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Abstract. 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 (NH 3 : 1998(NH 3 : -2014) and particulate ammonium (NH + 4 : 1999-2014) across the UK. Extensive spatial heterogeneity in NH 3 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 NH + 4 concentrations show less spatial variability (e.g. range of 0.14 to 1.8 µg m −3 annual mean in 2005). Temporally, NH 3 concentrations are influenced by environmental conditions and local emission sources. In particular, peak NH 3 concentrations are observed in summer at background sites (defined by 5 km grid average NH 3 emissions < 1 kg N ha −1 yr −1 ) and in areas dominated by sheep farming, driven by increased volatilization of NH 3 in warmer summer temperatures. In areas where cattle, pig and poultry farming is dominant, the largest NH 3 concentrations are in spring and autumn, matching periods of manure application to fields. By contrast, peak concentrations of NH + 4 aerosol occur in spring, associated with long-range transboundary sources. An estimated decrease in NH 3 emissions by 16 % between 1998 and 2014 was reported by the UK National Atmospheric Emissions Inventory. Annually averaged NH 3 data from NAMN sites operational over the same period (n = 59) show an indicative downward trend, although the reduction in NH 3 concentrations is smaller and nonsignificant: Mann-Kendall (MK), −6.3 %; linear regression (LR), −3.1 %. In areas dominated by pig and poultry farming, a significant reduction in NH 3 concentrations between 1998 and 2014 (MK: −22 %; LR: −21 %, annually averaged NH 3 ) is consistent with, but not as large as the decrease in estimated NH 3 emissions from this sector over the same period (−39 %). By contrast, in cattle-dominated areas there is a slight upward trend (non-significant) in NH 3 concentrations (MK: +12 %; LR: +3.6 %, annually averaged NH 3 ), despite the estimated decline in NH 3 emissions from this sector since 1998 (−11 %). At background and sheep-dominated sites, NH 3 concentrations increased over the monitoring period. These increases (non-significant) at background (MK: +17 %; LR: +13 %, annually averaged data) and sheep-dominated sites (MK: +15 %; LR: +19 %, annually averaged data) would be consistent with the concomitant reduction in SO 2 emissions over the same period, leading to a longer atmospheric lifetime of NH 3 , thereby increasing NH 3 concentrations in remote areas. The observations for NH 3 concentrations not decreasing as fast as estimated emission trends are consistent with a larger downward trend in annual particulate NH + 4 concentrations (1999-2014: MK: −47 %; LR: −49 %, p < 0.01, n = 23), associated with a lower formation of particulate NH

Abstract. 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 southern and eastern England and smallest in western Scotland and Northern Ireland, whereas HCl are highest in south-eastern, south-western, 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 aerosol. Key pollutant events were captured by the AGANet. In 2003, a spring episode with elevated concentrations of HNO3 and NO3− was driven by meteorology and transboundary transport of NH4NO3 from Europe. A second, but smaller episode occurred in September 2014, with elevated concentrations of SO2, HNO3, SO42−, NO3−, and NH4+ that was shown to be from the Icelandic Holuhraun volcanic eruptions. Since 1999, AGANet has shown substantial decrease in SO2 concentrations relative to HNO3 and NH3, consistent with estimated decline in UK emissions. At the same time, large reductions and changes in the aerosol components provide evidence of a shift in the particulate phase from (NH4)2SO4 to NH4NO3. The potential for NH4NO3 to release NH3 and HNO3 in warm weather, together with the surfeit of NH3 also means that a larger fraction of the reduced and oxidized N is remaining in the gas phase as NH3 and HNO3 as indicated by the increasing trend in ratios of NH3 : NH4+ and HNO3 : NO3− over the 16-year period. Due to different removal rates of the component species by wet and dry deposition, this change is expected to affect spatial patterns of pollutant deposition with consequences for sensitive habitats with exceedance of critical loads of acidity and eutrophication. The changes are also relevant for human health effects assessment, particularly in urban areas as NH4NO3 constitutes a significant fraction of fine particulate matter ( < 2.5 µm) that are linked to increased mortality from respiratory and cardiopulmonary diseases.

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SUMMARYA seroepidemiological study of the prevalence of mumps virus specific antibodies reveals a pattern of endemic peristence on the island of St Lucia in the West Indies. In the unvaccinated population the proportion seropositive rose rapidly in the child age classes to attain a stable plateau close to unity in value in the teenage and adult age groups. The average age at infection was estimated to be between 3 and 4 years of age and the average duration of detectable levels of maternally derived antibodies was approximately 3 months. Analyses based on mathematical models of the transmission dynamics of the virus suggest that in excess of 75 % of each cohort of 1-to 2-year-old children must be effectively immunized to eliminate mumps virus transmission. A mumps radial haemolysis test, developed for quantitative measurements of antibody, is discussed.TNTRODt'CTION Age-stratified scrological surveys for the presence or absence of antibodies specific to defined viral antigens are an important component of the epidemiological data required for the effective design of mass immunization programmes for the control of common childhood viral infections such as measles, mumps and rubella (Anderson & May, 1983, 1985 a; Nokes, Anderson & Grenfell, 1986; McLean & Anderson, 1988a, b). In this paper we report the results of a recent study of the transmission dynamics of the mumps virus in the small island community of St Lucia in the Caribbean. The research forms part of a seroepidemiological study of three common childhood viral infections (measles, mumps and rubella) on the island. The overall objective was to provide empirical data necessary for the development of a mass immunization programme, based on the use of MMR (measles, mumps and rubella) vaccine, which has recently been introduced by the Government of St Lucia.