Behavior Assessment Model for Trace Organics in Soil: II. Chemical Classification and Parameter Sensitivity

Abstract

In this paper, the organic chemical transport screening model developed in Jury et al. (1983) is simplified by dividing chemicals into volatilization and mobility categories. The volatilization classification is based on whether or not the predominant resistance to volatilization loss lies in the soil or in the boundary layer above the soil surface. This categorization reduces to a condition on the Henry's constant (KH) and organic C partition coefficient (Koc) when standard values are used to represent soil and chemical parameters. The mobility categories are based on the calculated time to convect or diffuse a given distance through the soil.Simulations are conducted for chemicals falling into one or another of these volatilization or mobility categories to examine the sensitivity of these processes to variations in water evaporation, water content, organic C fraction, and boundary layer thickness. The dependence of both volatilization flux and leaching flux on these parameters is summarized.

Volatilization of Organic Chemicals from Soil as Related to Their Henry's Law Constants

“…Laboratory research established that the rate of volatilization from soil is controlled by rate of movement of the organic chemical to the soil surface by mass flow in water and by diffusion . The output from a pesticide screening model (Jury et al, 1984a) indicated that rate of movement to the soil surface relative to movement of the pesticide through the stagnant air boundary ,layer above the surface can also control volatilization and accumulation at the soil surface.Volatilization rate from a surface deposit depends only on the rate of movement of the chemical away from the evaporating surface and its vapor pressure. In contrast, .…”

“…Models developed for estimating volatilization rates are based on equations describing the rate of movement of the chemical to the surface by diffusion and/or by convection, and away from the surface through the air boundary layer by diffusion Mayer et al, 1974;Jury et al, 1980Jury et al, , 1983. Additionally, the proportion of the chemical in soil that will be lost by volatilization depends on the resistance of the chemical to degradation.In a series of papers, Jury et al (1983Jury et al ( , 1984a, b, c) described and applied a model for assessing relative volatility, mobility, and persistance of pesticides and other trace organics in soil. The model allows the organica to be present in the soil in the adsorbed, solution, and …”

Environmental Impact to the Chemical Signature Emanating from Buried Unexploded Ordinance

“…The first model used was the Behavior Assessment Model for Trace Organics in Soil (Jury et al, 1983(Jury et al, , 1984a(Jury et al, , 1984b(Jury et al, , 1984c(Jury et al, , and 1991. Application of the phase partitioning components of this model showed that the mass fractions of TNT and DNT in soils were predominantly sorbed to the soil particles (90+%), the majority of the remaining mass is dissolved in the soil pore water (10+%), and only a trace is found in the soil gas (~ 10 -6 %).…”

Hydrogeologic setting and simulation of pesticide fate and transport in the unsaturated zone of a regolith-mantled, carbonate-rock terrain near Newville, Pennsylvania

“…Digital computer models to evaluate pesticide fate and transport in agricultural soils have been developed by numerous researchers, including Jury and others (1983;1984a;1984b;1984c;, Rutledge and Helgesen (1989), Mackay (1991), and Mackay and Stiver (1991). Rao and others (1985) compared ranks of pesticide leaching potentials produced by six simple models.…”