Study On The Nonlinear Responses Of Air Quality To Primary Pollutant Emissions

At present, most Chinese cities are suffering from serious PM2.5and ozonepollution. To develop the regional air pollution control policies, we need adecision-making tool which is accurate, efficient and effective. This study aims todevelop an efficient and effective simulation model to address the non-linearrelationship between air pollutant emissions and air quality, and to provide theoreticaland technical support for the integrated control of multi-pollutants and multi-regions inChina.A bottom-up nesting emission inventory with high spatial and temporal resolutionswas established for China. With the emission inventory, the third generation regional airquality model (Model-3/CMAQ) was applied to simulate the air quality in China in2005. The emission inventory and air quality model were validated through thecomparison of CMAQ simulations with satellite and surface observations. The responsesurface model (RSM) of air pollutant emissions and air quality was established basedon the computer simulation. The performance of RSM was evaluated through theleave-one-out cross validation, out of sample validation and2-D isopleths validation.Based on the results of RSM, the "Peak Ratio" and "Nitrate Flex Ratio" were defined toindicate the chemistry of ozone and fine particle formation, respectively. Their spatialand temporal variations in East China were analyzed. The nonlinear air quality impactsfrom various emission sources, pollutants, and regions were quantified for key areas andcities. The application of RSM in decision-making was demonstrated using three casestudies.The results suggest that RSM developed in this study is accurate and efficient, andfulfills the needs of air pollution control policy-making. The changes of "Peak Ratio"indicate that the ozone chemistry changes from VOC-limited regime in urban area to theNO_x-limited in rural area. Similar changes are found for ozone chemistry fromground-level to upper air. NO_x control appears to be more effective than anthropogenicVOC control during heavy photochemical pollution episode. In summer, both local andregional emissions contribute to ozone pollution in the three mage-cities includingBeijing, Shanghai and Guangzhou. Local NO_x emissions are the major contributor inBeijing. VOC and NO_x emissions from Zhejiang and Jiangsu have significant impacts on ozone pollution in Shanghai, where local emissions have small contributions.Regional NO_x emission control is important to solve regional ozone pollution in China.The spatial distribution of "Nitrate Flex Ratio" as the indicator of fine particlechemistry suggests that heavy polluted regions such as North China Plain and YangtzeRiver Delta are mainly under NH3-rich conditions. Besides, the heavy NO3-pollutionepisodes usually happen in NH3-rich conditions. The fine particle pollution in Beijing,Shanghai and Guangzhou shows obvious regional characteristics. Local emissioncontrol is not enough to improve regional air quality. Jointly prevention and control ofmulti-pollutants and multi-regions must be implemented.