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Sulphate dynamics of podzols from paired impacted and pristine catchments

1990; Elsevier BV; Volume: 92; Linguagem: Inglês

10.1016/0048-9697(90)90333-p

1879-1026

T.A.B. Walker, R. McMahon, A. Hepburn, Robert C. Ferrier,

Groundwater and Isotope Geochemistry

The similarity in the physical and chemical parameters of the soil profiles located at Loch Chon (central Scotland) and Høylandet (mid Norway) enabled the comparison of soil sulphate adsorption and accumulation under two different levels of sulphate deposition. The Loch Chon site, due to its proximity to the industrialized central belt in Scotland, has received a history of anthropogenic sulphur loadings, while the Høylandet site is situated in an area of Norway subjected to precipitation generated from unpolluted air masses originating over the North Atlantic ocean. Both soils show accumulation of water-soluble sulphate in the organic horizons (45 mg S kg−1 at Chon and 65 mg S kg−1 at Høylandet), with low levels (0–5 mg S kg−1) being found in the mineral horizons. The iron podzol from the pristine (unpolluted) site at Høylandet had levels of adsorbed sulphate in the range of 0–17 mg S kg−1, which may have arisen through microbial mineralization of translocated organic matter and dead root tissue. In contrast, the humus iron podzol from Loch Chon, which had similar levels of mineralizable sulphate, showed a build-up of high levels of adsorbed sulphate throughout the profile (15–90 mg S kg−1). This additional sulphate may reflect a history of high anthropogenic sulphate deposition in this area, as laboratory based adsorption isotherm studies indicated that both soils were capable of adsorbing sulphate. Regression analysis indicated that adsorbed sulphate was correlated (5% level) with dithionite-soluble aluminium in the Loch Chon soil, but with the similar iron fraction in the Høylandet soil.