Changes in global groundwater organic carbon driven by climate change and urbanization

McDonough, Liza; Santos, Isaac R.; Andersen, Martin S.; O'Carroll, D. M.; Rutlidge, Helen; Meredith, Karina; Oudone, Phetdala; Bridgeman, John; Gooddy, Daren C.; Sorensen, James; Lapworth, Dan; MacDonald, Alan; Ward, Jade; Baker, A.

doi:10.1038/s41467-020-14946-1

Cited by 179 publications

(82 citation statements)

References 56 publications

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“…Groundwater replenishment can occur either as diffuse recharge through the OM-rich soil zone or as indirect recharge originating from streams and wetlands that have the potential to contain high concentrations of OM. Despite the many sources of OM, groundwater dissolved organic carbon (DOC) concentrations are typically low (∼ 1 mg L −1 for the global median DOC concentration; McDonough et al, 2020a), suggesting significant processing in the subsurface.…”

Section: Introductionmentioning

confidence: 99%

Isotopic and chromatographic fingerprinting of the sources of dissolved organic carbon in a shallow coastal aquifer

Meredith

Baker

Andersen

et al. 2020

Hydrol. Earth Syst. Sci.

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Abstract. The terrestrial subsurface is the largest source of freshwater globally. The organic carbon contained within it and processes controlling its concentration remain largely unknown. The global median concentration of dissolved organic carbon (DOC) in groundwater is low compared to surface waters, suggesting significant processing in the subsurface. Yet the processes that remove this DOC in groundwater are not fully understood. The purpose of this study was to investigate the different sources and processes influencing DOC in a shallow anoxic coastal aquifer. Uniquely, this study combines liquid chromatography organic carbon detection with organic (δ13CDOC) carbon isotope geochemical analyses to fingerprint the various DOC sources that influence the concentration, carbon isotopic composition, and character with respect to distance from surface water sources, depth below surface, and inferred groundwater residence time (using 3H activities) in groundwater. It was found that the average groundwater DOC concentration was 5 times higher (5 mg L−1) than the global median concentration and that the concentration doubled with depth at our site, but the chromatographic character did not change significantly. The anoxic saturated conditions of the aquifer limited the rate of organic matter processing, leading to enhanced preservation and storage of the DOC sources from peats and palaeosols contained within the aquifer. All groundwater samples were more aromatic for their molecular weight in comparison to other lakes, rivers and surface marine samples studied. The destabilization or changes in hydrology, whether by anthropogenic or natural processes, could lead to the flux of up to 10 times more unreacted organic carbon from this coastal aquifer compared to deeper inland aquifers.

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Section: Introductionmentioning

confidence: 99%

Isotopic and chromatographic fingerprinting of the sources of dissolved organic carbon in a shallow coastal aquifer

Meredith

Baker

Andersen

et al. 2020

Hydrol. Earth Syst. Sci.

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“…The source of such high concentration is assumed to be from surface vegetation, mobilized particulate organic matter and in-situ peat in that sandy environment (Meredith et al). This concentration is about 5 times higher than median global groundwater DOC concentration (McDonough et al, 2020a). X-ray Fluorescence spectrometry (XRF) analysis show that the major chemical composition of the soil is SiO2 (94%) while only 0.20% Fe2O3 is present.…”

Section: Factors Controlling Natural Hs Sorptionmentioning

confidence: 74%

“…Despite their interaction, natural organic matter (NOM) concentration in groundwater is much lower compared to rivers. The global median groundwater dissolved organic carbon (DOC) is only 1.0 mg C L -1 (McDonough et al, 2020a). This leads to questions such as where does the missing fraction go?…”

Section: Introductionmentioning

confidence: 99%

“…Organic matter processes have been intensively studied as they play an important role in the global carbon cycle (Falkowski et al, 2000, Brown and Lugo, 1982, Santín et al, 2015, degraded water quality (Li et al, 2013, Delpla et al, 2009, affected water treatment efficiency (Paria, 2008, Wang et al, 2007, Rosenberger et al, 2006, modified water chemistry such as acidity environment (Delpla et al, 2009, Evans et al, 2005 and affect the heterogenous and complex nature of OM (Middelburg and Herman, 2007). Recently, groundwater DOC has been of interest to numerous investigators for identifying climate change and urbanization on altering global groundwater organic carbon (McDonough et al, 2020a), examining how different sources and processes influence shallow coastal groundwater DOC (Meredith et al, 2020), investigating changes in groundwater DOC after rainfall (McDonough et al, 2020b). However, the existing studies focused on natural DOC processing in groundwater are limited.…”

Section: Introductionmentioning

confidence: 99%

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Characterisation and controls on mineral-sorbed organic matter from a variety of groundwater environments

