HR: 16:00h
AN: B24A-01    [Abstracts]
TI: Alternative Explanations for Increased Dissolved Organic Carbon Concentrations in UK Surface Waters
AU: * Chapman, P
EM: p.j.chapman@leeds.ac.uk
AF: School of Geography, University of Leeds, Leeds, LS2 9JT
AU: Evans, C
EM: cev@ceh.ac.uk
AF: Centre for Ecology and Hydrology, Deiniol Road, Bangor, LL57 2UP
AU: Monteith, D
EM: ucfadom@ucl.ac.uk
AF: Environmental Change Research Unit, University College London, London, WC1H 0AP
AU: Clark, J
EM: geojmcl@leeds.ac.uk
AF: School of Geography, University of Leeds, Leeds, LS2 9JT
AU: Cresser, M
EM: msc5@york.ac.uk
AF: Environment Department, University of York, York, YO10 5DD
AB: Since 1988, there has been a 91% increase in dissolved organic carbon (DOC) concentrations of UK lakes and streams in the Acid Waters Monitoring Network (AWMN). Similar increases in DOC have been observed in surface waters across Europe and North America. This has generated great debate about the factors driving DOC rises. The role of global warming has been a topic of great attention, as DOC production is known to increase with temperature. Although recent research has suggested changes in temperature cannot sufficiently explain this trend, data from our own warming experiment on a peat soil has shown higher rates of DOC release under both anaerobic and aerobic conditions. These data suggest that temperature is quantitatively significant, but may not explain the full magnitude of DOC increases. Additional monitoring and experimental work has identified a clear, inverse link between DOC and sulphate (SO4), such that doubling the SO4 concentration decreased DOC by a factor of 1.5. Increased concentrations of SO4 are associated with a reduction in pH and increase in ionic strength, with both factors known to control DOC solubility. Further statistical analysis of 11 AWMN lakes has revealed that rising temperature and declining sulphur deposition can account for the majority (average 66%) of the observed DOC trend. Therefore a key driver of DOC increase observed at AWMN sites across the UK appears to have been the major (50%) decrease in sulphur (S) deposition, and associated recovery from acidification, which has occurred in the UK (and other parts of Europe and North America) since the mid 1980s, in addition to rising temperatures.
DE: 1803 Anthropogenic effects
DE: 1806 Chemistry of fresh water
DE: 1615 Biogeochemical processes (4805)
DE: 1655 Water cycles (1836)
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting