Modelling Seasonal Dynamics from Temporal Variation in Agricultural Practices in the UK Ammonia Emission Inventory

Abstract

Most ammonia (NH 3 ) emission inventories have been calculated on an annual basis and do not take into account the seasonal variability of emissions that occur as a consequence of climate and agricultural practices that change throughout the year. When used as input to atmospheric transport models to simulate concentration fields, these models therefore fail to capture seasonal variations in ammonia concentration and dry and wet deposition. In this study, seasonal NH 3 emissions from agriculture were modelled on a monthly basis for the year 2000, by incorporating temporal aspects of farming practice. These monthly emissions were then spatially distributed using the AENEID model (Atmospheric Emissions for National Environmental Impacts Determination). The monthly model took the temporal variation in the magnitude of the ammonia emissions, as well as the fine scale (1-km) spatial variation of those temporal changes into account to provide improved outputs at 5-km resolution. The resulting NH 3 emission maps showed a strong seasonal emission pattern, with the highest emissions during springtime (March and April) and the lowest emissions during summer (May to July). This emission pattern was mainly influenced by whether cattle were outside grazing or housed and by the application of manures and fertilizers to the land. When the modelled emissions were compared with measured NH 3 concentrations, the comparison suggested that the modelled emission trend corresponds fairly well with the seasonal trend in the measurements. The remaining discrepancies point to the need to develop functional parametrisations of the interactions with climatic seasonal variation.

Author response to reviewer 2

“…As a primary pollutant emitted from ground-level sources, NH 3 exhibits high spatial variability in concentrations Hellsten et al, 2008;Vogt et al, 2013), confirmed by NH 3 data from the NAMN (e.g. range of 0.06-8.8 µg m −3 annual mean in 2005) (Fig.…”

Towards a climate-dependent paradigm of ammonia emission and deposition

“…In the case of the UK and Danish ammonia networks, areas dominated by cattle and pig show peak emissions in spring, which are reproduced by models accounting for the timing of manure spreading [30,58]. However, the UK also includes substantial background areas (see the electronic supplementary material, figure S1) with a pronounced summer maximum and winter minimum of 0. , respectively).…”

Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK

“…In areas with more intensive livestock farming, where emissions come from either cattle or from pig and poultry farming, the largest concentrations are observed in spring and autumn, corresponding to periods of manure application to land. The spring peak in March is larger than the autumn peak in September, which coincides with the main period for manure application being in spring, before the sowing of arable crops or early on in the grass-growing period (Hellsten et al, 2007). Ammonia concentrations in these areas are also larger in summer than winter, due to warmer conditions promoting volatilization.…”

“…In the UK, agriculture accounts for > 80 % of total NH 3 emissions and is estimated by the National Ammonia Reduction Strategy Evaluation System (NARSES) model (Webb & Misselbrook 2004;Misselbrook et al, 2015). For the agricultural NH 3 emission maps, parish statistics on livestock numbers and crop areas are combined with satellitebased land cover data to model emissions at a 1 km resolution, using the AENEID model Hellsten et al, 2007). For reasons of data confidentiality, the 1 km data need to be aggregated to produce annual agricultural NH 3 emissions maps at a 5 km by 5 km grid resolution.…”