Twelve organic compounds commonly found at hazardous waste sites were studied for uptake by hybri... more Twelve organic compounds commonly found at hazardous waste sites were studied for uptake by hybrid poplar trees. The vegetative uptake of many of these compounds has not previously been demonstrated for plant species being utilized for phytoremediation, such as hybrid poplar trees. Experiments were conducted hydroponically utilizing 14 C-labeled compounds to ascertain translocation and fate. Predictive relationships for the translocation and partitioning to plant tissues were developed from the experimental data. Translocation and partitioning relationships based on compounds' octanol-water partitioning coefficients (log K ow) produced the best results, but the relationships did not allow for fully accurate prediction of each contaminant's fate. Translocation and subsequent transpiration of volatile organic compounds (VOCs) from the leaves to the atmosphere was shown to be a significant pathway. As full-scale phytoremediation systems are deliberated, the pathways investigated here should be considered in terms of a contaminant removal mechanism and potential contamination of the vegetation.
Bromophenols occur naturally and are used globally as man-made additives in various industrial pr... more Bromophenols occur naturally and are used globally as man-made additives in various industrial products. They are decomposition products of many emerging organic pollutants, such as tetrabromobisphenol A, polybrominated dibenzo-p-dioxin (PBDD), polybrominated diphenyl ethers (PBDE), and others. To characterize their biotransformation pathways, bromophenol congener 2,4,6-tribromophenol, being used most frequently in the synthesis of brominated flame retardants and having the greatest environmental abundance, was selected to hydroponically expose rice plants. After exposure for 5 days, 99.2% of 2,4,6-tribromophenol was metabolized by rice. Because of the lack of relative reference standards, an effective screening strategy was used to screen for potential metabolites that were further qualitatively identified by gas and liquid chromatography combined with high-resolution mass spectrometry. Forty transformation products were confirmed or tentatively identified at different confidence levels, including 9 phase I and 31 phase II metabolites. A large number of metabolites (39) were found in rice root, and 10 of them could be translocated and detected in rice stems or leaves. Many transformation pathways were proposed, including debromination, hydroxylation, methylation, coupling reactions, sulfation, and glycosylation. It was remarkable that a total of seven hydrophobic, persistent, and toxic OH-PBDEs and PBDD/Fs were found, indicating the biotic dimeric reactions of 2,4,6-tribromophenol that occurred in the rice plants. These results improve our understanding of the transformation and environmental fates of bromophenols, and they indicate new potential sources for OH-PBDEs and PBDD/Fs in the environment, especially in food chains.
Polychlorinated biphenyls (PCBs) can be metabolized to hydroxylated polychlorinated biphenyls (OH... more Polychlorinated biphenyls (PCBs) can be metabolized to hydroxylated polychlorinated biphenyls (OH-PCBs) as reported in a number of animal studies. However, there are few studies on OH-PCBs in vivo in whole plants. In order to explore the formation of OH-PCBs in whole plants in detail, poplars (Populus deltoides × nigra, DN34) were exposed to 3,3′,4,4′-tetrachlorobiphenyl (CB 77) in hydroponic solution. Poplars are widely used in phytoremediation applications and the complete genome has been sequenced. In this research, a HPLC-MS method was developed to directly determine the hydroxylated metabolites of CB77 (OH-CB77s), avoiding the experimental errors introduced by derivatization pretreatments required by gas chromatography-based methods. Three potential hydroxylated metabolites of CB 77, including 6-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (6OH-CB77), 5-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (5OH-CB77) and 4′-hydroxy-3,3′,4,5′tetrachlorobiphenyl (4′OH-CB79), were determined in poplar tissues. The major product, 6OH-CB77, was detected in the roots, bottom bark, bottom wood, middle bark and middle wood for the whole poplar plants, but the minor product, 5OH-CB77, was detected only in the poplar roots. The concentration of 6OH-CB77 was about 10 times greater than that of 5OH-CB77 in the roots. However, the major mammalian metabolite, 4′OH-CB79 was not detected in any of the samples. The results suggest that the hydroxylated metabolic pathway of CB77 is via an epoxide intermediate in poplar.
