title: Organochlorine pesticides in residential soils and sediments within two main agricultural areas of northwest Mexico: Concentrations, enantiomer compositions and potential sources.
abstract: The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico were heavily treated with organochlorine pesticides in the past. Residential soils and agricultural drain sediments were sampled in 2008-2009 and analyzed for DDTs (o,p'- and p,p'- isomers of DDE, DDD and DDT); hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exo-epoxide). Geometric means (GMs) (ng g-1dry weight) were: MV soils (n = 27) ΣDDT 22, ΣHCH 0.80, ΣCHL 0.88; YV soils (n = 25) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.67; MV sediments (n = 3) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.53; YV sediments (n = 8) ΣDDT 2.6, ΣHCH 0.12, ΣCHL 0.090. GMs were significantly higher (p < 0.05) in MV than YV soils for ΣDDT and ΣHCH, but not for ΣCHL. Comparison to worldwide regulatory guideline values (RGVs) for residential soils showed all compounds below mean or GM RGVs, but above the lowest RGV in some cases. Low p,p'-DDT/(p,p'-DDT + p,p'-DDE) in most soils indicated aged residues. Lack of p,p'-DDT metabolism might account for its dominance in a few soils. HCH isomer profiles suggested aged technical HCH in the YV, and technical HCH + lindane in the MV. Heptachlor dominated the ΣCHL, probably from application of technical heptachlor as well as chlordane. Chiral compounds were nonracemic in soils and sediments and indicated enantioselective microbial degradation of (+)α-HCH, (-)trans-chlordane, (-)cis-chlordane and (+)o,p'-DDT. Depletion of (+)o,p'-DDT in soils may account for similar enantiomer signatures previously reported in air of northwest Mexico.
authors.affiliation: Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Km 106 Carretera Tijuana-Ensenada, 22860, Ensenada, Baja California, Mexico.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Sánchez-Osorio
authors.affiliation: Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Km 106 Carretera Tijuana-Ensenada, 22860, Ensenada, Baja California, Mexico. Electronic address: vmacias@uabc.edu.mx.
authors.forename: José Vinicio
authors.initials: JV
authors.lastname: Macías-Zamora
authors.affiliation: Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Km 106 Carretera Tijuana-Ensenada, 22860, Ensenada, Baja California, Mexico.
authors.forename: Nancy
authors.initials: N
authors.lastname: Ramírez-Álvarez
authors.affiliation: Department of Chemistry, Umeå University, Umeå, SE-901 87, Sweden. Electronic address: terry.bidleman@umu.se.
authors.forename: Terry F
authors.initials: TF
authors.lastname: Bidleman
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000032:analysis* / Q000737:chemistry; D008800:Mexico; D010575:Pesticides / Q000032:analysis* / Q000737:chemistry; D012111:Residence Characteristics; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry
chemical_list: D006843:Hydrocarbons, Chlorinated; D010575:Pesticides; D012987:Soil; D012989:Soil Pollutants
keywords: Enantiomers; Mexico; Organochlorine pesticides; Sediment; Soil