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Soil greenhouse gas (GHG) fluxes of methane (CH4) and nitrous oxide (N2O) were measured over a two year period from several land-use systems on adjacent sites under the same soil and climatic conditions to assess the influence of the transition from arable agricultural (barley) and fallow to perennial bioenergy crops short rotation coppice (SRC) willow (Salix spp.) and short rotation forest (SRF) Scots pine (Pinus silvestris). There were no significant differences between CH4 and N2O fluxes measured from the SRC, SRF and fallow but the arable agricultural site showed an order of magnitude larger N2O emissions compared with the others. Fertiliser application to the arable crop was the major factor influencing N2O emissions and both air and soil temperature showed no significant effects on fluxes between the different land-use systems. Soil moisture was significantly different from the arable crop, showing a greater range than from SRF and SRC. Hence these bioenergy crops might be viable options for water stressed areas.

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 fertiliser 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.

Ammonia (NH3) is an important atmospheric base which can contribute to eutrophication, acidification of ecosystems and the formation of secondary aerosol. In order to monitor potential policy driven reductions and provide information on NH3 emissions, transport and deposition, active sampling is required. There are, however, many challenges in measuring NH3 as it is a ‘sticky’ reactive molecule which is readily soluble and rapidly interacts with other trace gases to form secondary inorganic aerosol. When undertaking ambient NH3 measurements, inlet set up, use of filters, reliable calibration standards and potential chemical interferences in the analytical technique thus need particular attention. Due to these complexities of NH3 active measurements, a metrology-centred project on “Metrology for Ammonia in Ambient Air” (MetNH3) funded by the European Metrological Research Programme (EMRP), was started in 2014, with the aim of developing traceable NH3 monitoring methods and NH3 certified reference material, which will be applicable under field conditions. In this project a commercial cavity ring down instrument is being characterised and further developed to be the traceable method of choice, alongside with the development of an open path absorption spectrometer. The following study presents the first results of a field intercomparison of different NH3 instrumentation verified against traceable methods developed and characterised as part of the MetNH3 project, held in South East Scotland. In addition, the applicability of dynamic calibration systems, under field conditions which have developed within the project is assessed. The overall objective of this study will be to establish recommendations for ambient NH3¬ measurements.

An integral part of the MetNH3 project is establishing the transfer of high-accuracy standards to field applicable methods. A field intercomparison of NH3 measurement techniques is planned for summer 2016 at a managed grassland in south-east Scotland. The aim of this experiment is to evaluate both the reference methods developed during the MetNH3 project and other state-of-the-art and older instrumentation currently available for field measurements. The challenge is to measure quantitatively both at background concentrations and elevated produced through fertilisation with urea. In addition to the instrument performance, the effect of meteorology (temperature, relative humidity, precipitation), inlet type and calibration method on the quality of data will be investigated. This presentation will outline the specific objectives of the study, as well as the provisional field setup. The talk will inform and lead to an open discussion on planning the experiment and the analysis of the data for all project partners and intercomparison participants.

Total gaseous mercury (TGM) was monitored during 2013 at the rural monitoring site, Harwell, England using the Tekran 2537A monitoring system. Average TGM for the year was 1.45 ± 0.24 ng m−3. This is comparable to other northern hemisphere studies, but on average 0.5 ng m−3 higher than at its sister monitoring station at Auchencorth Moss, Scotland, but 14% lower than that found in a similar study at the same location of 1.68 ng m−3 in 1995/6. Using wind sector analysis we show the important influence of local emissions, with our data showing that the largest influence on TGM observed is that of the adjacent Science & Innovation campus, making the site more a ‘suburban background’. By using co-located measurements of black carbon and sulphur dioxide as tracers, we present an initial investigation into the impact of the closure of Didcot A coal fired power station, which ceased operating in March 2013. Further analysis using air mass back trajectories shows the long-range contribution to TGM from continental Europe, and that the lowest levels are associated with marine air masses from the west.

Gaseous elemental (GEM), particulate bound (PBM) and gaseous oxidised (GOM) mercury species were monitored between 2009-2011 at the rural monitoring site, Auchencorth Moss, Scotland using the Tekran speciation monitoring system. GEM average for the three year period was 1.40 ± 0.19 ng m-3 which is comparable with other northern hemisphere studies. PBM and GOM concentrations are very low in 2009 and 2010 with geometric mean (x/÷ Standard Deviation) PBM values of 2.56 (x/÷ 3.44) and 0.03 (x/÷ 17.72) pg m-3 and geometric mean (x/÷ Standard Deviation) GOM values of 0.11 (x/÷ 4.94) and 0.09 (x/÷ 8.88) pg m-3 respectively. Using wind sector analysis and air mass back trajectories, the importance of local and regional sources on speciated mercury are investigated and we show the long range contribution to GEM from continental Europe, and that the lowest levels are associated with polar and marine air masses from the north west sector.

Peatlands represent a vast carbon reserve that has accumulated under conditions of low nitrogen availability. Given the strong coupling between the carbon and nitrogen cycles, we need to establish the consequences of the increase in reactive nitrogen deposition for the sustainability of peatlands, and whether the form in which the nitrogen is deposited makes a difference. We have addressed these questions using a globally unique field simulation of reactive N deposition as dry deposited ammonia and wet deposited reduced N, ammonium and oxidised N, nitrate, added as ammonium chloride or sodium nitrate, to an ombrotrophic peatland, Whim bog in SE Scotland. Here we report the fate of 56 kg N ha−1 yr−1 additions over 10 yr and the consequences. The effects of 10 yr of reactive N additions depended on the form in which the N was applied. Ammonia-N deposition caused the keystone Sphagnum species, together with the main shrub Calluna and the pleurocarpous mosses, to disappear, exposing up to 30% of the peat surface. This led to a significant increase in soil water nitrate and nitrous oxide emissions. By contrast wet deposited N, despite significantly reducing the cover of Sphagnum and Pleurozium moss, did not have a detrimental effect on Calluna cover nor did it significantly change soil water N concentrations or nitrous oxide emissions. Importantly 10 yr of wet deposited N did not bare the peat surface nor significantly disrupt the vegetation enabling the N to be retained within the carbon rich peatland ecosystems. However, given the significant role of Sphagnum in maintaining conditions that retard decomposition, this study suggests that all nitrogen forms will eventually compromise carbon sequestration by peatlands through loss of some keystone Sphagnum species.

Fluxes of methane (CH4) and nitrous oxide (N2O) are commonly measured with closed static chambers. Here, we analyse several of the uncertainties inherent in these measurements, including the accuracy of calibration gases, repeatability of the concentration measurements, choice of model used to calculate the flux and lack of fit to the model, as well as inaccuracies in measurements of sampling time, temperature, pressure and chamber volume. In an analysis of almost 1000 flux measurements from six sites in the UK, the choice of model for calculating the flux and model lack-of-fit were the largest sources of uncertainty. The analysis provides confidence intervals based on the measurement errors, which are typically 20%. Our best estimate, using the best-fitting model, but substituting the linear model in the case of concave fits, gave a mean flux that is 25% greater than that calculated with the linear model. The best-fit non-linear model provided a better (convex) fit to the data than linear regression in 36% of the measurements. We demonstrate a method to balance the number of gas samples per chamber (nsamples) and the number of chambers, so as to minimize the total uncertainty in the estimate of the mean flux for a site with a fixed number of gas samples. The standard error generally decreased over the available range in nsamples, suggesting that more samples per chamber (at the expense of proportionally fewer chambers) would improve estimates of the mean flux at these sites.