A pink-pigmented symbiotic bacterium was isolated from hybrid poplar tissues (Populus deltoides ؋... more A pink-pigmented symbiotic bacterium was isolated from hybrid poplar tissues (Populus deltoides ؋ nigra DN34). The bacterium was identified by 16S and 16S-23S intergenic spacer ribosomal DNA analysis as a Methylobacterium sp. (strain BJ001). The isolated bacterium was able to use methanol as the sole source of carbon and energy, which is a specific attribute of the genus Methylobacterium. The bacterium in pure culture was shown to degrade the toxic explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazene (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5-tetrazocine (HMX). [U-ring-14 C]TNT (25 mg liter ؊1) was fully transformed in less than 10 days. Metabolites included the reduction derivatives amino-dinitrotoluenes and diamino-nitrotoluenes. No significant release of 14 CO 2 was recorded from [ 14 C]TNT. In addition, the isolated methylotroph was shown to transform [U-14 C]RDX (20 mg liter ؊1) and [U-14 C]HMX (2.5 mg liter ؊1) in less than 40 days. After 55 days of incubation, 58.0% of initial [ 14 C]RDX and 61.4% of initial [ 14 C]HMX were mineralized into 14 CO 2. The radioactivity remaining in solution accounted for 12.8 and 12.7% of initial [ 14 C]RDX and [ 14 C]HMX, respectively. Metabolites detected from RDX transformation included a mononitroso RDX derivative and a polar compound tentatively identified as methylenedinitramine. Since members of the genus Methylobacterium are distributed in a wide diversity of natural environments and are very often associated with plants, Methylobacterium sp. strain BJ001 may be involved in natural attenuation or in situ biodegradation (including phytoremediation) of explosive-contaminated sites.
Plants metabolize polychlorinated biphenyls (PCBs) into hydroxylated derivatives (OH-PCBs), which... more Plants metabolize polychlorinated biphenyls (PCBs) into hydroxylated derivatives (OH-PCBs), which are sometimes more toxic than the parent PCBs. The objective of this research was to compare the toxicity of a suite of PCBs and OH-PCBs toward the model plant, Arabidopsis thaliana. While parent PCBs and higher-chlorinated OH-PCBs exhibited a low or nondetectable toxicity, lower-chlorinated OH-PCBs significantly inhibited the germination rate and plant growth, with inhibition concentration 50% (IC 50) ranging from 1.6 to 12.0 mg L −1. The transcriptomic response of A. thaliana to 2,5-dichlorobiphenyl (2,5-DCB), and its OH metabolite, 4′-OH-2,5-DCB, was then examined using whole-genome expression microarrays (Affymetrix). Exposure to 2,5-DCB and 4′-OH-2,5-DCB resulted in different expression patterns, with the former leading to enrichment of genes involved in response to toxic stress and detoxification functions. Exposure to 2,5-DCB induced multiple xenobiotic response genes, such as cytochrome P-450 and glutathione S-transferases, potentially involved in the PCB metabolism. On the contrary, exposure to both compounds resulted in the down-regulation of genes involved in stresses not directly related to toxicity. Unlike its OH derivative, 2,5-DCB was shown to induce a transcriptomic profile similar to plant safeners, which are nontoxic chemicals stimulating detoxification pathways in plants. The differentiated induction of detoxification enzymes by 2,5-DCB may explain its lower phytotoxicity compared to 4′-OH-2,5-DCB.
The potential for aerobic and anaerobic microbial natural attenuation of PCBs in freshwater sedim... more The potential for aerobic and anaerobic microbial natural attenuation of PCBs in freshwater sediments is described by PCB congener, quantitative PCR, and 16S rRNA gene amplicon sequencing datasets generated, in duplicate, from 27 sediment samples collected from a PCB-contaminated freshwater lagoon (54 samples total). Sediment samples were subjected to a hexane PCB extraction protocol and the concentrations of 209 PCB congeners were determined in hexane extracts by gas chromatography with a tandem mass spectrometry detection. DNA was extracted from sediments sediment samples and used for qPCR and 16S rRNA amplicon sequencing. The abundance of 16S rRNA genes (i.e., Dehalococcoides and putative dechlorinating Chloroflexi) and functional genes (i.e., reductive dehalogenase (rdhA) and biphenyl dioxygenase (bphA)) associated with aerobic and anaerobic PCB biodegradation, along with the total 16S rRNA genes abundance, was determined by SYBR green qPCR. The microbial community composition and structure in all sediment samples was obtained by 16S rRNA gene amplicon sequencing. Primers targeting the 16S rRNA gene V4 region were used to produce 16S rRNA gene amplicons that were sequencing with the high-throughput Illumina MiSeq platform and sequencing chemistry. The 16S rRNA gene sequencing dataset along with PCB congener and qPCR datasets included as metadata, could be reused in meta-analyses that aim to determine microbial community interactions in contaminated environments, and uncover relationships between microbial community structure and environmental variable (e.g., PCB congener concentrations).
