Evaluation of Lower East Fork Poplar Creek Mercury Sources

Watson, David B.; Brooks, Scott C.; Mathews, Teresa J.; Bevelhimer, Mark S.; DeRolph, Christopher R.; Brandt, Craig C.; Peterson, Mark J.; Ketelle, R.H.

doi:10.2172/1257903

Cited by 13 publications

(36 citation statements)

References 17 publications

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“…At EFPC, sediments exhibit two zones of slightly higher Hg concentrations downstream from Y-12 (Brooks et al 2017). Previous studies have identified the importance of streambank erosional processes that contribute particle-bound Hg to the stream (Southworth et al 2010(Southworth et al , 2013Watson et al 2016Watson et al , 2017 but have not specifically examined how contaminant distribution in the streambank soils is related to the streambed sediments. The goal of this study is to better understand the distribution of Hg and MeHg in streambank soils and streambed sediments and to assess the potential for soils to serve as a source of contamination to streambed sediments.…”

Section: +mentioning

confidence: 99%

“…EFPC is classified as an impaired water body because Hg levels in fish exceed the US EPA National Recommended Water Quality Criteria (NRWQC) and the state of Tennessee guidelines (both 0.3 mg kg −1 in fish tissue). A recent series of modelling studies found that the greatest flux of Hg is related to erosion of streambank soils during storm events, followed by inputs from Y-12 (Watson et al 2016(Watson et al , 2017. Streambank soil erosion rates ranged from 4 to 46 cm year −1 (Watson et al 2016).…”

Section: +mentioning

confidence: 99%

“…A recent series of modelling studies found that the greatest flux of Hg is related to erosion of streambank soils during storm events, followed by inputs from Y-12 (Watson et al 2016(Watson et al , 2017. Streambank soil erosion rates ranged from 4 to 46 cm year −1 (Watson et al 2016). Fluxes from bank erosion were estimated at 38.6 kg year −1 for Hg and as 5.6 g year −1 for MeHg (Watson et al 2017).…”

Section: +mentioning

confidence: 99%

“…The stream is partitioned into four creek reaches according to similarity in floodplain properties and stream channel gradients ( Fig. 1) (Watson et al 2016). The dominant soils identified in the streambanks are Inceptisols from the Chenneby Series (Fluvaquentic Dystrudepts) and the Hamblen Series (Fluvaquentic Eutrudepts) (Dickson et al 2017).…”

Section: Site Descriptionmentioning

confidence: 99%

“…For all longitudinal samples, the outermost 2.5 cm of the cores was analyzed for total Hg and MeHg, while other soil chemical and physical properties were measured in bulk samples. A limited set of cores that extended horizontally up to 20 cm into the streambanks was collected from six locations in April 2014, and Hg analyses were performed in increments of 2.5 cm throughout the length of the cores (Watson et al 2016).…”

Section: Streambank Soil Sample Collectionmentioning

confidence: 99%

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Source relationships between streambank soils and streambed sediments in a mercury-contaminated stream

et al. 2018

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Purpose In contaminated streams, understanding the role of streambank and streambed source contributions is essential to developing robust remedial solutions. However, identifying relationships can be difficult because of the lack of identifying signatures in source and receptor pools. East Fork Poplar Creek (EFPC) in Oak Ridge, TN, USA received historical industrial releases of mercury that contaminated streambank soils and sediments. Here, we determined relationships between the contaminated streambank soils and sand-sized streambed sediments. Materials and methods Field surveys revealed the spatial trends of the concentrations of inorganic total mercury (Hg) and methyl mercury (MeHg), Hg lability as inferred by sequential extraction, particle size distribution, and total organic carbon. Statistical tests were applied to determine relationships between streambank soil and streambed sediment properties. Results and discussion Concentrations of Hg in streambank soils in the upper reaches averaged 206 mg kg −1 (all as dry weight) (n = 457), and 13 mg kg −1 in lower reaches (n = 321), while sand-sized streambed sediments were approximately 16 mg kg −1 (n = 57). Two areas of much higher Hg and MeHg concentrations in streambank soils were identified and related to localized higher Hg concentrations in the streambed sediments; however, most of the streambank soils have similar Hg concentrations to the streambed sediments. The molar ratio of Hg to organic carbon, correlation between MeHg and Hg, and particle size distributions suggested similarity between the streambank soils and the fine sand-sized fraction (125-250 μm) collected from the streambed sediments. Mercury in the fine sand-sized streambed sediments, however, was more labile than Hg in the streambank soils, suggesting an in-stream environment that altered the geochemistry of sediment-bound Hg.

