No description available.

Many sites world-wide are contaminated with a range of pollutants of environmental concern. Bioremediation has the potential to be a cost-effective and efficient alternative clean-up technology. The success of bioremediation is influenced by both biological and environmental factors. A site, therefore, needs extensive characterisation to determine the extent of contamination and to evaluate the potential for bioremediation. Chemical analysis has traditionally been used to determine pollutant concentrations, but it provides no information about the bioavailability of the pollutants. Bioassays are able to complement chemical analyses by showing the bioavailability and ecotoxico logical effects of pollutants. Bioluminescent bacteria have been adapted as biosensors where the response to environmental stresses is monitored by a reduction in light output. Only metabolically active cells produce light and any substance or environmental condition which impairs cell metabolism and, thus, compromises cellular activity and viability will lead to a reduction in light output. Naturally bioluminescent marine bacteria (e.g. Vibrio fischeri) have been used for ecotoxicity testing, but soil and freshwater bacteria that have been marked with lux genes have several advantages. These genetically modified biosensors do not require high salinity and a neutral pH, and they have environmental relevance. A suite of biosensors has been developed at the University of Aberdeen that responds to a wide range of pollutants. These biosensors have been successfully used for acute ecotoxicity measurements. The research carried out in this study was part of a larger ICI project for the assessment and management of bioremediation of a BTEX contaminated site. The aim of this study was to develop a lux-marked biosensor based on a BTEX-degrader. None of the existing biosensors are known to be degraders. Environmental isolates from the ICI site that were able to degrade BTEX were characterised and assessed for their suitability for lux-marking. An appropriate isolate was selected for lux-marking, but the marking was not successful. It was concluded that there are several problems associated with obtaining suitable isolates in pure culture from a site. The enrichment, isolation, identification and characterisation of isolates is laborious and time-consuming, and the lack of characterisation of the isolates can complicate the Iwc-marking attempts. Selecting a well-characterised bacterium for lux-marking avoids these problems. Therefore, Pseudomonas putida FI was selected as the bacterium for lux-marking as a biosensor in this study. It was selected because it is a toluene-degrader and the degradative genes are located on the chromosome. P. putida FI also has environmental relevance for the ICI site. P. putida FI and P. putida FI06 (an isogenic mutant of P. putida FI) were lux-marked with the plasmid pUCD607, and P. putida FI and FI06 pUCD607 were characterised. Characterisation of P. putida FI and FI06 pUCD607 suggested that pUCD607 was not stable even under selective conditions due to segregational instability. This study, therefore, concluded that the plasmid pUCD607 is not appropriate for lux-marking bacteria as biosensors. P. putida FI was lux-marked with the mini-Tn5 luxCDABE transposon and P. putida FI Tn5 luxCDABE was characterised. The integration of the mini-Tn5 luxCDABE cassette did not affect growth of P. putida FI Tn5 luxCDABE and luminescence levels were higher than in P. putida FI pUCD607. P. putida FI Tn5 luxCDABE was also stable in the absence of selective pressure over time. This study, therefore, concluded that the mini-TnJ luxCDABE transposon is appropriate for lux-marking bacteria as biosensors.

Ph.D.

No description available.

No description available.

