title: Adsorption of organophosphorus pesticides in tropical soils: The case of karst landscape of northwestern Yucatan.
abstract: This article discusses the adsorption of four organophosphorus pesticides-diazinon, dimethoate, methyl parathion, and sulfotep-in soil samples from four sites-Komchén, Xcanatún, Chablekal and Mocochá- in the northwest of Yucatan, Mexico. These pesticides have been detected in groundwater at concentrations greater than 5 (μg/L) during recent monitoring campaigns in the study area. In this region, groundwater contamination is exacerbated by its karst aquifer, which is susceptible to contamination and is considered very vulnerable. The experimental work was carried out using the batch equilibrium technique. Pesticide analyses by solid-phase extraction and gas chromatography were performed. The equilibrium adsorption data were analyzed by Henry, Langmuir and Freundlich models. The results indicate that the Freundlich model provides the best correlation of the experimental data. Freundlich adsorption coefficients Kfwere in the range of 1.62-2.35 for sulfotep, 2.43 to 3.25 for dimethoate, from 5.54 to 9.27 for methyl parathion, and 3.22 to 5.17 for diazinon. Freundlich adsorption coefficients were normalized to the content of organic carbon in the soil to estimate the sorption coefficient of organic carbon (KOC). KOCvalues were in the range of 9.45-71.80, indicated that four pesticides have low adsorption on the four studied soils, which represents a high risk of contamination to the aquifer.
authors.affiliation: Faculty of Engineering, Postgraduate and Research Unit, Autonomous University of Yucatan, Mexico. Electronic address: lorenzo.alfonso@yahoo.com.mx.
authors.forename: Lorenzo-Flores
authors.initials: LF
authors.lastname: Alfonso
authors.affiliation: Faculty of Engineering, Postgraduate and Research Unit, Autonomous University of Yucatan, Mexico. Electronic address: giacoman@correo.uady.mx.
authors.forename: Giácoman Vallejos
authors.initials: GV
authors.lastname: Germán
authors.affiliation: Faculty of Engineering, Postgraduate and Research Unit, Autonomous University of Yucatan, Mexico. Electronic address: cponce@correo.uady.mx.
authors.forename: Ponce Caballero
authors.initials: PC
authors.lastname: María Del Carmen
authors.affiliation: University of Florida, United States. Electronic address: hghoveisi@ufl.edu.
authors.forename: Ghoveisi
authors.initials: G
authors.lastname: Hossein
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry; D003976:Diazinon / Q000032:analysis*; D004117:Dimethoate / Q000032:analysis*; D004785:Environmental Pollutants; D052918:Environmental Restoration and Remediation; D060587:Groundwater / Q000737:chemistry; D008743:Methyl Parathion / Q000032:analysis*; D008800:Mexico; D009946:Organothiophosphorus Compounds / Q000032:analysis*; D010575:Pesticides / Q000032:analysis*; D010710:Phosphates / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D004785:Environmental Pollutants; D009946:Organothiophosphorus Compounds; D010575:Pesticides; D010710:Phosphates; D012987:Soil; D012989:Soil Pollutants; D008743:Methyl Parathion; D002244:Carbon; C009359:sulfotepp; D004117:Dimethoate; D003976:Diazinon
keywords: Adsorption; Groundwater; Isotherms; Karst; Organophosphorus pesticides