Impact Assessment of Ammonia Emissions on Inorganic Aerosols in East China Using Response Surface Modeling Technique

Abstract

Ammonia (NH(3)) is one important precursor of inorganic fine particles; however, knowledge of the impacts of NH(3) emissions on aerosol formation in China is very limited. In this study, we have developed China's NH(3) emission inventory for 2005 and applied the Response Surface Modeling (RSM) technique upon a widely used regional air quality model, the Community Multi-Scale Air Quality Model (CMAQ). The purpose was to analyze the impacts of NH(3) emissions on fine particles for January, April, July, and October over east China, especially those most developed regions including the North China Plain (NCP), Yangtze River delta (YRD), and the Pearl River delta (PRD). The results indicate that NH(3) emissions contribute to 8-11% of PM(2.5) concentrations in these three regions, comparable with the contributions of SO(2) (9-11%) and NO(x) (5-11%) emissions. However, NH(3), SO(2), and NO(x) emissions present significant nonlinear impacts; the PM(2.5) responses to their emissions increase when more control efforts are taken mainly because of the transition between NH(3)-rich and NH(3)-poor conditions. Nitrate aerosol (NO(3)(-)) concentration is more sensitive to NO(x) emissions in NCP and YRD because of the abundant NH(3) emissions in the two regions, but it is equally or even more sensitive to NH(3) emissions in the PRD. In high NO(3)(-) pollution areas such as NCP and YRD, NH(3) is sufficiently abundant to neutralize extra nitric acid produced by an additional 25% of NO(x) emissions. The 90% increase of NH(3) emissions during 1990-2005 resulted in about 50-60% increases of NO(3)(-) and SO(4)(2-) aerosol concentrations. If no control measures are taken for NH(3) emissions, NO(3)(-) will be further enhanced in the future. Control of NH(3) emissions in winter, spring, and fall will benefit PM(2.5) reduction for most regions. However, to improve regional air quality and avoid exacerbating the acidity of aerosols, a more effective pathway is to adopt a multipollutant strategy to control NH(3) emissions in parallel with current SO(2) and NO(x) controls in China.

Persistent sensitivity of Asian aerosol to emissions of nitrogen oxides

“…As expected, secondary inorganic aerosol is most sensitive to SO 2 emissions during most of the year [Wang et al, 2012a[Wang et al, , 2012b. In winter, secondary inorganic aerosol is most sensitive to NH 3 emissions [Wang et al, 2011;Wang et al, 2012aWang et al, , 2012b. However, secondary inorganic aerosol remains sensitive to NO x emissions in all seasons.…”

“…A large fraction of the aerosol mass in Asia is composed of secondary inorganic ions as sulfate (SO 4 2À ), nitrate (NO 3 À ), and ammonium (NH 4 + ) [Huang et al, 2012a[Huang et al, , 2012b. Emission control strategies are complicated by complex chemical feedbacks that affect the relation of secondary inorganic mass with precursor emissions of SO 2 , NH 3 , and NO x [Pinder et al, 2007;Wang et al, 2011Wang et al, , 2012.…”

Local and Regional Contributions to Fine Particle Pollution in Winter of the Yangtze River Delta, China

“…For example, the non-linear response of pollutant concentrations to precursors' emissions has not been well considered in current zero-out method. More advanced sensitivity analysis methods such as high-order direct decoupled methods (Hakami et al, 2003;Cohan et al, 2005), response surface modeling (Wang et al, 2011b;Xing et al, 2011;Zhao et al, 2015) are recommended for further sensitivity studies. Besides, uncertainties still exists for the aerosol concentration predictions and future work is needed in to get better model performance.…”

Continuous Measurement of Ambient Aerosol Liquid Water Content in Beijing

“…Strict emission limits on coal burning power plants and factories and vehicle emissions, and control of factories on emissions of SO 2 and NO x are measures put in place by the government that have resulted in reduction of the corresponding particulate components. However, very little has been done on the reduction of ammonia emissions, which continue in the rising (Meng et al, 2011;Wang et al, 2011), and reflects on the alkalinity that aerosol in Beijing shows. A comparison of ACSM aerosol mass and Acidity ratio shows how the aerosol is predominately alkaline during the sampling period, particularly for low aerosol masses (i.e., clean period) (Fig.…”