Natural attenuation, biostimulation and bioaugmentation on biodegradation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments

Abstract

The biodegradability of a mixture of PAHs, namely fluorene (Fl), phenanthrene (Phe) and pyrene (Pyr), in mangrove sediment slurry was investigated. At the end of week 4, natural attenuation based on the presence of autochthonous microorganisms degraded more than 99% Fl and Phe but only around 30% of Pyr were degraded. Biostimulation with addition of mineral salt medium degraded over 97% of all three PAHs, showing that nutrient amendment could enhance Pyr degradation. Bioaugmentation with inoculation of a PAH-degrading bacterial consortium enriched from mangrove sediments did not show any promotion effect and the degradation percentages of three PAHs were similar to that by natural attenuation. Some inhibitory effect was observed in bioaugmentation treatment in week 1 with only 50% Fl and 70% Phe degraded. These results indicate that autochthonous microbes may interact and even compete with the enriched consortium during PAH biodegradation. Natural attenuation appeared to be the most appropriate way to remedy Fl- and Phe-contaminated mangrove sediments while biostimulation was more capable to degrade Pyr-contaminated sediments. The study also shows that although a large portion of the added PAHs (more than 95%) was adsorbed onto the sediments at the beginning of the experiment, most PAHs were degraded in 4 weeks, suggesting that the degraders could utilize the adsorbed PAHs efficiently.

Enhanced Degradation of Benzo[α]Pyrene in Coal Tar Contaminated Soils Using Biodiesel

“…Although volatilisation is probably also contributory to the losses observed in the un-amended samples [31], the degrading activities of the indigenous microbes cannot be ruled out. It has been demonstrated previously that autochthonous microorganisms have high degradation potential for three ring PAHs (Fl and Phe) during natural attenuation, as reported for contaminated mangrove sediments [32]. Bacterial strains (Sphingomonas sp.)…”

Biodegradation of Polycyclic Aromatic Hydrocarbons in Mangrove Sediments Under Different Strategies: Natural Attenuation, Biostimulation, and Bioaugmentation with Rhodococcus erythropolis T902.1

“…For the degradation of three PAHs (fluorene, phenanthrene, and pyrene) found in mangrove sediments, Yu et al (2005) used an enriched bacterial consortium containing three bacterial species (Rhodococcus sp., Acinetobacter sp., and Pseudomonas sp.). The starting PAH concentrations (total of 16 priority PAHs from the US EPA) in sediments varied from 1.162 to 3.322 ng g −1 of dry matter.…”

“…and 7.24 ± 0.24 %, respectively (Yu et al 2005). PAHs present in soil can have a toxic effect on many plants, microorganisms and invertebrates (Tian et al 2008).…”

Natural attenuation of contaminated marine sediments from an old floating dock Part II: Changes of sediment microbial community structure and its relationship with environmental variables

“…Similarly, other hydrographic parameters, such sea bed topography and morphology, tides and water currents, as well as water temperature, turbidity, salinity, dissolved oxygen saturation and suspended solids, also showed minimal and insignificant variations after the removal of the Dock, according to the monitoring work carried out by a consultancy company from August to October, 2007. Fresh sediment was used for measuring microbial biomass and enzyme activities. The former parameter was estimated by the population size of total aerobic heterotrophic bacteria (THB), according to the most probable number (MPN) method described by Yu et al (2005). The activities of dehydrogenase (DHA) and catalase (CAT), the two common oxidoreductase enzymes in microorganisms indicating the oxidative microbial activity and antioxidant potential under pollutant stress, respectively (Friedel et al, 1994;Sies, 1997) were also measured.…”