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Increased emphasis on toxics control in oil and gas industry NPDES permits

Description: The 1987 amendments to the Clean Water Act emphasized stricter control of toxics in wastewater discharges. Although state and U.S. Environmental Protection Agency permit writers have had the authority to incorporate strict water quality-based controls in permits, they did not widely use this authority in the past. However, general permits proposed in the past year by Region VI for discharges into the territorial seas of Louisiana and by Region X for coastal and offshore discharges in Alaska are much stricter than their predecessors. The Region VI permit requires numerical produced water limits on arsenic, lead, benzene, total phenols, radium, and whole effluent toxicity. The Region X permit requires numerical produced water limits on copper, arsenic, zinc, total aromatic hydrocarbons, total aqueous hydrocarbons, and whole effluent toxicity. The additional requirements increase the cost of complying with the permit, present more opportunities for exceeding one of the permit limits, and serve as a precedent for future permits. The industry should be prepared to accept the additional costs of these requirements or develop data to convince the regulatory agencies that the increased level of monitoring and permit limits is not necessary to protect water quality. Regulatory agencies should be receptive to new data provided by the industry and flexible in setting additional toxics controls.
Date: October 1, 1996
Creator: Veil, J.A.
Partner: UNT Libraries Government Documents Department

Complex diffusive processes in silicon

Description: Diffusion is often viewed as a simple process of atoms in an equilibrium configuration making a jump along some path overcoming an energy barrier. First-principles calculations have revealed that even seemingly simple processes can hide enormous complexity. This paper reviews several such cases that have been recently investigated by the authors. In one such case, namely the segregation of As impurities in Si grain boundaries, the theoretical predictions have been complimented and confirmed by high-resolution microscopy.
Date: March 1, 1998
Creator: Pantelides, S.T.; Ramamoorthy, M.; Maiti, A.; Chisholm, M.F. & Pennycook, S.J.
Partner: UNT Libraries Government Documents Department

Complex impurity dynamics in silicon

Description: The authors review results of recent first-principles calculations that have led to comprehensive descriptions of a wide range of dynamical properties of impurities in Si. In particular they review the dynamics of clustering and declustering of As impurities in heavily-doped crystalline Si, the segregation of As impurities in the form of ordered chains in grain boundaries, and the very complex though seemingly simple migration of oxygen impurities in Si.
Date: March 1, 1998
Creator: Pantelides, S.T.; Maiti, A.; Ramamoorthy, M.; Chisholm, M.F. & Pennycook, S.J.
Partner: UNT Libraries Government Documents Department

1993 to 1995 environmental surveillance data collected at or near Area G

Description: This report summarizes Environmental Surveillance data collected by the Water Quality and Hydrology Group during 1993, 1994, and 1995 at or in the vicinity of TA-54, Area-G of the Los Alamos National Laboratory, New Mexico. The summary includes radiochemical, metals, general inorganic, and organic analytical results. The tables list measured concentrations (or detection limits for results below detection limits), analytical uncertainties for radiochemical data, sample locations, and sample dates. A map showing sample locations is also included. Preparation of this report was funded by the Solid Waste Management Group (CST-14) in support of the Waste Management Program.
Date: September 1, 1996
Creator: Mullen, K.; Collins, S. & Rogers, D.
Partner: UNT Libraries Government Documents Department

Ab initio calculations of As-vacancy interactions in silicon

Description: Atomistic simulation of a vacancy-assisted dopant diffusion in silicon needs details of the dopant-vacancy interaction, i.e., the potential as a functional of dopant-vacancy separations. In this paper, the authors present a detailed study on the energetics of As-vacancy reaction in silicon and the lattice distortions surrounding the As-vacancy defect by using an ab initio plane wave pseudopotential method and the density functional theory (DFT). A potential-energy diagram as a function of As-vacancy separation is provided, which can be used in the atomistic diffusion simulations. The authors also calculate the binding energy and the formation energy of different complexes such as AsV, As{sub 2}V and AsV{sub 2} (V represents vacancy). They find that the stable configuration of As{sub 2}V is As-V-As, while the stable configuration of AsV{sub 2} is As-V-V. The nature of the binding between As and vacancy is explained from the lattice distortions and the change of chemical bond configuration introduced by the As-vacancy complex.
Date: April 1, 1999
Creator: Xie, J. & Chen, S.P.
Partner: UNT Libraries Government Documents Department

