A bottom-up agricultural emissions inventory and its analysis via CMAQ and IASI-NH₃

The global increase in population has led to higher emissions from livestock and synthetic fertilizers. This study investigates the impact of agricultural ammonia emissions on NH₃ concentrations and provides insights into PM_2.5 levels and their components in agriculturally intensified areas. We developed a bottom-up emission inventory focused on fertilizer application over croplands and livestock, instead of relying on the EMEP database. This approach utilized an improved spatial and temporal distribution of these emissions. We compared annual total NH₃ emissions from livestock and fertilizer, estimated at 598.5 kt and 187.2 kt in the EMEP inventory (Base case), and 245.2 kt and 536 kt in the bottom-up inventory (Scenario case). Using the CMAQ modelling framework, we estimated atmospheric concentrations for both cases and evaluated the model results by comparing them with IASI-NH₃ satellite retrievals. This comparison revealed significant differences in column concentrations between the Base and Scenario cases, with the Scenario case showing substantial improvement. Over a period of seven months, which contributed 80 % of the annual agricultural emissions for the Scenario case, the domain averages of NH₃ were 3.02 × 10¹⁵, 4.15 × 10¹⁵, and 4.17 × 10¹⁵ molecules/cm² for the Base and Scenario cases and IASI-NH₃, respectively. The Scenario case closely matched IASI measurements, indicating a more accurate representation of NH₃ emissions and concentrations. This enhanced reliability underscores the effectiveness of the bottom-up inventory approach. Additionally, using the CMAQ model, we found that in the IASI hotspots, the averages were 1.67 μg/m³ for sulfate, 0.57 μg/m³ for nitrate, and 0.62 μg/m³ for ammonium, with a total PM_2.5 mean of 10.45 μg/m³.