Reconstructing long‐term records of dissolved CO 2

The dissolved CO 2 concentration of stream waters is an important component of the terrestrial carbon cycle. This study reconstructs long‐term records of dissolved CO 2 concentration for the outlets of two large catchments (818 and 586 km 2 ) in northern England. The study shows that: 1. The flux of dissolved CO 2 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 CO 2 is closely correlated with dissolved organic carbon (DOC) export and is unrelated to dissolved CO 2 export from the headwaters of the study catchments. 3. The evasion rate of CO 2 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 CO 2 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 CO 2 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 CH 4 flux from peats within the catchment and approximately 50% of the net CO 2 exchange to the peats of the catchment. Copyright © 2005 John Wiley & Sons, Ltd.