Ultra High Efficiency ESP for Fine Particulate and Air Toxics Control

Description: Nearly ninety percent of U.S. coal-fired utility boilers are equipped with electrostatic precipitators (ESP). Cost effective retrofittable ESP technologies are the only means to accomplish Department of Energy's (DOE) goal of a major reduction in fine particulate and air toxic emissions from coal-fired power plants. Particles in the size range of 0.1 to 5 {micro}m typically escape ESPs. Metals, such as arsenic, cadmium, lead, molybdenum and antimony, concentrate on these particles. This is the main driver for improved fine particulate control. Vapor phase emissions of mercury, selenium and arsenic are also of major concern. Current dry ESPs, which operate at temperatures greater than 280 F, provide little control for vapor phase toxics. The need for inherent improvement to ESPs has to be considered keeping in perspective the current trend towards the use of low sulfur coals. Switching to low sulfur coals is the dominant approach for SO{sub 2} emission reduction in the utility industry. Low sulfur coals generate high resistivity ash, which can cause an undesirable phenomenon called ''back corona.'' Higher particulate emissions occur if there is back corona in the ESP. Results of the pilot-scale testing identified the ''low temperature ESP'' concept to have the biggest impact for the two low sulfur coals investigated. Lowering the flue gas temperature to 220 F provided the maximum impact in terms of decreased emissions. Intermediate operating temperatures (reduction from 340 to 270 F) also gave significant ESP performance improvement. A significant reduction in particulate emissions was also noted when the flue gas humidity was increased (temperature held constant) from the baseline condition for these moderately high resistivity ash coals. Independent control of flue gas humidity and temperature was an important and a notable element in this project. Mercury emissions were also measured as a function of flue gas temperature. Mercury emissions decreased ...
Date: July 1, 1997
Creator: Srinivasachar, Srivats; Pease, Benjamin R.; Porle, Kjell; Mauritzson, Christer & Haythornthwaite, Sheila
Partner: UNT Libraries Government Documents Department

Baseline risk assessment of ground water contamination at the Uranium Mill Tailings Sites near Rifle, Colorado

Description: The ground water project evaluates the nature and extent of ground water contamination resulting from the uranium ore processing activities. This report is a site specific document that will be used to evaluate current and future impacts to the public and the environment from exposure to contaminated ground water. Currently, no one is using the ground water and therefore, no one is at risk. However, the land will probably be developed in the future and so the possibility of people using the ground water does exist. This report examines the future possibility of health hazards resulting from the ingestion of contaminated drinking water, skin contact, fish ingestion, or contact with surface waters and sediments.
Date: May 1, 1995
Partner: UNT Libraries Government Documents Department

Adsorption isotherm special study. Final report

Description: The study was designed to identify methods to determine adsorption applicable to Uranium Mill Tailings Remedial Action (UMTRA) Project sites, and to determine how changes in aquifer conditions affect metal adsorption, resulting retardation factors, and estimated contaminant migration rates. EPA and ASTM procedures were used to estimate sediment sorption of U, As, and Mo under varying groundwater geochemical conditions. Aquifer matrix materials from three distinct locations at the DOE UMTRA Project site in Rifle, CO, were used as the adsorbents under different pH conditions; these conditions stimulated geochemical environments under the tailings, near the tailings, and downgradient from the tailings. Grain size, total surface area, bulk and clay mineralogy, and petrography of the sediments were characterized. U and Mo yielded linear isotherms, while As had nonlinear ones. U and Mo were adsorbed strongly on sediments acidified to levels similar to tailings leachate. Changes in pH had much less effect on As adsorption. Mo was adsorbed very little at pH 7-7.3, U was weakly sorbed, and As was moderately sorbed. Velocities were estimated for metal transport at different pHs. Results show that the aquifer materials must be characterized to estimate metal transport velocities in aquifers and to develop groundwater restoration strategies for the UMTRA project.
Date: May 1, 1993
Partner: UNT Libraries Government Documents Department

Radionuclide concentrations in/on vegetation at radioactive-waste disposal Area G during the 1995 growing season. Progress report

