East Fork Poplar Creek Research Articles

Extractability and Bioavailability of Mercury from a Mercury Sulfide Contaminated Soil in Oak Ridge, Tennessee, USA

Historically as part of its national security mission, the U.S. Department of Energy’s Y-12 National Security Facility in Oak Ridge, TN acquired a significant fraction of the world’s supply of elemental mercury. During the 1950s and 1960s, a large amount of elemental mercury escaped confinement and is still present in the watershed surrounding the Y-12 facility. A series of remediation efforts have been deployed in the watersheds around the Oak Ridge site. However, most recently, concentration of total mercury in fish and water of the lower East Fork Poplar Creek (EFPC) of Oak Ridge has increased although majority of the mercury contamination in the local soils is present in the form of mercury sulfide. We have studied the extractability, solubility, and bioavailability of mercury sulfide in Oak Ridge soils. Dynamics of the dissolution of mercury sulfide by various extractants, including acids and a chelating agent, have been investigated. After three seasons of planting, soil mercury sulfide is more easily dissolved by both 4 M and 12 M nitric acid than is pure mercury sulfide reagent as indicated by their dissolution kinetics. Mercury release by EDTA from HgS-contaminated soil increased with time of reaction and soil mercury level. This chelating chemical increases the solubility of mercury in HgS-contaminated Oak Ridge soil. The results also show that mercury sulfide in contaminated Oak Ridge soils was still to some extent bioavailable to plants. The increase of bioavailability of soil mercury sulfide after three seasons of planting may contribute to the recent increase of mercury levels in water of the Lower East Fork Popular Creek (LEFPC) of Oak Ridge.

Use of Central Stonerollers (Cyprinidae: Campostoma anomalum) from Tennessee as a Bioindicator of Metal Contamination

We compared the levels of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in a small species of fish (Central stonerollers, Campostoma anomalum) collected from East Fork Poplar Creek (EFPC) and a reference site in eastern Tennessee. Stonerollers are minnows in the Cyprinidae family that serve as prey for many carnivores in aquatic systems. Fish were collected from East Fork Poplar Creek within the U.S. Department of Energy's Y-12 National Security Complex, part of the Oak Ridge Reservation, and from a reference stretch of the Little River in East Tennessee. Whole fish were homogenized for analysis. Concentrations of all metals (except arsenic) were significantly higher in stonerollers from EFPC compared to the reference site. Mercury levels in minnows from EFPC averaged 0.4 ppm (microg/g), four times higher than the average for fish in the U.S. in general. This was higher than levels in fish from the nearby Clinch River and higher than fillets of white bass (Morone chrysops) from the same creek. Most metal levels were inversely related to size and weight of the stonerollers, perhaps due to growth dilution.

Heavy Metal Concentrations in Northern Water Snakes (Nerodia sipedon) from East Fork Poplar Creek and the Little River, East Tennessee, USA

We compared the levels of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the blood, kidney, liver, muscle, and skin of northern water snakes (Nerodia sipedon) collected from the upper reach of East Fork Poplar Creek (EFPC) within the United States Department of Energy's (USDOE's) Y-12 National Security Complex with concentrations in tissues of northern water snakes from a reference reach of the Little River downstream from the Great Smoky Mountains National Park in East Tennessee. Our objectives were to determine whether concentrations of these metals were higher in tissues of water snakes collected from EFPC compared with the reference site and if northern water snakes were suitable bioindicators of metal contamination. Except for chromium, metal levels were significantly higher in tissues (kidney, liver, muscle, and skin) of EFPC northern water snakes compared with those in tissues of snakes from the reference site. Although female northern water snakes were significantly larger than male snakes, their tissues did not contain significantly higher metal concentrations compared with those from male snakes, possibly because of maternal transfer of metals to eggs. This study was the first to examine the accumulation of contaminants resulting from the operations of the USDOE's Oak Ridge Reservation in snakes.

