Impact Of Ammonia Emissions On Fine Particle Pollution In China

Since fine particle (PM2.5) harmful effect is well known, it’s important tounderstand how the emission reduction of its precursors affects the PM2.5concentrations in order to focus policy-based efforts on the right direction to lowerfuture air pollution. A modeling software-based approach was adopted to predict theimpact of ammonia emissions on PM2.5over Chinese mainland in2030. TheCommunity Multiscale Air Quality (CMAQ) system was used to estimate the absoluteconcentration of PM2.5including three key species which are closely related toammonia transformation in the atmosphere: ammonium (NH4+), sulfate (SO42-) andnitrate (NO3-). A seasonal/annual estimation of such compounds concentrations in sixkey regions of China was made, including the Eastern China (ECH), North China Plain(NCP), Yangtze River Delta (YRD), Pearl River Delta (PRD), Sichuan Basin (SCB)and Eastern Hubei (EHB). Differently from previous studies, this investigationincluded the development of six new emission scenarios of ammonia while four ofthem were adopted to simulate PM2.5formation and diffusion in2030, and thencompared with2010data. The obtained results showed similarities and discrepancieswith previous research. Among all regions, the annual mean percentage fraction ofammonium PM2.5compared to the total fine particle ranged from6.88%to10.24%,which was consistent with previous simulation studies. EHB and YRD regionspresented the highest concentrations of NH4+. The reduction of ammonia emissionsaccording to different control policies mostly affected NO3-concentrations rather thanSO42-. Not significant variations in formation of NH4+and other ions in response ofammonia emissions variation was observed, with exception for the strictest policiesscenario that was implemented. Thus, ammonia reduction will have an important rolein the reduction of nitrate PM2.5which was the first species to decrease. However, themodel showed also some substantial limitations in terms of quantitative estimations ofPM2.5species, and this factor will be a fundamental trigger for further investigationsrelated to ammonia transformation in the modeling field.