Transformation and Sorption of 1,2‐Dibromo‐3‐Chloropropane in Subsurface Samples Collected at Fresno, California

Abstract

The transformation rate of 1,2‐dibromo‐3‐chloropropane (DBCP) was determined in phosphate buffer solution, in groundwater, and in groundwater/aquifer solid slurries from ambient temperatures to 72 °C. From the disappearance data, the apparent Arrhenius constants for DBCP transformation were calculated and found to decrease in Ea with temperature from 19.2 (±2.4) kcal mol−1 in the 55 to 72 °C range to 12.5 (±1.8) kcal mol−1 in the 21 to 55 °C range. Low sorption values were an indication that sorption does not play a major role in the aquifer being studied. No significant difference in the disappearance rates was observed in the buffer solution (corrected for buffer effects) and in groundwater with and without solids added. However, in the phosphate buffer solution, dehydrohalogenation appeared to be the favored transformation process in contrast to the groundwater systems where hydrolysis seemed to predominate. This apparent influence of dissolved constituents or temperature on transformation mechanism or rate may restrain the use of direct extrapolation of data between systems. Applying the transformation data from this study to median field parameters, a DBCP half‐life of 6.1 yr was calculated for typical groundwater conditions in California (pH 7.8 and 21.1 °C).

The Geochemistry of Pesticides

“…Under the comparatively mild conditions of most natural waters, only singly bonded carbons are likely to undergo this reaction, leading to the formation of the corresponding alkene. Pesticide compounds that have been observed to undergo dehydrohalogenation under environmentally relevant conditions include a number of fumigants, insecticides, and volatile adjuvants (Barbash and Reinhard, 1992a,b;Burlinson et al, 1982;Cline and Delfino, 1989;Deeley et al, 1991;Haag and Mill, 1988a;Jeffers et al, 1989;Kuhn and Suflita, 1989;Ngabe et al, 1993;Vogel and Reinhard, 1986).…”

“…In natural waters, these other species -which may be of biological or abiotic origin, or may be associated with the surfaces of natural materials -consist primarily of Brønsted acids and bases, nucleophiles, oxidants, reductants, and catalysts. Although there are some exceptions (e.g., Hemmamda et al, 1994;Huang and Stone, 2000), the rates of abiotic bimolecular transformation of pesticide compounds in homogeneous aqueous solution (i.e., in the absence of a solid phase) have been found to be first order with respect to the aqueous concentrations of both the substrate and the other reactant -and thus second-order overall -for a wide range of reactions (e.g., Burlinson et al, 1982;Curtis and Reinhard, 1994;Deeley et al, 1991;Haag and Mill, 1988b;Jafvert and Wolfe, 1987 Hypothesized mechanism for the reductive transformation of a pesticide compound through the transfer of electrons from a bulk electron donor (e.g., FeS, Kenneke and Weber, 2003) to a pesticide molecule (e.g., methyl parathion, Tratnyek and Macalady, 1989) by an electron carrier (e.g., hydroquinone, Schwarzenbach et al, 1990). Reproduced from Schwarzenbach RP, Stierli R, Lanz K, and Zeyer J (1990) Quinone and iron porphyrin mediated reduction of nitroaromatic compounds in homogeneous aqueous solution.…”

“…Arrhenius plots exhibiting a significant departure from linearity are usually interpreted to imply the simultaneous operation of more than one transformation mechanism, with different mechanisms dominating over different temperature ranges. Pesticides for which this phenomenon has been observed include malathion (Wolfe et al, 1977), 1,2-dibromo-3-chloropropane (DBCP) (Deeley et al, 1991), triasulfuron, and primisulfuron (Dinelli et al, 1998).…”

Project Work Plan Carbon Tetrachloride and Chloroform Attenuation Parameter Studies: Heterogeneous Hydrolytic Reactions

“…Haag and Mill (1988) did see a clear effect of the sediment on hydrolysis of styrene oxide, an epoxide compound. Deeley et al (1991) studied the transformation of 1,2-dibromo-3-chloropropane (a soil fumigant) at concentration of 1 ppm in a sediment slurry and saw no significant effect of the sediment on hydrolysis rate. In 2000, we contacted Peter Jeffers and Ted Mill, two of the primary researchers in this field.…”

Pesticide transport and transformation modeling in soil column and groundwater contamination prediction

“…Some researches provided a model for predicting the fate of nonvolatile pesticides (Wagenet and Huston, 1986;Wagenet et al,1989). In many cases, they considered a distribution coefficient for this case (Deeley et al, 1991). Developing models with molecular diffusion and other important factors have been done by other researchers (Jury et al, 1983;Kalita et al, 1998).…”