Description: Overstory (pinon pine) and understory (grass and forb) vegetation were collected within and around selected points at Area G--a low- level radioactive solid-waste disposal facility at Los Alamos National Laboratory--for the analysis of tritium ({sup 3}H), strontium ({sup 90}Sr), plutonium ({sup 238}Pu and {sup 239}Pu), cesium ({sup 137}Cs), and total uranium. Also, heavy metals (Ag, As, Ba, Be, Cd, Cr, Hg, Ni, Pb, Sb, Se, and Tl) in/on vegetation were determined. In general, most (unwashed) vegetation collected within and around Area G contained {sup 3}H, uranium, {sup 238}Pu, and {sup 239}Pu in higher concentrations than vegetation collected from background areas. Tritium, in particular, was detected as high as 7300 pCi mL{sup -1} in understory vegetation collected from the west side of the transuranic (TRU) pads. The south and west ends of the tritium shaft field also contained elevated levels of {sup 3}H in overstory, and especially in understory vegetation, as compared to background; this suggests that {sup 3}H may be migrating from this waste repository through surface and subsurface pathways. Also, understory vegetation collected north of the TRU pads (adjacent to the fence line of Area G) contained the highest values of {sup 238}Pu and {sup 239}Pu as compared to background, and may be a result of surface holding, storage, and/or disposal activities.
Date: March 1, 1996
Creator: Fresquez, P.R.; Vold, E.L. & Naranjo, L. Jr.
Partner: UNT Libraries Government Documents Department

Analysis of TRU waste for RCRA-listed elements

Description: Analytical methods for RCRA listed elements on Portland cement type waste have been employed using both microwave and open hot plate digestions with subsequent analysis by inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), graphite furnace atomic absorption (GFAA) and cold vapor atomic absorption and fluorescence (CVAA/CVAFS). Four different digestion procedures were evaluated including an open hot plate nitric acid digestion, EPA SW-846 Method 3051, and 2 methods using modifications to Method 3051. The open hot plate and the modified Method 3051, which used aqua regia for dissolution, were the only methods which resulted in acceptable data quality for all 14 RCRA-listed elements. Results for the nitric acid open hot plate digestion were used to qualify the analytical methods for TRU waste characterization, and resulted in a 99% passing score. Direct chemical analysis of TRU waste is being developed at Los Alamos National Laboratory in an attempt to circumvent the problems associated with strong acid digestion methods. Technology development includes laser induced breakdown spectroscopy (LIBS), laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), dc arc CID atomic emission spectroscopy (DC-AES), and glow discharge mass spectrometry (GDMS). Analytical methods using the Portland cement matrix are currently being developed for each of the listed techniques. Upon completion of the development stage, blind samples will be distributed to each of the technology developers for RCRA metals characterization.
Date: July 1, 1996
Creator: Mahan, C.; Gerth, D. & Yoshida, T.
Partner: UNT Libraries Government Documents Department

Baseline concentrations of radionuclides and heavy metals in soils and vegetation around the DARHT facility: Construction phase (1997). Progress report

Description: As part of the Department of Energy`s Mitigation Action Plan for the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory (LANL), baseline concentrations of radionuclides ({sup 3}H, {sup 137}Cs, {sup 90}Sr, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, and {sup tot}U) and heavy metals (Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, and Tl) in soil, sediment, and vegetation (overstory and understory) around the DARHT facility during the construction phase in 1997 were determined. Most radionuclides and heavy metals in soils, sediments, and vegetation, with the exception of {sup 90}Sr in soils and sediments, were within upper (95%) limit background concentrations. Although the levels of {sup 90}Sr in soils and sediments around the DARHT facility were higher than background, they were below LANL screening action levels (<4.4 pCi g{sup {minus}1} dry) and are of no concern.
Date: June 1, 1998
Creator: Fresquez, P.R.; Haagenstad, H.T. & Naranjo, L. Jr.
Partner: UNT Libraries Government Documents Department

Corrective Action Investigation Plan for Corrective Action Unit 405: Area 3 Septic Systems, Tonopah Test Range, Nevada(April 2001, Rev. 0) with Record of Technical Change No. 1

