Contribution of canopy leaching to sulphate deposition in a Scots pine forest.

Cape, J.N.; Sheppard, Lucy; Fowler, David; Harrison, Anthony; Parkinson, J A; Dao, P; Paterson, I S. 1992 Contribution of canopy leaching to sulphate deposition in a Scots pine forest. Environmental Pollution, 75 (2). 229-236.

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Radioactive sulphate (35SO4) was applied to the soil below a Scots pine forest on 23 June 1989, and its movement into the canopy and into throughfall and stemflow was measured over 4 months. The specific activity, Bq (mg S)−1, of the canopy increased monotonically; uptake by current-year (1989) expanding needles was initially twice as fast as by older needles or live twigs. By 10 October the canopy average specific activity was 62 Bq (mg S)−1. The specific activity of net throughfall (throughfall + stemflow - rain), deduced from measurements from six throughfall collectors, six stemflow collectors and two rain collectors, fell rapidly from 12·6 Bq (mg S)−1 in late July to <1 Bq (mg S)−1 in mid-August. The results suggest (assuming rapid equilibration of 35S with sulphate in soil) that root-derived sulphate contributed c. 3% of sulphate in net throughfall and that dry deposition of SO2 and sulphate particles contributed c. 97% of the 0·56 g S m−2 measured in net throughfall over the period. Simultaneous measurements of SO2 at canopy height and of NH3 above and within the canopy gave mean concentrations of 5·9 and 0·86 μg m−3, respectively, sufficient to account for the sulphate measured in net throughfall only if codeposition of NH3 and SO2 occurred to canopy surfaces. The large values of specific activity observed in July, however, indicate that throughfall composition may be closely related to recent soil input of sulphate, and that equilibrium cannot be safely assumed. The possibility of a significant contribution of soil-derived sulphate to sulphate deposition in net throughfall cannot be ruled out on the basis of this experiment.

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: 0269-7491
NORA Subject Terms: Ecology and Environment
Atmospheric Sciences
Date made live: 13 May 2009 10:34 +0 (UTC)

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