Status: this preprint was under review for the journal BG but the revision was not accepted.
Linking dissolved organic matter composition to metal bioavailability in agricultural soils: effect of anionic surfactants
M. C. Hernandez-Sorianoand J. C. Jimenez-Lopez
Abstract. The bioavailability of metals in soil is only partially explained by their partition among the solid and aqueous phase and is more related to the characterization of their speciation in the soil solution. The organic ligands in solution that largely determine metal speciation involve complex mixtures and the characterization of fluorescence components of dissolved organic matter (DOM) can identify pools of molecules that participate in metal speciation, this being essential for risk assessment. The bioavailability of Cd, Cu, Pb and Zn in three agricultural soils was examined in the laboratory to recreate irrigation with greywater enriched in anionic surfactants (Aerosol 22 and Biopower). Field capacity and saturation regimes were considered for this study. Irrigation with aqueous solutions of the anionic surfactants increased total DOM concentrations and metals in the soil solution (Pb > Cu > Zn > Cd). Significant correlation (p < 0.05) between the readily available pool of metals with the concentration of DOM was determined for Cu (r = 0.67), Pb (r = 0.82) and Zn (r = 0.68). However, speciation analysis performed with the software WHAM indicated that mobilisation of DOM and metals into the soluble phase resulted in a low concentration of free ion activities and promoted the formation of metal-organo complexes. The characterization of fluorescence components revealed that DOM in soil solution from soils irrigated with Aerosol 22 was enriched in a reduced quinone-like and a humic-like component. Besides, fluorescence quenching provided further evidence of metal complexation with organic ligands in solution. Hence, metal mobilization in soil irrigated with surfactant enriched greywater occurs with solubilisation of high affinity organic ligands, which substantially decreases the potential risk of metal toxicity.
Received: 31 Jan 2015 – Discussion started: 14 Apr 2015
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Department of Earth and Environmental Science, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
Department of Soil Science, College of Agriculture and Life Sciences, North Carolina State University, Campus Box 7619, 101 Derieux Street, 2232 Williams Hall, Raleigh, NC 27695, USA
The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4072, Australia
J. C. Jimenez-Lopez
The UWA Institute of Agriculture, The University of Western Australia, Crawley, Perth Western Australia 6009, Australia
Irrigation with greywater can increase the risk of metal toxicity to plants and soil organisms due to the presence of anionic surfactants derived from household products.
Three agricultural soils were treated with anionic surfactants and the total concentration of soluble metal increased. However, that was accompanied by the solubilisation of soil organic compounds that bind metals and yield complexes of low bioavailability, which substantially reduces the potential risk of metal toxicity.
Irrigation with greywater can increase the risk of metal toxicity to plants and soil organisms...
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