Atmospheric inputs and catchment solute fluxes for major ions in five Welsh upland catchments

Reynolds, B.; Fowler, D.; Smith, R. I.; Hall, J. R.. 1997 Atmospheric inputs and catchment solute fluxes for major ions in five Welsh upland catchments. Journal of Hydrology, 194 (1-4). 305-329.

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The hydrochemical budgets of major inorganic ions in three grassland and two forest catchments (ranging from 72 to 376 ha) in the uplands of Wales have been measured over a 2 year period. The catchment outputs of major ions have been compared with the total atmospheric inputs, the latter comprising dry deposition of NO2, SO2 and NH3, cloud droplet (occult) deposition of SO42−, NO3−, Cl−, Na+, Ca2+, Mg2+ and NH4+, and wet deposition of the same ions. The enhancement in wet deposition by orographic effects was modelled to provide wet deposition. The catchment output over 2 years is in good agreement with atmospheric inputs for the marine ions Cl− (±5%) and, to a lesser extent, Na+ (±10%). For sulphur, good agreement between inputs and outputs is also generally obtained (±10%), demonstrating the need to quantify all of the major atmospheric deposition pathways. The majority of the sulphur (approximately 70%) is wet deposited, and these studies provide strong support for the procedures to modify orographic enhancement of wet deposition in the UK uplands. The cloud droplet deposition pathway is generally a minor component of the budget but may approach 25% for afforested catchments. Dry deposition of SO2 and NO2 is a relatively small component (20–30%) of the S and N budgets, whereas dry deposition of NH3 is a major input (approximately 50%), although current estimates of annual NH3 inputs are subject to large uncertainties. If chloride is assumed to behave as a conservative ion in the catchments, then the mass flux estimates show that the annual base cation weathering within catchments unaffected by bedrock mineralisation and agricultural liming may be estimated directly from the mass budget, and should range from 1–11 kg ha−1 year−1 (Ca2+) and from 2–6 kg ha−1 year−1 (Mg2+).

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
UKCEH and CEH Sections/Science Areas: _ Pre-2000 sections
ISSN: 0022-1694
NORA Subject Terms: Atmospheric Sciences
Date made live: 03 Sep 2008 12:58 +0 (UTC)

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