Simulating the Fate of a Volatile Pesticide in Unsaturated Soil: A Case Study with DBCP
- R. J. Wagenet *,
- J. L. Hutson and
- J. W. Biggar
A field experiment that measured DBCP (1,2-dibromo-3-chloropropane) distribution during leaching through unsaturated soil was interpreted with the aid of a numerical model designed to describe the movement of a volatile pesticide under field conditions. Field-measured relationships between hydraulic conductivity, water content, and matric potential were used as model input. Simulated matric potential and water flux compared well with values measured in the field plots. The accuracy of simulated water flow inferred accurate solute description, particularly considering good agreement of the model with a published analytical solution and other reported field tests of the model. Simulated and measured DBCP solution concentrations were different, probably due to the use of a vacuum extraction apparatus to obtain soil solution samples. It was hypothesized that substantial quantities of DBCP were lost in the gaseous form during the extraction process, minimizing the usefulness of the data for the purpose of estimating DBCP fate under field conditions. Given these facts, the numerical model provided estimates of DBCP fate in field soils that were perhaps more reliable and accurate than could be obtained for this volatile chemical by standard field sampling techniques.
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