Thesis (M. Sc.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 53-69).

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains ix, 58 p. : ill. Includes abstract. Includes bibliographical references (p. 49-50).

Thesis (doctoral)--University of Helsinki, 1981. / Errata slip and notice of public dissertation discussion inserted. Includes indexes. Includes bibliographical references (p. [299]-336).

Thesis (doctoral)--University of Helsinki, 1981. / Errata slip and notice of public dissertation discussion inserted. Includes indexes. Includes bibliographical references (p. [299]-336).

No description available.

The longterm fate of petroleum in four marine environments was Investigated: The fate of petroleum on the surface of the ocean was elucidated by undertaking a detailed study of petroleum residues polluting the Pacific Ocean. First, the extent of contamination of the Pacific by petroleum residues was assessed by measuring the amounts of tar in 2092 neuston tows over a nine-year period (1967-1975). The South Pacific was found to be free of tar; the Northeast Pacific was slightly polluted, with an average of 0.03 mg/m² . The Northwest Pacific, particularly the Kuroshio current system, was the most severely polluted area: all 55 tows between 25° and 40°N in the Northwest Pacific were contaminated. The average concentration in that area 2 was 2.1 mg/m² , representing a standing stock of about 25,000 metric tons of tar. Chemical analyses of the tar as well as its distribution pattern strongly imply that it originates primarily from tanker traffic, and from tanker sludge in particular. The pollutants appear to be discharged by tanker on the very large Middle East to Japan tanker route, then become entrained in the Kuroshio current and create a plume of contamination which extends downstream for 7000 kilometers across the Pacific. Initially evaporation is the most important weathering mechanism acting on the tar, removing component up to the volatility of pentadecane over a period of days or perhaps weeks. Thereafter, microbial degradation is dominant, probably acting for over a year on many particles. Both of these processes increase the density of the residues, and this effect, combined with the overburden of fouling growth that develops, eventually results in the slow sinking of the tar into the depths of the ocean. The fate of petroleum in the intertidal environment was studied by following the natural degradation of the oil after a small (200 ton) oil spill of #5 fuel oil. The most important weathering process was microbial degradation. Evaporation played only a minor role, while photo-oxidation and dissolution had no apparent effect. The microbal attack took approximately one year to complete the degradation of the n-paraffin fraction of the spilled oil, leaving a thin asphaltic residue on the beach. The combined effect of microbial degradation and abrasive weathering removed roughly 95% of the oil from the beach over the period of a year. The fate of oil in the benthic environment was studied by treating 500 ml quantities of crude oil with a commercial sinkant, then placing the oil on soft sediments in about 6 meters of water. Again in the benthic environment, microbial action was the process responsible for the degradation of the oil. Evaporation had no opportunity to act, dissolution was ineffective, and photo-oxidation did not occur because of the low energy and intensity of the light reaching the sediment. The benthic petroleum samples were slow to degrade: the oil remained unchanged in chemical composition for at least 6 months, and after 16 months the n-paraffins were only partly degraded. Oil dissolved in the water column was investigated by adding a spike of #2 fuel oil to an enclosed column of water 2 m in diameter by 15 m deep, and monitoring its fate by fluorescence spectroscopy. For water a meter or two in depth, exchange with the atmosphere played the dominant role in removing the hydrocarbons from the water column, but at 7 m and below, microbial degradation and sedimentation were the more important processes. The disappearance of the oil approximately followed an exponential decay curve. The half life for a large dissolved oil spike was about 3 days (less for a smaller spike) so that 95% removal occurred within 2 weeks. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Thesis (M. Sc.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf [64-67]).

The rise in global energy demand has motivated the exploration and production of oil and gas in increasingly challenging marine environments and there is a continuous risk of accidental oil spills. One of the many fates of spilled oil is deposition on the seabed, which has been extensively studied following the Deepwater Horizon oil spill. However, post-depositional fates of oil in sediments are not well understood. Similarly, the effects of chemical dispersant on oil fate are currently under investigation as their overall contribution to mitigating oil spills environmental impacts remains debated. This project aimed to evaluate the potential for spilled oil to entrain marine sediments and the effects dispersant application had on the process under three transport regimes; (1) post-depositional transport via oil-sediment aggregate deposition in deep-sea sediments, (2) percolative transport in intertidal sands and (3) advective pore-water transport in intertidal and subtidal sands. Investigations into the sorption dynamics of two polyaromatic hydrocarbons in sediment-dispersantseawater systems were also undertaken to evaluate the influence of dispersant application on sorption of hydrocarbons to sediments. Finally, the effects of oil exposure at in situ conditions of pressure and temperature on sediment bacterial community composition were investigated. Oil transport experiments revealed that the tested regimes resulted in significant entrainment of hydrocarbons in marine sediments. Dispersant application resulted in enhanced oil entrainment into sands but not in silts and this effect depended on the water-solubility of hydrocarbons. Watersoluble components were less affected by dispersant than less water-soluble ones. Investigations into sediment bacterial responses to oil exposure at in situ conditions of pressure and temperature revealed a significant effect of both variables on diversity and community composition, highlighting the importance of conducting deep-sea microbial studies at conditions as close to in situ as possible.

