Numerical Simulation Of Secondary Inorganic Aerosols And The Effects Of Ammonia Emissions

Sulfate,nitrate and ammonium（SNA）areimportant species of fine particles（PM2.5）,which have significant impacts on environment,climate change and human health.As a main precursor of SNA,ammonia（NH3）is important to SNA.However,uncertainties still exsit for the emission inventories of SNA precursors,especially NH3.Additionally,the simulated sulfate concentrations are underestimated for most air quality model.This study aims toimprovethe NH3 emission inventory and explore the efficient method for SNA modeling,and then simulates the concentration level and distribution of SNA in China,and investigates the impacts of NH3 emission on SNA.It’s meaningful for PM2.5 pollution control.In this study,we developed a modeling system for NH3 emissionsfrom the fertilizer usein China.It considers the bi-directional exchange of NH3 and more influencing factors,such as crop distribution,meteorological fields,soil and the fertilizer application,and provides improved temporal resolution.By comparing the simulated and observed NH3 concentration,the reliability of this NH3 emission inventory was evaluated.In addition,in order to improve the underestimation of modeled sulfate concentrations,we estimated the emissions of mineral particles and added the heterogeneous reaction of SO₂ on the surface of the mineral particles to CMAQ,and evaluated the reliability of its simulation results against field observations.On this basis,we simulated the concentration level and distribution of SNA in China,and analyzed the impacts of NH3 emission on SNA.The results show that:（1）In 2013,the NH3 emissions from fertilizer use and livestock are 5.5 Tg and 5.6Tg,respectively,which areconcentrated in Henan,Shandong,Hebei,Sichuan,Anhui and Jiangsu Province.The emissions in summer are larger than winter.The simulated results can reproduce the spatial and temperal characteristics of NH3 concentration well,indicating the reliability of this NH3 emission inventory.（2）By including the enhancement role of mineral aerosol on sulfate production,the model performance for SNA is improved significantly,especially for sulfate.The Normalized Mean Bias of simulated sulfate concentrations for spring,summer,autumn and winter are improved from-59.5%,-41.9%,-38.2% and-35.8%to-26.5%,-16.7%,24.3% and 16.8%,respectivly.（3）Multi-pollutants emission reduction can decrease SNA concentration more.It is more efficient to control NH3 emissions from now than in the future.Therefore,the control of NH3 emission should be brought into the policy of PM_2.5 pollution control as soon as possible.