Description: This Corrective Action Investigation Plan contains the U.S. Department of Energy, Nevada Operations Office's (DOE/NV's) approach to collect the data necessary to evaluate corrective action alternatives appropriate for the closure of Corrective Action Unit (CAU) 405, Area 3 Septic Systems, Tonopah Test Range (TTR), under the Federal Facility Agreement and Consent Order. Corrective Action Unit 405 consists of Corrective Action Sites 03-05-002-SW03, 03-05-002-SW04, and 03-05-002-SW07 (also collectively known as: Septic Waste Systems [SWSs] 3, 4, and 7). Located in Area 3 in the northwest section of the TTR, approximately 140 miles northwest of Las Vegas, this location was historically (between 1960 and 1990) used as a research facility with the mission to perform defense-related projects, and whose operations generated sanitary and industrial wastewaters potentially contaminated with COPCs and disposed of in septic tanks and leachfields. Though Septic Waste Systems 3, 4, and 7 were origin ally constructed to receive sanitary sewage, they may have inadvertently received effluent containing potentially hazardous and radiological constituents containing acetone, benzene, ethylbenzene, 4-methyl-2-pentanone, toluene, xylenes, volatile organic compound constituents, phenols, arsenic, barium, lead, mercury, hydrocarbons of oil and grease, and uranium-234, -235, and -238. The Area 3 septic systems were documented in a DOE/NV 1996 report as being included in the septic tank abandonment program conducted by Sandia National Laboratories in 1993; however, this program was not completed and the possibility exists that some of the Area 3 septic tanks may not have been abandoned. Even though all of the SWSs addressed in this CAIP are inactive, geophysical surveys conducted in 1993 were generally inconclusive and did not provide useful data for the purposes of this investigation. The scope of this current investigation, therefore, will be to determine the existence of the identified CO PCs and excavation will be the primary investigation method employed for ...
Date: April 26, 2001
Creator: /NV, DOE
Partner: UNT Libraries Government Documents Department

Evaluation of metal and radionuclide data from neutron activation and acid-digestion-based spectrometry analyses of background soils: Significance in environmental restoration

Description: A faster, more cost-effective, and higher-quality data acquisition procedure for natural background-level metals and radionuclides in soils is needed for remedial investigations of contaminated sites. In this project, a total of 120 soil samples were collected from uncontaminated areas on and near the Oak Ridge Reservation. The samples were taken at three different depths and from three different geologic groups to establish background concentrations of metals and radionuclides. The objective of this presentation is to discuss the advantages and disadvantages of neutron activation analysis (NAA) compared with those of acid-digestion-based spectrometry (ADS) methods; the advantages and disadvantages were evaluated from Al, Sb, As, Cr, Co, Fe, Mg, Mn, Hg, K, Ag, {sup 232}Th, {sup 235}U, {sup 238}U, V, and Zn data. The ADS methods used for this project were inductively coupled plasma (ICP), ICP-mass spectrometry (ICP-MS), and alpha spectrometry. The scatter plots showed that the NAA results for As, Co, Fe, Mn, {sup 232}Th, and {sup 238}U are reasonably correlated with the results from the other analytical methods. Compared to NAA, however, the ADS methods underestimated Al, Cr, Mg, K, V, and Zn. The skew distributions were caused by incomplete dissolution of the analytes during acid digestion of the soil samples. Because of the high detection limits of the spectrometric methods, the NAA results and the ADS results for some elements, including Sb, Hg, and Ag, did not show a definite relationship. The NAA results were highly correlated with the alpha spectrometry results for {sup 232}Th and {sup 238}U but poorly correlated for {sup 235}U, probably because of a larger counting error associated with the lower activity of the isotope. The NAA methods, including the delayed neutron counting method, were far superior techniques for quantifying background levels of radionuclides ({sup 232}Th, {sup 235}U, and {sup 238}U) and metals (Al, Cr, ...
Date: December 31, 1995
Creator: Lee, S.Y.; Watkins, D.R.; Jackson, B.L.; Schmoyer, R.L.; Lietzke, D.A.; Burgoa, B.B. et al.
Partner: UNT Libraries Government Documents Department

Cooperative chemical rebonding in the segregation of impurities in silicon grain boundaries

Description: With ab initio calculations the authors show that the experimentally observed large segregation energies of As at Si grain boundaries can be explained by the formation of isolated dimers or ordered chains of dimers of threefold-coordinated As along the cores of grain boundary dislocations. They also find the intriguing possibility that As segregation may drive structural transformation of certain grain boundaries. Recently, they have obtained the first atomic-resolution STEM images of As in a Si grain boundary, consistent with the formation of As dimers. Segregation energy of As dimers was found to be significantly higher in isolated dislocation cores, where larger site-variation in strain than in grain boundaries lead to further lowering of the electronic levels of As deep into the bandgap.
Date: December 1996
Creator: Maiti, A.; Chisholm, M. F.; Pennycook, S. J. & Pantelides, S. T.
Partner: UNT Libraries Government Documents Department

