Journal article
Seasonal exports and drivers of dissolved inorganic and organic carbon, carbon dioxide, methane and δ(13)C signatures in a subtropical river network
The Science of the Total Environment, Vol.575, pp.545-563
2017
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Abstract
<p><p id="x-x-x-sp0095">Riverine systems act as important aquatic conduits for carbon transportation between atmospheric, terrestrial and oceanic pools, yet the magnitude of these exports remain poorly constrained. Interconnected creek and river sites (n = 28) were sampled on a quarterly basis in three subcatchments of the subtropical Richmond River Catchment (Australia) to investigate spatial and temporal dynamics of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>), and carbon stable isotope ratios (δ<sup>13</sup>C). The study site is an area of high interest due to potential unconventional gas (coal seam gas or coal bed methane) development. DIC exports were driven by groundwater discharge with a small contribution by in situ DOC remineralization. The DIC exports showed seasonal differences ranging from 0.10 to 0.27 mmol m<sup>− 2</sup> catchment d<sup>− 1</sup> (annual average 0.17 mmol m<sup>− 2</sup> catchment d<sup>− 1</sup>) and peaked during winter when surface water discharge was highest. DOC exports (sourced from terrestrial organic matter) had an annual average 0.07 mmol m<sup>− 2</sup> catchment d<sup>− 1</sup>and were 1 to 2 orders of magnitude higher during winter compared to spring and summer. CO<sub>2</sub> evasion rates (annual average of 347 mmol m<sup>− 2</sup> water area d<sup>− 1</sup>) were ~ 2.5 fold higher during winter compared to spring. Methane was always supersaturated (0.19 to 62.13 μM), resulting from groundwater discharge and stream-bed methanogenesis. Methane evasion was highly variable across the seasons with an annual average of 3.05 mmol m<sup>− 2</sup> water area d<sup>− 1</sup>. During drier conditions, stable isotopes implied enhanced CH<sub>4</sub> oxidation. Overall, carbon losses from the catchment were dominated by CO<sub>2</sub> evasion (60%) followed by DIC exports (30%), DOC exports (9%) and CH<sub>4</sub> evasion (< 1%). Our results demonstrated broad catchment scale spatial and temporal variability in carbon dynamics, and that groundwater discharge and rain events controlled carbon exports.</p>
Details
- Title
- Seasonal exports and drivers of dissolved inorganic and organic carbon, carbon dioxide, methane and δ(13)C signatures in a subtropical river network
- Creators
- Marnie L Atkins - Southern Cross UniversityIsaac R Santos - Southern Cross UniversityDamien T Maher - Southern Cross University
- Publication Details
- The Science of the Total Environment, Vol.575, pp.545-563
- Identifiers
- 4030; 991012820962902368
- Academic Unit
- School of Environment, Science and Engineering; Faculty of Science and Engineering; Science
- Resource Type
- Journal article