Environmental Science & Technology Letters, 2021
The glycosylation process was investigated for the common brominated flame retardant tetrabromobi... more The glycosylation process was investigated for the common brominated flame retardant tetrabromobisphenol A (TBBPA) in hydroponic exposure systems with pumpkin seedlings. Two typical glycosylation m...
Experiments were conducted to measure biodegradation of polychlorinated biphenyl (PCB) congeners ... more Experiments were conducted to measure biodegradation of polychlorinated biphenyl (PCB) congeners contained in mixture Aroclor 1248 and congeners present in wastewater lagoon sediment contaminated decades earlier at Altavista, Virginia. A well-characterized strain of aerobic PCB-degrading bacteria, Paraburkholderia xenovorans LB400 was incubated in laboratory bioreactors with PCB-contaminated sediment collected at the site. The experiments evaluated strain LB400's ability to degrade PCBs in absence of sediment and in PCB-contaminated sediment slurry. In absence of sediment, LB400 transformed 76% of Aroclor 1248 within seven days, spanning all homolog groups present in the mixture. In sediment slurry, only mono- and di-chlorinated PCB congeners were transformed. These results show that LB400 is capable of rapidly biodegrading most PCB congeners when they are freely dissolved in liquid but cannot degrade PCB congeners having three or more chlorine substituents in sediment slurry. Finally, using GC/MS-MS triple quadrupole spectrometry, this work distinguishes between physical (sorption to cells) and biological removal mechanisms, illuminates the process by which microorganisms with LB400-type congener specificity can selectively transform lower-chlorinated congeners over time, and makes direct comparisons to other studies where individual congener data is reported.
Methoxylated polychlorinated biphenyls (MeO-PCBs) are overlooked metabolites of PCBs. In general,... more Methoxylated polychlorinated biphenyls (MeO-PCBs) are overlooked metabolites of PCBs. In general, they are more toxic to plants than their parent congeners. However, information on the fate of MeO-PCBs and the relationship between methoxylated, hydroxylated and sulfated metabolites of PCBs in plants is scarce. In this work, poplar plants (Populus deltoides × nigra, DN34) were hydroponically and separately exposed to 4'-methoxy-4-monochlorobiphenyl (4'-MeO-PCB 3) and 4'-PCB 3 sulfate for 10 days to investigate the uptake, translocation and metabolism of MeO-PCBs and the relationship between methoxy-PCBs, hydroxyl-PCBs and PCB sulfates within plants. Results showed that 4'-MeO-PCB 3 and 4'-PCB 3 sulfate were taken up by the roots of poplar plants and translocated from roots to shoots and leaves. 4'-OH-PCB 3 and 4'-PCB 3 sulfate were identified as the hydroxylated metabolite and sulfate metabolite of 4'-MeO-PCB 3 in poplar, respectively. In the backward reaction, 4'-OH-PCB 3 and 4'-MeO-PCB 3 were found as metabolites of 4'-PCB 3 sulfate. For exposure groups, the yields of 4'-OH-PCB 3 produced from 4'-MeO-PCB 3 and 4'-PCB 3 sulfate were 1.29% and 0.13% respectively. The yield of 4'-PCB 3 sulfate which originated from 4'-MeO-PCB 3 in wood and root samples of exposure groups was only 0.02%. Only 0.04% of the initial mass of 4'-PCB 3 sulfate was transformed to 4'-MeO-PCB 3 in the exposure groups. The sulfation yield of 4'-OH-PCB 3 was higher than hydrolysis yield of 4'-PCB 3 sulfate, indicating that formation of PCB sulfates was predominant over the reverse reaction, the formation of hydroxy-PCBs. These results provide new perspective on the transport, metabolism, and fate of MeO-PCBs, and also help to better understand sources of OH-PCBs and PCB sulfates in the environment. This study provides the first evidence of interconversion of sulfate metabolites from methoxy-PCBs and methoxy-PCBs from PCB sulfates.
h i g h l i g h t s Transformation of SCCPs in air phase was shown experimentally for the first t... more h i g h l i g h t s Transformation of SCCPs in air phase was shown experimentally for the first time. First evidence of increased transformation of SCCPs by PVOCs is provided. Carbon chain decomposition, dechlorination and chlorine rearrangement occurred.