Human activity has affected metal emissions to the atmosphere on a global scale for several thousand years, resulting in widespread contamination of the environment with toxic heavy metals such as Pb and Hg, thereby threatening both human and environmental health. In recent years ombrotrophic peat bogs have been used to study the changing rates and sources of atmospheric metal deposition, as they receive all their water and nutrients from the atmosphere by dry and wet deposition alone. Cores from such bogs have proved especially useful as archives of atmospheric Pb deposition as Pb is essentially immobile in ombrotrophic peat. The work described in this thesis is primarily concerned with the use of ombrotrophic peat bogs to investigate environmental contamination in Scotland during pre-industrial, industrial and post-industrial (i.e. ca. post-1970 A.D.) times. Cores were collected from ombrotrophic peat bogs at four different geographical locations (Carsegowan Moss, SW; Flanders Moss, W Central; The Red Moss of Balerno, E Central; Turclossie Moss, NE) in Scotland. Air-dried peat samples were dry-ashed and dissolved using microwave-assisted HF IHN03 digestion. Elemental concentrations (e.g. AI, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Sc, Se, Ti, V, Y, Zn and Zr) and Pb isotope ratios (e.g. 206PbP07Pb) were determined using ICP-OES and ICP-MS as appropriate. For Hg determination, samples were digested with HN03/H2S04 and then analysed by CV AAS. Certified reference materials (e.g. Ombrotrophic Peat (NIMT/UOE/FM001), Canadian Peat (1878 P), Bush Branches and Leaves (DC73349), Peach Leaves (GBW 08501) and Coal (BCR CRM No. 40 and NBS SRM 1635) were used for quality control purposes. The distribution and behaviour of the potentially toxic trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Sb, Se, V and Zn) and of major elements (Ca, Fe, Mg, Mn, P and S) within the four ombrotrophic peat bogs was investigated and there was strong evidence that Ca, Fe, Mg, Mn, P, S, Se and Zn were mobile in ombrotrophic peat, while As, Cd, Co, Cr, Cu, Hg (at least during industrial and post-industrial periods), Ni, Sb and V, like Pb, were essentially immobile in ombrotrophic peat. Deposition records of conservative lithogenic elements (e.g. concentrations of AI, Sc, Ti, Y and Zr) that occur predominantly in soil dust were also investigated and the chosen conservative elements Sc, Ti and Zr were used in calculations to estimate anthropogenic enrichments of As, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in peat bog profiles. 210Pb- and 14C- dated peat cores were used to reconstruct historical records of atmospheric anthropogenic As, Cd, Co, Cr, Cu, Ni, Pb, Sb and V deposition (since the pre-Roman (i.e. to ca. 380 B.C.)/Roman period) and atmospheric Hg deposition (since the onset of the industrial period) across Scotland. For Pb, on the basis of Pb isotopic composition (e.g. 206PbP Pb), clear indications of contamination during the preRoman/Roman and Mediaeval periods were attributed to the mining and smelting of Pb ores (from Britain and elsewhere in Europe). During the industrial and post-industrial periods, variations in the relative importance of contributions of anthropogenic Pb from different sources were apparent. From ca. the early 17th century A.D. at three of the peat bog sites, the mining and smelting of indigenous Scottish Pb ores, until the early 20th century A.D., were found to be the most important sources of anthropogenic Pb deposition. In contrast, at the most southerly site (Carsegowan Moss), influences from the use of both British Ph ores and imported Australian Ph ores (in more southern parts of Britain) since the late 19th century A.D. were evident. At each of the sites, the increasing importance of Australian-Ph-influenced car-exhaust emissions from the 1930s to late 1990s A.D., along with significant contributions from coal combustion (until the late 1960s A.D.) was evident. For Sb, in general, similarities between the major trends in the concentration profiles of anthropogenic Sb and Ph suggested common sources of these two elements. Perturbations in the anthropogenic Sb/Pb ratios since ca. 1800 A.D., however, were attributed to temporal variations in the relative importance of atmospheric emissions from different sources such as Ph ore mining/smelting, coal combustion and, in recent decades, automobile-related use of compounds of Ph (in leaded petrol) and of Sb (in brake linings). For Hg, in general, during the industrial and post-industrial periods, coal combustion and waste incineration, respectively, were likely to be the most important sources of Hg. For As, clear indications of contamination during the Mediaeval period were probably attributable to the mining and smelting of Ph and Cu ores, and for As, Cd, Co, Cr, Cu, Ni and V, during the industrial and post-industrial periods, a variety of sources (e.g. metallurgical activities, coal and oil combustion, use of phosphate fertilisers and waste incineration) were important to varying extents. Also, in recent years, atmospheric Cu emissions from automobile-related use of compounds of Cu (in motor oil, brake linings and tyres) may have been important. Inter-site and inter-elemental comparison of records of atmospheric metal deposition across Scotland indicated that, in general, atmospheric As, Cr, Hg, Ph and Sb deposition was greatest during the industrial period (between the late 1880s and late 1960s A.D.) and atmospheric Cd, Co, Cu, Ni and V deposition was greatest during the industrial and post-industrial periods (between ca. 1900 and the early 2000s A.D.), although increases in As, Co, Cr, Hg, Ph and Sb deposition were earliest (during the late 19th and early 20th century A.D.) at the most southerly site (Carsegowan Moss). During the industrial and post-industrial periods, levels of As, Ph and Cd contamination were generally highest in the south of Scotland, Cu, Co and Sb in south and central Scotland, and Cr, Ni and V in central Scotland. Overall, the existence of a south to north As, Cd, Co, Cr, Cu, Ni, Ph, Sb and V pollution gradient in Scotland was evident.

No description available.

No description available.

No description available.

No description available.