Transformations of chloronitrobenzenes in anaerobic sediment

The transformations of chloronitrobenzenes (CNBs) in anaerobic estuarine sediment were examined. The sediment had been preexposed to various anthropogenic chemicals from the surrounding industries. The sulfate content of the interstitial and overlaying waters was approximately 20 mmole/1 indicating that the sediment was sulfidogenic. All the CNBs tested transformed without any lag period. The kinetic data followed a first-order reaction mechanism with rate constants ranging from 0.216 to 0.866 day−1 or half-lives from 0.8 to 3.2 days. The intermediates detected in the experiment indicated that the reduction of the nitro group was the first stage in the transformation of chloronitro aromatic compounds, resulting in the formation of corresponding chloroanilines (CAs). The CAs further transformed via ortho and para dechlorination pathways.