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We examined the consequences of the spatial heterogeneity of atmospheric ammonia (NH₃) by measuring and modelling NH₃ concentrations and deposition at 25 m grid resolution for a rural landscape containing intensive poultry farming, agricultural grassland, woodland and moorland. The emission pattern gave rise to a high spatial variability of modelled mean annual NH₃ concentrations and dry deposition. Largest impacts were predicted for woodland patches located within the agricultural area, while larger moorland areas were at low risk, due to atmospheric dispersion, prevailing wind direction and low NH3 background. These high resolution spatial details are lost in national scale estimates at 1 km resolution due to less detailed emission input maps. The results demonstrate how the spatial arrangement of sources and sinks is critical to defining the NH₃ risk to semi-natural ecosystems. These spatial relationships provide the foundation for local spatial planning approaches to reduce environmental impacts of atmospheric NH₃., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

Effects and implications of reduced and oxidised N, applied under 'real world' conditions, since May 2002, are reported for Calluna growing on an ombrotrophic bog. Ammonia has been released from a 10 m line source generating monthly concentrations of 180-6 microg m(-3), while ammonium chloride and sodium nitrate are applied in rainwater at nitrate and ammonium concentrations below 4mM and providing up to 56 kg N ha(-1) year(-1) above a background deposition of 10 kg N ha(-1) year(-1). Ammonia concentrations, >8 microg m(-3) have significantly enhanced foliar N concentrations, increased sensitivity to drought, frost and winter desiccation, spring frost damage and increased the incidence of pathogen outbreaks. The mature Calluna bushes nearest the NH3 source have turned bleached and moribund. By comparison the Calluna receiving reduced and oxidised N in rain has shown no significant visible or stress related effects with no significant increase in N status.

Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.

The main source of atmospheric ammonia (NH3) in Scotland is livestock agriculture, which accounts for 85% of emissions. The local magnitude of emissions therefore depends on livestock density, type, and management, with major differences occurring in various parts of Scotland. Local differences in agricultural activities therefore result in a wide range of NH3 emissions, ranging from less than 0.2 kg N ha(-1) year(-1) in remote areas of the Scottish Highlands to over 100 kg N ha(-1) year-1 in areas with intensive poultry farming. Scotland can be divided loosely into upland and lowland areas, with NH3 emission being less than and more than 5 kg N ha(-1) year(-1), respectively. Many semi-natural ecosystems in Scotland are vulnerable to nitrogen deposition, including bogs, moorlands, and the woodland ground flora. Because NH3 emissions occur in the rural environment, the local deposition to sensitive ecosystems may be large, making it essential to assess the spatial distribution of NH3 emissions and deposition. A spatial model is applied here to map NH3 emissions and these estimates are applied in atmospheric dispersion and deposition models to estimate atmospheric concentrations of NH3 and NH4+, dry deposition of NH3, and wet deposition of NHx. Although there is a high level of local variability, modelled NH3 concentrations show good agreement with the National Ammonia Monitoring Network, while wet deposition is largest at high altitude sites in the south and west of Scotland. Comparison of the modelled NHx deposition fields with estimated thresholds for environmental effects ("critical loads") shows that thresholds are exceeded across most of lowland Scotland and the Southern Uplands. Only in the cleanest parts of the north and west is nitrogen deposition not a cause for concern. Given that the most intense effects occur within a few kilometres of sources, it is suggested that local spatial abatement policies would be a useful complement to traditional policies that mitigate environmental effects based on emission reduction technologies.

The article discusses a study on the relationship between ammonia emissions from a poultry farm and nitrogen trace gas emissions. It offers an overview of ammonia deposition and nitrogen trace gas emissions. It includes the description of the site and methodologies used in the study. The results of the study are also presented.

There is substantial uncertainty in the effectiveness of measures to reduce emissions of agricultural trace gases, including ammonia (NH3), methane (CH4) and nitrous oxide (N2O). The only way to test whether emission abatement programmes are successful is through monitoring of air concentrations and deposition. However, where NH3 emissions have been reduced in Europe, either through abatement policies or reductions in agricultural activity, it was difficult to demonstrate the link with reduced concentrations and deposition.The outbreak of Foot and Mouth Disease (FMD) in Great Britain in 2001 provides a major case study to test the link between agricultural emissions and air concentrations. This paper examines the spatial distribution of anticipated change in emissions and concentrations of NH3, CH4 and N2O as a result of the FMD outbreak. It then assesses the extent to which atmospheric monitoring could be used to detect the changes and attribute them to the effect of FMD. Two of the areas worst affected by FMD were selected for detailed analysis: in Cumbria (N.W. England) and in Devon (S.W. England). Compared with values prior to FMD, average agricultural emissions were reduced by as much as 50–100%, with estimated reductions in atmospheric mixing ratios of 0.7–3.3 ppb for NH3, 10–60 ppb for CH4 and 0.1–0.7 ppb for N2O.For NH3 and CH4, modelled changes are larger than the precision of analytical techniques and, where sampling is made at replicate sites, the changes are also larger than the inter-annual variability of existing monitoring data. By contrast, for N2O only the largest changes occurring in Cumbria are expected to be detectable and distinguishable from inter-annual variability. Based on the results, a measurement strategy has been established to follow NH3 and CH4 concentrations during and after the period of restocking. By comparing NH3 (a reactive gas) with CH4 (an inert tracer), the measurements aim to distinguish constraints on the link between changing emissions and air concentrations. Improving this linkage is essential to demonstrate that the economic costs of emission abatement translate into environmental benefits. [Copyright &y& Elsevier]

