NONPOINT-SOURCE GROUNDWATER CONTAMINATION BY 1,2,2-TRICHLOROPROPANE, A TRACE IMPURITY IN SOIL FUMIGANT FORMULATIONS

Groundwater samples were collected from 60 piezometers and 23 domestic wells from March 1991 to April 1992 as part of a study to quantify NO 3- and pesticide contamination of the Abbotsford Aquifer, located in t he lower Eraser Valley, southwestern British Columbia, Canada. A new c ontaminant, 1,2,2-tricchooropropane (1,2,2-TCP), was detected and conf irmed in 296 of the 514 samples by purge and trap GC/MS, and its conce ntration was determined in 150 of the samples collected between Januar y and April 1992. The contaminant was detected in 34 (57%) of the piez ometers sampled, and 10 (44%) of the domestic wells sampled. Mean 1,2, 2-TCP concentration (+/- 1 SD) was 0.12 +/- 0.11 mu g L(-1) in 123 pie zometer samples and 0.14 +/- 0.09 mu g L(-1) in 27 domestic well sampl es. The highest 1,2,2-TCP concentrations measured were 0.62 and 0.32 m u g L(-1) for piezometers and domestic wells, respectively. The probab le nonpoint sources of the contaminant are the synthetic pesticides, T elone (mixture of 1,3-dichloropropene and 1,2-dichloropropane) and Tel one II (1,3-dichloropropene), used to control pathogenic nematodes in raspberry (Rubus idaeus L.) production. Analyses of Telone and Telone II confirmed the presence of 1,2,2-TCP as impurities in both products. The study demonstrates that an impurity present in pesticide formulat ions in trace quantities, which Is persistent in soil and water, has t he potential to result in significant groundwater contamination under the appropriate soil and climatic conditions.