• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 5
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 12
  • 12
  • 12
  • 8
  • 6
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Preference avoidance reactions of rainbow trout (Salmo gairdneri) following long term sublethal exposure to chromium and copper

Anestis, Ioannis D. January 1988 (has links)
No description available.
2

Chromium contamination in the vicinity of [the] Xstrata Wonderkop plant.

Sedumedi, Hilda N. January 2009 (has links)
M. Tech. Chemistry. / The aim of this study was to develop and evaluate an analytical method for the determination of Cr(VI) in ferrochrome dusts and to apply the method in the analysis of environmental samples (grass, soil and tree bark) for Cr(VI) content (that might be caused by dust emissions originating from the smelter). Both the public and Xstrata Wonderkop ferrochrome plant will benefit from data of Cr(VI) determination generated from the study. The information can potentially be incorporated into health risk assessments of the affected geographical areas. The results of the investigation showed that ferrochrome smelter dust emissions were the source of contamination of the environment with Cr(VI). With time, Cr(VI) could accumulate in soil to unacceptable levels, thereby endangering both plants and animals.
3

Preference avoidance reactions of rainbow trout (Salmo gairdneri) following long term sublethal exposure to chromium and copper

Anestis, Ioannis D. January 1988 (has links)
A standard methodology was developed for performing avoidance-preference tests, using Rainbow Trout (Salmo gairdneri) as the test organism. Experiments were conducted in a hydraulic channel, 9.15 m long by 0.30 m wide, partly divided along its length, and at a flow depth of 0.30 m. The design combined steep and shallow gradient characteristics. The toxicants investigated included Cu(II), Cr(III) and Cr(VI). The lowest avoidance threshold values were established at 2.1 $ mu$g/l for Cu(II) and 0.0026 mg/l and 0.026 mg/l for Cr(III) and Cr(VI) respectively while avoidance reactions increased with levels of toxicant in the channel. Similar experiments were performed with rainbow trout which were pre-exposed at sublethal levels to the toxicant, in order to assess the influence of toxic pre-exposure to the subsequent fish avoidance response. The length of pre-exposure varied between 7-20 weeks. Avoidance threshold values were correlated with safe levels of toxicant exposure. / Pre-exposed fish exhibited decreasing avoidance reactions compared to non-exposed populations. Increased tolerance to the toxicant, was suggested by the increase in avoidance threshold values with pre-exposure levels. Fish exposed to test concentrations matching their pre-exposure levels, clearly preferred this same concentration over the adjacent lower or higher test concentration. / A two mechanism avoidance model was proposed independent of toxicant used or level of pre-exposure. The toxicant concentration where the second mechanism begins to dominate was referred to as avoidance breakpoint, and was correlated to a MATC level for the toxicant in question. Olfactory responses were proposed to be associated with fish avoidance responses below the avoidance breakpoint, while hypoxic stress along with osmo- and iono regulatory stress appeared to be responsible for driving fish avoidance reactions beyond the avoidance breakpoint. / A clearance period of 7 days was sufficient to allow fish to recover normal avoidance behaviour following pre-exposure to Cr(VI) below the avoidance breakpoint.
4

Management of chromium wastes in industry

Like, David E. 09 January 1991 (has links)
Chromium hydroxide sludge is the end product of the aluminum phosphate coating process used by a truck manufacturer in the Pacific Northwest. This sludge is listed as an (F019) hazardous waste by the Environmental Protection Agency, and must be landfilled in a hazardous waste landfill site. The purpose of this thesis is to evaluate the characteristics of this sludge, and to then recommend suitable methods for handling and disposal. The chemical analysis of the sludge found total chromium to be 5.4% by weight. Industrial hygiene monitoring found the highest concentrations of 0.002 mg/m3 total chromium and 0.00006 mg/m3 hexavalent chromium at the waste treatment plant. The eight hour permissible exposure limit for total chromium is 0.5 mg/m3 and 0.05 mg/m3 for hexavalent chromium. Given the chemical analysis and industrial hygiene monitoring, a management plan is proposed for this truck manufacturer that discusses possible options for handling the (F019) waste, and provides a cost analysis for each of the options. The options that were investigated were onsite treatment, recycling, no change, and delisting. Onsite treatment was not required since the sludge passed the TCLP extraction test. Recycling costs were determined by contacting four recycling firms. Costs were found to be $600/ton and above, which exceeded the current disposal costs of $466/ton. Delisting the sludge from the hazardous waste listing was determined to be the most feasible from a management, cost, and environmental standpoint. Delisting would reduce the costs of handling the waste, would allow a reduction in landfilling costs, and reduce recycling costs. A literature survey provides background information on industrial uses of chromium, health problems associated with chromium, and discusses the regulations that govern disposal of these chromium sludges. / Graduation date: 1991
5

