Browsing by Subject "Radium"
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Item Open Access Embryotoxicty in medaka (Oryzias latipes) following exposure to select alkaline earth metals: a screening bioassay(2008-04-25T15:34:27Z) Nelson, ClayEnvironmental exposure to radium, a radioactive alkaline earth metal, and barium, a chemically similar but non-radioactive earth metal, are of growing concern. Radium and barium levels in some groundwater aquifers exceed maximum contaminant levels, and future groundwater resources may be increasingly at risk. Surface waters may also be at risk from disposal of residual waters enriched in metals, including radium and barium, from the increased use of chemical filtration processes such as ion exchange or reverse-osmosis desalination to treat groundwater. Leaching of uranium mine tailings generated during mining activities and industrial uses of barium, including use in high-density oil and gas well drilling muds, serve as additional anthropogenic sources of these metals to surface waters. Currently, there is a lack of information on the effects of radium and barium on fish development. Such lack of data may complicate ecological risk assessment, as recruitment of young of the year fishes have been demonstrated to be major drivers of fish populations. I employed a high throughput, screening level bioassay to experimentally characterize toxicity in developing medaka fish embryos and eleutheroembryos (an embryonic phase starting with hatching and ending with absorption of yolk sac) following exposure to radium (radium-226 chloride) and barium (barium chloride). The ability to follow individual embryos over time and view embryonic development through the transparent chorion were key design characteristics of this experiment. Two endpoints, time to hatch and mortality, were concurrently assessed. Results of the bioassay failed to demonstrate evidence of embryotoxicity from exposure to radium at levels up to 60,000 pCi/L. Exposure to high levels of barium (100 ppm) resulted in earlier hatching time. Additionally, an increase in post-hatch mortality was observed, suggesting that the chorion may play a protective role with regard to alkaline earth metal exposure. Water chemistry appeared to affect the magnitude of post-hatch mortality, although results between different exposure scenarios used in the study were ambiguous. The lack of observed embryotoxicity from radium exposure does not definitively demonstrate that radium is not toxic, as other endpoints not assessed in this screening level bioassay may be more sensitive indicators of toxicity and effects from exposure during development may manifest themselves at later life stages. Results of the barium analysis suggest that young of the year fishes may be particularly sensitive to acute exposure to high levels of alkaline earth metals. This suggests that better management of radium and barium in the environment, including the disposal of brine solutions enriched in alkaline earth metals to surface waters, may be needed to reduce ecological risks to fish populations.Item Open Access Radioactivity of Fossil Fuel Waste Products and Associated Environmental Implications(2018) Lauer, Nancy EllenExtraction of energy resources and energy production can redistribute and concentrate naturally occurring radioactive materials (NORM), particularly from the uranium (238U t1/2=4.5 x 109 yr) and thorium (232Th t1/2=1.4 x 1010 yr) decay series, posing potential human and environmental health risks if not managed properly. In particular, elevated activities of NORM have been measured in coal combustion residuals (CCRs) generated from coal combustion and oil and gas wastewater (OGW) drawn from both conventional and unconventional oil and gas producing wells. This dissertation characterizes the radioactivity associated with CCRs and OGW and further investigates the use of this radioactivity as a tracer and timer of contamination, particularly from OGW following its accidental or intentional release to the environment.
232Th and its decay product 228Ra and 238U and its decay products 226Ra and 210Pb were measured in coals and CCRs from the majors coal producing basins in the United States as well as in coals and CCRs from high-U coal producing basins in China. 228Ra and 226Ra were measured in OGW from the Appalachian Basin in the United States. Finally, 228Ra, 228Th, 226Ra, and 210Pb were measured in soils and sediments impacted by spills of OGW and the permitted release of treated OGW to surface water.
Characteristic 228Ra and 226Ra activities 228Ra/226Ra activity ratios were found in CCRs and OGW derived from distinct formations, suggesting that the radioactivity can serve as a potential fingerprint of for contamination when CCRs and OGW are accidentally or intentionally released to the environment. Additionally, the decay of 226Ra and 228Ra into their respective decay products 210Pb and 228Th offers the ability to source and age date contamination from OGW. The 228Th/228Ra activity ratio in particular is useful for age dating contamination in impacted sediments up to about 10 years old, which is ideal for age dating recent contamination. The 228Ra/226Ra and 228Th/228Ra activity ratios were successfully used to constrain the age and source of contamination from two scenarios including OGW spills and treated OGW disposal to surface water.
