Sources of mercury in a contaminated stream—implications for the timescale of recovery

Southworth, G.R.; Mathews, Teresa J.; Greeley, Mark S.; Peterson, Mark J.; Brooks, Scott C.; Ketelle, Dick

doi:10.1002/etc.2115

Cited by 26 publications

(46 citation statements)

References 22 publications

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“…A previously identified zone of higher Hg concentration (Southworth et al 2010(Southworth et al , 2013 was associated with finegrained, dark-colored layers within the upper 6 km of EFPC. These layers are herein referred to as historical release deposits (HRD).…”

Section: Streambank Soil Sample Collectionmentioning

confidence: 74%

“…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%

“…The historical release deposit (HRD) was previously identified as a discontinuous Hg-rich horizon in the soil (Southworth et al 2010(Southworth et al , 2013 and was suspected to exert an important influence on Hg flux to EFPC (Watson et al 2017). During the March 2015 longitudinal survey, the absence of green vegetative cover on the streambanks and the dark color of the HRD due to inclusions of coal fines and ash (Fig.…”

Section: Mercury Spatial Trendsmentioning

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: Streambank Soil Sample Collectionmentioning

confidence: 74%

Section: +mentioning

confidence: 99%

Section: Mercury Spatial Trendsmentioning

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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“…Because the upstream sections of EFPC are surrounded by 80% developed land cover (McManamay, Smith, Jett, Mathews, & Peterson, ) and large areas of impervious pavement, EFPC exhibits flashy flow characteristics that have contributed to active streambank incision and erosion and high sedimentation rates (Southworth et al., ). Although exposed bedrock is a prominent feature throughout the creek, substrate at all EFPC sites consists of a mixture of rubble, gravel, sand, and silt (Smith, Brandt, & Christensen, ).…”

Section: Methodsmentioning

confidence: 99%

“…Largescale stonerollers Campostoma oligolepis (Cyprinidae), from here on stonerollers, are a very abundant, making up to 90% of the biomass of the fish community in upstream reaches. Sediment Hg concentrations and periphyton biofilms are thought to be major controlling variables on net Hg methylation, and perhaps bioaccumulation, in this system (Olsen et al, 2016;Southworth et al, 2013). Periphyton was collected monthly at EFPC study sites from 2015 to 2017 (n = 434 total Hg samples, n = 85 MeHg samples).…”

Section: Study Sitesmentioning

confidence: 99%

Scaling mercury biodynamics from individuals to populations: Implications of an herbivorous fish on mercury cycles in streams

et al. 2019

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Mercury (Hg) is a widespread environmental pollutant anthropogenically released into aquatic ecosystems where it is tightly retained and cycled through abiotic and biotic processes. Understanding the transport and fate of Hg, including the role of organisms in these cycles, is important. However, few studies, if any, have evaluated the role of macroconsumers in Hg cycling. This requires accounting for organismal regulation of body methylmercury (MeHg) via biodynamics and then scaling individual MeHg concentrations to the population level. Recent evidence suggests that MeHg concentrations will become decrease within an organism as it displays higher growth efficiency (i.e. somatic growth dilution [SGD] concept). However, the implications of individual concentrations, SGD, population size, and individual growth on ecosystem‐level mass‐storage and accumulation of MeHg are uncertain. We examined the influence of population size and individual growth on total MeHg standing stock and accumulation in stoneroller (Campostoma oligolepis) populations in a stream contaminated by Hg in east Tennessee, U.S.A. We assessed patterns in periphyton and stoneroller MeHg concentrations in relation to relative growth and population density to determine evidence of SGD and density‐dependent growth, respectively. We simulated the internal regulation of MeHg concentration in stonerollers using a biodynamic model, which was then scaled to the population level to analyse the effects of population density and growth on MeHg standing stock (μg/m2) in stoneroller populations and accumulation rates (i.e. flux, μg m−2 day−1) from periphyton communities to stonerollers. MeHg storage and flux in stoneroller populations were compared to standing stocks and methylation rates in periphyton communities. We found evidence of both density‐dependent and density‐independent growth patterns for stonerollers in East Fork Poplar Creek. Stoneroller MeHg concentrations were positively related to periphyton MeHg concentrations; however, evidence of SGD was equivocal. Total MeHg standing stock and accumulation in stoneroller populations was positively related to population density, irrespective of growth. Additionally, higher relative growth was positively related to a higher MeHg accumulation, regardless of density dependence. We found that the standing stock of MeHg in stoneroller populations could be as high as 32× the standing stock of MeHg in periphyton. Finally, the rate of accumulation of MeHg in stonerollers ranged from 5% to over 100% of previously documented methylation rates in periphyton. Our results suggest that abundant macroconsumers may play significant roles in contaminant cycles by mobilising considerable quantities of Hg, storing significant reservoirs of Hg and MeHg, and transferring MeHg to higher trophic levels. Furthermore, the implications of population size and growth of macroconsumers on the storage and flux of MeHg in streams are complicated and dependent upon age structure, density‐dependence, and MeHg concentrations. Our...

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Seasonal and flow-driven dynamics of particulate and dissolved mercury and methylmercury in a stream impacted by an industrial mercury source

Riscassi

Miller

Brooks

2015

Environmental Toxicology and Chemistry

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Sediments and floodplain soils in the East Fork Poplar Creek watershed (Oak Ridge, TN, USA) are contaminated with high levels of mercury (Hg) from an industrial source at the headwaters. Although baseflow conditions have been monitored, concentrations of Hg and methylmercury (MeHg) during high-flow storm events, when the stream is more hydrologically connected to the floodplain, have yet to be assessed. The present study evaluated baseflow and event-driven Hg and MeHg dynamics in East Fork Poplar Creek, 5 km upstream of the confluence with Poplar Creek, to determine the importance of hydrology to in-stream concentrations and downstream loads and to ascertain whether the dynamics are comparable to those of systems without an industrial Hg source. Particulate Hg and MeHg were positively correlated with discharge (r(2) = 0.64 and 0.58, respectively) and total suspended sediment (r(2) = 0.97 and 0.89, respectively), and dissolved Hg also increased with increasing flow (r(2) = 0.18) and was associated with increases in dissolved organic carbon (r(2) = 0.65), similar to the dynamics observed in uncontaminated systems. Dissolved MeHg decreased with increases in discharge (r(2) = 0.23) and was not related to dissolved organic carbon concentrations (p = 0.56), dynamics comparable to relatively uncontaminated watersheds with a small percentage of wetlands (<10%). Although stormflows exert a dominant control on particulate Hg, particulate MeHg, and dissolved Hg concentrations and loads, baseflows were associated with the highest dissolved MeHg concentration (0.38 ng/L) and represented the majority of the annual dissolved MeHg load. Environ Toxicol Chem 2016;35:1386-1400. Published 2015 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work, and as such, is in the public domain in the United States of America.

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Sources of mercury in a contaminated stream—implications for the timescale of recovery

Cited by 26 publications

References 22 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

Scaling mercury biodynamics from individuals to populations: Implications of an herbivorous fish on mercury cycles in streams

Seasonal and flow-driven dynamics of particulate and dissolved mercury and methylmercury in a stream impacted by an industrial mercury source

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