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Risk assessment of pesticide impacts on remote ecosystems makes use of model-estimated degradation in air. Recent studies suggest these degradation rates to be overestimated, questioning current pesticide regulation. Here, we investigated the concentrations of 76 pesticides in Europe at 29 rural, coastal, mountain, and polar sites during the agricultural application season. Overall, 58 pesticides were observed in the European atmosphere. Low spatial variation of 7 pesticides suggests continental-scale atmospheric dispersal. Based on concentrations in free tropospheric air and at Arctic sites, 22 pesticides were identified to be prone to long-range atmospheric transport, which included 15 substances approved for agricultural use in Europe and 7 banned ones. Comparison between concentrations at remote sites and those found at pesticide source areas suggests long atmospheric lifetimes of atrazine, cyprodinil, spiroxamine, tebuconazole, terbuthylazine, and thiacloprid. In general, our findings suggest that atmospheric transport and persistence of pesticides have been underestimated and that their risk assessment needs to be improved.

Risk assessment of pesticide impacts on remote ecosystems makes use of model-estimated degradation in air. Recent studies suggest these degradation rates to be overestimated, questioning current pesticide regulation. Here, we investigated the concentrations of 76 pesticides in Europe at 29 rural, coastal, mountain, and polar sites during the agricultural application season. Overall, 58 pesticides were observed in the European atmosphere. Low spatial variation of 7 pesticides suggests continental-scale atmospheric dispersal. Based on concentrations in free tropospheric air and at Arctic sites, 22 pesticides were identified to be prone to long-range atmospheric transport, which included 15 substances approved for agricultural use in Europe and 7 banned ones. Comparison between concentrations at remote sites and those found at pesticide source areas suggests long atmospheric lifetimes of atrazine, cyprodinil, spiroxamine, tebuconazole, terbuthylazine, and thiacloprid. In general, our findings suggest that atmospheric transport and persistence of pesticides have been underestimated and that their risk assessment needs to be improved.

A submission to the Air Quality Expert Group (AQEG), an expert committee of the Department for Environment, Food and Rural Affairs (Defra) • Ammonia gas (NH3) is a priority pollutant both as a precursor to particulate matter and for ecosystem impacts. • Three scenarios for UK emission reductions during COVID-19 in emission sectors, where activity is likely reduced ,have been assessed. • Total UK emissions of NH3 are likely to have decreased slightly (~2%), which is within the uncertainty and meteorological variability of the UK atmosphere. • Urban background and urban on road and roadside emissions of NH3 are likely to have decreased, by as much as 30% and 90% respectively compared with usual emissions before COVID-19. • Unratified data from three of the five UK automatic NH3 analysers (Auchencorth Moss, Chilbolton Observatory, and Manchester OSCA Observatory) show typical springtime NH3 concentrations across the UK. • Data from the non-automatic National Ammonia Monitoring Network will enable analysis at UK level in the months ahead. This includes roadside data from London Cromwell Rd. • Evidence gaps & future approaches are outlined. Future analysis of the Defra UKEAP rural networks proposed. • The key measurement gap is urban roadside NH3 (and PM ammonium) as there is only one long-term site in the UK measuring roadside NH3 concentrations. It is suggested that a roadside network of samplers and/or analysers are urgently put in place (perhaps aligned with the UK Urban NO2 Network; UUNN) to monitor NH3 at roadsides during and post COVID-19 lock down where possible.

