Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 47

Report summarising statistical analysis of controls on DOC variations at UK long-term monitoring sites

This deliverable takes the form of a paper published in Environmental Pollution in June 2005. The paper presents the most recent DOC trend data for UK Acid Waters Monitoring Network (AWMN) sites, reviews the possible causes of rising DOC, and identifies the potential consequences of these changes. A statistical analysis was undertaken for the 11 lakes in the network, in which DOC time series were compared to a range of potential driving variables including temperature, rainfall, and lake acidity, non−marine sulphate concentration and ionic strength. Within−year DOC variations appear to be most strongly linked to temperature. Long−term trends are more difficult to attribute to particular drivers, but positive correlations were found with temperature, and negative correlations with non−marine sulphate and the sum of acid anions. The initial conclusion from this assessment is that both climate (temperature) and deposition chemistry (a combination of pollutant sulphate and natural seasalt deposition) have contributed to DOC trends in the UK. Temperature appears to influence the rate of potential dissolved organic carbon production, while deposition chemistry influences its solubility through its influence on soil water acidity and ionic strength. These findings indicate that changes in climate and acid deposition will need to be considered together in order to model future changes in surface water DOC, and its ecological effects. Further statistical analysis of DOC data for the UK and other partners in the project is ongoing, and will contribute to the development of a final spatial/temporal model of DOC for Task 5.2

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