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    ABSTRACT: The role of organoclays in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clays used for this study were Na-montmorillonite and saponite. These two clays were treated with didecyldimethylammonium bromide to produce organoclays which were used in this study. The study indicated that clays with high cation exchange capacity (CEC) such as Na-montmorillonite produced an organomontmorillonite that was inhibitory to biodegradation of the crude oil hydrocarbons. Extensive hydrophobic interaction between the organic phase of the organoclay and the crude oil hydrocarbons is suggested to render the hydrocarbons unavailable for biodegradation. However, untreated Na-montmorillonite was stimulatory to biodegradation of the hydrocarbons and is believed to have done so because of its high surface area for the accumulation of microbes and nutrients making it easy for the microbes to access the nutrients. This study indicates that unlike unmodified montmorillonites, organomontmorillonite may not serve any useful purpose in the bioremediation of crude oil spill sites where hydrocarbon removal by biodegradation is desired within a rapid time period.
    Journal of environmental management. 06/2014; 144C:197-202.
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    ABSTRACT: This research assumes lidar as a reference dataset against which in-flight camera system calibration and validation can be performed. The methodology utilises a robust least squares surface matching algorithm to align a dense network of photogrammetric points to the lidar reference surface, allowing for the automatic extraction of so-called lidar control points (LCPs). Adjustment of the photogrammetric data is then repeated using the extracted LCPs in a self-calibrating bundle adjustment with additional parameters. This methodology was tested using two different photogrammetric datasets, a Microsoft UltraCamX large format camera and an Applanix DSS322 medium format camera. Systematic sensitivity testing explored the influence of the number and weighting of LCPs. For both camera blocks it was found that when the number of control points increase, the accuracy improves regardless of point weighting. The calibration results were compared with those obtained using ground control points, with good agreement found between the two.
    ISPRS Journal of Photogrammetry and Remote Sensing. 01/2014;
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    ABSTRACT: Cation exchange capacity, surface acidity and specific surface area are surface properties of clay minerals that make them act as catalysts or supports in most biogeochemical processes hence making them play important roles in environmental control. However, the role of homoionic clay minerals during the biodegradation of polycyclic aromatic compounds is not well reported. In this study, the effect of interlayer cations of montmorillonites in the removal of some crude oil polycyclic aromatic compounds during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The homoionic montmorillonites were prepared via cation exchange reactions by treating the unmodified montmorillonite with the relevant metallic chloride. The study indicated that potassium-montmorillonite and zinc-montmorillonite did not enhance the biodegradation of the polycyclic aromatic hydrocarbons whereas calcium-montmorillonite, and ferric-montmorillonite enhanced their biodegradation significantly. Adsorption of polycyclic aromatic hydrocarbons was significant during biodegradation with potassium- and zinc-montmorillonite where there was about 45% removal of the polycyclic aromatic compounds by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil.
    Journal of Environmental Management. 01/2014; 142:30–35.
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    ABSTRACT: Large scale rainfall models are needed for collective risk estimation in flood insurance, infrastructure networks and water resource management applications. There is a lack of models which can provide simulations over large river basins (potentially multi-national) at appropriate spatial resolution (e.g., 5–25 km) that preserve both the local properties of rainfall (i.e., marginal distributions and temporal correlation) and the spatial structure of the field (i.e., the spatial dependence structure). In this study we describe a methodology which merges meta-Gaussian random fields and generalized additive models to simulate realistic rainfall fields at daily time scale over large areas. Unlike other techniques previously proposed in the literature, the suggested approach does not split the rainfall occurrence and intensity processes and resorts to a unique discrete–continuous distribution to reproduce the local properties of rainfall. This choice allows the use of a unique meta-Gaussian spatio-temporal random field substrate that is devised to reproduce the spatial properties and the short term temporal characteristics of the observed precipitation. The model is calibrated and tested on a 25 km gridded daily rainfall data set covering the 817000km2 of the Danube basin. Standard and ad hoc diagnostics highlight the overall good performance over the whole range of rainfall values at multiple scales of spatio-temporal aggregation with particular attention to extreme values. Moreover, the modular structure of the model allows for refinements, adaptation to different areas and the introduction of exogenous forcing variables, thus making it a valuable tool for classical hydrologic analyses as well as for new challenges of network and reinsurance risk assessment over extensive areas.
    Journal of Hydrology. 01/2014; 512:285–302.
