中国对流层二氧化硫光化学氧化过程的数值研究

A numerical study on the troposphere photochemical oxidation process of sulfur dioxide over China

利用一个三维非静力区域大气化学输送模式与中尺度气象模式MM5相连接构成一个数值模拟系统 ,模拟了中国地区对流层臭氧与其前体物的分布以及二氧化硫转化为硫酸盐的过程 ,模式包括地面源排放、大气输送和扩散、干沉积、气相化学反应和云雨过程 .结果表明 :日间 ,O3 浓度主要由NOx 和NMHC的源排放和光化学反应过程支配 ,大气辐射是光化学反应强弱的决定因子 ,其强度可使SO2 、O3 和SO4 2 -的生成浓度呈现不同的日变化和季节变化 ,结果表明高浓度的O3 对二氧化硫转化为硫酸盐的化学过程有很大的促进作用 ,然而 ,这种作用受NMHC浓度的影响很大 ,较高浓度的NMHC使O3 浓度上升 ,但同时增加了对OH等自由基的消耗 ,使SO2 的转化率降低 .

A three dimensional non-hydrostatic regional chemical transport model was used to connected to a meso-scale meteorological model (MM5) in order to simulate the distribution of tropospheric ozone and photochemical oxidation processes of sulfur dioxide over China The physics and chemical processes considered in the model involve photochemical mechanism, dynamics transport and diffusion, dry and wet deposition , gas phase and aqueous chemistry The results showed that the concentration of ozone is mainly dominated by the emission of NO X and photochemical process in daytime, radiation is the decisive factor of strength of photochemical process and may cause the different daily variation of sulfur dioxide and ozone concentrations The results also showed that higher value of ozone will increase the transformation rate of sulfur dioxide to sulfate, but this effect is influenced by the ratio of NMHC to NO x Higher NMHC concentration will reduce the concentration of OH radical and then decrease the transformation rate of SO 2