Water, Air, & Soil Pollution

, Volume 218, Issue 1, pp 213–226

Understanding Phosphorus Mobility and Bioavailability in the Hyporheic Zone of a Chalk Stream

Authors

    • British Geological Survey
  • Daren C. Gooddy
    • British Geological Survey
  • Helen P. Jarvie
    • Centre for Ecology and Hydrology
Article

DOI: 10.1007/s11270-010-0636-1

Cite this article as:
Lapworth, D.J., Gooddy, D.C. & Jarvie, H.P. Water Air Soil Pollut (2011) 218: 213. doi:10.1007/s11270-010-0636-1

Abstract

This paper investigates the changes in bioavailable phosphorus (P) within the hyporheic zone of a groundwater-dominated chalk stream. In this study, tangential flow fractionation is used to investigate P associations with different size fractions in the hyporheic zone, groundwater and surface water. P speciation is similar for the river and the chalk aquifer beneath the hyporheic zone, with ‘dissolved’ P (<10 kDa) accounting for ~90% of the P in the river and >90% in the deep groundwaters. Within the hyporheic zone, the proportion of ‘colloidal’ (<0.45 μm and >10 kDa) and ‘particulate’ (>0.45 μm) P is higher than in either the groundwater or the surface water, accounting for ~30% of total P. Our results suggest that zones of interaction within the sand and gravel deposits directly beneath and adjacent to river systems generate colloidal and particulate forms of fulvic-like organic material and regulate bioavailable forms of P, perhaps through co-precipitation with CaCO3. While chalk aquifers provide some degree of protection to surface water ecosystems through physiochemical processes of P removal, where flow is maintained by groundwater, ecologically significant P concentrations (20–30 μg/L) are still present in the groundwater and are an important source of bioavailable P during baseflow conditions. The nutrient storage capacity of the hyporheic zone and the water residence times of this dynamic system are largely unknown and warrant further investigation.

Keywords

NutrientsPhosphorusHyporheicGroundwaterRiverChalkTangential flow fractionation (TFF)

Copyright information

© Springer Science+Business Media B.V. / British Geological Survey-NERC 2010