Redox effects on resin extraction of herbicides from soil

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Relative soil aeration affects the surfaces upon which pesticides adsorb and non-ionic resins offer a means of observing and evaluating this factor. A non-ionic resin extractor, developed for pesticide extraction under reducing conditions, was used to adsorb a fraction of the reversibly adsorbed (active portion) herbicides. The extractor consists of cleaned XAD-2 resin encased in a dialysis membrane composed of regenerated cellulose. Anaerobiosis was achieved by incubating soil suspensions with glucose under a 95% N 2–5% H 2 environment until the redox potential reached −150 mV. Nine soils with a range of physical and chemical characteristics were examined for atrazine, metribuzin, and alachlor content. Amounts of atrazine, metribuzin, and alachlor extracted from soil ranged to 100, 140, and 75 ng g −1, respectively. Resin extractions (RE) conducted under aerobic conditions recovered about 25–50% of the pesticide extractable with conventional solid phase solvent extraction at 60 °C (SPE 60). Under anaerobic conditions, equal amounts of atrazine were extracted with RE and SPE 60. Slightly less metribuzin was recovered under anaerobic extraction with the exception of those soils lacking detectable amounts by SPE 60. Larger amounts of alachlor were extracted with resins under anaerobic conditions than under aerobic conditions but the amounts were not correlated with those determined by SPE 60. Large amounts of soil organic matter were solublized under anaerobiosis and smaller molecular weight material was extracted with the herbicides. The nature and amounts of co-extracted organic matter varied among soils. RE directly from soil suspensions enabled simultaneous determination of all three herbicides.