Soil microcosm experiments were conducted to identify soil amendments which enhance the biodegradation of a No. 2 (diesel) fuel in soil. Microcosm amendments in Phase 1 included yeast extract, acetate, methane, and activated sludge. Combinations of these amendments resulted in 16 different treatments. Phase 2 soil microcosms contained combinations of methane and methanotroph additions resulting in four different treatments. Gas chromatography was used to determine the time and treatment-dependent concentration of C12-C18 n-alkanes during Phase 1 and, C14-C19 n-alkanes during Phase 2. Results from Phase 1 indicated that the most extensive biodegradation occurred in methane and activated sludge-supplemented microcosms. Acetate and/or yeast extract inhibited biodegradation by soil and/or activated sludge microorganisms. Addition of methane relieved inhibition by these amendments. Methane and/or methanotroph additions to Phase 2 microcosms did not enhance biodegradation relative to unamended microcosms. In general, n-alkanes longer than n-C12 were equally degraded in soil microcosms.

No description available.

A polyphasic approach was used to examine the impact of contamination on soil microbial community structure. Two systems were examined using a combined biochemical and molecular biological approach. Petroleum hydrocarbon contaminated soils from two Northern Canadian sites, representing long-term contamination, were examined using Biolog GN plates and PCR-denaturing gradient gel electrophoresis (DGGE) analysis of total community 16S rDNA. Results obtained using both methods demonstrated a positive correlation between samples that was based on the geographical origin of the samples, not on contamination level. In the second system, non-contaminated soil was contaminated with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to monitor the effect of short- to medium-term contamination. Changes in the soil microbial community were examined using PCR-DGGE of total community 16S rDNA combined with RDX mineralization and chemical analysis of intermediates. The non-contaminated loam soil had an inherent RDX degradative capability and contamination of soil columns with 1000 mg RDX/kg soil did not significantly change the 16S rDNA bacterial community profile. The bacterial diversity remained high as estimated by the number of bands present in the DGGE and by NQ-78704 statistical rarefaction analysis of 16S rDNA clone RFLPs. The same soil, used in 10% soil slurries (w/v), demonstrated two apparently different RDX degradation mechanisms based on mineralization and chemical analysis. The differences were based on aerobic versus anaerobic conditions and the presence/absence of Na3 citrate. PCR-DGGE performed on 16S rDNA from aerobic slurries amended with Na3-citrate detected the stimulation of 3 operational taxonomic units, identified as Stenotrophomonas sp., Sphingomonas sp. and a member of the Alcaligenaceae. The results from the two systems examined (short- to medium-term and long-term contamination) demonstrated the utility of a polyphasic approach in the examina

No description available.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2009. / In the last two centuries, the natural state of the environment has changed significantly due to anthropogenic activities. With an estimated half-life of 15 - 1100 years for cadmium in soils, the metal remains a threat to the ecosystem. In general, most soils contain <1 mg/kg, except those contaminated from discrete sources or developed on parent materials with very high cadmium contents. Anthropogenic lead in soil has several well recognized major sources, namely, lead based paint, mining and smelting activities, manures, sewage sludge usage in agriculture and contamination from vehicle exhausts. Since lead is a heavy metal, over time it will settle down and build up in soil. The main aim of this study was to determine the degree of cadmium and lead contamination of soil, in and around selected pre-school facilities in the City of Cape Town (CCT). A number of pre-school facilities, particularly those nearby heavy traffic, were selected in the CeT. Natural soil and sand pit soil samples were collected and analysed for cadmium and lead. Low soil moisture is normally associated with high pH, as found in the present study. High pH values are in turn associated with low toxicity of metal contaminants. Most urban populations rely heavily on motor vehicles and vehicle-related pollution has been an increasing concern in recent years (before 2006). Air pollution in the CCT is trapped by inversion layers. In this study it has been found that cadmium is not a significant contaminant in the soils of pre-school facilities in the CCT. The Cape Town administration area was found to be the most contaminated with this metal. This study showed that the Cape Town administration area also had the highest lead concentrations in pre-school soils in the CCT. This can be attributed to the higher density of industry and traffic activities (study conducted pre-2006) in this area. There is a need for further research to determine the relationship between soil metal concentrations and blood metal levels, especially in children.

