We examined the anaerobic biodegradability and transformation of dicamba under denitrifying, iron Fe(III) reducing, sulfate reducing, and methanogenic conditions. Anaerobic microcosms were established with dicamba treated agricultural soil and golf course drainage stream sediments, which were each spiked with dicamba as the sole carbon source. Transformation of dicamba to 3,6dichlorosalicylate via demethylation of the methoxy substituent (O-demethylation) occurred in cultures under methanogenic conditions in cultures from both sites. In methanogenic enrichments from golf course sediments, the O-demethylated product (3,6-dichlorosalicylate) was reductively dechlorinated to 6-chlorosalicylate and subsequently to salicylate, which was ultimately mineralized to CH 4 and CO 2 . Sulfate reducing cultures from golf course drainage stream sediments O-demethylated dicamba and partially dechlorinated 3,6-dichlorosalicylate to 6-chlorosalicylate (<10%). Neither denitrifying nor iron reducing conditions promoted the biotransformation of dicamba. This study shows the effect of different electron acceptors on the transformation of dicamba in anaerobic environments and demonstrates the degradation pathway under methanogenic conditions. The work suggests that the electron acceptors present will influence in situ degradation of herbicides in anoxic soils and sediments.

We examined the anaerobic degradation of catechol (1,2‐dihydroxybenzene), resorcinol (1,3‐dihydroxybenzene), and hydroquinone (1,4‐dihydroxybenzene), which are widely used industrial reagents and central intermediates in the biodegradation of numerous aromatic compounds. Anaerobic denitrifying enrichments were established with sediments from an estuarine tidal strait in New Jersey, USA. The three dihydroxybenzene isomers were provided as a sole carbon source in separate enrichment series. Resorcinol‐ and catechol‐degrading consortia used their respective substrates over repeated feedings. Initial loss of hydroquinone was observed, but activity could not be maintained. The degradation of resorcinol and catechol was coupled to denitrification and was dependent on nitrate or nitrite as an electron acceptor. Nitrate consumption and N2 production corresponded to the stoichiometric values predicted for the oxidation of dihydroxybenzenes to CO2.

Abstract-We examined the anaerobic degradation of catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene), which are widely used industrial reagents and central intermediates in the biodegradation of numerous aromatic compounds. Anaerobic denitrifying enrichments were established with sediments from an estuarine tidal strait in New Jersey, USA. The three dihydroxybenzene isomers were provided as a sole carbon source in separate enrichment series. Resorcinol-and catechol-degrading consortia used their respective substrates over repeated feedings. Initial loss of hydroquinone was observed, but activity could not be maintained. The degradation of resorcinol and catechol was coupled to denitrification and was dependent on nitrate or nitrite as an electron acceptor. Nitrate consumption and N 2 production corresponded to the stoichiometric values predicted for the oxidation of dihydroxybenzenes to CO 2 .

The anaerobic biodegradability and transformation of the mono-and dichlorinated salicylates (2-hydroxybenzoates) was examined under denitrifying, Fe (III) reducing, sulfate reducing and methanogenic conditions. 3,6-Dichlorosalicylate and 6-chlorosalicylate are anaerobic microbial metabolites of dicamba, a widely used herbicide. Anaerobic microcosms were established with dicamba treated soil from Wyoming, and golf course drainage stream sediments from New Jersey, which were each spiked with salicylate, 3,6-dichlorosalicylate or one of the four monochlorosalicylate isomers. Salicylate was degraded under denitrifying, sulfidogenic and methanogenic conditions. In methanogenic enrichments 5-chlorosalicylate and 3-chlorosalicylate were reductively dehalogenated to salicylate which was then utilized. Dehalogenation of monochlorinated salicylates to salicylate was also observed in denitrifying chlorosalicylate degrading cultures. The study revealed that the position of the chlorine substituent as well as the predominant electron accepting process affect the rate and extent of chlorosalicylate degradation in anoxic environments.