Effects of Groundwater Nitrate and Sulphate Enrichment on Groundwater-Fed Mires: A Case Study

Gijs van Dijk*, J. Wolters, Christian Fritz, Hans de Mars, Gert-Jan van Duinen, K.F. Ettwig, N. Straathof, Albert Grootjans, Fons Smolders

*Corresponding author for this work

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    Mires and peatlands in general are heavily influenced by anthropogenic
    stressors like acidification, eutrophication, desiccation and fragmentation.
    Groundwater-fed mires are, in contrast to rainwater-fed mires, often well
    protected against desiccation due to constant groundwater discharge.
    Groundwater-fed mires can however be influenced by groundwater pollution
    such as groundwater nitrate enrichment, a threat which has received minor
    attention in literature. The present case study demonstrates how groundwater
    nitrate enrichment can affect the biogeochemical functioning and vegetation
    composition of groundwater-fed mires through direct nitrogen enrichment and
    indirect nitrate-induced sulphate mobilisation from geological deposits.
    Biogeochemical and ecohydrological analyses suggest that the Dutch
    groundwater-fed mire studied is influenced by different water sources
    (rainwater; groundwater of local and regional origin) with differing chemical
    compositions. The weakly buffered and nitrate-enriched groundwater leads,
    where it reaches the uppermost peat, to nitrogen enrichment, enhanced isotopic
    nitrogen signatures and altered the vegetation composition at the expense of
    characteristic species. Nitrate-induced sulphate mobilisation in the aquifer led
    to enhanced sulphate reduction, sulphide toxicity and elemental sulphur
    deposition in the mire. Despite sulphate reduction and nitrate enrichment,
    internal eutrophication did not play an important role, due to relatively low
    phosphorus concentrations and/or low iron-bound phosphorus of the peat soil.
    Future management of groundwater-fed mires in nitrate-polluted aquifers
    should include the reduction of nitrate leaching to the aquifer at the recharge
    areas by management and ecohydrological restoration measures on both a local
    and landscape scale.
    Original languageEnglish
    Article number122
    Number of pages17
    JournalWater Air and Soil Pollution
    Issue number6
    Publication statusPublished - Jun-2019


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