Item Open Access Radium and barium removal through blending hydraulic fracturing fluids with acid mine drainage.(Environ Sci Technol, 2014-01-21) Kondash, Andrew J; Warner, Nathaniel R; Lahav, Ori; Vengosh, AvnerWastewaters generated during hydraulic fracturing of the Marcellus Shale typically contain high concentrations of salts, naturally occurring radioactive material (NORM), and metals, such as barium, that pose environmental and public health risks upon inadequate treatment and disposal. In addition, fresh water scarcity in dry regions or during periods of drought could limit shale gas development. This paper explores the possibility of using alternative water sources and their impact on NORM levels through blending acid mine drainage (AMD) effluent with recycled hydraulic fracturing flowback fluids (HFFFs). We conducted a series of laboratory experiments in which the chemistry and NORM of different mix proportions of AMD and HFFF were examined after reacting for 48 h. The experimental data combined with geochemical modeling and X-ray diffraction analysis suggest that several ions, including sulfate, iron, barium, strontium, and a large portion of radium (60-100%), precipitated into newly formed solids composed mainly of Sr barite within the first ∼ 10 h of mixing. The results imply that blending AMD and HFFF could be an effective management practice for both remediation of the high NORM in the Marcellus HFFF wastewater and beneficial utilization of AMD that is currently contaminating waterways in northeastern U.S.A.Item Open Access Radium Isotope Geochemistry in Groundwater Systems: The Role of Environmental Factors(2011) Vinson, David StewartPrior studies of groundwater systems have associated increasing salinity and anoxic conditions with increasing radium (Ra) activities in water due to the decreasing effectiveness of Ra removal processes. However, the components of salinity (e.g. Ca vs. Na and SO42- vs. Cl--dominated waters), and the relative importance of salinity-sensitive vs. redox-sensitive processes for Ra mobilization, are less well understood. In this research, the response of Ra to hydrochemical change was examined using a multiple tracer approach to obtain detailed information on divalent cation and Ra mobility. A range of salinity and redox conditions was examined in five field-based studies in the United States and Morocco: (1) fresh waters in fractured crystalline rocks in the Piedmont region of North Carolina; (2) the Willcox Basin, an oxic alluvial basin-fill aquifer in southeastern Arizona; (3) the Jordan sandstone aquifer, a carbonate-cemented quartz sandstone in southeastern Minnesota; (4) an unconfined coastal aquifer undergoing salinization in the city of Agadir, Morocco; and (5) the confined, fresh to saline Cretaceous and Pliocene aquifers of the Atlantic Coastal Plain in North Carolina.
In addition to analysis of major element concentrations, trace metal concentrations, and 224Ra, 226Ra, and 228Ra activities, complementary isotope systems were applied to gain insights on the relative stability of chemical processes that remove radium and other alkaline earth metals: (1) strontium isotope ratios (87Sr/86Sr) trace divalent cation release from sources such as clay and carbonate minerals in the aquifer solids and also indicate conditions in which divalent cation release (rather than uptake) is dominant; (2) boron concentrations and isotopes (δ11B) coincide with the opposite condition in freshening conditions of the Atlantic Coastal Plain, in which divalent cations are removed in exchange for Na; and (3) sulfur and oxygen isotopes (δ34S, δ18O) of sulfate trace sulfate sources and provide information on sulfate-reducing conditions, which can inhibit barite (BaSO4) from removing Ra by coprecipitation. In addition, other isotopic and ion measurements trace salinity sources and groundwater residence time, including δ2H, δ18O, 3H, Br-/Cl-, Na/Cl-, and Ca/Na.
