Assessment of the impact of emissions reductions on air quality over North China Plain

Özet

The production rate of secondary pollutants was highly non-linear with the emission intensity of theirprecursors. In this study, the air quality modeling system RAMS-CMAQ with zero-out sensitivity test wasapplied to conduct source sensitivity approaches of PM2.5 for four source categories (industry, powerplants, transport, and residential) over the North China Plain (NCP) in January and July of 2013. Theresults show that the residential and industry emission sector were the greatest contributors to domainwidePM2.5 in January and July, respectively. The largest variation could exceed 200 mg m3 attributed tothe residential sector in January when a heavy pollution period appeared, and could reach 40e60 mg m3attributed to the industry sector in July in the heavy pollution area, respectively. The nonlinear relationshipbetween the secondary pollutant formation and its precursors was reflected by this sourcesensitivity approaches, as the summation of the secondary pollutant variations attributed to the foursources was obviously different from the simulated baseline concentration and the mass burden ofnitrate would increase upon removal of the power plants or transport emission sector in the heavypollution regions in January. Further analysis indicated that the improvement of atmospheric oxidationcapacity due to emission sector removal coupled with the sufficient precursor nitrogen oxide undersevere pollution background should be the main reason of the negative variation of nitrate appeared inthe sensitivity test. This feature indicates that the atmospheric oxidation capacity is an important impactfactor in determining the production rate of nitrate formation, and could further influence the variationfeature of PM2.5 mass burden during the pollution episode. Thus, it is suggested that the comprehensivepollution control strategies should be implemented based on the specific pollution condition. Additionally,the nonlinearity of secondary pollutants formation should be reasonably considered fordeveloping effective emission control strategies.