Use of Skin and Blood as Nonlethal Indicators of Heavy Metal Contamination in Northern Water Snakes (Nerodia sipedon)

Relatively little is known about contaminants in reptiles, particularly snakes. The concentrations of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium were examined in blood and skin of 46 northern water snakes (Nerodia sipedon) in Tennessee and correlated with concentrations in internal tissues (liver, kidney, muscle) to determine if blood or skin could serve as a nonlethal indicator of internal metal exposure or body burden. Snakes were collected from the East Fork Poplar Creek (EFPC) within the United States Department of Energy's Y-12 National Security Complex (part of the Oak Ridge National Laboratory) and from a reference stretch of the Little River in East Tennessee. For blood, the only consistent positive correlations with internal organs were for mercury, and correlations were low except for muscle. Skin showed significant positive correlations with all three organs for mercury, chromium, selenium, and lead. For manganese and cadmium, skin level was positively correlated with liver level. Blood generally reflects recent exposure, not necessarily body burden, but in water snakes it correlates with body burden for mercury. Skin proved useful for more metals, although patterns were not necessarily consistent across sex and locality subgroups. The most consistent pattern was for mercury, the metal of greatest concern in many aquatic ecosystems, including EFPC.

Rank kriging for characterization of mercury contamination at the East Fork Poplar Creek, Oak Ridge, Tennessee

AbstractThe spatial interpolation method of kriging, originally developed for estimation of ore reserves in mining and prediction in meteorology, is an important geostatistical tool for characterization of a Superfund site. Point kriging uses an estimated variogram to compute the best linear unbiased estimates (BLUE) of contaminant concentration at an unsampled location. When the contaminant concentration data is heavily skewed, the data are typically log‐transformed and kriging is performed on the transformed data. The results obtained from kriging the log‐transformed data are then back‐transformed. This back‐transformation formula involves not only the estimated log‐transformed values but also their kriging standard deviations (ksd). This method of kriging, referred to in the geostatistical literature as log‐normal kriging, was initially used to characterize the East Fork Poplar Creek (EFPC) Superfund site in Oak Ridge, Tennessee. The back‐transformed values for the EFPC site produced estimates of mercury contamination that were orders of magnitude higher than the maximum observed mercury concentration at the site. The method of rank variogram modeling/rank kriging was developed by the authors to estimate mercury contamination at the EFPC site. We present the method of rank variogram modeling/rank kriging, illustrate it with an example, and briefly describe the kriging results obtained for the EFPC site.The log‐normal probability model is routinely applied in statistical analysis of contaminant concentration data as well. The upper confidence limit (UCL) for log‐normally distributed data is typically calculated by using the H‐statistics based formula. The UCL of the mean at times turns out to be orders of magnitude higher than the maximum observed contaminant concentration. An example is presented to illustrate this unreasonable behavior of the H‐UCL formula. Copyright © 2002 John Wiley & Sons, Ltd.

Bioaccessibility of Mercury in Soils

The initial risk assessment for the East Fork Poplar Creek (EFPC) floodplain in Oak Ridge, Tennessee, a superfund site heavily contaminated with mercury, was based on a reference dose for mercuric chloride. Mercuric chloride, however, is a soluble mercury compound not expected to be present in the floodplain, which is frequently saturated with water. Previous investigations had suggested mercury in the EFPC floodplain was less soluble and therefore potentially less bioavailable than mercuric chloride, possibly making the results of the risk assessment unduly conservative. A bioaccessibility study, designed to measure the amount of mercury available for absorption in a child's digestive tract (the most critical risk pathway endpoint), was performed on 20 soils from the EFPC floodplain. The average bioac-cessible mercury for the 20 soils was 5.3%, compared with 100% of the mercuric chloride subjected to the same conditions. The alteration of the procedure to more closely mimic conditions in the digestive tract did not significantly change the results. Therefore, the use of a reference dose for mercuric chloride at EFPC, and potentially at other mercury-contaminated sites, without incorporating a corresponding bioavailability adjustment factor may overestimate the risk posed by the site.

