Release of dissolved phosphorus from riparian wetlands: Evidence for complex interactions among hydroclimate variability, topography and soil properties

In agricultural landscapes, establishment of vegetated buffer zones in riparian wetlands (RWs) is promoted to decrease phosphorus (P) emissions because RWs can trap particulate P from upslope fields. However, long-term accumulation of P risks the release of dissolved P, since the unstable hydrologic...

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Bibliographic Details
Published in:The Science of the total environment 2017-11, Vol.598, p.421-431
Main Authors: Gu, Sen, Gruau, Gérard, Dupas, Rémi, Rumpel, Cornélia, Crème, Alexandra, Fovet, Ophélie, Gascuel-Odoux, Chantal, Jeanneau, Laurent, Humbert, Guillaume, Petitjean, Patrice
Format: Article
Language:English
Subjects:
Biogeochemical processes
Earth Sciences
Geochemistry
Groundwater
Hydroclimate
Hydrology
Phosphorus
Riparian wetland
Sciences of the Universe
Topography
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Summary:In agricultural landscapes, establishment of vegetated buffer zones in riparian wetlands (RWs) is promoted to decrease phosphorus (P) emissions because RWs can trap particulate P from upslope fields. However, long-term accumulation of P risks the release of dissolved P, since the unstable hydrological conditions in these zones may mobilize accumulated particulate P by transforming it into a mobile dissolved P species. This study evaluates how hydroclimate variability, topography and soil properties interact and influence this mobilization, using a three-year dataset of molybdate-reactive dissolved P (MRDP) and total dissolved P (TDP) concentrations in soil water from two RWs located in an agricultural catchment in western France (Kervidy-Naizin), along with stream P concentrations. Two main drivers of seasonal dissolved P release were identified: i) soil rewetting during water-table rise after dry periods and ii) reductive dissolution of soil Fe (hydr)oxides during prolonged water saturation periods. These mechanisms were shown to vary greatly in space (according to topography) and time (according to intra- and interannual hydroclimate variability). The concentration and speciation of the released dissolved P also varied spatially depending on soil chemistry and local topography. Comparison of sites revealed a similar correlation between soil P speciation (percentage of organic P ranging from 35–70%) and the concentration and speciation of the released P (MRDP from
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2017.04.028