LABORATORY EXPERIMENTS EVALUATING THE TRANSPORT AND FATE OF DBCP IN HANFORD SANDY LOAM

Soil column, batch adsorption, and batch biodegradation experiments we re conducted to determine the fate of DBCP applied in irrigation water at low concentrations (almost-equal-to 3 mug L-1) to unsaturated Hanf ord sandy loam soil (coarse-loamy, mixed, nonacid, thermic Typic Xeror thents). The objective was to determine the extent that soil might tre at DBCP-contaminated groundwater proposed for irrigation of citrus in the Redlands California area. Water applications were performed cyclic ally to simulate citrus irrigation practices. Volatilization of DBCP t o the atmosphere between irrigations was the dominant mechanism contro lling its fate once applied to the soil. Soil adsorption was found to retard the transport of DBCP 3 to 5 times when compared with the wetti ng front movement. Batch biodegradation experiments suggested that DBC P may also be significantly metabolized by subsurface microorganisms. The half-life was estimated to be approximately 7 d. Soil water charac teristic curve hysteresis was observed with the soil column experiment s and water content distributions calculated from soil water pore pres sures required that scanning curves be developed to accurately simulat e experimental data.