A high-resolution inventory of ammonia emissions from agricultural fertilizer application and crop residue in Taiwan

The presence of ammonia (NH₃) in the atmosphere has an impact on atmospheric nitrogen (N) deposition, air quality, and environmental systems. NH₃ emissions in Taiwan are mainly driven by N fertilizer application and livestock operations, and their estimates are associated with considerable inaccuracies and uncertainties. In this study, a high-resolution (1 × 1 km) NH₃ emissions inventory for agricultural fertilizers and crop residues in Taiwan was developed for 2016. The NH₃ emissions were estimated based on detailed local activity data, such as seasonally varying planted areas and fertilizer application rates, and emissions from 88 different crops were resolved to better capture the seasonality and spatial heterogeneity. Emissions factors (EFs) are governed by ambient temperature, soil acidity and other factors. We further estimated NH₃ emissions from two agricultural management scenarios, conventional farming (CF) and appropriate fertilization for crops (AF), to quantify the potential reduction in NH₃ emissions due to government policy. The NH₃ emissions from agricultural fertilizers and crop residues in Taiwan were approximately 25010 (20298.3) tons in 2016 for the CF (AF) scenario. Synthetic N fertilizer contributed 66.9% to the total emissions, followed by organic N fertilizer (32.1%), with crop residue (1.0%) being a relatively small source in the CF scenario. The NH₃ emissions hotspots were located in the central to southern part of western Taiwan, where intense agricultural activities are conducted. The peak NH₃ emissions occurred in spring and summer and were mainly associated with the cultivation of the first and second seasons of rice. We validated our estimated NH₃ emissions with a satellite NH₃ column, finding that the spatial-temporal variations in NH₃ emissions from fertilizer application were in good coherency with the NH₃ column concentration.