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

Waldron, S., Scott, E. and Soulsby, C. (2007) Stable isotope analysis reveals lower-order river dissolved inorganic carbon pools are highly dynamic. Environmental Science and Technology, 41, pp. 6156-6162. (doi: 10.1021/es0706089)

Abstract

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, δ13CDIC, and concentration, [DIC], of fluvial samples collected diurnally, over 14 months, reveal the DIC pools to be dynamic in range (−22 to −4.9‰, 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. δ18O of dissolved oxygen (DO) corroborates the δ13CDIC interpretation. A nested catchment sampling matrix reveals that similar processes affect the DIC pool and thus δ13CDIC 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 δ13C 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 δ13CDIC, 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.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Waldron, Professor Susan
• Authors: Waldron, S., Scott, E., and Soulsby, C.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Environmental Science and Technology
• Journal Abbr.: EST
• Publisher: American Chemical Society
• ISSN: 0013-936X
• ISSN (Online): 1520-5851