Browsing by Subject "Water pollution"
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Item A general method for modeling coastal water pollutant loadings(2009-08) Johnson, Stephanie Lynn, 1977-; Maidment, David R.; Kirisits, Mary JoThe focus of this work was to develop a general methodology for modeling water quality in coastal waterbodies. The methods were developed in the context of modeling bacterial total maximum daily loads (TMDLs), but the general approach is applicable to a wide variety of pollutants. The study area for this dissertation was the Copano Bay watershed, which is located on the Texas Gulf Coast. The developed approach combines simple modeling techniques, of the type recommended by state and national advisory groups, in a GIS (geographic information system) framework, resulting in a methodical, easily transferred approach. This work addresses coastal systems where water quality is a function of operations in non-tidal rivers, tidal rivers, and bays, combined with the effects of watershed contributions. An uncertainty analysis was done to quantify a subset of the variance in the modeled results. Outcomes from this work include modeling tools, a documented workflow for modeling water quality in coastal watersheds, procedures to quantify the uncertainty associated with the developed approach, insight to the factors affecting water quality in the study area, and mean annual bacterial TMDLs for the impaired waterbodies of the Copano Bay watershed.Item Legal issues and modeling related to perchlorate contamination in Bosque and Leon watershed(Texas Tech University, 2004-05) Dogru, Ilkay PinarNot availableItem The Asiatic clam (Corbicula fluminea) as a bio-monitor for determining the distribution of antimony, arsenic and thallium in the water column and sediments of Manadas Creek, Laredo, Texas(Texas A&M International University, 2016-02) Garcia, Natasha; Vaughan, TomManadas Creek is an urban tributary of the Rio Grande that flows past a decommissioned antimony smelter. This smelter is associated with the heavy metal contamination in the creek and still poses a threat to the surrounding aquatic environment. With concerns on the rise of metal pollution, the biomonitor, the Asiatic clam (Corbicula fluminea) was used to determine bioaccumulation from the water column and sediments in Manadas Creek. The metals arsenic (As), antimony (Sb) and thallium (Tl) were analyzed in the water, sediments, gills, mantle, foot, digestive (DI) tract, gonads and shell of clams collected from sites between March to August 2013. Metal analysis of arsenic, antimony and thallium was performed by ICP-OES. High levels of antimony, arsenic and thallium in the water (13.45±6.65; 10.33±3.4; 7.47±1.73) and sediments (75.77±1.59; 6.41±1.19) at the site downstream from the smelter were observed. Additionally, tissue samples from this site had the highest concentrations, however there was no direct correlation between the metal concentrations in the water column and sediments with the tissues. There were no detectable concentrations of arsenic, antimony and thallium in shell samples. Site 3 had the highest thallium concentration in the sediments (3.00±0.68). No detectable thallium concentrations were detected in the tissues. Based on the results, the organotropism for arsenic is DI tract > gills > gonads > foot > mantle > shell and the organotropism for antimony is gills > DI tract > gonads > mantle > foot > shell. The Asiatic clam (Corbicula fluminea) is a useful biomonitor to provide data on the status of metal pollution in Manadas Creek, Laredo, Texas.Item Zero-valent iron's effectiveness at dehalogenating chlorobenzenes and its feasibility as a reactive cap(2006-12) Moderow, Shawn Michael; Reible, Danny D.Through the deliberate or inadvertent release to the environment, contaminants have polluted the nation's waterways leaving a residual of refractory pollutants that reside in sediments. The Bayou d'Inde is a tributary of the Calcasieu River outside Lake Charles, Louisiana that has been contaminated by several industrial pollutants including hexachlorobenzene (HCB). Due to HCB's high organic carbon partition coefficient (Koc), its availability to reducing microorganisms is extremely limited and natural attenuation has been found to be ineffective at reducing HCB concentrations in-situ. The effectiveness of an active cap is being evaluated to reduce contaminant flux to the benthos and water column. This study was designed to explore the fate of chlorinated benzenes during capping of the contaminated sediment, specifically the fate associated with zero-valent iron in an active capping layer. Experiments exploring the degradation of chlorinated benzenes with mirco-scale and nano-scale zero-valent iron and the potential for zero-valent iron as an active capping material to encourage dechlorination under environmentally relevant and ideal conditions were carried out. Less than 1% of the chlorinated benzenes were observed to dechlorinate within 48 hours by micro-scale zero-valent iron and transport through a 1.25 cm thick CETCO mat would dechlorinate 8% of the mobile hexachlorobenzene before release to the water column. That is why zero-valent iron should not be employed as an active capping material in the Bayou d'Inde for the purposes of reductively dechlorinating chlorinated benzenes.