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    ABSTRACT: The role of “homoionic” montmorillonites in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clay mineral used for this study was montmorillonite which was treated with the corresponding metal chloride salt to produce Na-, K-, Mg-, Ca-, Zn-, Al-, Cr-, and Fe-montmorillonites used in this study. The study indicated that Zn- and K-montmorillonites were inhibitory to biodegradation of the crude oil hydrocarbons and appears to do so as a result of extensive adsorption of the hydrocarbons. However, Na-, Ca- and Fe-montmorillonites with relatively high surface area and cation exchange capacity (CEC) were stimulatory to biodegradation of the crude oil hydrocarbons. This study reveals that whereas surface area and the ‘local bridging effect’ were important factors from the clay minerals that conferred stimulatory effect on the biodegradation of the hydrocarbons, the hydrolysis of the interlayer water by trivalent cations of the clay to generate protons and increase acidity of the medium is suggested to be inhibitory to biodegradation of the crude oil hydrocarbons. The interlayer cations (trivalent cations) that impart the highest local bridging effect which is stimulatory to biodegradation also impart the highest hydrolysis of interlayer water which is inhibitory. This study showed that interlayer cations play a crucial role on the ability of the clay mineral to influence biodegradation of the hydrocarbons.
    Applied Clay Science 01/2014; 87:81–86.
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    ABSTRACT: The role of acid activated clays and unmodified clays in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clay minerals used for this study were Na-montmorillonite, palygorskite, saponite and kaolinite. The clay mineral samples were treated with hydrochloric acid to produce acid activated clays which were used in this study. The study indicated that acid activated clays and untreated kaolinite were inhibitory to biodegradation of the hydrocarbons via different mechanisms whereas the untreated saponite was neutral to biodegradation of the hydrocarbons. However, untreated palygorskite and Na-montmorillonite were stimulatory to biodegradation and appears to do so as a result of the clays' ability to provide high surface area for the accumulation of microbes and nutrients such that the nutrients are within the ‘vicinity’ of the microbes. Adsorption of hydrocarbons was significant during biodegradation especially with unmodified palygorskite, where there was more than 40% removal of total petroleum hydrocarbons (TPH) by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil.
    International Biodeterioration & Biodegradation 01/2014; 88:185–191.
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    ABSTRACT: The impact of modified montmorillonites on adsorption and biodegradation of crude oil C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. Consequently, the effect on C1-dibenzothiophenes/C1-phenanthrenes, C2-dibenzothiophenes/C2-phenanthrenes, 2+3-methyldibenzothiophene/4-methyldibenzothiophene and 1-methyldibenzothiophene/4-methyldibenzothiophene ratios commonly used as diagnostic ratios for oil forensic studies was evaluated. The clay mineral samples were treated to produce acid activated montmorillonite, organomontmorillonite and homoionic montmorillonite which were used in this study. The different clay minerals (modified and unmodified) showed varied degrees of biodegradation and adsorption of the C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes. The study indicated that as opposed to biodegradation, adsorption has no effect on the diagnostic ratios. Among the diagnostic ratios reviewed, only C2-dibenzothiophenes/C2-phenanthrenes ratio was neither affected by adsorption nor biodegradation making this ratio very useful in forensic studies of oil spills and oil-oil correlation.
    Biodegradation 11/2013;
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    ABSTRACT: A significant characteristic of the UK’s rapidly ageing population is the high percentage of older adults who rely extensively on their private automobile to stay mobile. There are, however, functional declines that occur with ageing that affect one’s ability to drive safely. Additionally, navigating becomes more difficult as we age and can result in older adults reducing the amount they drive on unfamiliar routes. Thus, understanding how older drivers currently plan and then way-find journeys will allow for future in-vehicle navigation systems to be more appropriate for the needs of older adults. The paper reports on the findings of six focus groups with older drivers; three groups with those who use in-vehicle navigation systems and three groups with those who do not. The focus groups found that the use of in-vehicle navigation systems provide older drivers with an increased confidence on the roads, companionship in the car and an element of pleasure in driving. When planning long distance trips, older drivers will use online planning tools that provide a familiarity with their traditional method of navigation the road atlas. Some participants who currently use no driving aids reported the use of potentially unsafe navigating behaviours to assist them on road network; indicating a clear need for assistance in navigating. Finally, there are some significant barriers for in-vehicle navigation systems to overcome before they can be considered beneficial for older drivers.
    Transportation Research Part F Traffic Psychology and Behaviour 11/2013; 21(1):173-180.
  • The ISME Journal 10/2013;
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    ABSTRACT: A simple "first generation" multi-scale computational model of the formation of activated sludge flocs at micro-scale and reactor performance at macro-scale is proposed. The model couples mass balances for substrates and biomass at reactor scale with an individual-based approach for the floc morphology, shape and micro-colony development. Among the novel model processes included are the group attachment/detachment of micro-flocs to the core structure and the clustering of nitrifiers. Simulation results qualitatively describe the formation of micro-colonies of ammonia and nitrite oxidizers and the extracellular polymeric substance produced by heterotrophic microorganisms, as typically observed in fluorescence in situ hybridization images. These results are the first step towards realistic multi-scale multispecies models of the activated sludge wastewater treatment systems and a generic modelling strategy that could be extended to other engineered biological systems.
    Water Research 10/2013;
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