We’re pleased to welcome a guest blog post from Dr Eloise Marais, University College London, regarding her latest research on ammonia emissions.
UK agricultural emissions of ammonia negatively impact human and ecosystem health by forming fine particles (PM2.5) and offsetting the natural nitrogen balance of aquatic and terrestrial ecosystems. There are few direct policies regulating agricultural ammonia emissions in the UK and routine surface measurements for evaluating bottom-up inventories used to inform policies and assess compliance are non-existent for fluxes and sparse for concentrations.
Satellite observations offer daily global coverage of ammonia abundances and include mature and extensively validated retrieval products from two instruments that pass overhead in the morning (called IASI) and the afternoon (called CrIS). These can be used in combination with a chemical transport model to derive surface emissions. In a recently published study, Dr Eloise Marais (UCL) and collaborators from the UK, the US, Belgium, Canada, and China used these data products and the chemical transport model GEOS-Chem to obtain monthly spring-summer (March-September) high-resolution (~10 km) emissions of ammonia totalling 271 kilotonnes from IASI and 389 kilotonnes from CrIS. These top-down ammonia emissions were then compared to bottom-up estimates of annual emissions from the UK National Atmospheric Emission Inventory (NAEI) and best representation of seasonality of emissions in models. The satellite-derived and bottom-up ammonia emissions exhibit similar spatial patterns (see accompanying figure comparing the two) and have relative uncertainties of comparable magnitude (11-36%) to the NAEI (31%), but the satellite-derived emissions exceed bottom-up estimates by 27-49% and include a summer peak that is missing in bottom-up emissions. The summer peak occurs over locations dominated by cattle farming in Northern Ireland and across western England and may be due to farming practices or warm summer temperatures. Further investigation is needed to resolve discrepancies identified in this study to better constrain a potentially large source of ammonia that is also a well-known and substantial contributor to UK climate-altering greenhouse gas emissions.
This research was funded by the UK Department for the Environment, Food and Rural Affairs (DEFRA) and a NERC/EPSRC Researcher in Residence (RiR) Award.
The emissions derived in this study are available for download from the UCL Data Repository. For questions or comments about the study, please email Dr Eloise Marais.
Several of our Scoping Studies are using STFC capabilities to develop research in ammonia: ‘On Track of NH3’ (Dr Anna Font), ‘MOREC-AQ’ (Dr Lekan Popoola), ‘Developing a compact, low-cost DELTA-Mi’ (Dr Yuk Sim Tang).