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  • 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.
111

APPLICATION OF THE TENAX TECHNIQUE TO ASSESS BIOACCESSIBILITY OF SEDIMENT-ASSOCIATED POLYCHLORINATED BIPHENYLS

Sinche Chele, Federico Leonardo 01 May 2018 (has links) (PDF)
Sediments can act as both reservoir and source of legacy organic contaminants such as polychlorinated biphenyls (PCBs). Due to their chemical stability and ubiquity, these contaminants remain as model class of compounds in the field of sediment contamination. Whole sediment and organism concentrations have been often used as exposure metrics for ecological risk assessments. However, whole sediment concentrations often overestimate the potential for exposure to contaminants; while organism concentrations based on bioassay provide a better estimate of exposure, bioassays can also be labor intense, time consuming and expensive. Alternatively, accessiblity-based techniques such as Tenax extractions have been gaining ground, in the last few decades, as a rapid, reliable, and cost-effective approach to estimate exposure to organic contaminants from sediments. Tenax extractions measure the bioaccessible fraction of the contaminant that desorbes from sediment. Despite the simplicity, accuracy and robustness of the Tenax technique to estimate bioaccessibility of organic contaminants, there are still some remaining questions regarding the methodological standardization, and the applicability of the technique in sediments containing diverse carbonaceous sorbents associated adsorption/desorption of the contaminant. Therefore, the chapters of this dissertation were designed to address these questions. To this end, PCBs were chosen as a model compound class to represent a wide range of physicochemical properties of persistent organic contaminants, and because these compounds remain a worldwide legacy contamination problem. The dissertation goals were to: determine the best operational conditions for Tenax technique (Chapter 2); monitor the changes in bioaccessibility of field-collected sediments with different holding time conditions (Chapter 3); examine the effects of the type and quantity of organic carbon on bioaccessibility (Chapter 4); and evaluate the applicability of the Tenax technique to assess remediation success in contaminated marine sediments (Chapter 5). To address the methodological standardization of the Tenax technique, the operational parameters of solvent extract volume, Tenax sorption rate from water, and Tenax:OC (Tenax:Organic Carbon) ratios were investigated in Chapter 2. The highest efficiency of extraction of sorbed PCBs from Tenax resulted from using a 10 mL per each solvent wash during Tenax extraction procedure. For the Tenax sorption, it was found that 0.01 g of Tenax cleared PCB in 40 mL of water in 30 min, thus it would clear the water 48 times in 24 h. When this is extrapolated to the 0.5 of Tenax, typical amount used, it was found that the amount should clear the typical volume of water used on Tenax extraction about 2400 times. This represents unequivocal evidence that the Tenax resin would remove PCBs dissolved in the liquid phase (e.g., overlying or interstitial water) present in the sediment sample and be limited only by compound desorption and not by the Tenax sorption capacity. The results examining the impact of the relationship between the amount of Tenax required and the amount of organic carbon in the sediment extraction indicated that a minimum of 5:1 Tenax:OC ratio be used to conduct Tenax extractions. This will reduce (eliminate) the possibility of re-adsorption by the native OC in the sediment in competition with the Tenax. After ascertaining the best operational conditions for Tenax extractions, two additional methodological uncertainties, the effect of storage time after collection and the preservation method associated with the handling of collected sediment samples were investigated in Chapter 3. The effect of holding time and the preservation method on PCB concentrations from field-collected sediments was examined for a period of 196 d. All samples were held at 4 ºC in the dark and several holding times were chosen. The parameters to track the changes in PCB concentration in two sediments used three exposure metrics: exhaustive solvent extraction, tissue concentrations and Tenax extractions (Chapter 3). The results showed that the total exhaustive concentrations representing the whole sediment concentrations did not significantly change (ANOVA, p> 0.05) in either sediment over the course of 196 d. Similar results were also found for the total Tenax concentrations that represented the bioaccessible sediment concentrations, and for the total organism tissue concentrations representing exposure. The likely equilibrium of PCB in the sediment, their chemical stability of PCB and slow degradation can be underlined as the main factors leading to these results. The long time that legacy contaminants such as PCBs have been in contact with contaminated sites (e.g., Superfund sites) might have contributed to an equilibrium to be reached between the sediment particles and PCB molecules. The significance of this chapter is that sediments collected from PCB-contaminated sites can be stored longer than the 14 d as recommended by current standard protocols without disturbing the measures of bioavailability. The role of organic carbon composition within sediment on contaminant sorption was also investigated to ascertain the effects of type and quantity of OC from different origins on the bioaccessibility of PCBs in contaminated sediments (Chapter 4). Changes in PCB bioaccessibility in sediments amended at either 3 or 6% by dry weight with black carbon (BC), humic acid (HA) or sawdust (SD), showed that the lowest and highest PCB bioaccessibilities were observed in the BC and SD amendments, respectively. Specifically, the total amount of PCBs desorbed ranges from 3 to 27% for BC amendments, 12 to 55% for HA amendments and 16 to 80% for SD amendments. The results showed the influence of OC quantity on bioaccessibility having a much slower desorption of PCBs in 6% amendments compared to 3% amendments, and this finding was most evident in HA and BC amendments. The results also showed that the Tenax technique can be applied to tract the variation in type of carbon and quantity of OC in contaminated sediment to estimate exposure. Finally, the applicability of the Tenax technique as tool to assess the remediation success of PCB-contaminated marine sediments upon AC amendment at either 4.3 or 0.026% AC by dw was examined in Chapter 5. The results showed that bioaccessibility of PCBs was greatly reduced in sediment amended at the higher AC dose (4.3%); while, reduction was also observed even in the sediment amended at 0.026% AC. Furthermore, the results revealed that Tenax concentrations reflected the PCB reduction among AC amended sediments in the same direction as the PCB reduction in the organism bioaccumulation. Overall, this dissertation provides further evidence that the Tenax technique is a rapid, reliable, and cost-effective tool for estimating exposure to recalcitrant organic contaminants such as PCBs from contaminated sites. The applicability of the technique to estimate bioaccessible compound from both freshwater and marine aquatic sediments underline the robustness of the technique to widen its use among risk ecological assessor and researchers.
112

