Agricultural emissions of reactive nitrogen (ANr), including nitrogen oxides (ANOX) and ammonia (ANH3), can substantially affect the formation of fine particulate matter (PM2.5) and ozone (O3). The Guanzhong Basin (GZB) is located in central China, with developed industries and a large area of cropland. Although industrial emissions have been substantially reduced since 2013, heavy air pollution episodes still occur frequently in the GZB, suggesting that the relative contribution of agricultural emissions has become more important. However, the season-dependent impacts of ANr emissions and their interactions with other anthropogenic emissions remain poorly quantified. In this study, the WRF-Chem model is used to estimate contributions of ANr emissions to O3 and PM2.5 concentrations in the GZB in August 2018 (summer) and January 2019 (winter). Summertime simulations show that ANOX emissions contribute 5.5 μg m−3 (42.4%) to the total NOX concentration and 10.1 μg m−3 (6.8%) to the maximum daily 8-h average O3 concentrations on average in the GZB. Additionally, ANOX induced O3 enhancement increases secondary aerosol formation and ANH3 emissions further facilitate secondary inorganic aerosol (SIA) formation, which contributes 7.2 μg m−3 (28.0%) to PM2.5 concentrations in the GZB. In the wintertime case, ANH3 emissions contribute 22.4 μg m−3 (61.3%) and 27.1 μg m−3 (25.2%) to SIA and PM2.5 mass, respectively. Neglecting ANr emissions contributions may lead to significant biases in assessing anthropogenic control efficiency: overestimating summer O3 reduction potential by 12.1%, while underestimating PM2.5 mitigation effects by 17.6% (summer) and 9.9% (winter). Therefore, reducing the ANr emissions constitutes an effective way to alleviate air pollution in the GZB.
