title: Speciation study in the sulfamethoxazole-copper-pH-soil system: implications for retention prediction.
abstract: Sulfamethoxazole (SMX) is a persistent sulfonamide antibiotic drug used in the veterinary and human medical sectors and is widely detected in natural waters. To better understand the reactive transport of this antibiotic in soil, the speciation of the SMX-Cu(II)-H(+) system in solution and the combined sorption of these components in a natural vineyard soil were investigated by acid-base titrimetry and infrared spectroscopy. Cu(II) is considered to represent a strongly complexing trace element cation (such as Cd(2+), Zn(2+), Pb(2+), Ni(2+), etc.) in comparison to more prevalent but more weakly binding cations (such as Ca(2+) and Mg(2+)). Titrimetric studies showed that, relative to other antibiotics, such as tetracycline, SMX is a weak copper chelating agent and a weak soil sorbent at the soil pH (pH6). However, the sorption of SMX in soil increases strongly (by a factor of 6) in the presence of copper. This finding strongly supports the hypothetical formation of ternary SMX-Cu-soil complexes, especially considering that copper is dominantly sorbed in a state at pH6. The data were successfully modelled with PhreeqC assuming the existence of binary and ternary surface complexes in equilibrium with aqueous Cu, SMX and Cu-SMX complexes. It is thought that other strongly complexing cations present on the surface of reactive organic and mineral soil phases, such as Cd(II), Ni(II), Zn(II), Pb(II), Fe(II/III), Mn(II/IV) and Al(III), affect the solid/solution partitioning of SMX. This study thus suggests that surface-adsorbed cations significantly increase the sorption of SMX.
authors.affiliation: UJF-Grenoble1/CNRS/IRD/G-INP/LTHE UMR 5564, University of Grenoble 1, Grenoble F-38041, France; Conservatoire National des Arts et Métiers, MAQIM Department, 292 rue Saint Martin, 75141 Paris, cedex 03, France. Electronic address: marie-christine.morel@ujf-grenoble.fr.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Morel
authors.affiliation: UJF-Grenoble1/CNRS/IRD/G-INP/LTHE UMR 5564, University of Grenoble 1, Grenoble F-38041, France. Electronic address: lorenzo.spadini@ujf-grenoble.fr.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spadini
authors.affiliation: UJF-Grenoble1/CNRS/IRD/G-INP/LTHE UMR 5564, University of Grenoble 1, Grenoble F-38041, France. Electronic address: khaledbrimo@yahoo.com.
authors.forename: Khaled
authors.initials: K
authors.lastname: Brimo
authors.affiliation: UJF-Grenoble1/CNRS/IRD/G-INP/LTHE UMR 5564, University of Grenoble 1, Grenoble F-38041, France. Electronic address: jean.martins@ujf-grenoble.fr.
authors.forename: Jean M F
authors.initials: JM
authors.lastname: Martins
mesh_terms: D000327:Adsorption; D002614:Chelating Agents / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013420:Sulfamethoxazole / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D012987:Soil; D012989:Soil Pollutants; D003300:Copper; D013420:Sulfamethoxazole
keywords: Antibiotic; Copper; Modelling; Soil; Sorption; Sulfamethoxazole