Generalized model of pentachlorophenol distribution in amended soil-water systems

This paper describes laboratory experiments and subsequent statistical data analysis performed to reevaluate the overall effect of soil characteristic s and liquid-phase composition on the extent of pentachlorophenol (PCP) ads orption in complex soil-water systems. The PCP adsorption isotherms were fi rst generated for eight soils of varying physical and chemical properties. Binding tests were then performed in the presence of different additives (s urfactant, oil, etc.) and conditions (temperature and pH), based on a fract ional factorial design. Statistical analysis of data showed strong interdep endencies, among several of the soil parameters, but confirmed that organic carbon content (f(oc)) and pH of the soils were the best predictors of the adsorption constant of PCP (K-d) for nonamended soil-water systems. It was determined that the effect on K-d of a 0.2 unit decrease in soil pH was ap proximately the same as increasing f(oc) by 1%. From studying the effect of the amendments, two interactions (surfactant-pH and surfactant-oil) and tw o primary effects (surfactant and oil) have been detected. The effectivenes s of the surfactant in decreasing K-d varied depending on the pH and oil co ntent of the soil. A generalized nonlinear model expressing K-d as a functi on of pH, f(oc), oil content of soil, and surfactant dose was developed for the range of conditions studied. The proposed model and modeling approach can be adapted to other types of contaminants or variables, for specific na tural and engineered systems.