Browsing by Subject "Toxicity"
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Item A protocol to evaluate the adsorptive removal of dissolved copper and zinc from highway runoff(2014-05) Ernst, Clayton Owen; Katz, Lynn EllenThe increasing urbanization of landscapes significantly alters the surface water hydrology of impacted watersheds. As a side effect, stormwater discharges to receiving water bodies are often of decreased quality due to pollutants deposited on impervious urban surfaces being entrained by runoff. A pertinent example of this problem is the presence of copper and zinc in highway runoff. Both copper and zinc have been shown to exert toxic effects on aquatic micro- and macro-biota. Copper in particular has been shown to harmfully disrupt the olfactory nervous system of fish species at concentrations as low as 3 [mu]g/L. To meet these limits, treatment of highway runoff for the removal of copper and zinc is necessary. However, due to the complexities associated with the behavior of heavy metals in natural systems, the appropriateness of removal techniques will necessarily depend on a variety of system-specific factors and chemical characteristics of highway runoff. Adsorption has been shown to be generally effective in the removal of dissolved heavy metals, but the choice of adsorptive media is again dependent on system-specific parameters. This study developed and evaluated a column testing protocol that can be used to quickly and reliably evaluate adsorptive removal of dissolved heavy metals from highway runoff. The protocol is demonstrated in an evaluation of iron oxide, manganese oxide, crab shell, concrete, and bone meal media for removing dissolved copper and zinc from highway runoff. The performance of these media was assessed as a function of various runoff characteristics including pH, ionic strength, alkalinity, and total organic carbon. The methodology was used to show that iron oxide media in combination with crab shell or concrete media provided the most effective removal of copper and zinc from highway runoff. Through this study, the convenience, flexibility, and robustness of the proposed protocol are compellingly established.Item Reproductive and developmental toxicity of highly energetic compounds in zebrafish (Danio rerio)(2006-08) Mukhi, Sandeep; Patino, Reynaldo; Anderson, Todd A.; Carr, James A.; Lee, Vaughan H.; Smith, Ernest E.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.Item Toxicity and bioavailability of explosive metabolites to invertebrates(Texas Tech University, 2006-12) Zhang, Baohong; Anderson, Todd A.; Cobb, George P.; McMurry, Scott T.; Cox, Stephen B.; Jackson, W. AndrewRDX and its N-nitroso metabolites were rapidly absorbed into earthworms. The BCFs were 1.86, 0.39, and 0.05 for RDX, MNX and TNX, respectively. It is unlikely that earthworms reduce RDX to MNX and MNX to TNX. Other biotransformation pathways may be involved in earthworm biodegradation of RDX. MNX and TNX were also absorbed by PSDs. Organic matter content is one soil factor that affected the ratio of MNX or TNX uptake into earthworms vs. uptake into PSDs. A linear relationship between PSD uptake and earthworm uptake was observed. These data indicate that C18 PSDs may be used as a surrogate for soil organisms such as earthworms and provide a simple and easy chemical test for assessing the bioavailability of contaminants in soils. MNX and TNX inhibited earthworm growth, caused death, and inhibited reproduction. Earthworms were more sensitive to TNX in sandy loam soil than other conditions. The LOLC for MNX and TNX was 100 mg/kg in sandy loam soil, and 200 mg/kg in silt loam soil. At 7 days of exposure, the LOEC for earthworm growth was 50 mg/kg for TNX and 100 mg/kg for MNX. After 35 days of exposure, earthworm growth was reduced 8-39% by TNX in sandy loam soil, whereas TNX only inhibited earthworm growth 5-18% in silt loam soil. MNX affected glutathione synthesis and the activity of GPX and ChE although no significant effects were observed on protein content, CAT, and GCS activity. Surprisingly, MNX enhanced ChE activity, especially the activity of AChE. AChE activity was enhanced more than 3-fold in earthworms exposed to 50 mg/kg MNX for 30 days. RDX N-nitroso metabolites, especially MNX, may cause oxidation stress in earthworms. MNX and TNX affected cricket egg hatching. TNX was more toxic to eggs than MNX. After 30 days exposure, the EC20, EC50, and EC95 were 47, 128, and 247 ìg/g for TNX, and 65, 140, and 253 ìg/g for MNX in topical tests and 21, 52, and 99 ìg/g for MNX, and 12, 48, and 97 ìg/g for TNX in sand. These data can be used for defining criteria for environmental management of RDX and performing specific risk assessment of RDX and its N-nitroso metabolites.