Biomedical subjects

Joel Harden

Publications and source records attributed to Joel Harden.

2 recordsLinked to original sources

PubMed2006

Benzidine transformation processes in natural sediments.

Aromatic amines, such as benzidine and 3,3'-dichlorobenzidine, are chemicals used in the pigment and dye processes. Release of these compounds into the environment is important because of their carcinogenic and toxic nature. In the present study, the sediment and water samples were collected from Lake Macatawa (Holland, MI, USA) and subsequently spiked with benzidine. The grain size distribution of the sediment samples investigated here ranged in composition from sandy to silty-clay sediment types. The sediment-water systems spiked with benzidine were incubated under anaerobic conditions at 4, 15, and 23 degrees C for 211 d. Degradation of benzidine was observed over the time-course analysis of the sediment-water mixtures. Three possible metabolites (aniline, 2-ethyl-1-hexanol, and 1-amino-2-hexene) were observed during this investigation as a result of gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. No metabolites were observed in autoclaved bottles, suggesting that the transformation of benzidine in the sediment-water mixtures was the result of microbial activity. From sediment-water distribution experiments, benzidine demonstrated higher sorption affinity for the different sediment phases than its degradation product, aniline. Therefore, microbially mediated transformation of benzidine to aniline is expected to yield a greater total concentration of the more mobile compound, aniline, in the water phase and a greater possibility for transport of aniline in the water phase.

Benzidines↗

PubMed2005

Concentrations and distribution of 3,3'-dichlorobenzidine and its congeners in environmental samples from Lake Macatawa.

Release of 3,3'-dichlorobenzidine (DCB), an intermediate in dye manufacturing processes, is of environmental concern due to its carcinogenic nature. An 11-year field study has been conducted to elucidate the fate and behavior of DCB and its congeners in the Lake Macatawa (Holland, MI, USA) sediment-water system. The sediments were variable in composition, ranging from sandy sediments with 1-8.7% total organic carbon (OC) to silty-clay sediments with 7.5-20.6% total OC. The pH ranged from 6.3 to 7.4. The findings from this field study confirmed that DCB and its congener, benzidine, are transported over long distances. The concentration of DCB in the water phase was found to be from non-detectable to approximately 1300 times greater than the water quality criteria established for DCB (0.021 microg/l). Its congener, benzidine, which is substantially more toxic for humans than its parent compound has been found up to approximately 12300 times higher levels than the EPA guidelines suggest (0.000086 microg/l). Both DCB and benzidine were found in the sediment phase. DCB was observed at almost 70 mg/kg in a sample collected in 1993. The concentrations in both phases have declined in recent years. To assess the threat of the released pollutants, it is necessary to understand how pollutants tend to behave in various media. Therefore, it is crucial to identify and quantify all sources of the chemical and its congeners in order to meaningfully predict the fate (and transport) of a hydrophobic organic compound (HOC) in the environment.

3,3'-Dichlorobenzidine↗