To what extent airborne particulate matters are influenced by ammonia and nitrogen oxides?

Intensive farming is known to significantly impact air quality, particularly f ine particulate matter (PM. 2.5). Understanding in detail their relation is important for scientific reasons and policymaking. Ammonia emissions convey the impact of farming but are not directly observed. They are computed through emission inventories based on administrative data and provided on a regular spatial grid at daily resolution. In this chapter, we aim to validate lato sensu the approach mentioned above by considering ammonia concentrations instead of emissions in the Lombardy Region, Italy. While the former are available only in few monitoring stations around the region, they are direct observations. Hence, we build a model explaining PM2.5 based on precursors, ammonia (NH3) and nitrogen oxides (NOX), and meteorological variables. To do this, we use a seasonal interaction regression model allowing for temporal autocorrelation, correlation between stations, and heteroskedasticity. It is found that ...