Biofilm formation may increase survival and persistence of Escherichia coli in the highly variable conditions of soil environments, though it remains unknown the extent variation in biofilm formation affects survival. We asked what genetic traits influence biofilm formation in phylogroup D E. coli isolates from surface soils, and are they associated with the soil environment? Biofilm density was analyzed and compared with soil environment characteristics. Isolates produced more biofilm per unit growth at 15°C than 37°C. Biofilm formation was greater in soil isolates than fecal isolates and in soils with moisture and higher calcium and pH levels. A GWAS analysis found variants involved in cell envelope formation and structure were associated with biofilm formed at 37°C, and stress response and iron acquisition variants were associated with biofilm formed at 15°C. Motility variants were associated with a negative effect on biofilm formed and adhesion variants associated with a positive effect. / National Science Foundation (NSF) award no. DEB-1453397 to P.W.B. / ND-EPSCoR

Traditionally, local above- and below-ground plant and microbial communities, temperature and precipitation, topography and texture and composition of parent material have been thought to govern the soil processes that lead to soil organic matter accumulation over decades or centuries. Soil organic matter is a substantial global reservoir of carbon and disturbance of equilibrated soils often leads to efflux of significant quantities of CO2. Anthropogenic influences shift the inputs, disturb the structure and alter the biochemistry of soil, profoundly disrupting soil-forming processes. Urbanization leads to soil organic matter equilibria that are different from those in naturally forming soils. Measurement of soil organic matter in diverse cities suggests that they differ in their capacity to accumulate soil organic matter. Here I quantify soil organic matter and examine the limitations of its accumulation within cities by comparing differences in soil organic matter and natural and anthropogenic characteristics at the neighborhood, city and regional scales in Portland, Oregon to that in the Pacific Northwest. I found that each Portland neighborhood has distinct urban characteristics and tree and shrub community composition, but soil organic matter content is indistinguishable among them. Across Portland, neither vegetation structure nor urban factors appear to directly influence soil organic matter content. Rather, microbial biomass, bulk density and total nitrogen appear to be important factors controlling soil organic matter content in Portland. The amount of soil organic matter stored in Portland's soils is statistically indistinguishable from Pacific Northwest soils, in contrast to other temperate cities.

No description available.

The effects of artificially supplied perennial water on soil properties, vegetation dynamics and the distribution of large herbivores was investigated in southeastern Zimbabwe. Data collection took place between March 1997 and July 1998. Water points were situated primarily on three different soil types (clay-loam, sandy-clay-loam and sand), and in four different vegetation types (Hill communities, Colophospermum mopane veld, Acacia nigrescens woodland and Albizia petersiana woodland). One water point in C. mopane veld (Bandama) had been closed two years prior to data collection, while another, in the Hill community (Manyoka), had been introduced, two years prior to data collection. Changes in physical (infiltration) and chemical (organic carbon and nutrients) properties of soils around water points were largely restricted to within 100 m of water. Chemical enrichment of the soil occurred only at water points that had been in place for more than two years. Soil surface conditions were altered to distances beyond 100 m from water. Manyoka (the new water point) was an exception, with extreme changes limited to within 100 m of water. Herbaceous and woody species composition changed in response to distance from water with changes best described by asymptotic equations. Changes in species composition of the woody component appeared to be longer lasting than changes to the herbaceous component. Most perennial grass species declined close to water, but Urochloa mosambicensis increased close to water in areas outside of the Hills. Herbaceous species diversity was adversely affected by distance from water on sandy soils (Hill communities and A. petersiana woodland), but was largely unaffected on clay-loam (A. nigrescens woodland) and sandy-clay-loam soils (C. mopane veld). Woody species composition and density was altered out to 500 m from perennial water in Acacia nigrescens woodland on clay-loam soils. Results suggest that this vegetation type may be susceptible to bush encroachment close to water. Trends in woody canopy utilisation were generally similar to trends in woody species composition, and it is proposed that the former may be used to indicate future changes in the latter. Conversion of trees to shrubs was highest at Manyoka (the new water point) indicating that woody destruction by elephants is extreme during the initial years following water introduction. Large herbivore biomass was greatest close to water (< 1 km) during the dry season but not during the wet season. Herbivore species distributions appeared to be influenced by the position of perennial water, but since all range was within easy access of water, it is unlikely that animal distributions were constrained directly by the position of surface water. It is more likely that herbivores were spatially separated on the basis of habitat type. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.