Reconstructing long-term records of dissolved CO2

Abstract

Abstract: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 0Ð39 t km 2 year 1 for the River Tees and between 0 and 0Ð65 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 0Ð0 and 1Ð49 kg m 2 year 1 , and calculated in-stream productions of CO 2 are estimated as between 0Ð5 and 2Ð5% 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 3Ð1 and 7Ð5 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.

The rate of and controls upon DOC loss in a peat catchment

“…This suggests that a significant amount of DOC removal may happen close to its source. Hope et al (2001); Worrall and Burt (2005a) have shown that dissolved CO 2 release is a significant percentage of the carbon release from a catchment and is a component of the carbon cycle of peatlands that will always result in addition of CO 2 to the atmosphere. However, the amount of dissolved CO 2 released from a catchment is critically dependent upon in-stream processes (Jones and Mulholland, 1998).…”

In situCO2profiles with complementary monitoring of O2in a drained peat layer

“…Worrall et al . (2005) and Worrall and Burt (2005), based on carbon discharge data over three decades, determined that the amount of dissolved CO 2 produced in peat soils ranged between 9.6 and 25.6 t C km −2 year −1 and that this would decrease the predicted value of the net CO 2 sink by up to 50%.…”

Climate change in the uplands: a UK perspective on safeguarding regulatory ecosystem services

“…The carbon flux depends on vegetation composition, organic matter input and substrate availability to enzymes (Davidson & Janssens 2006, Laiho 2006. Older peat formations can only decay, but decomposition and carbon release from newer peat layers may be offset by rates of new peat growth (Worrall & Burt 2005). Furthermore, fluvial export of carbon as undissolved particulate organic carbon (POC) is secondary to losses through gaseous exchange in eroding peatlands and at least equivalent to the net gaseous flux from intact peatlands (Worrall et al 2003, Evans et al 2006b).…”

“…A study of moorland fire frequency in the Pennines showed a high incidence during the hot dry summer of 1976 and dry spring of 2003, and the greatest frequency of fires tended to be on eroded bare peat . Water treatment plants downstream of blanket bogs can incur increased costs when DOC emissions rise following upland fires (Worrall & Burt 2005). A further complicating factor is that some moorland is regularly burnt as part of a deliberate management strategy to encourage new vegetation growth for game birds.…”

“…Some issues could be addressed by research that identifies the benefits of upland management to other sectors such as water colour treatment likely to become increasingly expensive and difficult under climate change (Worrall & Burt 2005). Voluntary and subsidised agri-environment schemes may be limited in terms of scale of effectiveness unless there is scope for land purchase or other economic returns from managing land just for the water resource for example.…”