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Research paper thumbnail of Characterization, sources and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated riverbank sediments

Environmental Earth Sciences, 2015

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants common in aquatic ecosystems.... more Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants common in aquatic ecosystems. Although there is a vast literature on PAH contamination, there is a scarcity of information in long-term contaminated ecosystems. This study is the first detailed characterization of PAHs and their sources from riverbank sediments with a historic legacy of pollution. A total of 27 cores were collected at two highly contaminated locations and at one upstream location where apparently there was no PAH contamination. At each location, three cores were taken at three different depths using stainless steel liners. PAHs were extracted by using a modified sonication method followed by identification and quantification by gas chromatography mass spectrometry. Twelve PAHs were quantified and sources were identified using PAH ratios. High PAH concentrations (94,000-560,000 lg/kg) were detected making this aquatic ecosystem one of the most polluted in the world. Pyrolytic sources of PAHs was indicated by the large relative contribution of four ring compounds, while high levels of low molecular weight PAHs also suggested input from petrogenic sources. Risk quotients assessment overwhelmingly demonstrated that the riverbank sediments of the Mahoning posed a very high ecological risk to aquatic organisms, even at what was previously considered an unpolluted location. These results suggest that there is a great need for implementation of remediation strategy of the riverbanks.

Research paper thumbnail of Bacterial community composition and biogeochemical heterogeneity in PAH-contaminated riverbank sediments

Journal of Soils and Sediments, 2014

PurposePredicting response of microbial communities to pollution requires an underlying understan... more PurposePredicting response of microbial communities to pollution requires an underlying understanding of the linkage between microbial community structure and geochemical conditions. Yet, there is scarce information about microbial communities in polycyclic aromatic hydrocarbons (PAH)-contaminated riverbank sediments. The aim of this study was to characterize bacterial communities in highly PAH-contaminated sediments and establish correlations between bacterial communities and environmental geochemistry of the sediments.Materials and methodsSediment core samples were collected from a highly PAH-contaminated site for (1) analysis of geochemical parameters including total nitrogen, total organic matter, moisture, total carbon, sulfate, pH, and PAH concentrations and (2) bacterial enumeration, 16S rDNA-based terminal restriction fragment length polymorphism analysis and sequencing.Results and discussionNon-metric dimensional scaling analyses revealed that bacterial community composition was strongly influenced by PAH concentration. Sulfate, organic matter, pH, and moisture were also related to community composition. A diverse microbial community was identified by the large number of operational taxonomic units recovered and by phylogenetic analyses. δ-Proteobacteria, firmicutes, and bacteriodetes were the dominant groups recovered. We also observed a high number of phylotypes associated with sulfate-reducing bacteria, some of which have been previously described as important in PAH degradation.ConclusionsOur study suggests that, despite intense pollution, bacterial community composition did exhibit temporal and spatial variations and were influenced by sediment geochemistry. Significant relationships between bacterial community composition and PAHs suggest that, potentially, extant microbial communities may contribute to natural attenuation and/or bioremediation of PAHs.

Research paper thumbnail of Evaluating degradation of polycyclic aromatic hydrocarbon (PAH) potential by indigenous bacteria isolated from highly contaminated riverbank sediments

Environmental Earth Sciences, 2021

The aim of this study was to identify and culture bacteria indigenous from heavily polycyclic aro... more The aim of this study was to identify and culture bacteria indigenous from heavily polycyclic aromatic hydrocarbons (PAH)-contaminated sediments and evaluate their degradative potential. Fifteen novel aerobic PAH degraders mostly associated with Stenotrophomonas, Pseudomonas, Brucella, and Achromobacter genera were isolated. MHR3A, related to Brucellamicroti CCM 4915, MHR3B, related to Pseudomonasputida NBRC 14164, and MHRN15A, related to Achromobacterkerstersii LMG 344, grew aggressively on PAHs as sole carbon sources and were used for degradation studies. With no amendment or added surfactant, within 15 days, MHR3B was able to degrade 78%, 82%, and 57%, respectively of fluorene, phenanthrene, and pyrene (FPP) compared to the controls which were statistically lower. MHR3A was able to degrade 81%, 84%, and 73% of FPP respectively, while MHRN15A was able to degrade 18%, 29%, and 20% of FPP. An anaerobic consortium enriched on FPP, consisting mainly of Gammaproteobacteria and Clostridia, was obtained and tested under sulfate-reducing conditions in the presence of anthraquinone-2,6 disulfonate (AQDS); however, FPP loss attributed to bacteria was only 15% over 120 days. This study demonstrated that isolation and culturing techniques coupled with standard molecular methods warrants continued investigation of indigenous microbes for in situ remediation of highly PAH-contaminated environments.

