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Dissolved inorganic geogenic phosphorus load to a groundwater-fed lake: Implications of terrestrial phosphorus cycling by groundwater

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

DOI

  • Catharina Simone Nisbeth, Københavns Universitet
  • ,
  • Jacob Kidmose, Geological Survey of Denmark and Greenland
  • ,
  • Kaarina Weckström, Geological Survey of Denmark and Greenland, Helsingin yliopisto
  • ,
  • Kasper Reitzel, Syddansk Universitet
  • ,
  • Bent Vad Odgaard
  • Ole Bennike, Geological Survey of Denmark and Greenland
  • ,
  • Lærke Thorling, Geological Survey of Denmark and Greenland
  • ,
  • Suzanne McGowan, University of Nottingham
  • ,
  • Anders Schomacker, Københavns Universitet, UiT The Arctic University of Norway
  • ,
  • David Lajer Juul Kristensen, Københavns Universitet
  • ,
  • Søren Jessen, Department of Geosciences and Natural Resource Management (IGN), Københavns Universitet

The general perception has long been that lake eutrophication is driven by anthropogenic sources of phosphorus (P) and that P is immobile in the subsurface and in aquifers. Combined investigation of the current water and P budgets of a 70 ha lake (Nørresø, Fyn, Denmark) in a clayey till-dominated landscape and of the lake's Holocene trophic history demonstrates a potential significance of geogenic (natural) groundwater-borne P. Nørresø receives water from nine streams, a groundwater-fed spring located on a small island, and precipitation. The lake loses water by evaporation and via a single outlet. Monthly measurements of stream, spring, and outlet discharge, and of tracers in the form of temperature, δ18O and δ2H of water, and water chemistry were conducted. The tracers indicated that the lake receives groundwater from an underlying regional confined glaciofluvial sand aquifer via the spring and one of the streams. In addition, the lake receives a direct groundwater input (estimated as the water balance residual) via the lake bed, as supported by the artesian conditions of underlying strata observed in piezometers installed along the lake shore and in wells tapping the regional confined aquifer. The groundwater in the regional confined aquifer was anoxic, ferrous, and contained 4-5 μmol/L dissolved inorganic orthophosphate (DIP). Altogether, the data indicated that groundwater contributes from 64% of the water-borne external DIP loading to the lake, and up to 90% if the DIP concentration of the spring, as representative for the average DIP of the regional confined aquifer, is assigned to the estimated groundwater input. In support, paleolimnological data retrieved from sediment cores indicated that Nørresø was never P-poor, even before the introduction of agriculture at 6000 years before present. Accordingly, groundwater-borne geogenic phosphorus can have an important influence on the trophic state of recipient surface water ecosystems, and groundwater-borne P can be a potentially important component of the terrestrial P cycle.

OriginalsprogEngelsk
Artikelnummer2213
TidsskriftWater
Vol/bind11
Nummer11
ISSN2073-4441
DOI
StatusUdgivet - 1 nov. 2019

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