Atmospheric ammonia is a precursor for secondary particulate matter formation, which harms human health and contributes to acidification and eutrophication. Under the 2012 Gothenburg Protocol, 2005 emissions must be cut by 6% by 2020. In the UK, 83% of total emissions originate from agricultural practices such as fertilizer use and rearing of livestock, with emissions that are spatially extensive and variable in nature. Such fugitive emissions make resolving and tracking of individual site performance challenging. The Directional Passive Air quality Sampler (DPAS) was trialled at Whim Bog, an experimental site with a wind-controlled artificial release of ammonia, in combination with CEH-developed ammonia samplers. Whilst saturation issues were identified, two DPAS-MANDE (Mini Annular Denuder) systems, when deployed in parallel, displayed an average relative deviation of 15% (2–54%) across all 12 directions, with the directions exposed to the ammonia source showing ∼5% difference. The DPAS-MANDE has shown great potential for directional discrimination and can contribute to the understanding and management of fugitive ammonia sources from intensive agriculture sites. [ABSTRACT FROM AUTHOR]

Abstract: A European scale network was established in 2006 as part of the NitroEurope Integrated Project to infer reactive nitrogen (Nr) dry deposition fluxes, based on low-cost sampling of gaseous and aerosol species and inferential modelling. The network provides monthly measurements of NH3, NH4 +, HNO3 and NO3 −, as well as SO2, SO4 2−, HCl, Cl− and base cations at 58 sites. Measurements are made with an established low-cost denuder methodology (DELTA) as a basis to: (1) examine temporal trends and spatial patterns across Europe, (2) improve and calibrate inferential modelling techniques to estimate exchange of Nr species, (3) provide best estimates of atmospheric dry N deposition, and (4) permit an analysis of net GHG exchange in relation to atmospheric and agricultural N inputs at the European scale. Responsibility for measurements is shared among seven European laboratories. An inter-comparison of the DELTA implementation by 6 laboratories at 4 test sites (Montelibretti, Italy; Braunschweig, Germany; Paterna, Spain and Auchencorth, UK) from July to October 2006 provided training for the laboratories and showed that good agreement was achieved in different climatic conditions (87% of laboratory site-means within 20% of the inter-laboratory median). Results obtained from the first year of measurements show substantial spatial variability in atmospheric Nr concentrations, illustrating the major local (NH3) and regional (HNO3, NO3 −, and NH4 +) differences in Nr concentrations. These results provide the basis to develop future estimates of site-based Nr dry deposition fluxes across Europe, and highlight the role of NH3, largely of agricultural origin, which was the largest single constituent and will dominate dry Nr fluxes at most sites. [Copyright &y& Elsevier]

Estimates of the dry deposition of ammonia (NH3) gas in a field fumigation experiment on an ombrotrophic bog have been made using the inferential technique, with measured wind speed at 2m, and air concentrations at two heights above the vegetation. The parameters for a concentration-dependent surface resistance term have been derived from flux measurements over the same vegetation in a chamber study, separating stomatal from non-stomatal resistances. Annual NH3-N deposition in each of the 4 years 2003–2006 was estimated to increase from 3.0±0.2kgNha−1 y−1 in ambient air, with an NH3 concentration at 0.5m above the canopy of 0.7μgm−3, to 50–70kgNha−1 y−1 where annual average air concentrations were 70–90μgm−3 and concentrations during fumigation were up to 1600μgm−3. The equivalent deposition velocities (at z =0.5m) were 0.016ms−1 in ambient air and 0.003ms−1 at 100μgm−3. The differences between annual deposition estimates made from independent air concentration data at 0.1m and 0.5m above the canopy were small for distances more than 10m from the source, after vertical mixing was complete. Over 4 years (2003–2006) and at eight sampling points more than 10m from the NH3 source, the mean difference between the dry deposition estimates, using NH3 concentrations measured independently at 0.1m and 0.5m above the canopy, was 2%. Use of a constant surface resistance, with no concentration dependence, as commonly used in inferential models of dry deposition, would have predicted deposition up to eight times too large. [Copyright &y& Elsevier]