Environmental Science and Pollution Research, 2019
Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious ri... more Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious risk to human and environmental health. One promising strategy to remediate PCB-contaminated sediments utilizes organohalide-respiring bacteria (OHRB) that dechlorinate PCBs. However, functional genes that act as biomarkers for PCB dechlorination processes (i.e., reductive dehalogenase genes) are poorly understood. Here, we developed anaerobic sediment microcosms that harbor an OHRB community dominated by the genus Dehalococcoides. During the 430-day microcosm incubation, Dehalococcoides 16S rRNA sequences increased two orders of magnitude to 10 7 copies/g of sediment, and at the same time, PCB118 decreased by as much as 70%. In addition, the OHRB community dechlorinated a range of penta-and tetra-chlorinated PCB congeners including PCBs 66, 70 + 74 + 76, 95, 90 + 101, and PCB110 without exogenous electron donor. We quantified candidate reductive dehalogenase (RDase) genes over a 430-day incubation period and found rd14, a reductive dehalogenase that belongs to Dehalococcoides mccartyi strain CG5, was enriched to 10 7 copies/g of sediment. At the same time, pcbA5 was enriched to only 10 5 copies/g of sediment. A survey for additional RDase genes revealed sequences similar to strain CG5's rd4 and rd8. In addition to demonstrating the PCB dechlorination potential of native microbial communities in contaminated freshwater sediments, our results suggest candidate functional genes with previously unexplored potential could serve as biomarkers of PCB dechlorination processes.
Microbial concentrations of denitrifiers, pseudomonads, and monoaromatic petroleum hydrocarbon (B... more Microbial concentrations of denitrifiers, pseudomonads, and monoaromatic petroleum hydrocarbon (BTX) degraders were significantly higher (p Ͻ 0.1) in soil samples from the rhizosphere of poplar trees than in adjacent agricultural soils, and atrazine degraders were found only in one rhizosphere sample. The relative abundance of these phenotypes (as a fraction of total heterotrophs) was not significantly different between rhizosphere and surrounding soils. Therefore, the poplar rhizosphere enhanced the growth of microbial populations that participate in natural bioremediation without exerting selective pressure for them.
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization, 2022
Water underpins every aspect of life, and the water industry is the guardian of human society's a... more Water underpins every aspect of life, and the water industry is the guardian of human society's and environmental water needs. From ancient Rome's aqueducts to modern water networks, the water sector has been playing a critical role in civilization and paving a pathway to a more sustainable and prospective world (Sedlak, 2014). Each nation's critical water infrastructure relies on the smooth operation of water and wastewater systems of different sizes. Water utilities treat and deliver billions of liters of water to homes and industries every day, and wastewater utilities collect and treat the generated wastewater to ensure the effluent can be safely discharged or reused. Acknowledging the interconnected nature of water management, the emerging 'OneWater' framework offers a holistic and integrated approach to consider all water resources from surface water, ground water, stormwater, potable water, wastewater, and recycled water as one to achieve reliable, sustainable, and resilient water systems (Figure 1.1). However, the water sector is facing exacerbated challenges caused by climate change: extreme weather events, frequent floods or prolonged droughts, degradation of water quality, along with aging infrastructure and population redistribution. The industry needs a paradigm shift from focusing on water treatment and supply from scarce natural water resources, wastewater collection and treatment to meet discharge permits, and processing of residuals from these operations, to integrated water management to enable a low-carbon circular water economy using the OneWater concept. The goal should be on overall sustainability including energy, greenhouse gas (GHG) emissions, resource recovery, water resiliency, and socioeconomic impacts in water management. Water industry is energy-and material-intensive in procurement, production, and renewal of used water. The International Energy Agency (IEA) estimates ∼4% of the world's electricity use goes toward moving and treating water and wastewater, and electricity consumption in the water sector is projected to increase by 80% over the next 25 years despite improvements in energy efficiency (Figure 1.2) (IEA, 2017). In search of more water, lower quality water sources, including non-traditional water sources,
Twelve organic compounds commonly found at hazardous waste sites were studied for uptake by hybri... more Twelve organic compounds commonly found at hazardous waste sites were studied for uptake by hybrid poplar trees. The vegetative uptake of many of these compounds has not previously been demonstrated for plant species being utilized for phytoremediation, such as hybrid poplar trees. Experiments were conducted hydroponically utilizing 14 C-labeled compounds to ascertain translocation and fate. Predictive relationships for the translocation and partitioning to plant tissues were developed from the experimental data. Translocation and partitioning relationships based on compounds' octanol-water partitioning coefficients (log K ow) produced the best results, but the relationships did not allow for fully accurate prediction of each contaminant's fate. Translocation and subsequent transpiration of volatile organic compounds (VOCs) from the leaves to the atmosphere was shown to be a significant pathway. As full-scale phytoremediation systems are deliberated, the pathways investigated here should be considered in terms of a contaminant removal mechanism and potential contamination of the vegetation.