Final project report on arsenic biogeochemistry in the Clinch River and Watts Bar Reservoir: Volume 2, Quality assurance/quality control summary report for arsenic biogeochemistry in the Clinch River and Watts Bar Reservoir. Environmental Restoration Program

Description: Arsenic contamination was studied in the Clinch River/Watts Bar Reservoir (CR/WBR) system downstream from the US Department of Energy`s Oak Ridge Reservation (ORR). Arsenic is of particular interest and concern because (1) it occurs commonly in coal-bearing rock and waste products such as fly ash associated with the burning of coal, (2) it is classified as a Class A carcinogen by the US Environmental Protection Agency, and (3) disposal of fly ash, both on and off the ORR, may have contaminated surface water and sediments in the Clinch River and Watts Bar Reservoir. The present study dffers from previous reports on arsenic concentrations in the CR/WBR system in the use of much more sensitive and precise processing and analytical techniques to measure arsenic species (arsenate, arsenite, and organic arsenic) at levels well below the ecological and human health risk screening criteria. The absolute detection limits using these techniques are approximately 20 to 40 pmol/L or 0.0015 to 0.003 {mu}g/L.
Date: April 1, 1995
Creator: Newman, K.A.; Ford, C.J. & Byrd, J.T.
Partner: UNT Libraries Government Documents Department

Corrective Action Plan for Corrective Action Unit 428: Area 3 Septic Waste Systems 1 and 5 Tonopah Test Range, Nevada

Description: Area 3 Septic Waste Systems 1 and 5 are located in Area 3 of the Tonopah Test Range (TTR) (Figure 1). The site is listed in the Federal Facility Agreement and Consent Order (FFACO, 1996) as Corrective Action Unit (CAU) 428 and includes Corrective Action Sites 03-05-002-SW01 (Septic Waste System 1 [SWS 1]), and 03-05-002-SW05 (Septic Waste System 5 [SWS 5]). The site history for the CAU is provided in the Corrective Action Investigation Plan (U.S. Department of Energy, Nevada Operations Office [DOE/NV], 1999). SWS 1 consists of two leachfields and associated septic tanks. SWS 1 received effluent from both sanitary and industrial sources from various buildings in Area 3 of the TTR (Figure 2). SWS 5 is comprised of one leachfield and outfall with an associated septic tank. SWS 5 received effluent from sources in Building 03-50 in Area 3 of the TTR (Figure 2). Both systems were active until 1990 when a consolidated sewer system was installed. The purpose of this Corrective Action Plan (CAP) is to provide the strategy and methodology to close the Area 3 SWS 1 and 5. The CAU will be closed following state and federal regulations and the FFACO (1996). Site characterization was done during May and June 1999. Samples of the tank contents, leachfield soil, and soil under the tanks and pipes were collected. The results of the characterization were reported in the Corrective Action Decision Document (CADD) (DOE/NV, 2000). Additional sampling was done in May 2000, the results of which are presented in this plan. Soil sample results indicated that two constituents of concern were detected above Preliminary Action Levels (PALs). Total arsenic was detected at a concentration of 68.7 milligrams per kilogram (mg/kg). The arsenic was found under the center distribution line at the proximal end of the SWS 5 ...
Date: August 1, 2000
Creator: Tobiason, D. S.
Partner: UNT Libraries Government Documents Department

Statement of basis/proposed plan for the Central Shops Burning/Rubble Pit (631-6G). Revision 1, Final

