Effect, and Statistical Evaluation, of Soil Sterilization on Aniline and Diuron Adsorption Isotherms

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Abstract
A laboratory study evaluated the effects of six treatments on the adsorptive capacity of three soils for a labile chemical, aniline hydrochloride (amino‐benzene‐HCl), and a relatively stable one, diuron (3‐3,4‐dichlorophenyl‐1,1‐dimethylurea). Detailed statistical procedures were outlined for presenting the reliability of the experimental results and were applied to compare the effects of air drying, oven drying, the addition of propylene oxide, autoclaving, cobalt‐60 irradiation, and moist preincubation on aniline‐HCl and diuron adsorptions on soil.Oven drying soil samples at 90°C for two 24‐h cycles resulted in increased aniline‐HCl adsorption but had no effect on diuron adsorption. Propylene oxide, inducing a soil pH change, decreased the adsorption of aniline‐HCl. It caused a general increase in diuron adsorption in the three soils due to the high amount of residue remaining in the treated soil. Although autoclaving and cobalt‐60 irradiation were effective methods of soil sterilization, both treatments decreased the adsorptive capacity of the soil samples. The above four treatments modified soil properties and altered the adsorption of organic chemicals on soil, when compared to the air‐dried and preincubated controls. Care must be exercised in the interpretation of adsorption data obtained using pretreated soil samples. Adsorption measurements should be taken preferably during a short period subsequent to soil‐solvent mixing, before enhanced microbial activity could take place in air‐dried soil samples.