Article

Biogeochemistry

, Volume 70, Issue 3, pp 369-402

Trends in Dissolved Organic Carbon in UK Rivers and Lakes

  • Fred WorrallAffiliated withDepartment of Earth Sciences, Science Laboratories Email author 
  • , Ron HarrimanAffiliated withThe Freshwater Laboratory, Faskally
  • , Chris D. EvansAffiliated withCentre for Ecology and Hydrology, University of Wales
  • , Carol D. WattsAffiliated withCentre for Ecology and Hydrology
  • , John AdamsonAffiliated withEnvironmental Change Network, Centre for Ecology and Hydrology, Merlewood
  • , Colin NealAffiliated withCentre for Ecology and Hydrology
  • , Ed TippingAffiliated withCentre for Ecology and Hydrology, Ferry House
  • , Tim BurtAffiliated withDepartment of Geography, Science Laboratories
  • , Ian GrieveAffiliated withDepartment of Environmental Science, University of Stirling
    • , Don MonteithAffiliated withEnvironmental Change Research Centre, University College London
    • , Pam S. NadenAffiliated withCentre for Ecology and Hydrology
    • , Tom NisbetAffiliated withDepartment of Earth Sciences, Science LaboratoriesForest Research, Alice Holt lodge
    • , Brian ReynoldsAffiliated withCentre for Ecology and Hydrology, University of Wales
    • , Paul StevensAffiliated withCentre for Ecology and Hydrology, University of Wales

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Abstract

Several studies have highlighted an increase in DOC concentration in streams and lakes of UK upland catchments though the causal mechanisms controlling the increase have yet to be fully explained. This study, compiles a comprehensive data set of DOC concentration records for UK catchments to evaluate trends and test whether observed increases are ubiquitous over time and space. The study analysed monthly DOC time series from 198 sites, including 29 lakes, 8 water supply reservoirs and 161 rivers. The records vary in length from 8 to 42 years going back as far as 1961. Of the 198 sites, 153 (77%) show an upward trend in DOC concentration significant at the 95% level, the remaining 45 (23%) show no significant trend and no sites show a significant decrease in DOC concentration. The average annual increase in DOC concentration was 0.17 mg C/l/year. The dataset shows: (i) a spatial consistent upward trend in the DOC concentration independent of regional effects of rainfall, acid and nitrogen deposition, and local effects of land-use change; (ii) a temporally consistent increase in DOC concentration for period back as far as the 1960s; (iii) the increase in DOC concentration means an estimated DOC flux from the UK as 0.86 Mt C for the year 2002 and is increasing at 0.02 Mt C/year. Possible reasons for the increasing DOC concentration are discussed.

Keywords

Climate change DOC Lakes Rivers Trends