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Pesticide sorption and diffusion in natural clay loam aggregates

van Beinum, W., Beulke, S. and Brown, C.D. (2005) Pesticide sorption and diffusion in natural clay loam aggregates. Journal of Agricultural and Food Chemistry, 53 (23). pp. 9146-9154. ISSN 1520-5118

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Abstract

Pesticide sorption in soils is controlled by time-dependent processes such as diffusion into soil aggregates and microscopic sorbent particles. This study examines the rate-controlling step for time-dependent sorption in clay loam aggregates. Aggregates (5 mm) were stabilized with alginate, and adsorption of azoxystrobin, chlorotoluron, and cyanazine was measured in batch systems equilibrated for periods between 1 h and 7 days. Stepwise desorption was measured at 1- or 3-day intervals following 1 or 7 days of adsorption. Time-dependent adsorption was also measured on dispersed soil. Results were interpreted using process-based modeling. Adsorption on dispersed soil was described by intraparticle sorption and diffusion. Adsorption in the aggregates was much less than in suspension, suggesting that part of the sorption capacity of the dispersed soil was not available within the aggregates (50%). Adsorption and desorption were reversible and could be described by pore diffusion into the aggregate with effective diffusion coefficients between 0.5 × 10-10 and 1 × 10-10 m2 s-1, a factor 3−6 slower than estimated theoretically. Intraparticle diffusion did not seem to contribute to sorption in the aggregates at this time scale. Apparent hysteresis was explained by nonattainment of equilibrium during the adsorption and desorption steps.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Environment (York)
Depositing User: York RAE Import
Date Deposited: 14 May 2009 15:27
Last Modified: 14 May 2009 15:27
Published Version: http://dx.doi.org/10.1021/jf050928g
Status: Published
Publisher: American Chemical Society
Identification Number: 10.1021/jf050928g
URI: http://eprints.whiterose.ac.uk/id/eprint/6397

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