Research paper thumbnail of Characterization, sources and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated riverbank sediments

Environmental Earth Sciences, 2015

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants common in aquatic ecosystems.... more Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants common in aquatic ecosystems. Although there is a vast literature on PAH contamination, there is a scarcity of information in long-term contaminated ecosystems. This study is the first detailed characterization of PAHs and their sources from riverbank sediments with a historic legacy of pollution. A total of 27 cores were collected at two highly contaminated locations and at one upstream location where apparently there was no PAH contamination. At each location, three cores were taken at three different depths using stainless steel liners. PAHs were extracted by using a modified sonication method followed by identification and quantification by gas chromatography mass spectrometry. Twelve PAHs were quantified and sources were identified using PAH ratios. High PAH concentrations (94,000-560,000 lg/kg) were detected making this aquatic ecosystem one of the most polluted in the world. Pyrolytic sources of PAHs was indicated by the large relative contribution of four ring compounds, while high levels of low molecular weight PAHs also suggested input from petrogenic sources. Risk quotients assessment overwhelmingly demonstrated that the riverbank sediments of the Mahoning posed a very high ecological risk to aquatic organisms, even at what was previously considered an unpolluted location. These results suggest that there is a great need for implementation of remediation strategy of the riverbanks.

Research paper thumbnail of Bacterial community composition and biogeochemical heterogeneity in PAH-contaminated riverbank sediments

Journal of Soils and Sediments, 2014

PurposePredicting response of microbial communities to pollution requires an underlying understan... more PurposePredicting response of microbial communities to pollution requires an underlying understanding of the linkage between microbial community structure and geochemical conditions. Yet, there is scarce information about microbial communities in polycyclic aromatic hydrocarbons (PAH)-contaminated riverbank sediments. The aim of this study was to characterize bacterial communities in highly PAH-contaminated sediments and establish correlations between bacterial communities and environmental geochemistry of the sediments.Materials and methodsSediment core samples were collected from a highly PAH-contaminated site for (1) analysis of geochemical parameters including total nitrogen, total organic matter, moisture, total carbon, sulfate, pH, and PAH concentrations and (2) bacterial enumeration, 16S rDNA-based terminal restriction fragment length polymorphism analysis and sequencing.Results and discussionNon-metric dimensional scaling analyses revealed that bacterial community composition was strongly influenced by PAH concentration. Sulfate, organic matter, pH, and moisture were also related to community composition. A diverse microbial community was identified by the large number of operational taxonomic units recovered and by phylogenetic analyses. δ-Proteobacteria, firmicutes, and bacteriodetes were the dominant groups recovered. We also observed a high number of phylotypes associated with sulfate-reducing bacteria, some of which have been previously described as important in PAH degradation.ConclusionsOur study suggests that, despite intense pollution, bacterial community composition did exhibit temporal and spatial variations and were influenced by sediment geochemistry. Significant relationships between bacterial community composition and PAHs suggest that, potentially, extant microbial communities may contribute to natural attenuation and/or bioremediation of PAHs.

Research paper thumbnail of Evaluating degradation of polycyclic aromatic hydrocarbon (PAH) potential by indigenous bacteria isolated from highly contaminated riverbank sediments

Environmental Earth Sciences, 2021

The aim of this study was to identify and culture bacteria indigenous from heavily polycyclic aro... more The aim of this study was to identify and culture bacteria indigenous from heavily polycyclic aromatic hydrocarbons (PAH)-contaminated sediments and evaluate their degradative potential. Fifteen novel aerobic PAH degraders mostly associated with Stenotrophomonas, Pseudomonas, Brucella, and Achromobacter genera were isolated. MHR3A, related to Brucellamicroti CCM 4915, MHR3B, related to Pseudomonasputida NBRC 14164, and MHRN15A, related to Achromobacterkerstersii LMG 344, grew aggressively on PAHs as sole carbon sources and were used for degradation studies. With no amendment or added surfactant, within 15 days, MHR3B was able to degrade 78%, 82%, and 57%, respectively of fluorene, phenanthrene, and pyrene (FPP) compared to the controls which were statistically lower. MHR3A was able to degrade 81%, 84%, and 73% of FPP respectively, while MHRN15A was able to degrade 18%, 29%, and 20% of FPP. An anaerobic consortium enriched on FPP, consisting mainly of Gammaproteobacteria and Clostridia, was obtained and tested under sulfate-reducing conditions in the presence of anthraquinone-2,6 disulfonate (AQDS); however, FPP loss attributed to bacteria was only 15% over 120 days. This study demonstrated that isolation and culturing techniques coupled with standard molecular methods warrants continued investigation of indigenous microbes for in situ remediation of highly PAH-contaminated environments.