rate of nitrogen pollutants significantly decreased the nitrogen deposition fluxes.A 20%reduction in the source emission rate led to a decrease in nitrogen deposition fluxes by 11%to 22%in the four representative lakes.This demonstrates that nitrogen emission sources is the major factor that affects nitrogen deposition compared to deposition velocity.The findings provide a scientific foundation for further understanding the role of atmospheric nitrogen deposition in the total nitrogen load of lakes and developing effective control measures.