This thesis reports a series of experiments investigating some aspects of seasonal C and nutrient cycling and microbial community responses in an alpine heathland under three environmental pressures: N deposition represented by N additions at four levels (0, 10, 20, 50 kg N ha^-1 yr^-1), climate change simulated by open top chambers (OTCs) and accidental burning (one low intensity fire event that occurred in autumn 1999). The Culardoch experimental site was used, which is located on an alpine heathland in the Eastern Cairngorms mountains, Scotland. The responses studied were related to litter decomposition dynamics, soil processes and the soil microbial community. Mass loss and nutrient status during decomposition of litter from the plots (“native”) and collected outside the plots (“standard”) were studied. Litter decomposition was not affected significantly by the treatments. Despite the decrease in initial C:N ratio by N additions, this treatment affected only phosphomonoesterase activity and a trend for increasing glucosidase and xylosidase activity with increasing N additions was seen. OTC impacts were limited to effects on P cycling in “native” decomposing litter in the later stages of decomposition and more P was accumulated in litter from the plots with the OTCs. Burning affected N cycling in “native” decomposing litter (more N was accumulated in litter incubated in the burnt plots) and mass loss, C, N and P content in “standard” litter. Increased cellulolytic activity was observed in litter from the burnt plots. Those changes were attributed to shifts in the bacterial and fungal communities due to burning and warming treatments, while N additions had only a minor effect on microbial community structure. Decomposition phase had the greatest effect on microbial community structure suggesting that a succession of communities occurred during decomposition. One of the most important findings was the lack of interactive effects among the three main treatments, indicating that they act independently on particular components of the ecosystem.

Submitted in partial fulfilment for the Master of Technology Degree: Chemistry, Durban Institute of Technology, 2003. / In urban environments motor vehicles are by far the largest source oflead. In areas subjected to heavy and slow moving vehicular traffic, the amount of lead exhausted may be quite high. Since exhaust fumes settle on kerb-sides, soil samples from these areas may not only give a good measure of the accumulation of lead but also eliminate the need to risk expensive sampling equipment in collecting air samples. In order to determine the levels of lead and other toxic metals such as chromium, cadmium, nickel, copper and aluminium, soil samples were collected from kerb-sides and road islands around the City of Durban and along the national road N3 in the vicinity of Shongweni. City, peri-urban and rural roads were selected for sampling. In a preliminary study, kerb-side dust from one of the streets with very heavy vehicular traffic was collected. It is also a street where many vendors have food stalls. The horizontal distribution of metals as a function of distance from the kerb was determined by analyzing samples which were collected at various distances from the edge of a road. The determination of vertical distribution of metals in the soil was also performed. Samples for this work were collected by digging 0 to 2 cm, 10 to 15 cm and 20 to 25 cm deep at various points along the National Highway (N3). 111 Some sub-samples were leached at pHs found in soils using a Hazardous Waste Filtration System while other sub-samples from the same gross sample were aciddigested in a Microwave Digester. The analyses were done using ICP-ABS, AAS and GF-AAS. As expected the values for lead were the highest for urban sites and lowest for rural ones and values from leaching experiments were lower than those for digested samples from the same site. Taken over all sites, the values for lead ranged from 0.02 to 298 ppm for leached samples and from 25 to 1900 ppm for digested samples. / M

No description available.

For the past several decades, industry has filled lagoons and landfills with significant quantities of polychlorinated biphenyls (PCBs). Other wastes such as carbon tetrachloride and various alcohols have mixed with PCBs. Soil columns spiked with Aroclor 1242 were leached with such solvents. Ninety-one days of deionized water flow did not move a detectable amount of Aroclor 1242 more than 2 cm. through soil columns. Sixty-nine days was sufficient time for an alcohol mixture to carry Aroclor 1242 over 7 cm, the soil depth of the column. Five days was sufficient time for carbon tetrachloride: ethanol to carry Aroclor 1242 the same distance. A mixture of organic solvents can promote mobility of lipophilic organics such as polychlorinated biphenyls in the soil when water alone would not be effective. While assessing the extent of a chemical spill or the contamination resulting from improper disposal, it is clear that the interactions of chemical contaminants must be considered. / Department of Natural Resources

Thesis (Ph.D.)--Tennessee Technological University, 2007. / Bibliography: leaves 172-182.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 54-55).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 185-190.).

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Apr. 21, 2009). Includes bibliographical references.

Thesis (Ph. D.)--Washington State University, August 2006. / Includes bibliographical references (p. 64).

No description available.