The risk to groundwater quality following a sub-surface spillage of immiscible pollutants such as oil, petroleum and other organic chemicals is an increasingly potent threat, through escalating industrial application of such pollutants. This study significantly enhances the understanding of the flow of immiscible pollutants within soil, through field scale investigations to define the spatial variability and extent of a contaminated area and the development of a comprehensive framework for the analysis of oil pollutant migration. This study represents a first attempt by researchers to analyse oil pollutant migration on a wide range of scales, from pore- to field-level. The research shows that quantity of pollutant is a critical factor in determining the extent of oil migration. Permeability and porosity of the sample material are also important secondary factors. High permeability assists the migration of oil pollutants. Soils with a high porosity allow the pollutant to migrate vertically under the influence of gravity, whereas soils with low porosity induce lateral oil migration, as the oil spreads from the point of injection. A Jull scale field study using contrasting soil types determines that oil migration is approximately symmetrical about the point of injection. Experimental data is used to establish modelling capabilities for the characterisation of pollutant migration. Modelling is undertaken at two levels. The first consists of the development of simple Gaussian equations based upon observations of oil glomuses. The glomus approach, newly developed in this work, can be compared to a fractal model, with the glomuses observed in each of the different scales studied.

Uranium and thorium are the only elements in the actinide series which naturally occur in the environment in sufficient amounts for practical extraction. They are both radiotoxic and chemotoxic to humans due to the effects of the ionising radiation produced by their radioactive decay, the decay of their daughter products, and due to the chemical toxicity resulting from absorption into the body. Thus it is important to be able to quantitatively determine the levels of uranium and thorium in the environment. Measurement of low levels of uramum and thorium in the presence of high levels of inorganic and organic matrix components has been achieved by coupling on-line solid phase extraction (SPE) with inductively coupled plasma mass spectrometry (ICP-MS) detection. This allowed direct analysis of water samples without any sample pre-treatment offering detection Umits of 0.01 ng ml uranium and 0.006 ng ml thorium. However, in many studies not only do the total levels of uranium and thorium need to be determined, but also their speciation, since this can effect their toxicity and mobility in the environment. An on-line uranium speciation method has successfiilly been developed using a chelating resin micro-column attached to an ICP-MS. This method has been applied to the analysis.pf natural water samples (from Dartmoor, Devon, UK) and the results obtained indicate that the uranium-organic species such as those formed with humic substances are the major species present. A comparison of the pH and level of organic carbon (in a range of natural and synthetic water samples), with the level of uraniumorganic species indicates that the organic carbon concentration is a controlling factor in determining the level of uranium-organic species formed. The kinetics of dissociation of uranium and thorium-humic substance species was also studied. The slow rate of dissociation, observed indicates that once the uranium-humic species have formed these species could remain in the environment for some time. These studies also indicate that even if a change in environmental conditions affected the speciation,it would take time before the uranium and thorium-humic species dissociated and the system equilibrated to a new speciation profile. Two computer programs (WHAM and PHREEQCI) were used to model uranium and thorium speciation in aquatic systems. The Nuclear Energy Agency Thermocheraical Database Project (NEA-TDB) values were incorporated into both programs, as differences in the thermodynamic data provided with the two programs were found to have a major effect on the predicted speciation profiles produced by the two programs. Using the NEATDB values, both programs produced similar inorganic speciation profiles for a given aqueous system but when an organic carbon component was added to the system the two programs produced different predictions for the level of uranium-organic species. This reflected the different organic speciation components utilised within the two programs. WHAM uses a discreet site electrostatic humic substance model and PHREEQCI uses an analogy type model based on a 'model fulvic acid' dataset. A comparison of model predictions with experimental data for the same water sample, indicates that the WHAM program produces closer predictions to the experimental results than the PHREEQCI program. A fiirther study of the WHAM program, using synthetic water solutions with a range of pH, organic carbon and uranium concentrations, indicates that the program has a bias towards low predictions at high pH and low organic carbon concentrations (pH>7, organic carbon < 0.5 ug ml), but wil function satisfactorily within the range of conditions found in the natural (Dartmoor) water samples. The results of these studies should aid environmental investigation based on uranium and thorium where model predictions are to be used.