Bromophenols occur naturally and are used globally as man-made additives in various industrial pr... more Bromophenols occur naturally and are used globally as man-made additives in various industrial products. They are decomposition products of many emerging organic pollutants, such as tetrabromobisphenol A, polybrominated dibenzo-p-dioxin (PBDD), polybrominated diphenyl ethers (PBDE), and others. To characterize their biotransformation pathways, bromophenol congener 2,4,6-tribromophenol, being used most frequently in the synthesis of brominated flame retardants and having the greatest environmental abundance, was selected to hydroponically expose rice plants. After exposure for 5 days, 99.2% of 2,4,6-tribromophenol was metabolized by rice. Because of the lack of relative reference standards, an effective screening strategy was used to screen for potential metabolites that were further qualitatively identified by gas and liquid chromatography combined with high-resolution mass spectrometry. Forty transformation products were confirmed or tentatively identified at different confidence levels, including 9 phase I and 31 phase II metabolites. A large number of metabolites (39) were found in rice root, and 10 of them could be translocated and detected in rice stems or leaves. Many transformation pathways were proposed, including debromination, hydroxylation, methylation, coupling reactions, sulfation, and glycosylation. It was remarkable that a total of seven hydrophobic, persistent, and toxic OH-PBDEs and PBDD/Fs were found, indicating the biotic dimeric reactions of 2,4,6-tribromophenol that occurred in the rice plants. These results improve our understanding of the transformation and environmental fates of bromophenols, and they indicate new potential sources for OH-PBDEs and PBDD/Fs in the environment, especially in food chains.
Polychlorinated biphenyls (PCBs) can be metabolized to hydroxylated polychlorinated biphenyls (OH... more Polychlorinated biphenyls (PCBs) can be metabolized to hydroxylated polychlorinated biphenyls (OH-PCBs) as reported in a number of animal studies. However, there are few studies on OH-PCBs in vivo in whole plants. In order to explore the formation of OH-PCBs in whole plants in detail, poplars (Populus deltoides × nigra, DN34) were exposed to 3,3′,4,4′-tetrachlorobiphenyl (CB 77) in hydroponic solution. Poplars are widely used in phytoremediation applications and the complete genome has been sequenced. In this research, a HPLC-MS method was developed to directly determine the hydroxylated metabolites of CB77 (OH-CB77s), avoiding the experimental errors introduced by derivatization pretreatments required by gas chromatography-based methods. Three potential hydroxylated metabolites of CB 77, including 6-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (6OH-CB77), 5-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (5OH-CB77) and 4′-hydroxy-3,3′,4,5′tetrachlorobiphenyl (4′OH-CB79), were determined in poplar tissues. The major product, 6OH-CB77, was detected in the roots, bottom bark, bottom wood, middle bark and middle wood for the whole poplar plants, but the minor product, 5OH-CB77, was detected only in the poplar roots. The concentration of 6OH-CB77 was about 10 times greater than that of 5OH-CB77 in the roots. However, the major mammalian metabolite, 4′OH-CB79 was not detected in any of the samples. The results suggest that the hydroxylated metabolic pathway of CB77 is via an epoxide intermediate in poplar.
