Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 5.153
IF5.153
IF 5-year value: 5.460
IF 5-year
5.460
CiteScore value: 7.8
CiteScore
7.8
SNIP value: 1.623
SNIP1.623
IPP value: 4.91
IPP4.91
SJR value: 2.092
SJR2.092
Scimago H <br class='widget-line-break'>index value: 123
Scimago H
index
123
h5-index value: 65
h5-index65
Volume 18, issue 11
Hydrol. Earth Syst. Sci., 18, 4687–4702, 2014
https://doi.org/10.5194/hess-18-4687-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 18, 4687–4702, 2014
https://doi.org/10.5194/hess-18-4687-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 27 Nov 2014

Research article | 27 Nov 2014

Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water

B. van der Grift1,2, J. C. Rozemeijer2, J. Griffioen1,2, and Y. van der Velde3 B. van der Grift et al.
  • 1Department of Innovation, Environmental and Energy Sciences – Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TA Utrecht, the Netherlands
  • 2Deltares, P.O. Box 85467, 3508 AL Utrecht, the Netherlands
  • 3Soil Geography and Landscape, Wageningen University and Research Centre, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands

Abstract. The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to structural phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.

Publications Copernicus
Download
Short summary
Exfiltration of anoxic groundwater containing Fe(II) to surface water is an important mechanism controlling P speciation in the lowland catchments. Due to changes in pH and temperature, the Fe(II) oxidation rates were much lower in winter than in summer. This study also shows a fast transformation of dissolved P to structural P during the initial stage of the Fe oxidation process resulting in low dissolved P concentrations in the surface water throughout the year.
Exfiltration of anoxic groundwater containing Fe(II) to surface water is an important mechanism...
Citation