Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
5 results
Search Results
Item Methods of neutralizing cyanide in mining wastes and waste waters(Montana State University - Bozeman, 1989) Rolfes, Herbert Steven; Chairperson, Graduate Committee: Frank F. MunshowerItem Linking microbial populations and geochemical processes in soils, mine tailings, and geothermal environments(Montana State University - Bozeman, College of Agriculture, 2004) Macur, Richard Eugene; Chairperson, Graduate Committee: William P. Inskeep.The primary goal of this work was to identify and characterize the microbial populations responsible for transformations of As and 2,4-D in soils and waters. Chemical, spectroscopic, and microscopic techniques were used to characterize the aqueous and solid phase geochemistry of soils, mine tailings, and a geothermal spring. The role of specific microbial populations in these systems was examined using cultivation-independent molecular methods [total DNA extraction, 16S rDNA amplification, denaturing gradient gel electrophoresis (DGGE), and sequence analysis] coupled with either characterization of microorganisms isolated from the same systems, or inference of physiological characteristics from (i) closely related (16S rDNA sequence) cultured microorganisms and (ii) the geochemical environments in which they were detected. The microbial reduction of As(V) to As(III) and the subsequent effects on As mobilization in contaminated mine tailings was examined under transport conditions. Enhanced elution of As from mine tailings apparently resulted from the enrichment of aerobic As(V)-reducing Caulobacter leidyi, Sphingomonas yanoikuyae, and Rhizobium loti -like populations after liming. Arsenite was rapidly oxidized to As(V) via microbial activity in unsaturated Madison River Valley soil columns. Eight aerobic heterotrophic bacteria with varying As redox phenotypes were isolated from these columns. Three isolates, identified as Agrobacterium tumefaciens, Pseudomonas fluorescens, and Variovorax paradoxus -like organisms, were As(III) oxidizers and all were apparently important members of the soil microbial community responsible for net As(III) oxidation. Successional changes in microbial communities colonizing an As-rich acid-sulfate-chloride geothermal spring stream channel in Norris Geyser Basin of Yellowstone National Park were examined. Enhanced As(III) oxidation correlated in time and space with the appearance of three Hydrogenobaculum -like populations. The formation of an As(V)-rich hydrous-ferric-oxide mat correlated with the detection of Thiomonas, Acidimicrobium, and Metallosphaera —like populations whose nearest cultivated relatives (based on 16S rDNA sequence) were Fe-oxidizers. Fingerprints of microbial communities (DGGE) established under increasing concentrations of 2,4-D (0 - 500 mg kg'1) in batch soil microcosms showed that at least 100 mg kg'1 2,4-D was required to obtain apparent shifts in community structure. The microbial community selected at high 2,4-D concentrations was predominantly composed of Burkholderia -like populations, which harbored homologs of tfdA genes.Item Residual cyanide distribution in a neutralized gold leach heap(Montana State University - Bozeman, College of Agriculture, 1994) Poell, James G.Item The effect of land application of neutralized cyanide solution on soil salinity and sodicity(Montana State University - Bozeman, College of Agriculture, 1996) Yang, Lih-AnItem Microbial and geochemical processes controlling the oxidation and reduction of arsenic in soils(Montana State University - Bozeman, College of Agriculture, 2007) Masur, Deanne Christine; Chairperson, Graduate Committee: William P. Inskeep.Arsenic (As) is a common contaminant in soil-water systems, where it exists predominately as arsenate (AsV) or arsenite (AsIII), the latter of which is considered to be the more mobile and toxic form. The amount of arsenite or arsenate in natural water systems is influenced by geochemical conditions and the presence of As transforming microorganisms. Consequently, the goals of this study were to evaluate the effects of: (i) arsenic concentration on microbial populations responsible for As oxidation-reduction in a previously uncontaminated soil, and (ii) phosphate:arsenic ratio on the oxidation or reduction of arsenic. Laboratory column experiments were conducted to evaluate the influence of soil arsenic concentration on microbial community composition and to identify microorganisms and mechanisms responsible for As transformations occurring under aerobic conditions. Indigenous microorganisms within a previously uncontaminated agricultural soil were exposed to arsenite or arsenate at three concentrations (2, 20 and 200 mg As L-1) for approximately 30 days.