Pyrethroid Insecticide Transport into Monterey Bay Through Riverine Suspended Solids
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Pyrethroid Insecticide Transport into Monterey Bay Through Riverine Suspended Solids Charlene M. Ng • Donald P. Weston Michael J. Lydy
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Received: 4 May 2012 / Accepted: 31 July 2012 / Published online: 30 August 2012 Ó Springer Science+Business Media, LLC 2012
Abstract Pyrethroid pesticides are used widely in both agricultural and urban landscapes. Toxicity has been recorded in creeks and rivers throughout California, confirming that pyrethroids move at least short distances from the areas of terrestrial application into downstream waterways. However, their further downstream transport into the marine ecosystem has received little study. The Monterey Bay was chosen as the study system in the current project due to the close proximity of both urban centers and intense agriculture. Suspended sediments were sampled from three major rivers during storm events and showed that pyrethroids were routinely discharged from these coastal rivers, with concentrations of bifenthrin and permethrin in suspended solids of 22 and 83 ng/g, respectively. These suspended solids were deposited in estuaries and downstream reaches of rivers as they approached the coast where concentrations of pyrethroids in the sediment were greater than those expected to be toxic. However, despite their transport onto the continental shelf, pyrethroid residues were not detected in bed sediments of the shelf or in the nearby deep sea canyon, presumably due to dilution and degradation.
Pyrethroids are current-use insecticides that are applied for agricultural purposes and urban pest management. They are a
C. M. Ng D. P. Weston Department of Integrative Biology, University of California, 1005 Valley Life Sciences Bldg, Berkeley, CA 94720-3140, USA M. J. Lydy (&) Fisheries and Illinois Aquaculture Center, Department of Zoology, Southern Illinois University, 171 Life Sciences II, Carbondale, IL 62901, USA e-mail: [email protected]
synthetic form of pyrethrin, which is a natural insecticide produced by some chrysanthemums. Acting as a neurotoxin, pyrethroids prolong the time that the sodium channels of neurons remain open, causing hyperexcitation of the cells and paralysis of the organism. Due to the withdrawal of some of the most widely used organophosphate insecticides from urban uses, pyrethroid use has been on the increase, e.g., nearly 422,000 kg were used by professional applicators in California in 2010 (http://www.cdpr.approximatelygov/docs/ pur/purmain.htm). This number is limited to commercial applications and does not include retail sales, which are likely to be quite significant, because pyrethroids are the most widely available insecticide sold to homeowners. Unlike organophosphates, pyrethroids are highly hydrophobic, with log octanol water-partition coefficients in the range of 4–7 (Laskowski 2002). This hydrophobicity results in association of the chemicals with organic carbon in sediment. The major routes of degradation are hydrolysis (particularly under alkaline conditions), photodegradation, or biodegradation. Depending on conditions and
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