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Title

Study of the fast competitive adsorption of pesticides in soils by simultaneous filtration and solid-phase extraction with subsequent GC-MS

AuthorsRamos, Lourdes ; Sojo, L. E.; Vreuls, J. J.; Brinkman, U. A. Th.
Issue Date2000
PublisherAmerican Chemical Society
CitationEnvironmental Science and Technology 34(6): 1049-1055 (2000)
AbstractA simultaneous filtration-plus-solid phase extraction (SPE) with subsequent GC-MS method previously validated for the study of the adsorption equilibria of pesticides in an organic soil has been used to study samples with different physicochemical characteristics, i.e., a sandy soil and a sediment. The results of this study are consistent with those found for the organic soil. The online filtration-SPE procedure allows the determination of the amount of pesticide adsorbed in the insoluble soil (or sediment) particles and of that remaining in the aqueous phase by a single injection of the total slurry in the system. The standard deviations for the whole procedure were less than 6.5% (adsorbed) and 10% (solution) for all sorbents and for all test compounds. Comparison of the results found for the various samples showed the organic matter content as a key factor governing the partition equilibrium. The relative merits of different adsorption isotherms, including linear, Langmuir and Freundlich, for analyzing the organic soil fast adsorption data were examined. Results showed that fast adsorption of relatively polar compounds, with log K(ow) values ranging from 1.51 to 3.74, on this soil was less ideal than simple partition and revealed the Freundlich coefficients n and K(f) to be time-dependent. Interactions between the pesticides and specific sites on the soil are proposed as a plausible cause for this nonlinear behavior. | A simultaneous filtration-plus-solid phase extraction (SPE) with subsequent GC-MS method previously validated for the study of the adsorption equilibria of pesticides in an organic soil has been used to study samples with different physicochemical characteristics, i.e., a sandy soil and a sediment. The results of this study are consistent with those found for the organic soil. The online filtration-SPE procedure allows the determination of the amount of pesticide adsorbed in the insoluble soil (or sediment) particles and of that remaining in the aqueous phase by a single injection of the total slurry in the system. The standard deviations for the whole procedure were less than 6.5% (adsorbed) and 10% (solution) for all sorbents and for all test compounds. Comparison of the results found for the various samples showed the organic matter content as a key factor governing the partition equilibrium. The relative merits of different adsorption isotherms, including linear, Langmuir and Freundlich, for analyzing the organic soil fast adsorption data were examined. Results showed that fast adsorption of relatively polar compounds, with log Kow values ranging from 1.51 to 3.74, on this soil was less ideal than simple partition and revealed the Freundlich coefficients n and Kf to be time-dependent. Interactions between the pesticides and specific sites on the soil are proposed as a plausible cause for this nonlinear behavior.
Publisher version (URL)https://doi.org/10.1021/es991088n
URIhttp://hdl.handle.net/10261/191839
DOI10.1021/es991088n
ISSN0013-936X
E-ISSN1520-5851
Appears in Collections:(IQOG) Artículos
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