Relationships between riverine and terrestrial dissolved organic carbon: concentration, radiocarbon signature, specific UV absorbance

Tipping, E. et al. (2022) Relationships between riverine and terrestrial dissolved organic carbon: concentration, radiocarbon signature, specific UV absorbance. Science of the Total Environment, 817, 153000. (doi: 10.1016/j.scitotenv.2022.153000) (PMID:35031358)

Abstract

The transfer of dissolved organic carbon (DOC) from land to watercourses plays a major role in the carbon cycle, and in the transport and fate of associated organic and inorganic contaminants. We investigated, at global scale, how the concentrations and properties of riverine DOC depend upon combinations of terrestrial source solutions. For topsoil, subsoil, groundwater and river solutions in different Köppen-Geiger climatic zones, we compiled published and new values of DOC concentration ([DOC]), radiocarbon signature (DO14C), and specific UV absorbance (SUVA). The average value of each DOC variable decreased significantly in magnitude from topsoil to subsoil to groundwater, permitting the terrestrial sources to be distinguished. We used the terrestrial data to simulate the riverine distributions of each variable, and also relationships between pairs of variables. To achieve good matches between observed and simulated data, it was necessary to optimise the distributions of water fractions contributed by each of the three terrestrial sources, and also to reduce the mean input terrestrial [DOC] values, to about 60% of the measured ones. One possible explanation for the required lowering of the modelled terrestrial [DOC] values might be unrepresentative sampling of terrestrial DOC, including dilution effects; another is the loss of DOC during riverine transport. High variations in simulated riverine DOC variables, which match observed data, are due predominantly to variations in source solution values, with a lesser contribution from the different combinations of source waters. On average, most DOC in rivers draining catchments with forest and/or grass-shrub land cover comes in similar amounts from topsoil and subsoil, with about 10% from groundwater. In rivers draining croplands, subsoil and groundwater solutions are the likely dominant DOC sources, while in wetland rivers most DOC is from topsoil.

• Item Type: Articles
• Additional Information: The research was partly funded by the UK Natural Environment Research Council Macronutrient Cycles Programme (LTLS project, Grant No. NE/J011533/1), and the Scottish Government.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark and Ascough, Dr Philippa
• Authors: Tipping, E., Eliasa, J. L., Keenan, P. O., Helliwell, R. C., Pedentchouk, N., Cooper, R. J., Buckingham, S., Gjessing, E., Ascough, P., Bryant, C. L., and Garnett, M. H.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Science of the Total Environment
• Publisher: Elsevier
• ISSN: 0048-9697
• ISSN (Online): 1879-1026
• Published Online: 11 January 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Science of the Total Environment 817: 153000
• Publisher Policy: Reproduced under a Creative Commons License