Determinants of the short term dynamics of PCB uptake by the plankton

Richer, Guylaine January 1991 (has links)
No description available.
113

Laboratory study of solvent extraction of polychlorinated biphenyls in soil

Valentin, Melissa McShea. January 2000 (has links)
No description available.
114

A laboratory study on the development and testing of a bioaugmentation system for contaminated soils /

Mehmannavaz, Reza. January 1999 (has links)
No description available.
115

Heavy Metal, Organochlorine Pesticide and Polychlorinated Biphenyl Contamination in Arctic Ground Squirrels (Spermophilus Parryi) in Northern Alaska

Allen-Gil, S. M., Landers, D. H., Wade, T. L., Sericano, J. L., Lasorsa, B. K., Crecelius, E. A., Curtis, L. R. 01 December 1997 (has links)
Heavy metal and organochlorine (OC) concentrations, including organochlorine pesticides and polychlorinated biphenyl congeners (PCBs), were determined in arctic ground squirrels (Spermophilus parryi) from three sites in the Brooks Range of northern Alaska in 1991-93. Heavy metals were present in most squirrel livers collected, with concentrations of trace elements (As, Cd, Hg, Ni, and Pb) averaging below 1 μg/g wet weight. Hexachlorobenzene (HCB), p,p'-DDE, gamma hexachlorocyclohexane (γ-HCH), trans-nonachlor, and PCBs 138, 153, and 170 were the most frequently detected OCs in fat and liver. Average concentrations of individual OC analytes were below 20 ng/g wet weight in liver and below 15 ng/g wet weight in fat. Rank correlations indicate that concentrations of heavy metals and of OCs accumulate in concert with one another (As, Cd, Cu, and Zn; PCBs 138, 170, and 180). Although heavy metal and OC concentrations are low relative to other areas and other arctic species, the occurrence of these compounds illustrates the global pervasiveness of persistent organic compounds and the potential for bioaccumulation in the terrestrial arctic food web.
116

Determination, mobilization and dechlorination of polychlorinated biphenyl (PCB) compounds in contaminated soils

Wu, Qixiang January 2001 (has links)
No description available.
117

Neurobehavioral and Neuroendocrine Assessment of Rats Perinatally Exposed to Polychlorinated Biphenyls: A Possible Model for Autism

Krishnan, Dena K. 25 June 2007 (has links)
No description available.
118

Investigating the Effects of Polychlorinated Biphenyls on Circulating Oxytocin Levels, Area of the Paraventricular Nucleus and Social Behavior in Juvenile Male Rats

Jolousjamshidi, Banafsheh 05 July 2007 (has links)
No description available.
119

Comparison Between PCB Exposure and Hypothyroidism: Behavioral Development in Sprague-Dawley Rats

Toth, Cynthia L. 29 July 2009 (has links)
No description available.
120

BIOACCUMULATION OF POLYCHLORINATED BIPHENYLS IN THE NORTHERN DIAMONDBACK TERRAPIN (Malaclemys terrapin terrapin)

Ismail, Niveen January 2010 (has links)
Polychlorinated biphenyls (PCBs) are persistent organic pollutants that can bioaccumulate in organisms. PCBs are documented endocrine disrupting chemicals and are known to cause developmental, reproductive, and neurobiological disorders. This study examines the bioaccumulation of PCBs in the northern diamondback terrapin (Malaclemys terrapin terrapin), a species that is endemic to the brackish waters of the East Coast salt marshes of the United States. The two populations studied are located in Cape May County, NJ, a site with low levels of contamination and Jamaica Bay, NY, which is a highly contaminated site. While PCBs bioaccumulation has been extensively researched, many studies involve lethal sampling techniques. Such techniques can be detrimental to populations and may not be viable for long-term studies. This study examined the utility of the chorioallantoic membrane (CAM) as a non-lethal sampling technique for PCB analysis. In order to determine the viability of the CAM, maternal transfer of contaminants was also analyzed. Ten terrapin samples from each field location were analyzed. Egg and CAM samples were obtained from both field sites and liver samples were also collected from Cape May County terrapins. PCB levels and congener profiles were similar in both field locations. While PCB congeners were detected in liver, egg, and CAM samples, less chlorinated congeners preferentially partitioned in the CAM. Liver and egg sample PCB concentrations were strongly correlated, but the CAM concentrations were weakly correlated to liver and egg samples. Examination of homolog groups indicated a strong correlation between hexachlorinated biphenyls in all three sample types. Preliminary study results indicated that maternal transfer of PCB contaminants does occur with selective partitioning of congeners into the CAM. / Biology

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