Microbial metabolism environmental fate

Highly halogenated organic compounds such as polychlorinated biphenyls and perchloroethylene appear to be too highly oxidised and low in energy content to serve as sources of electrons and energy for microbial metabolism. Bacteria are more likely to use them as electron acceptors in cell-membrane-based respiration processes [154]. The environmental fate of halogenated polymers such as polyvinylchloride or Teflon may depend on the question of whether it will be appropriate to sustain de-halorespiration processes. 

Zoxamide has low toxicity to mammals except for the potential to cause skin sensitization [28]. Based on laboratory studies, it poses very low risk to most non-target species [1, 28]. Environmental fate studies have shown that zoxamide dissipates rapidly in the environment due to hydrolysis, photodegradation in water and microbial metabolism. It has a half-life in soil of 2-10 days, low water solubility, and low soil mobility [1], resulting in little potential for leaching into groundwater. 

Environmental Fate of Hydrocarbons, A few studies have shed light on the fate of hydrocarbons in the marine environment. In coastal marine sediments, PAHs accumulate from urban sources and are converted to intermediate products and CO2 by metabolism, photooxidation, and other processes. In their Controlled Ecosystem Pollution Experiment (CEPEX), Lee et al. (1978) concluded that hydrocarbons were deposited in the sediment by falling particles, although they did not specifically study the direct uptake of waterborne PAH by sediment. Their results show that in the first few days of a one-time addition of oil that the sediment concentration of naphthalenes was high and then steadily decreased to below detection by day 17, whereas anthracene, fluoranthene, benz[a]anthracene, and benzo-[a]pyrene concentrations in the sediment steadily increased over the 17 d of the experiment. It was also proposed by Lee et al. (1978) that hydrocarbons from an oil slick that are smaller than 15 carbons volatilize quickly and only to a limited degree for those with 15-25 carbons. They concluded that most LPAHs were removed primarily by microbial degradation and that HPAHs were removed by photooxidation and sedimentation. Another study has shown that when oil is added to the water column, total hydrocarbons rapidly decrease in the water but aromatic hydrocarbons increase in the sediment (Gordon et al. 1976). 

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