The fate of 3,3'-dichlorobenzidine in the aqueous environment
Abstract
Release of 3,3$\sp\prime$-dichlorobenzidine (DCB), an intermediate in dye manufacturing, and its congeners are of environmental concern due to their carcinogenic nature. Laboratory experiments have been conducted to elucidate the fate of these compounds in sediment-water systems. The sediments and water used in this study were collected from Lake Macatawa (Holland, MI). The sediments were variable in composition, ranging from sandy sediments with 1-8.7% total organic carbon to silty-clay sediments with 7.5-32.3% total organic carbon. Laboratory experiments have been conducted to determine the fate of DCB in sediment/water systems. Bottles containing sediment/water mixtures were spiked with DCB and incubated at 4$\sp\circ$C, 20$\sp\circ$C, and 30$\sp\circ$C for twelve months under anaerobic conditions. Autoclaved sediment samples in distilled water were also spiked with DCB and incubated for use as a control. Dehalogenation of DCB to benzidine appeared to take place through a transient intermediate, 3-chlorobenzidine (MCB), which was observed in time-course analyses of the sediment/water mixtures. No metabolites were observed in autoclaved samples, suggesting that dehalogenation of DCB in anaerobic sediment/water systems was mediated by microbial activity. Photodechlorination of DCB was observed in water mixtures which were irradiated with monochromatic radiation at wavelengths ranging from 290 to 360 nm. No dechlorination was observed with radiation from the visible range $\lambda$ = 532 nm). Product studies revealed that MCB was produced as a transient intermediate in the photodechlorination process; benzidine was identified as a stable photoproduct. The data also provided evidence of other photochemical pathways as a result of irradiation of DCB in water. Sediment/water partitioning behavior demonstrated non-linearity in all experiments. DCB showed a greater affinity for the sediment phase than its non-chlorinated derivative, benzidine. Therefore, progressive dehalogenation of DCB in anaerobic sediments and water phase is expected to yield a greater total concentration of lesser-chlorinated amines in the solution phase, a shift to a more toxic form, and a greater potential for transport in the environment.
Degree
Ph.D.
Advisors
Blatchley, Purdue University.
Subject Area
Civil engineering|Environmental engineering|Environmental science|Hydrology
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