Three simplistic models are developed for evaluating the transport of organic pollutants through soil to ground water. The models consider mobility and first‐order degradation. The first calculates linear sorption/desorption of the pollutant and first‐order degradation without considering dispersion. The second is similar to the first but also considers dispersion. The third considers nonlinear sorption following a Freundlich equation and first‐order degradation but does not consider dispersion. The models are compared to field data for the pesticides aldicarb and DDT. The models projected a lower mobility for DDT than was observed in the field.

Phosphorous in concentrations exceeding those generally observed through agricultural activities has been encountered at land application wastewater treatment sites. To predict the environmental impact of these systems, a model was developed to describe the reaction of orthophosphate with mineral soils. The model is based on instantaneous reversible absorption theory plus time‐dependent solubility theory. It was assumed, in the model, that first‐order kinetics would adequately describe the formation or dissolution of phosphate minerals. Statistical regression analyses were performed on batch sorption data for 14 mineral soils where two equilibrium compounds were considered. The two compounds considered were hydroxyapatite (Ca10HPO4·2H2O) and dicalcium phosphate dihydrate (CaHPO4·2H2O). Comparisons of correlation coefficients between this model and previous models using a common data set indicate the current model with a mean correlation coefficient of 0.93 is more accurate in describing phosphate reactions in calcareous soils than earlier models with mean correlation coefficients ranging from 0.75 to 0.91.

A first‐order kinetic model was employed to predict, for selected soils, the response of the soil to phosphorus (P) applied in solution with 0.01M CaCl2 in the laboratory, and the response of P in municipal wastewater at two rapid infiltration wastewater treatment systems. The one‐dimensional steady‐state hydraulic model appears to accurately predict (±50% of estimate) both the concentration of P in the solution phase as well as the accumulation of P in the solid phase.

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