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Evaluation of SO2 dry deposition over short vegetation in Portugal

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Resumo:SO2 dry deposition was studied over short vegetation, in Portugal, by means of the concentration gradient method. The experimental study involved one first phase of long-term measurements carried out in a grassland and, subsequently, a second period of several 1997 intensive field campaigns performed in three places representing different climate and surface conditions. Temporal and spatial patterns of dry deposition parameters show that downward fluxes of SO2 are by some extent affected by surface processes. Median Rc varied from 140 s cm-1 to values around 200 s cm-1, in a wide range of environmental conditions. Stomatal uptake is an important sink when vegetation is biologically active, but its contribution is effectively low when compared with non-stomatal mechanisms, especially when the surface is wet. Under dry conditions Rc increases by a factor of two, but SO2 deposition rates then still are signifficant. The parameterisation of the surface resistance for SO2 proved to be difficult, but Vd derived with the Erisman parameterisation (Erisman et al., Atmos. Environ. 28 (16) (1994) 2595) compared best with measured values, at low time resolution scale and especially under moisture conditions.
Autores principais:Feliciano, Manuel
Outros Autores:Pio, Casimiro; Vermeulen, Alex
Assunto:Sulfur dioxide Dry deposition Vegetation Portugal
Ano:2001
País:Portugal
Tipo de documento:artigo
Tipo de acesso:acesso restrito
Instituição associada:Instituto Politécnico de Bragança
Idioma:inglês
Origem:Biblioteca Digital do IPB

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