Temporal variability of phosphorus fractions in Irish karst springs |
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| Authors: | Garrett Kilroy Catherine Coxon |
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| Institution: | (1) Shannon River Basin Project, Newtown Centre, Annacotty, County Limerick, Ireland;(2) Centre for the Environment and Department of Geology, University of Dublin, Trinity College, , Dublin 2, Ireland |
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| Abstract: | Transfer pathways of phosphorus (P) from soil to surface waters are the subject of much current research because of concerns about eutrophication. However, P transfer via groundwater discharge has received little attention. Temporal P changes at eight Carboniferous limestone karst springs from two catchments in western Ireland are examined. The eight springs were sampled fortnightly between June and October 1999 and thereafter monthly until February 2000. Each sample was analysed for total P (TP), total dissolved P (TDP) and dissolved reactive P (DRP). Total P exhibited some hydrological response at all springs (e.g. increase from 45 to 107 µg l–1) reflecting significant changes in particulate P (PP) (e.g. increase from 7 to 44 µg l–1) and dissolved organic P (DOP) (e.g. increase from 0 to 27 µg l–1), with DRP displaying greatest temporal stability. Greatest response to rainfall events occurred after the first major autumnal rains in September 1999, when there appeared to be dislodging of loosely bound PP and DOP, which was transported to groundwater. This response to the first autumnal rains probably reflects the hydrological switch where the catchments change from a soil moisture deficit to a soil moisture surplus situation. Daily autosampling demonstrated TP concentrations of up to 1,814 µg l–1 due to local pollution, highlighting the need to adopt storm event driven sampling rather than discrete sampling in karstic springs. Identification and management of springs in karst areas, with associated point recharge via swallow holes, presents an urgent and demanding challenge. |
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| Keywords: | Phosphorus Karst aquifer Temporal variability Groundwater |
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