Atmospheric Ammonia over China: Emission Estimates and Deposition Budget (Invited Presentation)

Ammonia (NH3) and its aerosol-phase product ammonium exert important influences on atmospheric chemistry and biodiversity. China is one of the countries with the largest ammonia emissions and concentrations due to its intensive agricultural activities. However, current estimates of Chinese agricultural ammonia emissions differ by more than a factor of two, hindering our understanding of their environmental consequences. Here we will present bottom-up and top-down estimates of agricultural ammonia emissions in China using TES satellite observations and surface wet deposition flux measurements interpreted by the GEOS-Chem chemical transport model and its adjoint. Our bottom-up emission inventory includes more detailed information on crop-specific fertilizer application practices and better accounts for meteorological modulation of ammonia emission factors in China. Annual anthropogenic ammonia emissions in China are about 11.4 Tg for 2008, mainly associated with fertilizer application and livestock waste. They show a distinct seasonality peaking in summer, consistent with top-down results from the satellite-based inversion. We will also present analyses of atmospheric nitrogen deposition to better understand deposition processes and nitrogen inputs to ecosystems over China, and to further quantify contributions from ammonia sources.