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Bioavailability of nonextractable (bound) pesticide residues to earthworms.

Gevao, Bondi and Mordaunt, Catriona and Semple, Kirk T. and Piearce, Trevor G. and Jones, Keith C. (2001) Bioavailability of nonextractable (bound) pesticide residues to earthworms. Environmental Science & Technology, 35 (3). pp. 501-507. ISSN 0013-936X

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Abstract

There is an ongoing debate regarding whether nonextractable (bound) pesticide residues in soils are occluded or may remain bioavailable in the long term in the environment. This study investigated the release of 14C-labeled residues, which were previously nonextractable after exhaustive extraction with organic solvents in soils, and their uptake by earthworms (Aporrectodea longa). After a 100-day incubation of soils treated with 14C-labeled atrazine, isoproturon, and dicamba and exhaustive Soxhlet extractions with methanol and dichloromethane, nonextracted 14C-labeled residues remaining in the soils were 18, 70, and 67%, respectively. Adding clean soil in the ratio of 7:1 increased the volumes of these extracted soils. After earthworms had lived in these previously extracted soils for 28 days, 0.02-0.2% of previously bound 14C activity was absorbed into the earthworm tissue. Uptake by earthworms was found to be 2-10 times higher in soils containing freshly introduced 14C-labeled pesticides as compared to soils containing nonextractable 14C-labeled residues. The differential bioavailability observed between freshly introduced 14C-labeled pesticides and those previously nonextractable may be related to the ease of transfer of the 14C activity into the solution phase. By the end of the 28-day incubation period, 3, 23, and 24% of previously nonextractable 14C-labeled isoproturon, dicamba, and atrazine residues, respectively, were extracted by solvents or mineralized to 14CO2. The amounts of 14C activity released were not significantly different in the presence or in the absence of earthworms in soils containing previously nonextractable residues. However, the formation of bound residues was 2, 2, and 4 times lower for freshly introduced 14C-labeled isoproturon, dicamba, and atrazine, respectively, suggesting that the presence of earthworms retarded bound residue formation.

Item Type: Article
Journal or Publication Title: Environmental Science & Technology
Subjects: Q Science > QH Natural history > QH301 Biology
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 9309
Deposited By: Dr Trevor G Piearce
Deposited On: 04 Jun 2008 10:06
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 18:35
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/9309

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