Soils 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] ... 

Kodaka R, Suzuki Y, Sugano T, Katagi T (2007) Aerobic metabolism and adsorption of pyrethroid insecticide metofluthrin in soil. J Pestic Sci 32 393-401... 

The strong adsorption of pyrethroids for minerals, especially minerals coated with natural organic matter such as are found in soils, is illustrated in our studies by the behaviour of tefluthrin. Thus Figure 9.3 shows sorption of tefluthrin onto organic-free kaolinite, alumina (aluminium oxide) and montmorillonite. Clearly the sorptive capacity of the minerals varies in the order montmorillonite > alumina > kaolinite but all three... 

Figure 9.5, the values obtained in this way vary not only with the extent of natural organic matter coating but also with the character of the OM. This corresponds also to increased adsorption with increased aromaticity of OM. Since the aromaticity of terrestrial-derived (i.e. soil) OM is likely to be high due in part to a preponderance of lignin residues, then soils can be expected to have a high affinity for pyrethroids (Zhou et al., 1994). 

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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