Seagrasses provide an important habitat for gillfish, crustacea and migratory birds. Extensive losses of seagrass in the Northern Hemisphere have occurred since the 1930's in what has been described as a 'wasting disease'. More recently, point-source contamination by nutrient inflows, herbicides (anti-fouling agents used on commercial shipping), heavy metals and fresh water inflows have helped explain localised losses of seagrass amounting to 20% in the case of Adelaide's metropolitan coastline, South Australia. However, losses of seagrass acreage have also occurred in regions that are far removed from anthropogenic activity and these are less easily explained by pointsource contamination. Intertidal seagrasses, such as Zostera muelleri, are subjected to environmental pressures imposed on them by the marine and terrestrial environments. For the purpose of this thesis, the intertidal environment is regarded as a complex of several components or micro-environments, each imposing a selective pressure or stress upon seagrass. The many stress factors create a tolerance zone in which Z. muelleri can survive. Zostera muelleri has adapted its physiology and biochemistry to the selective pressures that operate within the intertidal region. Zostera muelleri's internal leaf morphology has many gas storage compartments (lacunae) that extend from the leaves to the roots of the plants and its photosynthetic biochemistry has also adapted to the intertidal region enabling the sequestering of carbon under conditions of high irradiance and temperatures. It is evident from the literature that the survival of intertidal seagrasses requires effective photosynthesis. It is also evident that events that interfere with the synthesis, translocation and release of photosynthesised oxygen from the roots of Z. muelleri will compromise seagrass survival. The present study has revealed that herbicides, used in broad- acre farming, can be transported to the intertidal environment and negatively impact upon Z. muelleri. Extensive studies by others have shown that transport mechanisms, such as 'spray drift' and 'run-off', can move herbicides from their point of usage. However, 'dust' (wind-eroded soil ) as a transport mechanism for herbicides to the intertidal environment is less well studied. This is surprising, inasmuch as there is a known rate of pedogenesis in Adelaide of five to ten tonnes per km2 per annum from the accretion of dust. Results of the present study suggest that farmed soils of the Yorke Peninsula have a range of potentials to form fine particulate matter ('dust') and this potential is likely determined by the soil type and farming practices. Soil surface applied herbicides, such as 2,4-D, are 'lost' from land at 5% of the applied rate while soil-incorporated herbicides, such as treflan (trifluralin), are lost at 1.5% of the applied rate. Indeed, such herbicides can be transported as dust for tens to thousands of kilometres. Instrumental analytical techniques used in the present study have detected 2,4-D, trifluralin and sulfonylurea herbicides on whole soil. Additionally, 2,4-D- like chemicals have also been detected in whole soil and in dust obtained from whole soil. Bioassay techniques using Z. muelleri have shown that its photosynthetic pathways are negatively impacted upon by micromolar concentrations of 2,4-D that are similar to the known losses of this herbicide from land. It is concluded that, at these concentrations, 2,4-D acts as an auxin, up-regulating growth in affected plants. Such up-regulation is unlikely to be problematic in terrestrial plants since gas flows to the external environment are largely controlled by stomata. However, seagrasses lack stomata and the auxin-like activity of 2,4-D appears to have a negative impact on Z. muelleri. This is probably caused by an up - regulation in oxygen production and a subsequent oxygen-inhibition of a key enzyme ( ribulose 1,5- bisphosphate carboxylase, RUBISCO ) used in the carbon-sequestering photosynthetic process. The proposed inhibition of RUBISCO is then likely to cause a carbon deficit and a subsequent energy deficit within affected plants. One interpretation of the results presented is that Z. muelleri simply outgrows its intertidal environment after a transient exposure to an auxin-like concentration of 2,4-D. With increasing use of auxin-like herbicides, and the associated increasing stress imposed on photosynthetic processes, it is likely that further negative impacts will occur on intertidal seagrass species. Continued depletion of seagrass acreage will further adversely affect fishing yields unless appropriate measures are not taken. Closer collaboration between regulators, farm managers and herbicide manufacturers is now necessary in order to minimise the negative impact of herbicides on intertidal species. / Thesis (M.App.Sc.)--School of Earth and Environmental Sciences, 2005.