Changes in groundwater dissolved organic matter character in a coastal sand aquifer due to rainfall recharge

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dc.contributor.authorMcDonough, LKen_AU
dc.contributor.authorO'Carroll, DMen_AU
dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorAndersen, MSen_AU
dc.contributor.authorBrügger, Cen_AU
dc.contributor.authorHuang, HXen_AU
dc.contributor.authorRutlidge, Hen_AU
dc.contributor.authorBehnke, MIen_AU
dc.contributor.authorSpencer, RGMen_AU
dc.contributor.authorMcKenna, AMen_AU
dc.contributor.authorMarjo, CEen_AU
dc.contributor.authorOudone, PPen_AU
dc.contributor.authorBaker, AAen_AU
dc.date.accessioned2022-06-02T22:48:49Zen_AU
dc.date.available2022-06-02T22:48:49Zen_AU
dc.date.issued2020-02-01en_AU
dc.date.statistics2022-06-02en_AU
dc.description.abstractDissolved organic matter (DOM) in groundwater is fundamentally important with respect to biogeochemical reactions, global carbon cycling, heavy metal transport, water treatability and potability. One source of DOM to groundwater is from the transport of organic matter from the vadose zone by rainfall recharge. Changes in precipitation patterns associated with natural climate variability and climate change are expected to alter the load and character of organic matter released from these areas, which ultimately impacts on groundwater quality and DOM treatability. In order to investigate potential changes in groundwater DOM character after rainfall recharge, we sampled shallow groundwater from a coastal peat-rich sand aquifer in New South Wales, Australia, during an extended period of low precipitation (average daily precipitation rate < 1.6 mm day−1 over the 8 months prior to sampling), and after two heavy precipitation events (84 mm day−1 and 98 mm day−1 respectively). We assess changes in DOM composition after correcting for dilution by a novel combination of two advanced analytical techniques: liquid chromatography organic carbon detection (LC-OCD) and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We also assess changes in water chemistry pre- and post-rainfall. Post-rainfall, we show that the dilution-corrected amount of highly aromatic DOM molecular formulae (i.e. those categorised into the groups polyphenolics and condensed aromatics) were 1.7 and 2.0 times higher respectively than in pre-rainfall samples. We attribute this to the flushing of peat-derived DOM from buried organic material into the groundwater. We also identify that periods of low precipitation can lead to low hydrophilic/HOC ratios in groundwater (median = 4.9, n = 14). Redundancy analysis (RDA) was used to compare the HOC fraction with FT-ICR MS compound groups. We show that HOC has a more aromatic character in pre-rainfall samples, and is less similar to the aromatic groups in post-rainfall samples. This suggests that the decline in water-borne hydrophobics observed post-rainfall could be associated with preferential adsorption of the hydrophobic aromatic DOM, making post-rainfall samples less treatable for potable water supply. Post-rainfall we also observe significant increases in arsenic (leading to concentrations greater than 3 times the World Health Organisation drinking water limit of 10 μg / L). Increases in coastal rainfall due to climate change may therefore alter the composition of groundwater DOM in coastal peatland areas in ways that may impact DOM bioavailability, and increase arsenic concentrations, reducing the ease of water treatment for human consumption. To the best of our knowledge, this is the first study to identify the chemical and molecular changes of shallow groundwater DOM pre-rainfall and post-rainfall in a sedimentary organic carbon rich environment through multiple analytical techniques. © 2019 Elsevier Ltden_AU
dc.description.sponsorshipThis work was supported by the Australian Research Council [Discovery Project number DP160101379]; the Australian Government Research Training Program and Australian Nuclear Science Technology Organisation (ANSTO) for scholarship funding. This work was also made possible by grants from the Federal Government initiative National Collaborative Research Infrastructure Strategy (NCRIS), the NSW Department of Primary Industries Office of Water and the National Centre for Groundwater Research and Training (NCGRT). A portion of this work was performed at the National High Magnetic Field Laboratory ICR User Facility, which is supported by the National Science Foundation Division of Chemistry through DMR-1644779 and the State of Florida.en_AU
dc.identifier.articlenumber115201en_AU
dc.identifier.citationMcDonough, L. K., O’Carroll, D. M., Meredith, K., Andersen, M. S., Brügger, C., Huang, H., Rutlidge, H., Benkhe, M. I., Spencer, R. G. M., McKenna, A., Marjo, C. E., Oudone, P., & Baker, A. (2020). Changes in groundwater dissolved organic matter character in a coastal sand aquifer due to rainfall recharge. Water Research, 169, 115201. doi:10.1016/j.watres.2019.115201en_AU
dc.identifier.issn0043-1354en_AU
dc.identifier.journaltitleWater Researchen_AU
dc.identifier.urihttps://doi.org/10.1016/j.watres.2019.115201en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/13267en_AU
dc.identifier.volume169en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectGround wateren_AU
dc.subjectGroundwater rechargeen_AU
dc.subjectOrganic matteren_AU
dc.subjectCoastal regionsen_AU
dc.subjectAquifersen_AU
dc.subjectRain wateren_AU
dc.subjectSanden_AU
dc.subjectSedimentsen_AU
dc.subjectPeaten_AU
dc.subjectCarbonen_AU
dc.subjectClimatic changeen_AU
dc.subjectNew South Walesen_AU
dc.titleChanges in groundwater dissolved organic matter character in a coastal sand aquifer due to rainfall rechargeen_AU
dc.typeJournal Articleen_AU
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