Saturday, 15 July 2006

Long Term Dissolved Organic Carbon Fluxes in Streams of Central Scotland.

Catherine L. Wearing, Ian C. Grieve, and David W. Hopkins. School of Biological and Environmental Sciences, Univ of Stirling, Stirling, United Kingdom

The export of Dissolved Organic Carbon (DOC) from catchments with peat soils in the UK has increased over the last decade, which may be linked to observed increases in temperature and rainfall. However it is not clear whether increases in DOC concentrations are caused by increases in DOC production in organic soils induced by temperature or other changes or by increased transport through greater incidence of high flows induced by rainfall changes. Increases in both temperature and rainfall have been predicted in Scotland over the next few decades and these may further increase DOC concentrations and exports. The implications of this include both a decrease in water quality and an increase in mobility of metals in upland water bodies. This study aims to separate the effects of temperature and hydrology controls of DOC in upland streams in central Scotland. To achieve this, a stream draining the Ochil Hills catchment, a grass moorland site in central Scotland, has been monitored intensively from September 2004. DOC concentrations showed a marked increase during high flow events when compared to base flows, particularly during the autumn period (September-November), where a strong regression relationship was identified between DOC and discharge. Previous research at the same site during the early 1980's, allowed the opportunity to compare the DOC/discharge regression relationship recorded then with the contemporary relationship. The comparison showed that the DOC/discharge regression relationship has not changed, except during high flow events where an increase in the slope of the regression line can be seen. The concentrations of DOC have increased over the last 20 years, particularly during high flow events in the late summer and autumn. This is when the highest concentrations of DOC are available for movement from the soil and the shift in the DOC/discharge regression relationship was identified.

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