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Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

Section: Site Descriptionmentioning

confidence: 99%

Section: Streambank Soil Sample Collectionmentioning

confidence: 99%

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Source relationships between streambank soils and streambed sediments in a mercury-contaminated stream

et al. 2018

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Assessing Microbial Communities Related to Mercury Transformations in Contaminated Streambank Soils

Abdelmageed

Miller

Sanders

et al. 2021

Water Air Soil Pollut

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In nature, the bioaccumulative potent neurotoxin methylmercury (MeHg) is produced from inorganic mercury (Hg) predominantly by anaerobic microorganisms. Hg-contaminated soils are a potential source of MeHg due to microbial activity. We examine streambank soils collected from the contaminated East Fork Poplar Creek (EFPC) in Tennessee, USA, where seasonal variations in MeHg levels have been observed throughout the year, suggesting active microbial Hg methylation. In this study, we characterized the microbial community in contaminated bank soil samples collected from two locations over a period of one year and compared the results to soil samples from an uncontaminated reference site with similar geochemistry (n = 12). Microbial community composition and diversity were assessed by 16S rRNA gene amplicon sequencing. Furthermore, to isolate potential methylators from soils, enrichment cultures were prepared using selective media. A set of three clade-specific primers targeting the gene hgcA were used to detect Hg methylators among the δ-Proteobacteria in EFPC bank soils across all seasons. Two families among the δ-Proteobacteria that have been previously associated with Hg methylation, Geobacteraceae and Syntrophobacteraceae, were found to be predominant with relative abundances of 0.13% and 4.0%, respectively. However, in soil enrichment cultures, Firmicutes were predominant among families associated with Hg methylation. Specifically, Clostridiaceae and Peptococcaceae and their genera Clostridium and Desulfosporosinus were among the ten most abundant genera with relative abundances of 2.6% and 1.7%, respectively. These results offer insights into the role of microbial communities on Hg transformation processes in contaminated bank soils in EFPC. Identifying the biogeochemical drivers of MeHg production is critical for future remediation efforts.

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Interaction of Soil Microbes with Organoclays and their Impact on the Immobilization of Hg under Aerobic Conditions

Egbo

Johs

Sahu

et al. 2021

Water Air Soil Pollut

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Immobilization of mercury (Hg) leaching from bank soils of East Fork Poplar Creek (EFPC) is considered part of remediation strategies to mitigate the amount of Hg entering the creek. Different approaches are currently being evaluated, such as utilizing engineered sorbents to immobilize Hg species in EFPC bank soils. However, the influence of environmental microbes on the immobilization of Hg by sorbents is unknown. Organocation-modified phyllosilicate clay minerals (organoclays) are widely used as sorbents for the immobilization of contaminants. This study evaluates the interactions of Serratia marcescens and Burkholderia thailandensis with the sorbent Organoclay PM-199 and their impact on the immobilization of Hg under aerobic conditions. We evaluated the competitive binding of Hg between sorbents and selected microorganisms in a series of pure culture studies using bacterial strains identified in EFPC bank soil samples. Our results suggest that Hg sorption by Organoclay PM-199 is not significantly impacted by common soil bacteria present in EFPC, specifically Serratia marcescens and Burkholderia thailandensis, which are known to form biofilms. These findings suggest that sorbent amendments are an effective strategy for the remediation of Hg contamination in natural ecosystems.

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Evaluation of Lower East Fork Poplar Creek Mercury Sources

Cited by 13 publications

References 17 publications

Source relationships between streambank soils and streambed sediments in a mercury-contaminated stream

Source relationships between streambank soils and streambed sediments in a mercury-contaminated stream

Assessing Microbial Communities Related to Mercury Transformations in Contaminated Streambank Soils

Interaction of Soil Microbes with Organoclays and their Impact on the Immobilization of Hg under Aerobic Conditions

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