High efficiency of livestock ammonia emission controls on alleviating particulate nitrate during a severe winter haze episode in northern China.

Although nitrogen oxide (NOx) emission controls have been implemented for several years in northern China, recent observations show particulate nitrate (NO₃^-) is becoming increasingly important during haze episodes. In this study, we find that particulate NO₃^- formation would easily become NH₃-limited under severe haze conditions, enhancing its sensitivity to NH₃ emission controls. Furthermore, improved manure management of livestock husbandry could reduce 40 % of NH₃ emissions (currently 100 kiloton per a month) in winter of northern China. Under this emission reductions scenario, simulations from the thermodynamic equilibrium model (ISORROPIA-II) and the Weather Research and Forecast model coupled chemistry (WRF-Chem) all show that particulate NO₃^- could be reduced by approximately 40 % during a typical severe haze episode (averagely from 40.8 to 25.7 μg/m³). Our results indicate that reducing livestock NH₃ emissions would be highly effective to reduce particulate NO₃^- during severe winter haze events. [ABSTRACT FROM AUTHOR]