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

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dc.contributor.authorOudone, PPen_AU
dc.contributor.authorRutlidge, Hen_AU
dc.contributor.authorAndersen, MSen_AU
dc.contributor.authorO'Carroll, DMen_AU
dc.contributor.authorCheong, Sen_AU
dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorMcDonough, LKen_AU
dc.contributor.authorMarjo, CEen_AU
dc.contributor.authorBaker, AAen_AU
dc.date.accessioned2022-07-21T23:43:00Zen_AU
dc.date.available2022-07-21T23:43:00Zen_AU
dc.date.issued2019-12-13en_AU
dc.date.statistics2022-06-27en_AU
dc.descriptionNon-peer reviewed preprinten_AU
dc.description.abstractDetailed 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 shallow-sandy 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 Fe2+ 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 regression predicts less DOC (HS) sorption in quartz sand system, agreeing with laboratory sorption results. HS sorption also correlated with aromaticity suggesting the chemical character of HS will control the degree of mineral sorption. The model also indicated that DOC sorption is negatively correlated with dissolved Fe2+ concentration in water samples presumably due to redox condition which is under anoxic environment iron oxide became electron acceptors under the process of DOC biodegradation leaving higher Fe2+ concentration and less available DOC for sorption.en_AU
dc.description.sponsorshipAustralian Research Council [Discovery Project number DP160101379]en_AU
dc.identifier.articlenumberpreprinten_AU
dc.identifier.citationOudone, P., Rutlidge, H., Andersen, M., O'Carroll, D., Cheong, S., Meredith, K., McDonough, L. K., Marjo, C. & Baker, A. (2019). Characterisation and controls on mineral-sorbed organic matter from a variety of groundwater environments. EarthArXiv, (Preprint). doi:10.31223/osf.io/ue86wen_AU
dc.identifier.journaltitleEarthArXiven_AU
dc.identifier.urihttps://doi.org/10.31223/osf.io/ue86wen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/13416en_AU
dc.language.isoenen_AU
dc.publisherEarthArXiven_AU
dc.subjectGround wateren_AU
dc.subjectAquifersen_AU
dc.subjectOrganic matteren_AU
dc.subjectMineralsen_AU
dc.subjectCarbon sourcesen_AU
dc.subjectCarbon sinksen_AU
dc.subjectBiodegradationen_AU
dc.subjectQuartzen_AU
dc.subjectSanden_AU
dc.subjectCalciteen_AU
dc.titleCharacterisation and controls on mineral-sorbed organic matter from a variety of groundwater environmentsen_AU
dc.typeJournal Articleen_AU
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