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Modelling of marine base cation emissions, concentrations and deposition in the UK

By M. Werner, M. Kryza, A.J. Dore, M. Blas, S. Hallsworth, M. Vieno, Y.S. Tang and R.I. Smith


Base cations exert a large impact on various geochemical\ud and geophysical processes both in the atmosphere\ud and at the Earth surface. One of the essential roles of these\ud compounds is impact on surface pH causing an increase in\ud alkalinity and neutralizing the effects of acidity generated\ud by sulphur and nitrogen deposition. During recent years anthropogenic\ud emissions of base cations in the UK have decreased\ud substantially, by about 70%, 78%, 75% and 48%\ud for Na+, Mg2+, Ca2+ and K+, respectively, over the period\ud 1990–2006. For the island regions, such as the UK,\ud the main source of base cation particles is the aerosol produced\ud from the sea surface. Here, the sea salt aerosol (SSA)\ud emissions are calculated with parameterisations proposed by\ud M°artensson et al. (2003) for ultra fine particles, Monahan et\ud al. (1986) for fine particles and Smith and Harisson (1998)\ud for coarse particles continuously with a 0.1 μm size step using\ud WRF-modelled wind speed data at a 5 km×5 km grid\ud square resolution with a 3 h time step for two selected years\ud 2003 and 2006. SSA production has been converted into base\ud cation emissions, with the assumption that the chemical composition\ud of the particle emitted from the sea surface is equal\ud to the chemical composition of sea water, and used as input\ud data in the Fine Resolution Atmospheric Multi-pollutant Exchange\ud Model (FRAME). FRAME model annual mean concentrations\ud and total wet deposition at a 5 km×5 km grid\ud resolution, are compared with concentrations in air and wet\ud deposition from the National Monitoring Network and measurements\ud based estimates of UK deposition budget. The\ud correlation coefficient for wet deposition achieves high values\ud (R =0.8) for Na+ and Mg2+, whereas for Ca2+ the correlation\ud is poor (R < 0.3). Base cation concentrations are\ud also represented well, with some overestimations on the west\ud coast and underestimations in the centre of the land

Topics: Atmospheric Sciences
Year: 2011
DOI identifier: 10.5194/acp-11-1023-2011
OAI identifier: oai:nora.nerc.ac.uk:13352
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