The flux of carbon from rivers: the case for flux from England and Wales

Abstract

This study uses the extensive monitoring datasets of the Environment Agency of England and Wales to calculate the flux of dissolved organic carbon (DOC); particulate organic carbon (POC); and excess dissolved CO 2 through English and Welsh rivers. The innovation of this study's approach is to account for the losses of carbon within the fluvial system as well as fluxes at the catchment outlet. In order to make this assessment this study considers: the biochemical oxygen demand (BOD) as a measure of the degradation of DOC; and the dissolved CO 2 concentration of groundwater as calculated and apportioned into surface waters on the basis of Ca concentrations. The study shows that the best estimate of carbon export, via rivers, from England and Wales is 10.34 Mg C/km 2 /year, with 4.19 Mg C/ km 2 /year of this going to the atmosphere. The mapping of the carbon export shows that there are regional hotspots of carbon export and in a small number of cases rivers could be net sinks of carbon due to their low dissolved CO 2 content relative to the atmosphere. The flux calculated by this approach is probably still an underestimate of the carbon flux through fluvial systems but the scale of the export is greater than that previously reported and there is evidence that the fluvial flux of carbon is increasing on a decadal scale.

The significance of organic carbon and nutrient export from peatland-dominated landscapes subject to disturbance, a stoichiometric perspective

“…If all DOC is converted to CO 2 the flux estimate ranges from 6.7-18.9 g cm −2 yr −1 across the catchments. This is larger than CO 2 efflux measured directly by at Auchencorth Moss, 4.6 g C m −2 yr −1 or the estimated average of 4.1 g C cm −2 yr −1 for the rivers of England and Wales (Worrall et al, 2007), but smaller than the measured efflux of 35.8 g cm −2 yr −1 from rivers in the NE European tundra (measured only during the ice free period) considered to have come from the respiration of organic matter and free CO 2 leached from the catchment (Heikkinen et al, 2004). It is likely that our estimate for potential CO 2 efflux based on stoichiometric excess is greater than that effluxed from the system as not all DOC will be respired prior to export from the catchment.…”

Fluvial organic carbon losses from a Bornean blackwater river

“…Several studies have shown that in-stream production of DOC (for example from POC degradation) is small in comparison to that which is derived from terrestrial sources (e.g. Worrall et al, 2007).…”

Continuous measurement of spectrophotometric absorbance in peatland streamwater in northern England: implications for understanding fluvial carbon fluxes

“…Significant increases in DOC concentrations in runoff from upland peat catchments have been observed over the past few decades (Worrall et al, 2003;Worrall et al, 2004;Evans et al, 2005;Evans et al, 2006;Worrall and Burt, 2007). Numerous mechanisms have been suggested to account for these increases (Evans et al, 2005;Worrall et al, 2007b) including land management change, decreases in sulphate deposition, and temperature change. The presence of DOC results in water becoming coloured, posing * Correspondence to: Richard Grayson, School of Geography, University of Leeds, Leeds, LS2 9JT, UK.…”

“…Most scientific studies involve absolute measurements of DOC (using TOC analysers) to establish the relationship between absorbance and DOC. Several studies reporting increased DOC losses from UK upland peat catchments have used absorbance at 400 nm as a proxy for DOC (Watts et al, 2001;Worrall et al, 2003Worrall et al, , 2007b. In addition to direct measurement of DOC the UK Environmental Change Network (ECN) measure absorbance at 436 nm, with Worrall et al (2002) having observed a strong linear relationship between DOC and absorbance at both 436 and 400 nm.…”