Relationship between genotoxicity, mutagenicity, and fish community structure in a contaminated stream

Genotoxic responses (chromosomal damage, DNA strandbreakage) of redbreast sunfish (Lepomis auritis)populations exposed to industrial effluent andmutagenicity of the associated sediments weredetermined in order to compare them to changes incommunity structure. Data were collected from areference stream and East Fork Poplar Creek (EFPC), afirst-order stream which originates on the grounds ofthe Department of Energy Y-12 Plant at Oak Ridge, TN. This stream is contaminated with mercury, PCBs, andnumerous other compounds. Previous studies have shownthat sediment contaminant concentrations, as well asphysiological biomarker responses of the local fishpopulations, are highest at the headwaters of EFPC anddecrease with increasing distance from the DOEfacility as contaminant loading decreases. Chromosomal damage was measured by flow cytometry – asreflected by variation in cellular DNA content – andstrand breakage was determined by agarose gelelectrophoresis using blood as the source of DNA. Mutagenicity was determined by theSalmonella/microsome assay using organic solventextracts of sediment surface samples. Community levelresponses included community diversity and percentpollution-tolerant species. Biomarker responses andmutagenicity were found to be highest at theheadwaters of EFPC, and tended to decrease withincreasing distance from the effluent. In general,biomarker responses appeared to be correlated withmutagenicity of the sediment, and both of theserelated to fish community disturbance and level ofstream contamination. Because responses at severallevels of biological organization show similarpatterns of downstream effects, this suggests thatthere may be a causal relationship betweencontamination and biological effects.

Risk‐based decision making: The east fork poplar creek case study

AbstractA Probabilistic risk assessment revealed that methylmercury released from the U.S. Department of Energy(DOE) Y‐12 weapons facility at Oak Ridge, Tennessee, USA, poses moderate risks to mink and kingfishers residing near the receiving waters of East Fork Poplar Creek. Polychlorinated biphenyls (PCBs) released from this facility pose severe risks to mink but little risk to kingfishers. The objective of this study was to use a risk‐based decision‐making approach to select remedial cleanup levels for each of these contaminants. We conducted Monte Carlo simulations to estimate total daily intakes of each contaminant by mink (mercury and PCBs) and kingfishers (PCBs only) for a range of exposure‐reduction scenarios. The resulting exposure distributions were then integrated with their respective dose–response curves to estimate postremediation risks. The results indicated that total mercury levels in surface water would need to be reduced from current levels (mean = 0.225 μg/L) to 0.03 to 0.05 μg/L to reduce risks to very low levels (<5% probability of ≥10% mortality) for both mink and kingfishers. If interested parties define acceptable risk as, for example, a 20% probability of ≥10% mortality, then mercury levels would need to be reduced to 0.14 μg/L. The PCBs analysis indicated that reducing water‐borne exposures would produce only a modest reduction in risk to mink because much of the current exposure is through terrestrial exposure pathways.

Formation of Mercuric Sulfide in Soil

Analysis of mercury-contaminated soil from the flood plain of East Fork Poplar Creek (EFPC) in Oak Ridge, TN, using a scanning electron microscope (SEM) with energy- and wavelength X-ray dispersive spectroscopy (EDS/WDS) and a transmission electron microscope (TEM) with select area electron diffraction (SAED) revealed the presence of submicron, crystalline mercuric sulfide (HgS) in the form of metacinnabar. The HgS formed in place after the deposition and burial of mercury-contaminated soils. A reaction path model developed to describe the geochemical evolution of the soil redox conditions during flooding predicted that the resultant pe and pH of the soil would be within the stability range of HgS. The reaction of mercury with other metal sulfides or sulfhydryl groups in the soil may have also contributed to the formation of HgS. The formation of HgS is significant to the remediation efforts at EFPC because the toxicity, leachability, and volatility of mercury in soils is dependent on the solid phase speciation. Because the local hydrogeochemical conditions are not unique, the forma tion of HgS at this site has implications to other environments as well.