A pink-pigmented symbiotic bacterium was isolated from hybrid poplar tissues (Populus deltoides ؋... more A pink-pigmented symbiotic bacterium was isolated from hybrid poplar tissues (Populus deltoides ؋ nigra DN34). The bacterium was identified by 16S and 16S-23S intergenic spacer ribosomal DNA analysis as a Methylobacterium sp. (strain BJ001). The isolated bacterium was able to use methanol as the sole source of carbon and energy, which is a specific attribute of the genus Methylobacterium. The bacterium in pure culture was shown to degrade the toxic explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazene (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5-tetrazocine (HMX). [U-ring-14 C]TNT (25 mg liter ؊1) was fully transformed in less than 10 days. Metabolites included the reduction derivatives amino-dinitrotoluenes and diamino-nitrotoluenes. No significant release of 14 CO 2 was recorded from [ 14 C]TNT. In addition, the isolated methylotroph was shown to transform [U-14 C]RDX (20 mg liter ؊1) and [U-14 C]HMX (2.5 mg liter ؊1) in less than 40 days. After 55 days of incubation, 58.0% of initial [ 14 C]RDX and 61.4% of initial [ 14 C]HMX were mineralized into 14 CO 2. The radioactivity remaining in solution accounted for 12.8 and 12.7% of initial [ 14 C]RDX and [ 14 C]HMX, respectively. Metabolites detected from RDX transformation included a mononitroso RDX derivative and a polar compound tentatively identified as methylenedinitramine. Since members of the genus Methylobacterium are distributed in a wide diversity of natural environments and are very often associated with plants, Methylobacterium sp. strain BJ001 may be involved in natural attenuation or in situ biodegradation (including phytoremediation) of explosive-contaminated sites.
Plants metabolize polychlorinated biphenyls (PCBs) into hydroxylated derivatives (OH-PCBs), which... more Plants metabolize polychlorinated biphenyls (PCBs) into hydroxylated derivatives (OH-PCBs), which are sometimes more toxic than the parent PCBs. The objective of this research was to compare the toxicity of a suite of PCBs and OH-PCBs toward the model plant, Arabidopsis thaliana. While parent PCBs and higher-chlorinated OH-PCBs exhibited a low or nondetectable toxicity, lower-chlorinated OH-PCBs significantly inhibited the germination rate and plant growth, with inhibition concentration 50% (IC 50) ranging from 1.6 to 12.0 mg L −1. The transcriptomic response of A. thaliana to 2,5-dichlorobiphenyl (2,5-DCB), and its OH metabolite, 4′-OH-2,5-DCB, was then examined using whole-genome expression microarrays (Affymetrix). Exposure to 2,5-DCB and 4′-OH-2,5-DCB resulted in different expression patterns, with the former leading to enrichment of genes involved in response to toxic stress and detoxification functions. Exposure to 2,5-DCB induced multiple xenobiotic response genes, such as cytochrome P-450 and glutathione S-transferases, potentially involved in the PCB metabolism. On the contrary, exposure to both compounds resulted in the down-regulation of genes involved in stresses not directly related to toxicity. Unlike its OH derivative, 2,5-DCB was shown to induce a transcriptomic profile similar to plant safeners, which are nontoxic chemicals stimulating detoxification pathways in plants. The differentiated induction of detoxification enzymes by 2,5-DCB may explain its lower phytotoxicity compared to 4′-OH-2,5-DCB.
The potential for aerobic and anaerobic microbial natural attenuation of PCBs in freshwater sedim... more The potential for aerobic and anaerobic microbial natural attenuation of PCBs in freshwater sediments is described by PCB congener, quantitative PCR, and 16S rRNA gene amplicon sequencing datasets generated, in duplicate, from 27 sediment samples collected from a PCB-contaminated freshwater lagoon (54 samples total). Sediment samples were subjected to a hexane PCB extraction protocol and the concentrations of 209 PCB congeners were determined in hexane extracts by gas chromatography with a tandem mass spectrometry detection. DNA was extracted from sediments sediment samples and used for qPCR and 16S rRNA amplicon sequencing. The abundance of 16S rRNA genes (i.e., Dehalococcoides and putative dechlorinating Chloroflexi) and functional genes (i.e., reductive dehalogenase (rdhA) and biphenyl dioxygenase (bphA)) associated with aerobic and anaerobic PCB biodegradation, along with the total 16S rRNA genes abundance, was determined by SYBR green qPCR. The microbial community composition and structure in all sediment samples was obtained by 16S rRNA gene amplicon sequencing. Primers targeting the 16S rRNA gene V4 region were used to produce 16S rRNA gene amplicons that were sequencing with the high-throughput Illumina MiSeq platform and sequencing chemistry. The 16S rRNA gene sequencing dataset along with PCB congener and qPCR datasets included as metadata, could be reused in meta-analyses that aim to determine microbial community interactions in contaminated environments, and uncover relationships between microbial community structure and environmental variable (e.g., PCB congener concentrations).