Description: The purpose of this plan is to describe the preferred alternative for addressing the Central Shops Burning/Rubble Pit 631-6G (BRP6G) located at SRS, in northwestern Barnwell County, South Carolina and to provide an opportunity for public input into the remedial action selection process. Arsenic, beryllium, iron, and octachloro-dibenzo-p-dioxin isomers (OCDD) concentrations in the pit soil are at levels consistent with those found in the background. Therefore, the only contamination attributable to actions in BRP6G is PCB-1254. After the risk contributions of these chemicals are eliminated, the only remaining risk attributable to the pit soil is from PCB-1254 (about 2 {times} 10{sup {minus}6} via ingestion of vegetables grown on-site). The maximum concentration of PCB-1254 detected in the pit was 0.115 mg/kg, approximately 10% of the residential action level for PCBs of 1 mg/kg. Based on the results of the remedial investigation and the BRA, it is proposed that No Action be performed for the BRP6G. Considering the low levels of residual contamination present principally below 1.2 meters (4 feet) within the pit and the associated risks (about 2 {times} 10{sup {minus}6}) within the lower level of EPA`s target risk range, action is not warranted for this unit.
Date: October 24, 1996
Creator: Palmer, E.
Partner: UNT Libraries Government Documents Department

Proposed Plan for the Burma Road Rubble Pit (231-4F)

Description: The purpose of this proposed plan is to describe the preferred alternative for addressing the Burma Road Rubble Pit (BRRP) source unit soils (231-4F) located at the SRS in Aiken, South Carolina and to provide an opportunity for public input into the remedial action selection process.
Date: November 1, 1995
Creator: Palmer, E.
Partner: UNT Libraries Government Documents Department

Atomic scale simulations of arsenic ion implantation and annealing in silicon

Description: We present results of multiple-time-scale simulations of 5, 10 and 15 keV low temperature ion implantation of arsenic on silicon (100), followed by high temperature anneals. The simulations start with a molecular dynamics (MD) calculation of the primary state of damage after 10ps. The results are then coupled to a kinetic Monte Carlo (MC) simulation of bulk defect diffusion and clustering. Dose accumulation is achieved considering that at low temperatures the damage produced in the lattice is stable. After the desired dose is accumulated, the system is annealed at 800{degrees}C for several seconds. The results provide information on the evolution for the damage microstructure over macroscopic length and time scales and affords direct comparison to experimental results. We discuss the database of inputs to the MC model and how it affects the diffusion process.
Date: January 23, 1995
Creator: Caturla, M.J.; Diaz de la Rubia, T. & Jaraiz, M.
Partner: UNT Libraries Government Documents Department

Cementitious stabilization of chromium, arsenic, and selenium in a cooling tower sludge

Description: The Federal Facility Compliance Agreement (FFCA) establishes an aggressive schedule for conducting studies and treatment method development under the treatability exclusion of RCRA for those mixed wastes for which treatment methods and capabilities have yet to be defined. One of these wastes is a radioactive cooling tower sludge. This paper presents some results of a treatability study of the stabilization of this cooling tower sludge in cementitious waste forms. The sample of the cooling tower sludge obtained for this study was found to be not characteristically hazardous in regard to arsenic, barium, chromium, lead, and selenium, despite the waste codes associated with this waste. However, the scope of this study included spiking three RCRA metals to two orders of magnitude above the initial concentration to test the limits of cementitious stabilization. Chromium and arsenic were spiked at concentrations of 200, 2,000, and 20,000 mg/kg, and selenium was spiked at 100, 1,000, and 10,000 mg/kg (concentrations based on the metal in the sludge solids). Portland cement, Class F fly ash, and slag were selected as stabilizing agents in the present study. Perlite, a fine, porous volcanic rock commonly used as a filter aid, was used as a water-sorptive agent in this study in order to control bleed water for high water contents. The highly porous perlite dust absorbs large amounts of water by capillary action and does not present the handling and processing problems exhibited by clays used for bleed water control.
Date: June 1, 1995
Creator: Spence, R.D.; Gilliam, T.M. & Bleier, A.
Partner: UNT Libraries Government Documents Department

Toxicological benchmarks for potential contaminants of concern for effects on soil and litter invertebrates and heterotrophic process

Description: An important step in ecological risk assessments is screening the chemicals occur-ring on a site for contaminants of potential concern. Screening may be accomplished by comparing reported ambient concentrations to a set of toxicological benchmarks. Multiple endpoints for assessing risks posed by soil-borne contaminants to organisms directly impacted by them have been established. This report presents benchmarks for soil invertebrates and microbial processes and addresses only chemicals found at United States Department of Energy (DOE) sites. No benchmarks for pesticides are presented. After discussing methods, this report presents the results of the literature review and benchmark derivation for toxicity to earthworms (Sect. 3), heterotrophic microbes and their processes (Sect. 4), and other invertebrates (Sect. 5). The final sections compare the benchmarks to other criteria and background and draw conclusions concerning the utility of the benchmarks.
Date: September 1, 1995
Creator: Will, M.E. & Suter, G.W. II
Partner: UNT Libraries Government Documents Department

