Gravel pit lake ecosystems reduce nitrate and phosphate concentrations in the outflowing groundwater

Author(s)

Andreas Weilhartner, Christian Müllegger, Martin J. Kainz, Francine Mathieu, Thilo Hofmann, Tom Battin

Abstract

Gravel excavation often bears conflicts with the use of drinking water as under-water-table mining can

directly impact groundwater quality downstream of the open gravel pit lake due to exposure of the groundwater

aquifer to the atmosphere and to human activities. To assess this potential impact of GPLs on groundwater,

we assessed the mass balance for nitrate (NO3) and phosphate (PO4) and whole-ecosystem

metabolism of five post-excavation GPLs in Austria. GPLs differed in both age and residence time of lake

water. We found that GPLs significantly reduced the concentration of NO3 and PO4 as groundwater passes

through the lake ecosystem, which in most cases acted as a net sink for these nutrients. Groundwaterderived

nutrients enhanced both epilithic and pelagic net primary production in the GPLs, which ultimately

leads to biomass accrual. Our data also suggest that this biomass accrual may induce, at least in part, clogging

of the GPLs and their successive hydrodynamic isolation from the adjacent groundwater. Despite continuous

biomass build-up and elevated concentrations of dissolved organic carbon (DOC) in the lake water compared

to the inflowing groundwater, DOC export into the outflowing groundwater remained low. Our data suggest

that GPLs could contribute to groundwater amelioration where agricultural land use increases nutrient concentrations

in the groundwater given a proper management of these man-made ecosystems.

Organisation(s)

External organisation(s)

WasserCluster Lunz

Journal

Science of the Total Environment

Volume

420

Pages

222-228

No. of pages

7

ISSN

0048-9697

Publication date

2012

Peer reviewed

Yes

Austrian Fields of Science 2012

105904 Environmental research

Sustainable Development Goals

SDG 15 - Life on Land

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