Selected Research Findings: Contaminant Transport

In this chapter, we present selected results related to subsurface aqueous transport of reactive contaminants, toxic chemicals adsorbed on colloids, and liquids that are immiscible with water. Results of field experiments on transport of reactive herbicides (e.g., atrazine, bromacil) and organophosphate (e.g., azinphosmethyl) insecticides, under irrigation and rainfall and with various sorption capacities, are compared with the transport of passive contaminants (e.g., bromide). Modeling of herbicide transport in irrigated, spatially variable fields, and comparison to measurements are reported. Examples of laboratory and outdoor studies demonstrate vertical distribution of a contaminant adsorbed on suspended particles, diffusion of degradable contaminants, two-dimensional transport of contaminants applied from a point source, and preferential flow in a structured clay soil. Results also reported for column and outdoor experiments on transport of a hydrocarbon mixture and nonaqueous-phase liquids in soil, as affected by changes in the chemical composition and physical properties.