Sorbents for High Temperature Removal of Arsenic from Coal-Derived Synthesis Gas

Description: Gasification technologies convert coal and other heavy feedstocks into synthesis gas feed streams that can be used in the production of a wide variety of chemicals, ranging from hydrogen through methanol, ammonia, acetic anhydride, dimethyl ether (DME), methyl tertiary butyl ether (MTBE), high molecular weight liquid hydrocarbons and waxes. Syngas can also be burned directly as a fuel in advanced power cycles to generate electricity with very high efficiency. However, the coal-derived synthesis gas contains a myriad of trace contaminants that may poison the catalysts that are used in the downstream manufacturing processes and may also be regulated in power plant emissions. Particularly, the catalysts used in the conversion of synthesis gas to methanol and other liquid fuels (Fischer-Tropsch liquids) have been found to be very sensitive to the low levels of poisons, especially arsenic, that are present in the synthesis gas from coal. TDA Research, Inc. (TDA) is developing an expendable high capacity, low-cost chemical absorbent to remove arsenic from coal-derived syngas. Unlike most of the commercially available sorbents that physically adsorb arsenic, TDA's sorbent operates at elevated temperatures and removes the arsenic through chemical reaction. The arsenic content in the coal gas stream is reduced to ppb levels with the sorbent by capturing and stabilizing the arsenic gas (As4) and arsenic hydrides (referred to as arsine, AsH3) in the solid state. To demonstrate the concept of high temperature arsenic removal from coal-derived syngas, we carried out bench-scale experiments to test the absorption capacity of a variety of sorbent formulations under representative conditions. Using on-line analysis techniques, we monitored the pre- and post-breakthrough arsine concentrations over different sorbent samples. Some of these samples exhibited pre-breakthrough arsine absorption capacity over 40% wt. (capacity is defined as lb of arsenic absorbed/lb of sorbent), while maintaining an arsine outlet concentration at less ...
Date: September 20, 2002
Creator: Alptekin, G.O.; Copeland, R.; Dubovik, M. & Gershanovich, Y.
Partner: UNT Libraries Government Documents Department

Remedial investigation/feasibility study of the Clinch River/Poplar Creek operable unit. Volume 4. Information related to the feasibility study and ARARs. Appendixes G, H, I

Description: This report presents the findings of an investigation into contamination of the Clinch River and Poplar Creek near the U.S. Department of Energy`s (DOE`s) Oak Ridge Reservation (ORR) in eastern Tennessee. For more than 50 years, various hazardous and radioactive substances have been released to the environment as a result of operations and waste management activities at the ORR. In 1989, the ORR was placed on the National Priorities List (NPL), established and maintained under the federal Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). Under CERCLA, NPL sites must be investigated to determine the nature and extent of contamination at the site, assess the risk to human health and the environment posed by the site, and, if necessary, identify feasible remedial alternatives that could be used to clean the site and reduce risk. To facilitate the overall environmental restoration effort at the ORR, CERCLA activities are being implemented individually as distinct operable units (OUs). This document is the combined Remedial Investigation and Feasibility Study Report for the Clinch River/Poplar Creek OU.
Date: March 1, 1996
Partner: UNT Libraries Government Documents Department

Atomic scale characterization of semiconductor interfaces by scanning transmission electron microscopy

Description: Recently, the scanning transmission electron microscope has become capable of forming electron probes of atomic dimensions. Through the technique of Z-contrast imaging, it is now possible to form atomic resolution images with high compositional sensitivity from which atomic column positions can be directly determined. An incoherent image of this nature also allows atomic resolution chemical analysis to be performed, by locating the probe over particular columns or planes seen in the image while electron energy loss spectra are collected. These powerful techniques, combined with atomic-scale calculations, constitute a powerful probe of the structural, kinetic and thermodynamic properties of complex materials. The authors show the direct observation of As segregated to specific sites in a Si grain boundary, and present a candidate model for the structure of the Si/SiO{sub 2} interface.
Date: May 1, 1997
Creator: Pennycook, S.J.; Chisholm, M.F.; Duscher, G.; Maiti, A. & Pantelides, S.T.
Partner: UNT Libraries Government Documents Department