Reconstructing long-term records of dissolved CO2

Abstract

The dissolved CO2 concentration of stream waters is an important component of the terrestrial carbon cycle. This study reconstructs long-term records of dissolved CO2 concentration for the outlets of two large catchments (818 and 586 km2) in northern England. The study shows that: 1. The flux of dissolved CO2 from the catchments (as carbon per catchment area), when adjusted for that which would be carried by the river water at equilibrium with the atmosphere, is between 0 and 0·39 t km−2 year−1 for the River Tees and between 0 and 0·65 t km−2 year−1 for the River Coquet. 2. The flux of dissolved CO2 is closely correlated with dissolved organic carbon (DOC) export and is unrelated to dissolved CO2 export from the headwaters of the study catchments. 3. The evasion rate of CO2 from the rivers (as carbon per stream area) is between 0·0 and 1·49 kg m−2 year−1, and calculated in-stream productions of CO2 are estimated as between 0·5 and 2·5% of the stream evasion rate. 4. By mass balance, it is estimated that 8% of the annual flux of DOC is lost within the streams of the catchment. The study shows that the loss of CO2 from the streams of the Tees catchment is between 3·1 and 7·5 kt year−1 (as carbon) for the River Tees, which is the same order as annual CH4 flux from peats within the catchment and approximately 50% of the net CO2 exchange to the peats of the catchment. Copyright © 2005 John Wiley & Sons, Ltd.