Occurrence of 1,2-Dichloropropane and 1,3-Dichloropropene in the Abbotsford Aquifer, British Columbia

Forty piezometers at 13 sites in the Canadian portion of the Abbotsford aquifer were tested for 1,2-dichloropropane (1,2-DCP) and 1,3-dichloropropene (1,3-DCP) on an approximate monthly interval from July 1991 to June 1994. Detectable levels of 1,2-DCP were found in 32 of the 40 piezometers. Average 1,2-DCP concentrations within a piezometer ranged up to 2.23 µg/L and a maximum concentration of 7.07 µg/L was recorded in one piezometer. 1,3-DCP was detected for only a short period of time in one piezometer and at a maximum concentration of 0.23 µg/L. 1,2-DCP contamination in the aquifer is attributed to application of fumigants containing this compound as an active ingredient or as an impurity for the control of root nematodes in red raspberry crops. The nature of the contamination is consistent with a non-point source that is highly variable in space and time. Although soil fumigants containing 1,2-DCP as an active ingredient are no longer used in the Abbotsford area, fairly constant values of 1,2-DCP would indicate there is still a contaminant source providing input to the groundwater. 1,2-DCP has apparently accumulated on the soil sediments above the water table and is slowly being released to the groundwater. In the top 15 m of the saturated zone, concentrations generally decreased with depth below the water table to near nondetectable levels. Correlation between contaminant levels and rainfall or other environmental factors that might affect the distribution of 1,2-DCP could not be established. More detailed soil measurements and controlled laboratory experiments are needed to determine 1,2-DCP movement as well as rates of dissipation in the Abbotsford aquifer.