Bermuda subtropical storms

Summary This investigation focuses on North Atlantic subtropical cyclones which tracked within 100 nautical miles (185 km) of Bermuda from 1957 to 2005, identified through subtropical structural characteristics distinguished using Cyclone Phase Space, from the European Centre for Medium-Range Weather Forecasts 45-year reanalyses. The study assesses the characteristics of these hybrid storms that affect the Island, in order to aid the local forecaster. Reanalysis charts, surface analyses, local observations, HURDAT tracks, and satellite pictures, where available, were examined. This data shows that subtropical cyclones affecting Bermuda usually form in close proximity, to the south-southwest, over water of an average of 26 °C, under moderate vertical wind shear, with an upper trough lying to the west-north-west. They then move in a north-northeastward direction, intensifying quickly, but not often reaching a peak intensity of more than 26 m s⁻¹. They generally have their beginnings along old baroclinic zones. September is the peak month of occurrence. A direct hit by a severe subtropical cyclone, producing locally observed winds of over 26 m s⁻¹, appears to be a rare event. However, these storms are certainly a threat to the Island, particularly due to their lack of predictability, and conditions conducive to an incipient subtropical cyclone with potential to affect the Island should always be closely monitored.     

Field Study of Soil Vapor Extraction for Reducing Off-Site Vapor Intrusion

Soil vapor extraction (SVE) is effective for removing volatile organic compound (VOC) mass from the vadose zone and reducing the potential for vapor intrusion (VI) into overlying and surrounding buildings. However, the relationship between residual mass in the subsurface and VI is complex. Through a series of alternating extraction (SVE on) and rebound (SVE off) periods, this field study explored the relationship and aspects of SVE applicable to VI mitigation in a commercial/light-industrial setting. The primary objective was to determine if SVE could provide VI mitigation over a wide area encompassing multiple buildings, city streets, and subsurface utilities and eliminate the need for individual subslab depressurization systems. We determined that SVE effectively mitigates offsite VI by intercepting or diluting contaminant vapors that would otherwise enter buildings through foundation slabs. Data indicate a measurable (5 Pa) influence of SVE on subslab/indoor pressure differential may occur but is not essential for effective VI mitigation. Indoor air quality improvements were evident in buildings 100 to 200 feet away from SVE including those without a measurable reversal of differential pressure across the slab or substantial reductions in subslab VOC concentration. These cases also demonstrated mitigation effects across a four-lane avenue with subsurface utilities. These findings suggest that SVE affects distant VI entry points with little observable impact on differential pressures and without relying on subslab VOC concentration reductions.     

Importance of Internal Biotic Concentrations in Risk Evaluations with Aquatic Systems

Ecological risk evaluations are commonly performed using aqueous concentrations and aqueous toxicity measurements as a starting point. However risk evaluations could be carried out using internal biotic concentrations and the internal lethal or sublethal concentrations. This has several advantages. Firstly, the internal lethal and sublethal concentrations are relatively consistent in groups of chemicals having a similar mode of action. Thus in field situations the internal concentration, in fish and possibly other biota, can be used to evaluate possible biotic effects. Also other histopathological, biochemical, biomolecular and physiological effects can be assessed and used with this information to give an overall assessment. There are, however, several limitations with this approach including sensitivity, health, age and nutritional status of the biota as well as a lack of data on dose/response relationships with internal concentrations.     

Trace organic contamination in biota collected from the Pearl River Estuary, China: a preliminary risk assessment

The marine ecosystem of the Pearl River Delta, located on the southern coast of China, has been heavily exploited following the rapid economic growth that has occurred since the 1980s. This investigation aimed to elucidate trace organic contamination in marine biota inhabiting the Pearl River Delta area. Biota samples, including green-lipped mussels (Perna viridis), oysters (Crassostrea rivularis) and shrimp (Penaeus orientalis) were sampled from 16 stations fringing the Estuary. Elevated concentrations (on a dry weight basis) of polycyclic aromatic hydrocarbons (27.8–1041.0 ng/g), petroleum hydrocarbons (1.7–2345.4 μg/g), polychlorinated biphenyls (2.1–108.8 ng/g), DDTs (1.9–79.0 ng/g), and hexachlorocyclohexanes (n.d.–38.4 ng/g) were recorded. A human health risk assessment was conducted to estimate the risk to local residents associated with the consumption of biota collected from the Pearl River Estuary. The results indicated that PCBs were at levels that may cause deleterious health effects in populations that consume large amounts of seafood. However, it would be instructive to establish health criteria for trace organic contaminants that are specific to the local populations, in order to derive a more accurate and relevant health risk assessment.     

Modelling of anisotropic coal swelling and its impact on permeability behaviour for primary and enhanced coalbed methane recovery

Coal swelling/shrinkage during gas adsorption/desorption is a well-known phenomenon. For some coals the swelling/shrinkage shows strong anisotropy, with more swelling in the direction perpendicular to the bedding than that parallel to the bedding. Experimental measurements performed in this work on an Australian coal found strong anisotropic swelling behaviour in gases including nitrogen, methane and carbon dioxide, with swelling in the direction perpendicular to the bedding almost double that parallel to the bedding. It is proposed here that this anisotropy is caused by anisotropy in the coal's mechanical properties and matrix structure. The Pan and Connell coal swelling model, which applies an energy balance approach where the surface energy change caused by adsorption is equal to the elastic energy change of the coal solid, is further developed to describe the anisotropic swelling behaviour incorporating coal property and structure anisotropy. The developed anisotropic swelling model is able to accurately describe the experimental data mentioned above, with one set of parameters to describe the coal's properties and matrix structure and three gas adsorption isotherms. This developed model is also applied to describe anisotropic swelling measurements from the literature where the model was found to provide excellent agreement with the measurement. The anisotropic coal swelling model is also applied to an anisotropic permeability model to describe permeability behaviour for primary and enhanced coalbed methane recovery. It was found that the permeability calculation applying anisotropic coal swelling differs significantly to the permeability calculated using isotropic volumetric coal swelling strain. This demonstrates that for coals with strong anisotropic swelling, anisotropic swelling and permeability models should be applied to more accurately describe coal permeability behaviour for both primary and enhanced coalbed methane recovery processes.     

Pacific islands in the global economy: Paradoxes of migration and culture

Predictions for the future of small islands and island states are invariably pessimistic. Poverty has increased, free trade offers limited possibilities, governance is weak and urban biased, and aid dependence has not declined despite aid fatigue. Populations are contracting from outer islands. One outcome has been increasing migration and remittances, as safety valve and diversification strategy. Selective migration and limited return migration have contributed to skill drain. Yet migration has enabled peripheries to survive through improved welfare and investment, and sustained social structures. Formal development strategies, whether international or national, emphasize 'modernity', with culture to be abhorred and ignored; yet hybridity offers possibilities for more equitable sustainable development. A combination of migration, economic diversification and cultural hybridity provides alternative development trajectories.