Rising importance of agricultural nitrogen oxide emissions in China’s future PM2.5 pollution mitigation

Abstract

Controlling ammonia (NH₃) emissions through agricultural management has been recognized as effectively mitigating fine particulate matter (PM_2.5) pollution in eastern China. However, agricultural nitrogen oxide (NO_x) emissions are often overlooked. Here we estimate agricultural NO_x emissions and design a set of atmospheric chemistry model experiments to assess their role in present and future PM_2.5 pollution mitigation in eastern China. The results show that when fossil fuel emissions decrease to 2060 levels, the contribution of agricultural NO_x emissions to secondary inorganic aerosol (SIA) concentrations during the crop-growing season will reach 40% over intensive agricultural areas such as North China Plain, and the efficiency of reducing agricultural NO_x emissions in mitigating SIAs will become comparable to reducing NH₃ emissions. By estimating the optimal reactive nitrogen (Nr) emission control pathway, we find that when including agricultural NO_x emissions, the strategies will shift in favor of controlling agricultural Nr emissions to achieve more efficient PM_2.5 mitigation. Such additional benefits of agricultural nitrogen management should be considered when designing future air quality strategies for agricultural-intensive regions.