Partitioning Behavior of Insecticides in Soil-Water Systems: I. Adsorbent Concentration Effects1
- B. T. Bowman and
- W. W. Sans2
Adsorption studies were conducted to determine whether adsorbent concentration (soil-solution ratio) affected insecticide adsorption by soils and clays. Adsorption isotherms were obtained for several insecticides in Bondhead sandy loam and Ca-saturated illite suspensions using adsorbent concentrations that were varied over several orders of magnitude. There was no evidence that altering adsorbent concentration exerted any influence on partitioning of insecticides between the adsorbent and solution phases. The centrifugation process, which in effect greatly increased adsorbent concentration at the bottom of the centrifugation tube, did not change the partitioning of the insecticides between the two phases. Dieldrin (1,2,3,4,10,10-hexachloro-exo-6,7-epoxyl, 4,4a,5,6,7,8,8a-octahydro-1,4-endo,exo-5,8-dimethanophthalene), unlike the other insecticides, exhibited strong concentration-dependent adsorption by glass surfaces, which invalidated the use of the normal “blank” (no adsorbent) sample for determining the initial solute concentration. Since glass adsorption appeared quite irreversible in aqueous solution, a sequential blank/sample adsorption technique was adopted whereby the stock solution was initially equilibrated in the glass bottle, then a small aliquot was removed for analysis before adding the adsorbent for its equilibration period. This technique produced consistent adsorption data that showed no evidence of being influenced by adsorbent concentration.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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