This dissertation documents correlations between salinity and radium in the brackish to saline North Carolina coastal plain aquifer with total dissolved solids (TDS) up to ~18,000 mg L-1 and to some degree in the Moroccan coastal aquifer, but even the lower-salinity waters (TDS <3000 mg L-1) exhibit a range of Ra activities spanning approximately 3 orders of magnitude. Among these low-TDS waters, the highest Ra activities were observed in the anoxic Jordan sandstone aquifer and the lowest were observed in the oxic Willcox Basin aquifer. Although the main control on radium activities in fresh groundwater is the U- and Th-series radionuclide content of the aquifer solids, important secondary controls include the stability of redox-sensitive radium adsorption sites (Mn and Fe oxides), the relative dominance of divalent vs. monovalent cations (e.g. the Ca/Na ratio), formation of the uncharged RaSO40 complex, and/or the saturation state with respect to barite. These processes interact in varied ways in the field-based studies. Increasing radium activities and decreasing 222Rn/226Ra ratios in the North Carolina fractured crystalline rock groundwater system are correlated with increasing Ba, Mn, and Fe concentrations and decreasing dissolved oxygen concentrations, related to weathering and/or organic carbon oxidation. Radium activities in the oxic, neutral to slightly basic Willcox Basin are very low (median 226Ra activity 2 mBq L-1), probably due to a combination of effective Ra removal processes including adsorption to Mn and/or Fe oxides and the overall removal of divalent cations during groundwater evolution in this system. These are the same surface charge conditions that release arsenic, of regional water concern, in this pH range. Radium in Jordan aquifer groundwater is dependent on local variations in solid-phase radionuclide levels, probably hosted in the carbonate cement phase. Also, Ra is inefficiently adsorbed to the aquifer solids in the aquifer's anoxic conditions, resulting in the highest radium levels reported in this dissertation (226Ra up to 420 mBq L-1) despite apparent barite precipitation that partially removes Ra. Radium-224 activity in the Moroccan coastal aquifer is associated with salinity, but Ra overall is apparently controlled by barite, indicated by conditions near BaSO4 saturation. Radium activity in the saline waters of the Atlantic Coastal Plain aquifers is associated with TDS concentrations, but the cation exchange properties of the aquifer may provide a major mechanism of Ra removal in the Na-HCO3- and Na-Cl- waters. Overall, the complex interaction between groundwater chemistry and Ra-removing processes implies that in waters with TDS below approximately 3,000 mg L-1, dissolved solids concentration alone does not fully describe radium's response to hydrochemical conditions, but rather that aquifer-specific examination of Ra removal mechanisms is needed.
Item Open Access Radium Isotopes as Tracers of Groundwater-Surface Water Interactions in Inland Environments(2011) Raanan Kiperwas, HadasGroundwater has an important role in forging the composition of surface water, supplying nutrients crucial for the development of balanced ecosystems and potentially introducing contaminants into otherwise pristine surface water. Due to water-rock interactions radium (Ra) in groundwater is typically much more abundant than in surface water. In saline environments Ra is soluble and is considered a conservative tracer (apart for radioactive decay) for Ra-rich groundwater seepage. Hence in coastal environments, where mostly fresh groundwater seep into saline surface water, Ra has been the prominent tracer for tracking and modeling groundwater seepage over more than three decades. However, due to its reactivity and non-conservative behavior, Ra is rarely used for tracing groundwater seepage into fresh or hypersaline surface water; in freshwater, Ra is lost mostly through adsorption onto sediments and suspended particles; in hypersaline environments Ra can be removed through co-precipitation, most notably with sulfate salts.
This work examines the use of Ra as a tracer for groundwater seepage into freshwater lakes and rivers and into hypersaline lakes. The study examines groundwater-surface water interactions in four different environments and salinity ranges that include (1) saline groundwater discharge into a fresh water lake (the Sea of Galilee, Israel); (2) modification of pore water transitioning from saline to freshwater along their flow through sediments (pore water in sediments underlying the Sea of Galilee, Israel); (3) fresh groundwater discharge into hypersaline lakes (Sand Hills, Nebraska); and (4) fresh groundwater discharge into a fresh water river (Neuse River, North Carolina). In addition to measurement of the four Ra isotopes (226Ra, 228Ra, 223Ra, 224Ra), this study integrates geochemical (major and trace elements) with additional isotopic tools (strontium and boron isotopes) to better understand the geochemistry associated with the seepage process. To better understand the critical role of salinity on Ra adsorption, this study includes a series of adsorption experiments. The results of these experiments show that Ra loss through adsorption decreases with increasing salinity, and diminishes in salinity as low as ~5% of the salinity of seawater.
Integration of the geochemical data with mass-balance models corrected for adsorption allows estimating groundwater seepage into the Sea of Galilee (Israel) and the Neuse River (North Carolina). A study of the pore water underlying the Sea of Galilee shows significant modifications to the geochemistry and Ra activity of the saline pore water percolating through the sediments underlying the lake. In high salinity environments such as the saline lakes of the Nebraska Sand Hills, Ra is shown to be removed through co-precipitation with sulfate minerals, its integration into barite (BaSO4) is shown to be limited by the ratio of Ra:Ba in the precipitating barite.
Overall, this work demonstrates that Ra is a sensitive tracer for quantifying groundwater discharge even in low-saline environments. Yet the high reactivity of Ra (adsorption, co-precipitation, production of the short-lived isotopes) requires a deep understanding of the geochemical processes that shape and control Ra abundances in water resources.