Virgil H. Freed

A Physical Concept of Soil-Water Equilibria for Nonionic Organic Compounds

Soil-water equilibrium data suggest that the transfer of nonionic chemicals from water to soil may be described in terms of a hypothesis of solute partitioning in the soil organic matter. This concept allows estimation of soil-water distribution coefficients either from solvent-water partition coefficients or aqueous solubilities.

Evaporation of solutes from water

Abstract A model is developed to define the evaporation rates of solutes from water. The rate equation, similar in form to the Knudsen equation, takes into consideration the effect of air and subwater turbulences on the evaporation loss. At given system conditions, the factor accounting for the air turbulence appears to be essentially constant and independent of temperature (3.5–25°C) for various organic chemicals and water. These characteristics allow one to study the rate of evaporation from water and the relative enhancement by subwater mixing for different solutes. This report shows that the volatilization loss of pure substances and solutes with low Henrys law constants is enhanced by air turbulence, not by subwater mixing. However, the loss of volatile solutes (high Henrys law constants) may be promoted both by air turbulence and by subwater mixing, in which the extent of enhancement by liquid mixing is determined primarily by the Henrys law constant. The present model provides a theoretical basis to explain these effects and others, which appear to be important for assessment of pollutant evaporative transport in the environment.

Degradation of the herbicides bromacil, diuron and chlortoluron in soil

Abstract In laboratory studies, the rate of degradation of 14 C-labeled diuron, chlortoluron, and bromacil in soil was determined by monitoring 14 CO 2 evolution at 25, 30, and 35°C. Degradation of the three herbicides was slow and followed the first-order rate law. The rate of 14 CO 2 evolution from the treated soil was nearly tripled by a 10°C rise in temperature from 25 to 35°C. The half-lives as well as the activation energies of degradation for the three chemicals were determined and discussed.

Physical chemical properties of several organophosphates: Some implication in environmental and biological behavior

Abstract The organophosphates are a class of chemicals noted for high biological activity. Their potential for transport and persistence in the environment, based on physical chemical properties, has not been thoroughly studied. Certain physical chemical properties of several organophosphates were measured and compared to organochlorine compounds whose transport and persistence are better known. Of interest was the potential for toxicity to human and other nontarget organisms. Certain organophosphates were found to have surprisingly high partition coefficients. This suggested the possibility of uptake by organisms, as well as indicating a propensity for storage and hence, a longer persistence. Rates of hydrolysis are some indication of the likelihood of persistence.

Predictions of evaporative loss rates of solutes in stagnant and turbulent waters in relation to rates of reference materials

Abstract A previously published kinetic model for evaporative rates of substances into air leads to the estimation of the dependence of solute transfer coefficients on turbulence to the system. The ratios of the transfer coefficients of all solutes become insensitive to air turbulence and to water mixing either when they have comparable Henrys law constants or when their Henrys law constants are sufficiently low, but not otherwise. Confirming data are presented and methods for simplifying the estimation of transfer coefficients are discussed.