To further a quantitative understanding of the effects of weathering on oil spilled at sea, a series of laboratory experiments were conducted to investigate the dissolution and photodegradation kinetics of Kuwait crude oil in seawater. A simple and practical method was developed for the preparation of stable homogeneous samples of sea water-soluble oil (SWSF) at 25 "C. The dissolution was monitored by two independent but complementary methods; total dissolved oil was measured by a photochemical dissolved organic carbon (DOC) technique whilst the dominant soluble constituents, aromatic hydrocarbons, were measured by ultraviolet-fluorescence (UVF) spectrophotometry. Maximum dissolution was observed after slowly stirring oil on seawater for 5 days when concentrations were, respectively, 3.2-3.6 fig C mL * seawater (DOC) and 2.4 /xg diesel equivalents mL ' seawater (UVF). C^ntification of the photodegradation of individual SWSF constituents required development and optimisation of a more specific analytical method. The final method involved addition of deuterated internal standards, extraction with n-pentane, controlled evaporation (micro Kudema-Danish concentration) and gas chromatography-mass spectrometry (GC-MS). Particular care was taken to eliminate sample contamination and storage conditions were also optimised. The recovery of deuterated internal standards through the isolation steps ranged from 30% for benzene-d^ to 100% for phenanihrene-diQ. The method allowed more than fifty compounds, mainly low molecular weight aromatic hydrocarbons, to be identified and quantified in the SWSF. Alkylated benzenes ( Q ^ were the most abundant (98% of the dissolved oil) followed by alkylated naphthalenes (C0.3) (= 2%). The oil to seawater partition coefficient of individual hydrocarbons (K^^) showed that hydrocarbons of high aqueous solubility (e.g C0.2 alkylbenzenes) also possessed the lowest partition values, whereas compounds with high partition coefficients (e.g. alkylnaphthalenes) remained mainly in the oil phase. A reproducible method of simulating solar irradiation was established under controlled environmental conditions using a calibrated 1.8 kW xenon lamp. The photodegradation of a model SWSF compound (phenanthrene) followed first-order kinetics (kp= 0.317+0.029) with a half life (tj^J of 2.2 hr at 25 "^C when irradiated at 194 Wm'-. The extrapolation of to latitude 30 *'N (Florida summer sunlight) showed that phenantiirene would degrade in = 9 hr. Some photoproducts including fluorene, fluorenone, 2,2'-diformylbiphenyl, 2,3:4,5-dibenzoxepin, 3,4-benzocoumarin, and 9,10- phenanthrenequinone were identified by GC-MS, although these accounted for only 11% of the initial mass of phenanthrene. UVF and GC-MS methods for examining the photodegradation of phenanthrene were compared. The photochemical fate of the characterised SWSF was investigated using the optimised irradiation system. Benzene and C^s alkylated benzenes showed no evidence of photodegradation after periods of up to 48 hour under the lamp, however, some C4 alkylbenzenes (jec-butylbenzene, 1,2- dimethylbenzene, 1,2,4,5- + 1,2,3,4-tetramethylbenzene and 1,2,3,4-tetrametiiylbenzene) appeared to follow first-order kinetics with respect to irradiation time. The photodegradation rate constants (kp) of the alkylated benzene and alkylated naphthalene isomers were statistically different demonstrating that certain isomers will phoiodegrade faster tiian others under the same conditions. Half lives ranged from 11.8 to 33.6 hr at 25 ''C. The majority of naphthalene (i.e. C^^^) identified in the SWSF of Kuwait crude oil exhibited first-order photodegradation kinetics with differing rate constants. Half lives were: naphtiialene. 15.7 hr; 1-methyl and 2-methyl naphthalene, 14.9 and 12 hr, respectively; l-l-2-ethylnaphthalene, 15.9; 1,6-dimethylnaphthalene, 10.4hr; 1,3,7-and 1,2,4-trimethylnaphthalene, 11.95 and 12 hr, respectively. The low initial concentration of other naphthalene isomers did not allow for accurate photodegradation kinetics to be determined. Extrapolating the data to latitude 30 "N showed that die photodegradation ti;^ expected for tiie determined SWSF compounds were between 4.2 to 7 days. This would make photodegradation an effective weathering process for the removal of spilled oil, particularly in high solar radiation environments.

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No description available.

An experimentally based study to investigate near infrared laser photoacoustic spectroscopy as a technique to measure oil pollution is described. Photoacoustic spectroscopy is shown to be well suited to the application of monitoring oil in water in a pipeline. The role of the physical parameters important to photoacoustic generation is shown to lead to an effective amplification of differences in the optical absorption coefficients for many hydrocarbons and alcohols in water. This amplification is typically an order of magnitude and persists at low concentrations of arialyte, such that a Nd:YAG source (2 mJ pulses) yields a 7.2 % increase in the photoacoustic signal magnitude for a 500 mg/I oil in water sample compared to distilled water, corresponding to a detection limit of 4 mg/I. Using a 904 nm diode laser as a source for photoacoustic generation, a detection limit of 400 mg/1 of oil is demonstrated. In addition there is found to be no discernible effect on the magnitude of the photoacoustic signal caused by the presence of optically scattering particles. The design and development of a photoacoustic instrument to measure oil in water is described, and the performance of such an instrument is compared to that of the competing technology.

No description available.

No description available.

No description available.

No description available.