title: Arsenic mobility controlled by solid calcium arsenates: a case study in Mexico showcasing a potentially widespread environmental problem.
abstract: An As-contaminated perched aquifer under an urban area affected by mining was studied over a year to determine the contamination source species and the mechanism of As mobilization. Results show that the dissolution of calcium arsenates in residues disposed on an inactive smelter has caused high levels of As pollution in the adjoining downgradient 6-km perched aquifer, reaching up to 158 mg/L of dissolved As, and releasing a total of ca. 7.5 tons of As in a year. Furthermore, free calcium ion availability was found to control As mobility in the aquifer through the diagenetic precipitation of calcium arsenates (Ca5H2(AsO4)4·cH2O) preventing further mobilization of As. Results shown here represent a model for understanding a highly underreported mechanism of retention of arsenate species likely to dominate in calcium-rich environments, such as those in calcareous sediments and soils, where the commonly reported mechanism of adsorption to iron(III) oxyhydroxides is not the dominant process.
authors: IPICyT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a Presa San Jose No. 2055, Col. Lomas 4a Secc., 78216 San Luis Potosi, SLP, Mexico. nadia.martinez@ipicyt.edu.mx
authors: Nadia
authors: N
authors: Martínez-Villegas
authors: Roberto
authors: R
authors: Briones-Gallardo
authors: José A
authors: JA
authors: Ramos-Leal
authors: Miguel
authors: M
authors: Avalos-Borja
authors: Alan D
authors: AD
authors: Castañón-Sandoval
authors: Elías
authors: E
authors: Razo-Flores
authors: Mario
authors: M
authors: Villalobos
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000032:analysis*; D001151:Arsenic / Q000032:analysis*; D017610:Calcium Compounds / Q000032:analysis*; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation; D019015:Geologic Sediments / Q000737:chemistry; D008800:Mexico; D008906:Mining; D008956:Models, Chemical; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D001149:Arsenates; D017610:Calcium Compounds; D012987:Soil; D012989:Soil Pollutants; C045817:calcium arsenate; D001151:Arsenic