Browsing by Subject "RDX (compound)"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Bioremediation of explosives in vadose zone soil using vapor phase carbon source additions(Texas Tech University, 2005-05) Radtke, Corey W.; Cobb, George P.; Anderson, Todd; Dickerson, Richard L.; Roberto, Francisco F.Explosives contamination in vadose zone soil presents difficulties in remediation. Because vadose zone contamination can extend deep into the subsurface and underneath existing buildings and utilities, excavation is often infeasible. In response, this dissertation focuses on the development and testing of a practical system to enhance the remediation of vadose zone explosives contamination. Soil at the DOE Idaho National Engineering and Environmental Laboratory field area was characterized for explosives contamination. Of the soil tested, the particulate TNT retained on a 3 mm screen contributed approximately 2000 ppm (96.4%) of the overall soil contamination, compared to the soil that passed through the sieve, which averaged 75 ppm TNT. Contributing significantly to the contamination profile, heterogeneously dispersed, and likely point sources of contamination, the particulates thereby present difficulties in estimating the extent, risk, and treatability of explosives contamination in the soil. For monitoring soil gases, a method was developed and validated using solid phase microextraction coupled with gas chromatography and mass selective detection (SPME-GCMS). The within-run precision (repeatability) was 3.5X tighter than the between-run precision (reproducibility) in the 4 days. The esters gave the best repeatability from 50 to 80 ppmv while the corresponding alcohols gave the best results at 10 to 20 ppmv. The method was applied to monitor gases in laboratory and field studies testing explosives remediation in vadose zone soil. Anaerobic and microaerobic batch and column studies using soil from the DOE Pantex Facility contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 1,3,5-trinitrobenzene (TNB) were performed using gaseous carbon source additions. In the anaerobic batch study, over 99 days, flasks periodically receiving headspace pulses of 330 to 570 ppmv n-propyl acetate yielded 97.5±0.3% TNB and 66.7±43.2% RDX removal. Using ethanol in place of n-propyl acetate yielded similar results. Two column studies were performed using throughputs of oxygen, nitrogen gas, and organic carbon combinations. The columns supported less robust HE degradation than the batch systems. This difference in HE degradation between batch and column work may indicate that a key factor accumulated in the headspace of batch flasks, but was continually removed in the columns.Item Reproductive and developmental toxicity of highly energetic compounds in zebrafish (Danio rerio)(Texas Tech University, 2006-08) Mukhi, Sandeep; Patino, Reynaldo; Smith, Ernest E.; Carr, James A.; Anderson, Todd A.; Lee, Vaughan H.There has been growing concern in recent years about a variety of toxicants, some of which are highly energetic in nature, that can affect human and ecosystem health. Highly energetic compounds such as perchlorate and hexahydro-1,3,5-trinitro-1,3,5-triazine (known as RDX) have been reported in various environments worldwide. The ecotoxicological impacts of these chemicals are relatively not fully understood. The overall objective of this study was to access the toxicological effects of these two chemicals on reproduction, development and other activities in a model aquatic organism, the zebrafish (Danio rerio). Perchlorate is a known thyroid-disrupting chemical. Exposure to environmental relevant concentrations of perchlorate caused several pathological alterations in thyroid follicles of zebrafish, which were used to establish novel and sensitive biomarkers of perchlorate exposure (Chapter 1). Namely, angiogenesis and ¡®colloidal T4 ring¡¯ intensity were far more sensitive indicators of thyroid disruption than previous available biomarkers. The developmental toxicity of perchlorate was studied in larval zebrafish (Chapter 2). Exposure to perchlorate at concentrations that inhibited thyroid function affected growth (length) and the sex ratio of exposed populations. Treatment with perchlorate skewed the sex ratio towards females, whereas co-treatment with thyroxine (T4) skewed the sex ratio towards males. This is the first report for teleost fishes indicating that thyroid hormone is involved in the process of gonadal sex determination and differentiation. An effect of perchlorate on the reproductive performance of zebrafish was also observed in a long-term exposure study (Chapter 3). After 16 weeks of exposure to perchlorate, a decline was observed in the level of T4, but not triiodothyronine, in whole-body homogenates of mothers and their embryos. Perchlorate also impaired fecundity (packed-egg volume), although egg diameters were increased and fertilization and hatching rates were unaffected. Analyses of the embryos also indicated impaired growth of jaw-forming cartilages (Meckel¡¯s and ceratohyal). Relatively little information is available concerning the lethal and sublethal effects of RDX in teleosts. The acute toxicity of RDX was determined for larval zebrafish (Chapter 4). The median lethal concentration of RDX was estimated (96-h LC50, 23-26 ppm), and effects on the surviving fish such as vertebral column deformities and behavioral abnormalities were also documented. The chronic toxicity and bioconcentration potential of RDX were subsequently determined in adult zebrafish (Chapter 5). Long-term exposure to RDX caused severe mortality at a concentration of 9.6 ppm. The bioconcentration factor for RDX was low but slightly increased with time of exposure, from ¡Ü1 at 4 and 8 weeks of exposure to >2 at 12 weeks. The RDX metabolite, MNX, was also found in whole-body extracts. Both RDX and MNX were undetectable in whole-body extracts 2 weeks after the fish were transferred to clean water. Lastly, the effects of RDX at sublethal concentrations on reproduction and egg quality were determined (Chapter 6). Exposure to RDX at the relatively low concentration of 0.5 ppm caused a short-lived increase in fecundity within 2 weeks of the onset of exposures; whereas no effects were noted at the higher concentration tested, 3.2 ppm. Egg fertilization rates and embryo hatching rates were unaffected by parental exposures to RDX. It is concluded that exposure to environmental perchlorate and RDX can potentially impact the health of teleosts, an important component of the aquatic biota.