Environmental Science & Technology Letters, 2021
The glycosylation process was investigated for the common brominated flame retardant tetrabromobi... more The glycosylation process was investigated for the common brominated flame retardant tetrabromobisphenol A (TBBPA) in hydroponic exposure systems with pumpkin seedlings. Two typical glycosylation m...
Experiments were conducted to measure biodegradation of polychlorinated biphenyl (PCB) congeners ... more Experiments were conducted to measure biodegradation of polychlorinated biphenyl (PCB) congeners contained in mixture Aroclor 1248 and congeners present in wastewater lagoon sediment contaminated decades earlier at Altavista, Virginia. A well-characterized strain of aerobic PCB-degrading bacteria, Paraburkholderia xenovorans LB400 was incubated in laboratory bioreactors with PCB-contaminated sediment collected at the site. The experiments evaluated strain LB400's ability to degrade PCBs in absence of sediment and in PCB-contaminated sediment slurry. In absence of sediment, LB400 transformed 76% of Aroclor 1248 within seven days, spanning all homolog groups present in the mixture. In sediment slurry, only mono- and di-chlorinated PCB congeners were transformed. These results show that LB400 is capable of rapidly biodegrading most PCB congeners when they are freely dissolved in liquid but cannot degrade PCB congeners having three or more chlorine substituents in sediment slurry. Finally, using GC/MS-MS triple quadrupole spectrometry, this work distinguishes between physical (sorption to cells) and biological removal mechanisms, illuminates the process by which microorganisms with LB400-type congener specificity can selectively transform lower-chlorinated congeners over time, and makes direct comparisons to other studies where individual congener data is reported.
Methoxylated polychlorinated biphenyls (MeO-PCBs) are overlooked metabolites of PCBs. In general,... more Methoxylated polychlorinated biphenyls (MeO-PCBs) are overlooked metabolites of PCBs. In general, they are more toxic to plants than their parent congeners. However, information on the fate of MeO-PCBs and the relationship between methoxylated, hydroxylated and sulfated metabolites of PCBs in plants is scarce. In this work, poplar plants (Populus deltoides × nigra, DN34) were hydroponically and separately exposed to 4'-methoxy-4-monochlorobiphenyl (4'-MeO-PCB 3) and 4'-PCB 3 sulfate for 10 days to investigate the uptake, translocation and metabolism of MeO-PCBs and the relationship between methoxy-PCBs, hydroxyl-PCBs and PCB sulfates within plants. Results showed that 4'-MeO-PCB 3 and 4'-PCB 3 sulfate were taken up by the roots of poplar plants and translocated from roots to shoots and leaves. 4'-OH-PCB 3 and 4'-PCB 3 sulfate were identified as the hydroxylated metabolite and sulfate metabolite of 4'-MeO-PCB 3 in poplar, respectively. In the backward reaction, 4'-OH-PCB 3 and 4'-MeO-PCB 3 were found as metabolites of 4'-PCB 3 sulfate. For exposure groups, the yields of 4'-OH-PCB 3 produced from 4'-MeO-PCB 3 and 4'-PCB 3 sulfate were 1.29% and 0.13% respectively. The yield of 4'-PCB 3 sulfate which originated from 4'-MeO-PCB 3 in wood and root samples of exposure groups was only 0.02%. Only 0.04% of the initial mass of 4'-PCB 3 sulfate was transformed to 4'-MeO-PCB 3 in the exposure groups. The sulfation yield of 4'-OH-PCB 3 was higher than hydrolysis yield of 4'-PCB 3 sulfate, indicating that formation of PCB sulfates was predominant over the reverse reaction, the formation of hydroxy-PCBs. These results provide new perspective on the transport, metabolism, and fate of MeO-PCBs, and also help to better understand sources of OH-PCBs and PCB sulfates in the environment. This study provides the first evidence of interconversion of sulfate metabolites from methoxy-PCBs and methoxy-PCBs from PCB sulfates.
h i g h l i g h t s Transformation of SCCPs in air phase was shown experimentally for the first t... more h i g h l i g h t s Transformation of SCCPs in air phase was shown experimentally for the first time. First evidence of increased transformation of SCCPs by PVOCs is provided. Carbon chain decomposition, dechlorination and chlorine rearrangement occurred.
