Sediments pyrethroid adsorption

The adsorption and desorption of pyrethroids to and from soil and sediment are usually described either by the linear or Freundlich isotherm by using the following equations [9] ... 

High hydrophobicity of pyrethroids is likely to result in their bioconcentration in biota which is mostly controlled by lipid content. On the other hand, the high hydrophobicity would reduce bioavailability of pyrethroids due to association with DOM and/or adsorption to suspended and bottom sediments [10]. The bioconcentration factor (BCF) from water to organisms is conveniently defined by... 

Despite the high toxicity of fenvalerate and other pyrethroids to aquatic organisms, few environmental problems have been documented, presumably due to the very low application levels needed to control insects, adsorption onto soil and organic matter, and comparatively rapid degradation. Nevertheless, fenvalerate is extremely toxic to aquatic organisms (Table 16.2), has high bioaccumulation, and is persistent in sediments ... 

Two synthetic pyrethroid insecticides, bifenthrin and permethrin (3-phenoxybenzyl (lR5)-cis-fra s-3-(2,2-dichlorovinyl)-2,2-dimcthylcyclopropane-carboxylate), are the major runoff constituents considered in our monitoring and evaluation studies. Bifenthrin has a solubility of <1 ppb, and a Koc of240,000 ml g. Permedirin has a solubility of 6 ppb in water, and a Ka- of 100,000 ml g (5). The stroi adsorption on soil suggests that a large fiaction of the pesticide is associated wifii die suspended solids in nursery runoff. This determines that the downstream distribution of these pesticides is closely related to distribution of sediments, and that practices aiming to remove suspended solids from runoff will also be effective in reducing the level of these pesticides. 

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