Nitrous Acid and Nitric Oxide Emissions from Agricultural Soils in Guangdong Province: Laboratory Measurement and Emission Estimation

Soil is recognized as an important source of atmospherically reactive gases, especially in agricultural soils. Nonetheless, there is scarcity of research estimating reactive nitrogen gas (Nr) emissions from agricultural soils at the regional to global scale. In this study, we examined nitrous acid (HONO) and nitric oxide (NO) emissions from seven representative agricultural soils in Guangdong Province, considering soil moisture and temperature, using a dynamic chamber system. Accordingly, empirical formulas for HONO and NO emissions for each soil in relation to moisture and temperature were developed. Utilizing these empirical formulas, specific land data, and fertilizer data, we estimated the annual HONO and NO emission fluxes from agricultural soils in Guangdong Province to be 97.41 and 37.08 Gg N yr–1, respectively. Their total quantity is equivalent to 12% of the 2017 NOx emission inventory for Guangdong Province, potentially exerting significant impacts on the atmospheric oxidizing capacity and regional air quality.