Reducing conditions in the vadose zone are associated with colloid and phosphorus release: evidence from lysimeters and depth profiles
| Autor: | Warrinnier, Ruben, Ysabie, Shy, RESSEGUIER, Camille, Gueudet, Jean-Christophe, Houot, Sabine, Cambier, Philippe |
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| Přispěvatelé: | Division of Geography - Department Earth and Environmental Sciences, Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Université Paris Saclay (COmUE) |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | 6th Symposium on Phosphorus in Soils and Plants 6th Symposium on Phosphorus in Soils and Plants, Sep 2018, Leuven, Belgium |
| Popis: | International audience; Vertical phosphate (PO4) leaching through the 'unsaturated zone' of agricultural soil can enrich groundwater with phosphorus (P). This zone is thought to be oxic and our previous work showed PO4 sorption on particulate and colloidal ferric iron- and aluminium (oxy)hydroxides (Fe(III)- and Al(oxy)hydroxides) controls P leaching. In wetlands, i.e. saturated soil, and in the presence of an electron donor such as organic matter, reductive dissolution of Fe(III) to ferrous iron (Fe(II)) releases bound PO4. The aim of this work was to elucidate field scale PO4 leaching. Wick lysimeter data (2013 to present), from an agricultural field trial, were analyzed. Soil cores were sampled in vicinity of the wicks in distinct layers. Extractions (fresh soil; 1 mM CaCl2; solid/liquid = 0.25 kg L-1; 24 hours shaken; 2500 relative centrifugal force; 0.45 μm filtered) were used to represent the soil solution. The same was done along a 'redox gradient', i.e. a slope from dry to wet. The P concentration ([P]) in the wick samples ranged from below limit of quantification (< LOQ) to 25 μM P. The iron concentrations ([Fe]) ranged from < LOQ to 162 μM and correlated with [Al] (r = +0.95*; * indicates p < 0.0001 on a log-log relationship). In turn, [Fe+Al] correlated with [P] (r = +0.69*). The manganese (Mn) concentration (< LOQ - 10 μM) correlated strikingly with [Fe+Al] and [P] (resp. r = +0.66* and +0.51*). Depth profiles. [P] in the model soil solutions ranged from 0.16 μM to 41 μM. [Fe] ranged from 0.86 to 99 μM and correlated with [Al] (r = +0.95*). [Fe+Al] correlated with [P] (r= +0.75*). However [Mn] (0.01 - 7.41 μM) correlated most strong with [P] (r = +0.94*) and again with [Fe+Al] (r = +0.88*). [P], [Mn] and [Fe+Al] were low plough zone, largest in the plough pan (28 - 35 cm depth) and decreased with increasing depth, i.e. decreasing organic matter (OM) content (all *). Redox gradient. Identical correlations were found. Pooling the data shows large [P], [Mn] and [Fe + Al] associate with reducing conditions (large OM, high water content and low pH). Reducing conditions in the vadose zone reduce and dissolve Mn(IV) to Mn(III or II) and later Fe(III) to Fe(II). When this cement-like structure of the matrix dissolves, colloids and sorbed PO4 are released. Next, the causality behind the presented correlations and the effect on P migration will be investigated. |
| Databáze: | OpenAIRE |
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