The use of PRBs (permeable reactive barriers) for attenuation of cadmium and hexavalent chromium from industrial contaminated soil / Title on signature form: Use of permeable reactive barriers (PRBs) for attenuation of cadmium and hexavalent chromium from industrial contaminated soil

Meza, Maria I. January 2009 (has links)
Permeable reactive barriers are considered among the most promising technologies for contaminated soil and groundwater remediation. Zero-valent iron (ZVI), hydroxyapatite (HA), and organic compost, with (OM) and without (OMx) dextrose/sulfate were assessed in column studies for their ability to attenuate chromium (Cr) or cadmium (Cd). PVC columns were packed with the reactive media and Cr or Cd solutions were pumped through the columns at concentrations of 5, 50 and 200 mg/l. These media were also assessed for their abilities to attenuate Cr and Cd from a contaminated soil. The order of Cr removal was: ZVI > OMx > OM > HA. The ZVI treatment maintained a removal rate of > 95% throughout the study. All treatments used for Cd removal had a removal rate of 98% across all treatments. The ZVI was the only treatment capable of retaining any of the mobile soil Cr and Cd from the contaminated soil. / Department of Natural Resources and Environmental Management
6

Biotic-abiotic transformations of chromium in long-term tannery waste contaminated soils : implications to remediation

Kamaludeen, Sara Parwin Banu. January 2002 (has links) (PDF)
Bibliography: leaves 166-180. Determines the effect of chromium on the soil microbial community and its activity, the biotic-abiotic mechanisms involved in chromium oxidation, and phytostabilization of chromium using plants and organic amendment in tannery-waste contaminated soil.
7

Biotic-abiotic transformations of chromium in long-term tannery waste contaminated soils : implications to remediation / by Sara Parwin Banu Kamaludeen.

Kamaludeen, Sara Parwin Banu January 2002 (has links)
Bibliography: leaves 166-180. / 180, [4] leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Determines the effect of chromium on the soil microbial community and its activity, the biotic-abiotic mechanisms involved in chromium oxidation, and phytostabilization of chromium using plants and organic amendment in tannery-waste contaminated soil. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002
8

Long-term tannery waste contamination: effect on chromium chemistry / by Avudainayagam Subramanian.

Avudainayagam Subramanian January 2002 (has links)
Corrigenda inside front cover. / Includes bibliographical references (leaves 205-232) / xii, 232, [27] leaves : ill., plates ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002
9

Soil column desorption studies on a chromium contaminated soil

Ball, Bruce L. 11 February 1992 (has links)
Soil column studies were performed on a chromium contaminated soil from the United Chrome Products Superfund Site currently undergoing a pump-and-treat cleanup process. The goal of the research was to provide insight into the feasibility of chemically changing the injection fluid of the pump-and-treat system to enhance hexavalent chromium (Cr(VI)) mobility. The parameters tested were pH, ionic strength, and competitive anion type and concentration. Ionic strength effects were investigated by adjusting the NaCl concentration of the extracting solution and by observing the influence of varying anion concentrations on desorption (bicarbonate, sulfate, and phosphate). The results indicated that high ionic strength solutions slow the rate of Cr(VI) desorption. This possibly indicates most of the Cr(VI) was in pore water solution and was adsorbing, slowing the removal process. Cr(VI) desorption was fastest for distilled water solution followed by competitive anion/distilled water solutions. The high ionic strength extracting solutions, 0.05 M and 0.10 M NaCl, had the slowest Cr(VI) desorption rates. Effluent pHs dropped as the ionic strength was increased (increasing NaCl concentrations) which was attributed to a Na-H exchange. Increased concentrations of bicarbonate, sulfate, and phosphate resulted in only small pH differences in the effluent of less than 0.5 pH units. The effect of pH was investigated by varying the pH of the 0.01 M NaCl solution with strong acid and base and by varying the pH of phosphate competitive anion solutions. The effects of changing 0.01 M NaCl solution pH were inconclusive. Differences between Cr(VI) desorption rates for the soil columns with adjusted influent pHs were small. Cr(VI) desorption curves and column effluent pH values for phosphate solutions of varying influent pH values were nearly identical, indicating that soil buffering and effluent pH are more important factors than influent pH in achieving Cr(VI) desorption. Nitrate, bicarbonate, sulfate, and phosphate were investigated to determine the effect of various competitive anions on Cr(VI) desorption. The effectiveness of each anion at extracting Cr(VI) from soil appeared to follow the order of adsorption affinity to the soil. / Graduation date: 1992
10

Laboratory study of chromium sorption and desorption in undisturbed soil

Muller, Heike K. 20 October 1992 (has links)
Graduation date: 1993

Page generated in 0.1205 seconds