Browsing by Author "Howley, EM"

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    Dissolved organic matter (DOM) concentration and quality in a coastal aquifer
    (Copernicus Publications, 2015-04-14) Zainuddin, NS; Andersen, MS; Baker, AA; Howley, EM; O'Carroll, DM; Jex, CN; Meredith, KT; Wells, E
    This study investigates the range of fluorescence properties of natural occurring DOM in a coastal aquifer at Anna Bay, NSW, Australia. The determination of the extent to which DOM varies in coastal groundwater has been distinguished through fluorescence spectroscopy by excitation-emission matrices (EEM), and the application of parallel factor analysis (PARAFAC). In addition, DOM was characterised by a combination of DOC-LABOR Liquid Chromatography - Trace Organic Carbon Detector (LC-OCD) method and PHREEQC modelling. In general, results show an anoxic aquifer featuring calcite dissolution in the upper regions of the aquifer and organic matter degradation with redox zonation dominated by iron and sulphate reduction as well as methanogenesis. Several fluorescence EEM patterns were identified. DOM in coastal environment was variable, but mainly composed of low molecular weight compounds. On overall system two humic-like substances (C1, C2) and one fulvic-like substance (C3) were identified by the PARAFAC model. C1 and C2 exhibited same trends and were very similar. Measurement of the fluorescence excitation-emission matrices (EEM) and subsequent PARAFAC reveal different fluorescent DOM fractions and hence variable contributions by DOM to the reduction process in the coastal aquifer zones. © 2015 The Author(s).
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    Lignin degradation in a coastal groundwater aquifer: a useful tracer?
    (American Geophysical Union, 2014-12) Howley, EM; Jex, CN; Andersen, MS; Baker, AA; Zainuddin, NS; Meredith, KT; Wells, E; McDonald, J; Kham, S; Blyth, AJ; Spencer, RGM
    Lignin as a biomarker in soils, peat, lakes and intertidal and marine sediment cores has been widely researched in the last four decades. The biogeochemical processes controlling their distribution and composition include fractionation due to phase changes, mineral binding, and abiotic and biotic decay. However, there appears to be no studies in the literature describing the concentration and composition of lignin in groundwater aquifers, despite lignin tracing having the potential to differentiate between types of vegetation and recharge source. In the latter case aquifers could potentially be a source of old, degradation resistant lignin. In this study, we characterise the lignin composition in groundwater samples from a coastal sand aquifer, in SE Australia. We compare these data with lignin composition of fresh vegetation samples from the study site, and with lignin data from other environments in the literature. Groundwater samples were also analysed for Dissolved Organic Carbon (DOC) and inorganic chemistry (major ions, Dissolved Inorganic Carbon (DIC) and redox sensitive species) to investigate lignin fractionation processes. To achieve this, the groundwater lignin composition was compared to the total DOC and DIC in the samples and the prevailing redox reactions. The lignin composition in groundwater was found to be unrelated to the surrounding surface vegetation, indicating significant alteration by biogeochemical processes along its flow paths. We identify potential lignin degradation zones, via determination of total OC consumed through redox reactions and microbial activity. In conclusion, this study, by closely examining the correlations of lignin phenols in groundwater with lignin in surface waters, as well as biogeochemical processes in the aquifer is shedding a new light on the ability of lignin as a biomarker in these subsurface systems. To our knowledge, this is the first attempt to assess the usefulness of lignin as a tracer in groundwater. © AGU