Modeling atmospheric ammonia using agricultural emissions with improved spatial variability and temporal dynamics
Authors: Ge Xinrui , Schaap Martijn , Kranenburg Richard , Segers Arjo , Reinds Gert Jan , Kros Hans , de Vries Wim 
Published: December 2020

Abstract. Ammonia emissions into the atmosphere have increased substantially in Europe since 1960, primarily due to the intensification of agriculture, as illustrated by enhanced livestock and the use of fertilizers. These associated emissions of reactive nitrogen, particulate matter, and acid
deposition have contributed to negative societal impacts on human health and terrestrial ecosystems. Due to the limited availability of reliable
measurements, emission inventories are used to assess large-scale ammonia emissions from agriculture by creating gridded annual emission maps and
emission time profiles globally and regionally. The modeled emissions are subsequently utilized in chemistry transport models to obtain ammonia
concentrations and depositions. However, current emission inventories usually have relatively low spatial resolutions and coarse categorizations
that do not distinguish between fertilization on various crops, grazing, animal housing, and manure storage in its spatial allocation. Furthermore,
in assessing the seasonal variation of ammonia emissions, they do not consider local climatology and agricultural management, which limits the
capability to reproduce observed spatial and seasonal variations in the ammonia concentrations. This paper describes a novel ammonia emission model that quantifies agricultural emissions with improved spatial details and temporal dynamics in
2010 in Germany and Benelux. The spatial allocation was achieved by embedding the agricultural emission model Integrated Nitrogen Tool across Europe
for Greenhouse gases and Ammonia Targeted to Operational Responses (INTEGRATOR) into the air pollution inventory Monitoring Atmospheric Composition
and Climate-III (MACC-III), thus accounting for differentiation in ammonia emissions from manure and fertilizer application, grazing, animal houses
and manure storage systems. The more detailed temporal distribution came from the integration of TIMELINES, which provided predictions of the timing of key agricultural operations, including the day of fertilization across Europe. The emission maps and time profiles were imported into LOTOS-EUROS
to obtain surface concentrations and total columns for validation. The comparison of surface concentration between modeled output and in situ
measurements illustrated that the updated model had been improved significantly with respect to the temporal variation of ammonia emission, and its
performance was more stable and robust. The comparison of total columns between remote sensing observations and model simulations showed that some
spatial characteristics were smoothened. Also, there was an overestimation in southern Germany and underestimation in northern Germany. The results suggested that updating ammonia emission fractions and accounting for manure transport are the direction for further improvement, and detailed land
use is needed to increase the spatial resolution of spatial allocation in ammonia emission modeling.