Lithological controls on biological activity and groundwater chemistry in Quaternary sediments

Authors

  • Rebecca Bartlett,

    Corresponding author
    1. Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
    2. School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
    • School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
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  • Simon H. Bottrell,

    1. Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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  • Karen Sinclair,

    Current affiliation:
    1. BWB Consulting Ltd, Integrated Engineering and Environmental Consultants, Nottingham, NG1 1PY, UK.
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  • Steve Thornton,

    1. Groundwater Protection and Restoration Group, Kroto Research Institute, North Campus, University of Sheffield, Broad Lane, Sheffield S3 7HQ, UK
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  • Ian D. Fielding,

    1. Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
    Current affiliation:
    1. Shell Global Solutions, Shell Technology Centre, Thornton, Chester, CH1 3SH, UK.
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  • Dave Hatfield

    1. Institute of Geological Sciences, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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Abstract

Depth profiles of solute chemistry and sulfate isotopic compositions are presented for groundwater and pore water in a sequence of Quaternary glacial outwash sediments. Sand units show evidence for hydraulic connection to the surface and thus modern sources of solutes. Finer-grained sediments show a general pattern of increasing solute concentrations with depth, with sulfate derived from ancient rainwater and pyrite oxidation in the soil/drift. In these sediments sulfate has undergone bacterial sulfate reduction (BSR) to produce biogenic sulfide. In clay sediments, with d10 ≤ 1·6 µm, high concentrations of sulfate and acetate now co-exist, implying that BSR is inhibited. The correlation with smaller sediment grain size indicates that this is due to pore size exclusion of the sulfate reducing bacteria. Mechanical restriction of microbial function thus provides a fundamental limitation on microbial respiration in buried clay-rich sediments, which acts as a control on the chemical evolution of their pore waters. Copyright © 2009 John Wiley & Sons, Ltd.

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