Three different nitrogen (N) fertiliser types, ammonium nitrate, urea and urea coated with a urease inhibitor (Agrotain®), were applied at standard rates (70 kg N ha−1) to experimental plots in a typical and intensively managed grassland area at the Easter Bush Farm Estate (Scotland). The nitrogen use efficiency of the fertilisers was investigated as well as nitrogen losses in the form of nitrous oxide fluxes (N2O) and ammonia (NH3) during fertilisation events in the 2016 and 2017 growing seasons. Nitrous oxide was measured by the standard static chamber technique and analysed using Bayesian statistics. Ammonia was measured using passive samplers combined with the Flux Interpretation by Dispersion and Exchange over Short Range (FIDES) inverse dispersion model. On average, fertilisation with ammonium nitrate supported the largest yields and had the highest nitrogen use efficiency, but as large spatial and seasonal variation persisted across the plots, yield differences between the three fertiliser types and zero N control were not consistent. Overall, ammonium nitrate treatment was found to increase yields significantly (p value < 0.05) when compared to the urea fertilisers used in this study. Ammonium nitrate was the largest emitter of N2O (0.76 % of applied N), and the urea was the largest emitter of NH3 (16.5 % of applied N). Urea coated with a urease inhibitor did not significantly increase yields when compared to uncoated urea; however, ammonia emissions were only 10 % of the magnitude measured for the uncoated urea, and N2O emissions were only 47 % of the magnitude of those measured for ammonium nitrate fertiliser. This study suggests that urea coated with a urease inhibitor is environmentally the best choice in regards to nitrogen pollution, but because of its larger cost and lack of agronomic benefits, it is not economically attractive when compared to ammonium nitrate.

A unique long-term dataset from the UK National Ammonia Monitoring Network (NAMN) is used here to assess spatial, seasonal and long-term variability in atmospheric ammonia (NH3: 1998–2014) and particulate ammonium(NH4+: 1999–2014) across the UK. Extensive spatial heterogeneity in NH3 concentrations is observed, with lowest annual mean concentrations at remote sites (< 0.2 μg m-3 and highest in the areas with intensive agriculture (up to 22 μg m-3), while NH4+ concentrations show less spatial variability (e.g. range of 0.14 to 1.8 μg m-3 annual mean in 2005). Temporally, NH3 concentrations are influenced by environmental conditions and local emission sources. In particular, peak NH3 concentrations are observed in summer at background sites (defined by 5 km grid average NH3 emissions < 1 kg N ha-1 yr-1 and in areas dominated by sheep farming, driven by increased volatilization of NH3 in warmer summer temperatures. In areas where cattle, pig and poultry farming is dominant, the largest NH3 concentrations are in spring and autumn, matching periods of manure application to fields. By contrast, peak concentrations of NH4+ aerosol occur in spring, associated with long-range transboundary sources. An estimated decrease in NH3 emissions by 16%between 1998 and 2014 was reported by the UK National Atmospheric Emissions Inventory. Annually averaged NH3 data from NAMN sites operational over the same period (n=59)show an indicative downward trend, although the reduction in NH3 concentrations is smaller and non-significant: Mann–Kendall (MK), -6.3 %; linear regression(LR), -3.1 %. In areas dominated by pig and poultry farming, a significant reduction in NH3 concentrations between 1998 and 2014 (MK: -22 %; LR: -21 %, annually averaged NH3/ is consistent with, but not as large as the decrease in estimated NH3 emissions from this sector over the same period (-39 %). By contrast, in cattle-dominated areas there is a slight upward trend (non-significant) in NH3 concentrations (MK: +12

The UK Acid Gases and Aerosol Monitoring Network (AGANet) was established in 1999 (12 sites, increased to 30 sites from 2006), to provide long-term national monitoring of acid gases (HNO3, SO2, HCl) and aerosol components (NO3-, SO42-, Cl-, Na+, Ca2+, Mg2+). An extension of a low-cost denuder-filter pack system (DELTA) that is used to measure NH3 and NH4+ in the UK National Ammonia Monitoring Network (NAMN) provides additional monthly speciated measurements for the AGANet. A comparison of the monthly DELTA measurement with averaged daily results from an annular denuder system showed close agreement, while the sum of HNO3 and NO3- and the sum of NH3 and NH4+ from the DELTA are also consistent with previous filter pack determination of total inorganic nitrogen and total inorganic ammonium, respectively. With the exception of SO2 and SO42-, the AGANet provides for the first time the UK concentration fields and seasonal cycles for each of the other measured species. The largest concentrations of HNO3, SO2, and aerosol NO3- and SO42- are found in south and east England and smallest in western Scotland and Northern Ireland, whereas HCl are highest in the southeast, southwest and central England, that may be attributed to dual contribution from anthropogenic (coal combustion) and marine sources (reaction of sea salt with acid gases to form HCl). Na+ and Cl- are spatially correlated, with largest concentrations at coastal sites, reflecting a contribution from sea salt. Temporally, peak concentrations in HNO3 occurred in late winter and early spring attributed to photochemical processes. NO3- and SO42- have a spring maxima that coincides with the peak in concentrations of NH3 and NH4+, and are therefore likely attributable to formation of NH4NO3 and (NH4)2SO4 from reaction with higher concentrations of NH3 in spring. By contrast, peak concentrations of SO2, Na+ and Cl- during winter are consistent with combustion sources for SO2 and marine sources in winter for sea salt aero

