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Abstract. A number of atmospherically important trace gases (dimethyl sulphide (DMS),

Abstract. The concentration and speciation of iodine have been determined in wet and dry •)deposition at a coastal site over a 15-month period. Deposition fluxes in rain (2.7 txmol m -2 yrand aerosol (3.6-6.5 txmol m -2 yr -•) are the major routes for removal of iodine from the marine atmosphere onto the Earth's surface, with only a minor contribution from direct deposition of methyl iodide (0.003-0.17 txmol m -• yr-•). Iodate (IO•-) is often considered to be the only species of iodine that is permanently removed to the aerosol phase, and IO• may therefore be expected to be the dominant form of iodine in precipitation. However, iodide (I-) was found to constitute a significant fraction (5-100%) of iodine in both rain and aerosol. This implies that the rates of iodate formation and iodide volatilization (through reaction with hypohalous acids) are relatively slow. A third pool of aerosol iodine (nonvolatile organic compounds) may also contribute to removal of iodine from the atmosphere in dry or wet deposition. In this work we present the results of a long-term study of iodine deposition at a coastal site in southeast England. We have determined iodine concentrations in rain and aerosol samples and used these to calculate wet and dry deposition fluxes of iodine to the ground at the site. In addition, we also use gas-phase concentrations of methyl iodide, the longest-lived iodocarbon, to calculate the potential contribution to dry deposition of direct gas-to-land transfen This work follows on from the study of Campos et al. [1996], who reported that the annual emission budget of methyl iodide was in near balance with the deposition budget of iodine in rainfall in the southern North Sea region. The current data set is used to extend the iodine deposition budget, by inclusion of dry deposition, which was neglected in the earlier work. In addition, by examining the speciation of iodine in aerosol and rain we consider the influence of meteorology on the atmospheric processing of iodine in aerosol.

[1] Ammonium salts represent a major component of fine mode marine aerosol that play an important role in climate regulation, atmospheric pH control and nutrient supply to the oceans. We report here the results of analyses of aerosol samples collected in remote areas of the Atlantic Ocean. We show the isotopic abundance of aerosol ammonium varies with concentration, with isotopically light ammonium (À5 to À8%) associated with the lowest ammonium concentrations compared to isotopically heavy ammonium (+10%) associated with higher ammonium concentrations. We interpret the light ammonium signature as arising from marine emissions of ammonia. These results provide further evidence for the existence of a marine ammonia source and offers a method to define the relative contribution of marine and terrestrial ammonium to aerosols in remote areas and thereby investigate the role of these emissions in climate regulation.

This research is concerned with the following environmental research questions: socio-ecological system complexity, especially when valuing ecosystem services; ecosystems stock and services flow sustainability and valuation; the incorporation of scale issues when valuing ecosystem services; and the integration of knowledge from diverse disciplines for governance and decision making. In this case study, we focused on ecosystem services that can be jointly supplied but independently valued in economic terms: healthy climate (via carbon sequestration and storage), food (via fisheries production in nursery grounds), and nature recreation (nature watching and enjoyment). We also explored the issue of ecosystem stock and services flow, and we provide recommendations on how to value stock and flows of ecosystem services via accounting and economic values respectively. We considered broadly comparable estuarine systems located on the English North Sea coast: the Blackwater estuary and the Humber estuary. In the past, these two estuaries have undergone major land-claim. Managed realignment is a policy through which previously claimed intertidal habitats are recreated allowing the enhancement of the ecosystem services provided by saltmarshes. In this context, we investigated ecosystem service values, through biophysical estimates and welfare value estimates. Using an optimistic (extended conservation of coastal ecosystems) and a pessimistic (loss of coastal ecosystems because of, for example, European policy reversal) scenario, we find that context dependency, and hence value transfer possibilities, vary among ecosystem services and benefits. As a result, careful consideration in the use and application of value transfer, both in biophysical estimates and welfare value estimates, is advocated to supply reliable information for policy making.