Histopathologic biomarkers in feral freshwater fish populations exposed to different types of contaminant stress

Histopathologic alterations of gill, liver, and spleen were studied in feral fish from three freshwater ecosystems that experience different types of contaminant stress. East Fork Poplar Creek (EFPC), a third-order stream in East Tennessee, receives point source discharges of mixed contaminants from a nuclear weapons facility located near its headwater. The Pigeon River (PR), a high-gradient fifth order stream, is impacted by bleached kraft mill effluent (BKME). Hartwell Reservoir (HR), a US Army Corp of Engineers impoundment of the Savannah River, contains high levels of PCBs in sediment and biota. Brushy Fork Creek (BFC), the Little River (LR), and the Tugaloo River (TR) are relatively free of contaminants, and served as reference sites for the three respective ecosystems of this study. Certain organ and tissue lesions, detected microscopically, were common to fish from both reference and contaminated sites. These included parasites, inflammation, glycogen deficiency, macrophage aggregates (MA), and diffuse fatty change in the liver; parasites and MA in the spleen; and parasites, secondary lamellar fusion, and variable epithelial cell hyperplasia in the gills. Lesions found only in fish from contaminated sites were: (1) cholangiomas in liver of redbreast sunfish ( Lepomis auratus) collected from EFPC; (2) amphophilic and eosinophilic foci of cellular alteration, diffuse biliary preductular and ductular hyperplasia with islands of hyperplastic basophilic hepatocytes, and two metastatic thyroidal carcinomas in spleen of redbreast sunfish from PR; (3) severe lipidosis, vacuolated and basophilic foci in largemouth bass ( Micropterus salmoides) from HR; (4) splenic lymphoid cell depletion and vascular congestion, with necrosis of reticuloendothelial cells in fish collected from EFPC and HR; (5) hyperplasia of mucous and chloride cells, deformed branchial cartilage, severe and diffuse aneurysms of lamellae, and edema at the base of the secondary lamellae were in gill of fish from all three sites. The finding of specific lesions only in fish from contaminated sites suggests a contaminant etiology. Histopathology biomarker lesions identified in this study are similar to those observed in laboratory exposures of fishes to specific pollutants. Further refinement of these biomarker approaches will be discussed in light of multiple stressors and their effects.

Distribution of Contaminants in Aquatic Organisms from East Fork Poplar Creek

The ecological risk assessment of East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee, investigated the nature and magnitude of the observed or expected adverse effects of the site's organic and inorganic contaminants on the ecosystem structure and function. Aquatic biota such as benthic macroinvertebrates, crayfish (Astacidae), redbreast sunfish (Lepomis auritus), and stonerollers (Campostoma anomalum), representative of various habitats, were sampled for whole-body contaminant analysis. The whole-body residue analysis of the representative aquatic organisms revealed the presence of over 50 contaminants in varying proportions. The relative whole-body distribution of organic contaminants such as mixtures of polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides was comparable among the indicator organisms. The relative whole-body distribution of inorganic contaminants was, however, less consistent. Physicochemical variables characteristic of organic contaminants—such as long octanol/water partition coefficient (logKow), log aqueous solubility, and log bioconcentration factors (log BCF), and chemical uptake efficiency (E) unique for the organisms sampled for chemical analysis—were used to explain the observed whole-body distribution of contaminants in the aquatic organisms from EFPC.

