Assessing ammonia deposition patterns and emission reduction scenarios in a livestock-dense region of the Netherlands...

In the Netherlands, ammonia (NH₃) emissions from livestock housing have become a major environmental concern, largely due to high density of livestock farms in certain areas of the country. After emission, NH₃ settles on the ground, lowering the soil pH, leading to increased acidity and creating harmful conditions for plants. To protect biodiversity, it is essential to reduce nitrogen emissions. This study investigates the spatial variation in NH₃ deposition from livestock farming in 2020 within one of the hotspot regions in the Netherlands (Foodvalley region), using a high resolution dispersion model (STACKS-D). The spatial mean NH₃ deposition from livestock emissions in Foodvalley was found to be 11.14 kg/ha/year. Levels above critical deposition load (17 kg/ha/year) were mainly observed in central areas and some nature reserves. To eliminate these exceedances, we tested various livestock emission reduction scenarios. All scenarios explored were able to reduce deposition in nitrogen-sensitive nature environments significantly. Scenarios targeting stable removal in buffer zones around nature areas, as well as those focused on veal calves, dairy cattle, and laying hens sectors, were highly effective in reducing deposition with potentially smaller influence on existing livestock sectors. The annual average deposition map generated by STACKS-D demonstrated consistent spatial characteristic with 2020 large-scale deposition map, which serves as a reference for assessing pollution distribution and policy making in the Netherlands. Furthermore, a strong (∼0.8) and statistically significant correlation between modelled and measured annual mean NH₃ air concentrations as observed for the period 2022-2023 indicates the model captures key spatial features.