Bioremediation of Sites Co-contaminated with Benzene or Toluene and Heavy Metals

Abstract

Co-contamination of both organics and heavy metals are a common occurrence in hazardous waste sites. The contaminants enter the environment due to human activity and can leech through the soil, entering groundwater sources used for irrigation and drinking water. This can lead to many health concerns for humans and the ecosystem. These sites are difficult to remediate due to the combined toxic effects heavy metals and the hazardous organics have on the microbes of the soil community. Little is known about the effects toxic heavy metals have on the bioremediation of organics. One solution is to characterize the ability of naturally occurring micro-organisms in the soil that are resistant to the heavy metal toxicity and have the ability to degrade the organic compounds. The study’s goal is to identify naturally occurring bacteria in soil that are able to degrade benzene and toluene while in presence of heavy metals. Microcosms were created with a range of two heavy metals (lead and cadmium) and 0.4488 mM of benzene or 0.1888 mM of toluene. Sterile controls were made to ensure only biological activity was the cause of the degradation in the microcosms. The results found that there were naturally occurring bacteria in the soil with the ability to degrade benzene or toluene, and resist heavy metal toxicity. Heavy metal concentrations had little to no effect on the degradation of the benzene and toluene. Toluene was degraded fastest by the microbes, likely due to its methyl group. With this information, further research will be performed to better identify the microbes responsible for the degradation of benzene and toluene in co-contaminated sites. These microbes can potentially be used for the bioremediation of benzene or toluene in water and soils co-contaminated with heavy metals.