Imaging and microanalyses of mercury in flood plain soils of east fork poplar creek

Electron probe microanalysis, scanning electron microscopy with energy dispersive spectrometry, optical microscopy, and x-ray diffractometry were used to locate, identify, and analyze Hg-bearing matter in the soils from the East Fork Poplar Creek floodplain located adjacent to D.O.E.'s Oak Ridge Y-12 Plant1 Oak Ridge, Tennessee. Several significant findings were made in this study; namely, that ash concentration in soils is an indicator of Hg enrichment, the modes of occurrence of Hg are identical in so-called Hg-rich and Hg-poor soils, and Hg was found to coexist with S in all cases. In addition to Hg other materials employed at the Oak Ridge site such as U, Th, alloys, and rare earth were also observed.

Determination of Hg and other trace elements in soil using neutron activation analysis

In the early 1950's, a federal facility in Oak Ridge, Tennessee, used a process that required the use of Hg to produce8Li. It was disclosed to the public in 1983 that about 2.4 millions pounds of Hg had been released into the ecosystem. The primary route of mercury into the environment was a stream, East Fork Poplar Creek, whose head waters are in the vicinity of the plant. As part of a study to determine the distribution of Hg as well as As, Cr, Sb, Se, U, and Zn along the flood plains of the creek, a procedure using neutron activation analysis was developed and is described below. The procedure, typical sample analysis results for Hg, and quality assurance and control data are discussed in this paper.

Transmission Electron Microscopy of Mercury Sulfide Particles From A Mercury-Contaminated Soil

Presently the East Fork Poplar Creek (EFPC) floodplain located in the city of Oak Ridge, Tennessee and adjacent to the Y-12 nuclear plant is reportedly contaminated with mercury. The metallic mercury which was used from 1955 to 1963 in the production of lithium enriched in the 6Li isotope, is the source of the present contamination.Previous analyses of these soils using electron probe micro-analysis (EPM) and scanning electron microscopy (SEM) revealed mercury to be present principally as discrete micrometer and submicrometer size particles which were observed to coexist with sulfur. These observations suggested that mercury might be present as mercury sulfide (perhaps even in a crystalline form) which could then affect the level of remediation required for this soil since the toxicity and mobility of mercury is dependent upon its speciation.The limited concentration of mercury in the EFPC soils (3000-100 mg/kg) and the relatively small size of these mercury bearing particles makes transmission electron microscopy (TEM) the ideal analytical method for unequivocally identifying these particles with micro-chemistry and select area electron diffraction (SAED).

Fate and biological effects of contaminated vegetation in a tennessee stream

Potamogeton foliosus (an aquatic plant) and filamentous algae from a settling basin with contaminated sediment became enriched with polychlorinated biphenyls (PCBs), Co, Cd, Cu, Hg, Ni, Mn, U, and Zn During the growing season, large amounts of the contaminated Potamogeton foliosus and algae were exported downstream from this basin to East Fork Poplar Creek (EFPC) We used drift nets to estimate the loading rates of the plants to EFPC, analyzed samples of the plants for metals, and conducted a series of experiments with snails (Elimia clavaeformis), amphipods (Gammarus sp), and a microcrustacean (Ceriodaphnia dubia) to evaluate the possible effects of inputs of the vegetation to EFPC biota Little of the vegetation that entered the stream was transported intact as far as 1 4 km During the growing season, inputs of organic carbon to this 1 4-km segment of stream due to the deposition of the plants were at least 2 4 times greater than autochthonous production Thus the vegetation was bioenergetically important to at least a 1 to 3-km reach of EFPC The experiments showed that all three types of animals could distinguish between contaminated (CON) and noncontaminated (NC) Potamogeton foliosus Snails preferred the NC plants over the CON plants, these animals also had lower growth rates on CON plants than on NC plants Amphipods preferred CON plants over NC plants in a 48-h experiment, but preferred NC plants over CON plants in a 7 d experiment Leachates prepared from CON Potamogeton foliosus were toxic to Ceriodaphnia, those prepared from NC Potamogeton foliosus were not Energy-subsidy and/or contaminated food aspects of the Potamogeton inputs could help explain why pollution sensitive invertebrates such as mayflies and stoneflies are not present in EFPC immediately downstream from the settling basin