A modeling study of the nonlinear response of fine particles to air pollutant emissions in the Beijing–Tianjin–Hebei region

摘要

The Beijing–Tianjin–Hebei (BTH) region has been suffering fromthe most severe fine-particle (PM) pollution in China, which causesserious health damage and economic loss. Quantifying the source contributionsto PM concentrations has been a challenging task because of thecomplicated nonlinear relationships between PM concentrations andemissions of multiple pollutants from multiple spatial regions and economicsectors. In this study, we use the extended response surface modeling (ERSM)technique to investigate the nonlinear response of PM concentrationsto emissions of multiple pollutants from different regions and sectors overthe BTH region, based on over 1000 simulations by a chemical transport model(CTM). The ERSM-predicted PM concentrations agree well withindependent CTM simulations, with correlation coefficients larger than 0.99and mean normalized errors less than 1 %. Using the ERSM technique, wefind that, among all air pollutants, primary inorganic PM makes thelargest contribution (24–36 %) to PM concentrations. Thecontribution of primary inorganic PM emissions is especially high inheavily polluted winter and is dominated by the industry as well asresidential and commercial sectors, which should be prioritized in PMcontrol strategies. The total contributions of all precursors (nitrogenoxides, NO; sulfur dioxides, SO; ammonia, NH; non-methanevolatile organic compounds, NMVOCs; intermediate-volatility organiccompounds, IVOCs; primary organic aerosol, POA) to PM concentrationsrange between 31 and 48 %. Among these precursors, PMconcentrations are primarily sensitive to the emissions of NH,NMVOC + IVOC, and POA. The sensitivities increase substantially forNH and NO and decrease slightly for POA and NMVOC + IVOC withthe increase in the emission reduction ratio, which illustrates the nonlinearrelationships between precursor emissions and PM concentrations. Thecontributions of primary inorganic PM emissions to PMconcentrations are dominated by local emission sources, which account forover 75 % of the total primary inorganic PM contributions. Forprecursors, however, emissions from other regions could play similar roles tolocal emission sources in the summer and over the northern part of BTH. Thesource contribution features for various types of heavy-pollution episodesare distinctly different from each other and from the monthly mean results,illustrating that control strategies should be differentiated based on themajor contributing sources during different types of episodes.