Oudone¹,

Rutlidge²,

Andersen³

et al. 2019

Preprint

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Detailed investigations into natural groundwater organic matter (OM) as carbon sources or sinks in the natural carbon cycle are generally limited. Groundwater OM concentration and composition is altered by biodegradation and sorption to minerals. In the saturated zone of an aquifer, dissolved organic matter (DOM) may represent a significant fraction of the natural groundwater dissolved organic carbon (DOC) pool, therefore understanding how mineral sorption influences OM will contribute to our understanding of how DOC is processed in groundwater. In this study we investigate the dominant fractions of natural DOC in groundwater and the extent of sorption on three common minerals found in the environment: iron-oxide coated sand, calcite and quartz sand. DOM sorption on these minerals was studied using groundwaters from three different geological environments in New South Wales, Australia: Anna Bay (quartz-sand coastal aquifer); Maules Creek (alluvial gravel and clay aquifer); and Wellington (alluvial karst limestone aquifer). Each groundwater and surface sample were characterised before and after sorption using size exclusion liquid chromatography with organic carbon detection (LC-OCD). Analysis revealed that humic substances (HS) are the dominant (13 -70%) fraction of natural groundwater DOC. HS sorption on iron-oxide coated sand was higher than that on calcite and quartz sand, respectively while sorption on the calcite was also higher than on quartz sand. In shallowsandy aquifer groundwater, due to less DOC sorption in sandy environment (Anna Bay), DOC concentration was found to be the highest compared to that from karst and other alluvial boreholes from Maules Creek and Wellington. HS sorption increases with the mineral mass and DOC concentration indicating that DOC sorption to the mineral surface did not reach saturation under the study conditions. Only the high-DOC alluvial groundwater produced significant sorption to each mineral phase and of the chemical fractions present (85% of 72 batch systems that HS sorption was found).Multiple linear regression showed that mineral mass, mineral type, depth of groundwater sample, DOC concentration, aqueous Fe 2+ concentration and DOM aromaticity are the controlling factors of DOC sorption in the various groundwater environments. The regression analysis showed sorption decreases with depth, which could be because of DOC sorption along the groundwater flow path, resulting in less DOC at depth. The multiple linear

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“…Long residence times of DOC derived from surface environments in groundwater is unlikely because biodegradation, oxidation, and adsorption to mineral surfaces in the aquifer will decrease groundwater DOC concentrations over time. A recent study has demonstrated that there is a global negative correlation between groundwater residence times and groundwater DOC concentrations (McDonough et al, ). It is therefore more likely that old DOC in groundwater with high residence times is derived from the uptake of geological organic carbon (e.g., hydrocarbons, kerogen, or ancient DOC adsorbed to mineral surfaces in the sedimentary aquifer matrix), or the incorporation of inorganic carbon from carbonate weathering into microbial biomass (Fellman et al, ).…”

Section: Further Questions: Where Does Old Groundwater Carbon Come From?mentioning

confidence: 99%

Groundwater Dependent Ecosystems in Arid Zones Can Use Ancient Subterranean Carbon as an Energy Source in the Local Food Web

Dean

2019

JGR Biogeosciences

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Groundwater dependent ecosystems (GDEs) are defined by their reliance on subterranean water resources, but GDE food webs may also depend on it as an energy source. Mazumder et al. (2019, https://doi.org/10.1029/2018JG004925), show a clear dependency of a local GDE food web on very old, potentially geological, carbon sourced from palaeo-groundwater discharge in the arid Great Artesian Basin in Australia. These findings support the emerging paradigm that ancient groundwater carbon is an important component of inland water carbon cycling and contemporary ecosystem functioning. Future work is needed to determine what proportion of total GDE energy needs are derived from groundwater carbon across a range of geological and hydroclimatic settings.Plain Language Summary Many arid ecosystems rely on groundwater for their water needs. A new study in the arid zone of Australia shows the incorporation of ancient carbon into living aquatic species in these ecosystems. This suggests that present-day ecosystems may rely on both water and carbon resources generated thousands of years ago when the prevailing environmental conditions were significantly different than today.

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Changes in global groundwater organic carbon driven by climate change and urbanization

Cited by 179 publications

References 56 publications

Isotopic and chromatographic fingerprinting of the sources of dissolved organic carbon in a shallow coastal aquifer

Isotopic and chromatographic fingerprinting of the sources of dissolved organic carbon in a shallow coastal aquifer

Characterisation and controls on mineral-sorbed organic matter from a variety of groundwater environments

Groundwater Dependent Ecosystems in Arid Zones Can Use Ancient Subterranean Carbon as an Energy Source in the Local Food Web

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