Environmental Science and Pollution Research, 2019
Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious ri... more Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious risk to human and environmental health. One promising strategy to remediate PCB-contaminated sediments utilizes organohalide-respiring bacteria (OHRB) that dechlorinate PCBs. However, functional genes that act as biomarkers for PCB dechlorination processes (i.e., reductive dehalogenase genes) are poorly understood. Here, we developed anaerobic sediment microcosms that harbor an OHRB community dominated by the genus Dehalococcoides. During the 430-day microcosm incubation, Dehalococcoides 16S rRNA sequences increased two orders of magnitude to 10 7 copies/g of sediment, and at the same time, PCB118 decreased by as much as 70%. In addition, the OHRB community dechlorinated a range of penta-and tetra-chlorinated PCB congeners including PCBs 66, 70 + 74 + 76, 95, 90 + 101, and PCB110 without exogenous electron donor. We quantified candidate reductive dehalogenase (RDase) genes over a 430-day incubation period and found rd14, a reductive dehalogenase that belongs to Dehalococcoides mccartyi strain CG5, was enriched to 10 7 copies/g of sediment. At the same time, pcbA5 was enriched to only 10 5 copies/g of sediment. A survey for additional RDase genes revealed sequences similar to strain CG5's rd4 and rd8. In addition to demonstrating the PCB dechlorination potential of native microbial communities in contaminated freshwater sediments, our results suggest candidate functional genes with previously unexplored potential could serve as biomarkers of PCB dechlorination processes.
Microbial concentrations of denitrifiers, pseudomonads, and monoaromatic petroleum hydrocarbon (B... more Microbial concentrations of denitrifiers, pseudomonads, and monoaromatic petroleum hydrocarbon (BTX) degraders were significantly higher (p Ͻ 0.1) in soil samples from the rhizosphere of poplar trees than in adjacent agricultural soils, and atrazine degraders were found only in one rhizosphere sample. The relative abundance of these phenotypes (as a fraction of total heterotrophs) was not significantly different between rhizosphere and surrounding soils. Therefore, the poplar rhizosphere enhanced the growth of microbial populations that participate in natural bioremediation without exerting selective pressure for them.
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization, 2022
Water underpins every aspect of life, and the water industry is the guardian of human society's a... more Water underpins every aspect of life, and the water industry is the guardian of human society's and environmental water needs. From ancient Rome's aqueducts to modern water networks, the water sector has been playing a critical role in civilization and paving a pathway to a more sustainable and prospective world (Sedlak, 2014). Each nation's critical water infrastructure relies on the smooth operation of water and wastewater systems of different sizes. Water utilities treat and deliver billions of liters of water to homes and industries every day, and wastewater utilities collect and treat the generated wastewater to ensure the effluent can be safely discharged or reused. Acknowledging the interconnected nature of water management, the emerging 'OneWater' framework offers a holistic and integrated approach to consider all water resources from surface water, ground water, stormwater, potable water, wastewater, and recycled water as one to achieve reliable, sustainable, and resilient water systems (Figure 1.1). However, the water sector is facing exacerbated challenges caused by climate change: extreme weather events, frequent floods or prolonged droughts, degradation of water quality, along with aging infrastructure and population redistribution. The industry needs a paradigm shift from focusing on water treatment and supply from scarce natural water resources, wastewater collection and treatment to meet discharge permits, and processing of residuals from these operations, to integrated water management to enable a low-carbon circular water economy using the OneWater concept. The goal should be on overall sustainability including energy, greenhouse gas (GHG) emissions, resource recovery, water resiliency, and socioeconomic impacts in water management. Water industry is energy-and material-intensive in procurement, production, and renewal of used water. The International Energy Agency (IEA) estimates ∼4% of the world's electricity use goes toward moving and treating water and wastewater, and electricity consumption in the water sector is projected to increase by 80% over the next 25 years despite improvements in energy efficiency (Figure 1.2) (IEA, 2017). In search of more water, lower quality water sources, including non-traditional water sources,
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Papers by jerald schnoor