The Auchencorth Moss atmospheric observatory has being measuring meteorological parameters since 1995. The site was originally set‐up to measure the deposition of sulphur dioxide at a site that represented the vegetation and climate typical of NW Europe, in relatively clean background air. It is one of the longest running flux monitoring sites in the region, over semi‐natural vegetation, providing infrastructure and support for many measurement campaigns and continuous monitoring of air pollutants and greenhouse gases. The meteorological sensors that are used, data processing and quality reviewing procedures are described for a set of core measurements up to 2016. These core measurements are essential for the interpretation of the other atmospheric variables.

This project developed reference standards and measurement techniques for traceable measurements of NH3 in air. These will enable validated high quality ammonia measurement data which will help monitor and compare NH3 levels and ensure compliance with environmental protection policies and legislation.

There is no regular quality assurance programme for ammonia passive samplers despite widespread use of these samplers across Europe and the rest of the world. In order to improve standards and begin to embed quality assurance in the measurement of ambient ammonia using passive samplers, within the EMRP MetNH3 project a passive sampler intercomparison was planned to enable side-by side exposure of the samplers to varying levels of ammonia in the field. From this experiment and in parallel the NPL CATFAC experiment (also within MetNH3), sufficient information and protocols could be developed. The method and infrastructure developed will then be available for future studies.

Volcanic emissions, specifically from Iceland, pose a pan-European risk and are on the UK National Risk Register due to potential impacts on aviation, public health, agriculture, the environment and the economy, from both effusive and explosive activity. During the 2014–2015 fissure eruption at Holuhraun in Iceland, the UK atmosphere was significantly perturbed. This study focuses one major incursion in September 2014, affecting the surface concentrations of both aerosols and gases across the UK, with sites in Scotland experiencing the highest sulfur dioxide (SO2) concentrations. The perturbation event observed was confirmed to originate from the fissure eruption using satellite data from GOME2B and the chemical transport model, EMEP4UK, which was used to establish the spatial distribution of the plume over the UK during the event of interest. At the two UK European Monitoring and Evaluation Program (EMEP) supersite observatories (Auchencorth Moss, SE Scotland, and Harwell, SE England) significant alterations in sulfate (SO42−) content of PM10 and PM2.5 during this event, concurrently with evidence of an increase in ultrafine aerosol most likely due to nucleation and growth of aerosol within the plume, were observed. At Auchencorth Moss, higher hydrochloric acid (HCl) concentrations during the September event (max = 1.21 µg m−3, cf. annual average 0.12 µg m−3 in 2013), were assessed to be due to acid displacement of chloride (Cl−) from sea salt (NaCl) to form HCl gas rather than due to primary emissions of HCl from Holuhraun. The gas and aerosol partitioning at Auchencorth Moss of inorganic species by thermodynamic modelling confirmed the observed partitioning of HCl. Using the data from the chemical thermodynamic model, ISORROPIA-II, there is evidence that the background aerosol, which is typically basic at this site, became acidic with an estimated pH of 3.8 during the peak of the event. Volcano plume episodes were periodically observed by the majority of the UK

