Stable isotope analysis reveals lower-order river dissolved inorganic carbon pools are highly dynamic

Susan Waldron, E. Marian Scott, Chris Soulsby

Research output: Contribution to journalArticlepeer-review

77 Citations (Scopus)


River systems draining peaty catchments are considered a source of atmospheric CO2,thus understanding the behavior of the dissolved inorganic carbon pool (DIC) is valuable. The carbon isotopic composition, delta C-13(DIC), and concentration, [DIC], of fluvial samples collected diurnally, over 14 months, reveal the DIC pools to be dynamic in range (-22 to -4.9 parts per thousand,0.012 to 0.468 mmol L-1 C), responding predictably to environmental influences such as changing hydrologic conditions or increased levels of primary production. 6180 of dissolved oxygen (DO) corroborates the delta C-13(DIC) interpretation. A nested catchment sampling matrix reveals that similar processes affect the DIC pool and thus delta C-13(DIC) across catchment sizes. Not so with [DIC]: at high flow, the DIC export converges across catchment size, but at low flow catchments diverge in their DIC load. Contextualizing delta C-13 with discharge reveals that organic soil-waters and groundwaters comprise end member sources, which in varying proportions constitute the fluvial DIC pool. Discharge and pH describe well [DIC] and delta C-13(DIC), allowing carbon to be apportioned to each end-member from continuous profiles, demonstrated here for the hydrological year 2003-2004. This approach is powerful for assessing whether the dynamic response exhibited here is ubiquitous in other fluvial systems at the terrestrial aquatic interface or in larger catchments.

Original languageEnglish
Pages (from-to)6156-6162
Number of pages7
JournalEnvironmental Science & Technology
Issue number17
Early online date28 Jul 2007
Publication statusPublished - 1 Sep 2007


  • aquatic ecosystems
  • catchment
  • Canada
  • waters
  • lakes
  • respiration
  • Scotland
  • dioxide
  • fluxes
  • basin


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