title: Herbicide monitoring in soil, runoff waters and sediments in an olive orchard.
abstract: Occurrences of surface water contamination by herbicides in areas where olive orchards are established reveal a need to understand soil processes affecting herbicide fate at field scale for this popular Mediterranean crop. A monitoring study with two herbicides (terbuthylazine and oxyfluorfen) in the first 2cm of soil, runoff waters, and sediments, was carried out after under natural rainfall conditions following winter herbicide application. At the end of the 107day field experiment, no residues of the soil applied terbuthylazine were recovered, whereas 42% of the oxyfluorfen applied remained in the top soil. Very low levels of both herbicides were measured in runoff waters; however, concentrations were slightly higher for terbuthylazine (0.53% of applied) than for oxyfluorfen (0.03% of applied), relating to their respective water solubilities. Congruent with soil residue data, 38.15% of the applied oxyfluorfen was found in runoff-sediment, compared to only 0.46% for terbuthylazine. Accordingly, the herbicide soil distribution coefficients measured within runoff field tanks was much greater for oxyfluorfen (Kd=3098) than for terbuthylazine (Kd=1.57). The herbicide oxyfluorfen is co-transported with sediment in runoff, remaining trapped and/or adsorbed to soil particle aggregates, due in part to its low water solubility. In contrast, terbuthylazine soil dissipation may be associated more so with leaching processes, favored by its high water solubility, low sorption, and slow degradation. By comparing these two herbicides, our results reaffirm the importance of herbicide physico-chemical properties in dictating their behavior in soil and also suggest that herbicides with low solubility, as seen in the case oxyfluorfen, remain susceptible to offsite transport associated with sediments.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, 10, 41012 Sevilla, Spain. Electronic address: mjcalderon@irnase.csic.es.
authors.forename: Maria Jesus
authors.initials: MJ
authors.lastname: Calderon
authors.affiliation: Area Producción Agraria, IFAPA, Av. Menéndez Pidal s/n, Campus Alameda del Obispo, 14004 Córdoba, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: De Luna
authors.affiliation: Instituto de Agricultura Sostenible, CSIC, Av. Menéndez Pidal s/n, Campus Alameda del Obispo, Apartado 4084, 14080 Córdoba, Spain.
authors.forename: Jose Alfonso
authors.initials: JA
authors.lastname: Gomez
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, 10, 41012 Sevilla, Spain.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Hermosin
mesh_terms: D000383:Agriculture; D019015:Geologic Sediments / Q000032:analysis*; D055768:Halogenated Diphenyl Ethers / Q000032:analysis*; D006540:Herbicides / Q000032:analysis*; D031658:Olea / Q000254:growth & development; D012989:Soil Pollutants / Q000032:analysis*; D013030:Spain; D014227:Triazines / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D012989:Soil Pollutants; D014227:Triazines; D014874:Water Pollutants, Chemical; C016027:oxyfluorofen; C037565:terbutylazine
keywords: Contamination; Leaching; Olive orchard; Oxyfluorfen; Sediments; Terbuthylazine