CEH has been monitoring the concentrations of a range of heavy metals in rural locations across the UK since 2004. This report presents the annual average concentrations and deposition of heavy metals in air and rainfall samples collected from rural locations during 2011 and it reviews the temporal and spatial trends in heavy metal concentrations and deposition between 2004 and 2011. The monitoring network was established to measure the background concentration of a range of heavy metals in samples of airborne particulate matter (the PM10 fraction), rainwater and cloudwater which have been collected at rural locations which are not unduly influenced by local sources of emissions. The data are compiled to provide information of the background concentrations of these pollutants, and are used to demonstrate compliance with relevant air quality legislation. The measured concentrations are also used to calculate annual deposition of heavy metals and to produce UK maps of concentration and deposition. The heavy metals (and metalloids) which are monitored are aluminium (Al), arsenic (As),antimony (Sb), barium (Ba), beryllium (Be), cadmium (Cd), caesium (Cs); chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), rubidium (Rb), scandium (Sc), selenium (Se),strontium (Sr),tin (Sn), titanium (Ti), tungsten (W), uranium (U), vanadium (V) and zinc (Zn). The concentrations of all metals measured in airborne particulate matter, rainfall and cloudwater are low, as would be expected in samples collected from rural areas. The concentrations are 1.5 to 8.5 times lower than the national average as reported in the Urban and Industrial Heavy Metals Monitoring network (see Table 5 for comparison). Although the reported emissions of heavy metals in the UK have declined considerably from their industrial peak in the 1970s,and more recently during the 1990s, the inter-year variability in measured concentration

The UK National Ammonia Monitoring Network (NAMN, Sutton et al. 2001a) was established in 1996 to quantify the spatial distribution and long-term trends in concentrations of atmospheric ammonia (NH3) and also aerosol ammonium (NH4 +) (since 1999). There are currently 94 sites. At 59 of these sites, the CEH DELTA methodology (Sutton et al. 2001b) is used to provide the spatial and temporal patterns of NH3 and aerosol NH4 + across the UK, while passive diffusion samplers (Tang et al. 2001) are used to assess regional and local scale variability in air NH3 concentrations in source regions. Monitoring is on a monthly timescale, which is optimal to provide information on seasonality and for estimating annual mean in air concentrations. Emissions of NH3 in the UK have fallen by 12% between 1990 and 2004 (http://www.naei.org.uk). The long-term dataset from the UK NAMN, which comprises 9 years of gaseous NH3 data (since September 1996) and 7 years of aerosol NH4 + data (since 1999) may therefore be analysed to assess trends in air concentrations. The data can also be used to compare with critical levels of NH3 concentrations set in the UK to protect vegetation and ecosystem.

Background Climate change, caused by greenhouse gas ( GHG) emissions, is one of the most serious threats facing our planet, and is of concern at both UK and devolved administration levels. Accurate predictions for the effects of changes in climate and land use on GHG emissions are vital for informing land use policy. Models which are currently used to predict differences in soil carbon (C) and nitrogen (N) caused by these changes, have been derived from those based on mineral soils or deep peat. None of these models is entirely satisfactory for describing what happens to organic soils following land-use change. Reports of Scottish GHG emissions have revealed that approximately 15% of Scotland's total emissions come from land use changes on Scotland's high carbon soils; the figure is much lower for Wales. It is therefore important to reduce the major uncertainty in assessing the carbon store and flux from land use change on organic soils, especially those which are too shallow to be deep peats but still contain a large reserve of C. In order to predict the response of organic soils to external change we need to develop a model that reflects more accurately the conditions of these soils. The development of a model for organic soils will help to provide more accurate values of net change to soil C and N in response to changes in land use and climate and may be used to inform reporting to UKGHG inventories. Whilst a few models have been developed to describe deep peat formation and turnover, none have so far been developed suitable for examining the impacts of land-use and climate change on the types of organic soils often subject to land-use change in Scotland and Wales. Organic soils subject to land-use change are often (but not exclusively) characterised by a shallower organic horizon than deep peats (e.g. organo-mineral soils such as peaty podzols and peaty gleys). The main aim of the model developed in this project was to simulate the impacts of land-use and climat