The impact of additives found in industrial formulations of TCE on the wettability of sandstone

The wettability of aquifer rocks is a key physical parameter which exerts an important control on the transport, residual trapping, distribution and eventual fate of chlorinated hydrocarbon solvents (CHSs) released into the subsurface. Typically chlorinated solvents are assumed to be non-wetting in water saturated rocks and unconsolidated sediments. However industrially formulated solvent products are often combined with basic additives such as alkylamines to improve their performance; and the mineral surfaces of aquifer rocks and sediments usually possess a range of acid and hydrogen-bonding adsorption sites. The presence of these sites provides a mechanism whereby the basic additives in CHSs can be adsorbed at the solvent phase/solid phase interface. Given the amphiphilic molecular structure of these additives, this may result in changes in the wetting conditions of the solid phase. The aim of this study was therefore to test this conjecture for two classes of additives (alkylamines and quaternary ammonium salts) that are often encountered in industrial solvent formulations. Wettability assessments were made on sandstone cores by means of measurements of spontaneous and forced water drainage and spontaneous and forced water imbibition and through contact angle measurements on a smooth quartz surface. No solvent/additive combination produced solvent wetting conditions, though dodecylamine and octadecylamine significantly reduced the water wetting preference of sandstone which frequently resulted in neutral wetting conditions. The large volume of spontaneous water drainage observed in wettability experiments involving cetyltrimethylammonium bromide and octadecyltrimethylammonium bromide, suggested that the sandstone cores in these tests remained strongly water wetting. However equilibrium static contact angles of around 60 degrees were measured on quartz suggesting that the sandstone surfaces should be close to neutral wetting conditions. This paradox was finally resolved by noting that contact between the solvent mixture and water in the sandstone core resulted in a final solvent phase which had an extremely low interfacial tension. It is therefore suspected that the observed spontaneous drainage of solvent from the core was driven by gravitational and buoyancy forces rather than strong water wetting conditions. Finally it was noted that the mobilisation of iron oxide coatings from the sandstone surface had a considerable influence in reducing the interfacial tension and in the formation and stabilisation of TCE/water emulsions.     

Gold mining in Australia: linking historical trends and environmental and resource sustainability

The mining of gold has been and continues to be an important aspect of Australian industry. Gold mining moved quickly from fossicking and alluvial sources in the 1850's to hard rock mining. This paper presents, arguably for the first time, a detailed historical compilation of Australian gold mining production data. This data is then analysed in the context of sustainability, focussing particularly on mineral resource sustainability and the broader aspects of environmental impacts now commonly reported by some mining companies in annual sustainability performance reports. The key trends which are demonstrated by the data include a long-term decline in ore grade, increased open cut mining, substantive increases in tailings and waste rock production, as well as showing the impact of new technologies and economics on available gold resources. The available environmental data on material and energy inputs to and pollutant emissions from gold production is also presented, showing a clear sensitivity to ore grade. In terms of sustainability, these relationships raise significant issues such as increasing greenhouse footprint per unit gold produced, potential impacts on energy and water consumption, as well as overall gold resource sustainability. The paper presents a unique case study of the resource and environmental sustainability of the Australian gold mining sector with major implications for sustainability policy and reporting.     

Habitat fragmentation lowers survival of a tropical forest bird.

Population ecology research has long been focused on linking environmental features with the viability of populations. The majority of this work has largely been carried out in temperate systems and, until recently, has examined the effects of habitat fragmentation on survival. In contrast, we looked at the effect of forest fragmentation on apparent survival of individuals of the White-ruffed Manakin (Corapipo altera) in southern Costa Rica. Survival and recapture rates were estimated using mark-recapture analyses, based on capture histories from 1993 to 2006. We sampled four forest patches ranging in size from 0.9 to 25 ha, and four sites in the larger 227-ha Las Cruces Biological Station Forest Reserve (LCBSFR). We found a significant difference in annual adult apparent survival rates for individuals marked and recaptured in forest fragments vs. individuals marked and recaptured in the larger LCBSFR. Contrary to our expectation, survival and recapture probabilities did not differ between male and female manakins. Also, there was no support for the existence of annual variation in survival within each study site. Our results suggest that forest fragmentation is likely having an effect on population dynamics for the White-ruffed Manakin in this landscape. Therefore, populations that appear to be persisting in fragmented landscapes might still be at risk of local extinction, and conservation action for tropical birds should be aimed at identifying and reducing sources of adult mortality. Future studies in fragmentation effects on reproductive success and survival, across broad geographical scales, will be needed before it is possible to achieve a clear understanding of the effects of habitat fragmentation on populations for both tropical and temperate regions.     

Continuing pollution from the Rum Jungle U-Cu project: A critical evaluation of environmental monitoring and rehabilitation

The former Rum Jungle uranium-copper project, Australia, is an internationally important case study on environmental pollution from and rehabilitation of mining. The Rum Jungle mining project is briefly reviewed, followed by a critical evaluation of monitoring data and pollution loads prior to and after rehabilitation - leading to the conclusion that rehabilitation has clearly failed the test of time after just two decades. The most critical findings are the need to understand pollution cycles holistically, and designing monitoring regimes to match, explicit inclusion of radiological criteria (lacking in original planning), and finally the need to set targets based on environmental criteria. Two examples include polluted groundwater which was excluded from rehabilitation and the poor design, construction and/or performance of engineered soil covers - both leading to increasing acid drainage impacts on the Finniss River. The critical review therefore presents a valuable case study of the environmental performance of uranium mine site rehabilitation.     

Comparison of heavy metal loads in stormwater runoff from major and minor urban roads using pollutant yield rating curves

Trace metal export by stormwater runoff from a major road and local street in urban Sydney, Australia, is compared using pollutant yield rating curves derived from intensive sampling data. The event loads of copper, lead and zinc are well approximated by logarithmic relationships with respect to total event discharge owing to the reliable appearance of a first flush in pollutant mass loading from urban roads. Comparisons of the yield rating curves for these three metals show that copper and zinc export rates from the local street are comparable with that of the major road, while lead export from the local street is much higher, despite a 45-fold difference in traffic volume. The yield rating curve approach allows problematic environmental data to be presented in a simple yet meaningful manner with less information loss.     

Developing indicators to measure post‐disaster community recovery in the United States

Disaster recovery is a key capability of federal, state, and local government. To support this capability effectively practitioners need useful and validated metrics to document how well a community is recovering from a particular disaster. This study developed and categorised recovery indicators according to the Federal Emergency Management Agency (FEMA)'s Recovery Support Functions and Recovery Mission Area Core Capabilities through a literature review, an evaluation of the pre‐disaster recovery plans for 87 coastal jurisdictions, and a case study of two communities (New Hanover County, North Carolina, and the City of Hoboken, New Jersey). Metrics identified in the literature were validated through the recovery plan review and the case study. The research team also identified sources for both baseline and current status data. Based on these findings, a user‐friendly checklist for practitioners was established, which will be piloted with practice partners during a future disaster recovery initiative.     

The Environmental sustainability of mining in Australia: key mega-trends and looming constraints

At first ‘sustainable mining’ could be perceived as a paradox—minerals are widely held to be finite resources with rising consumption causing pressure on known resources. The true sustainability of mineral resources, however, is a much more complex picture and involves exploration, technology, economics, social and environmental issues, and advancing scientific knowledge—predicting future sustainability is therefore not a simple task. This paper presents the results from a landmark study on historical trends in Australian mining, including ore milled, ore grades, open cut versus underground mining, overburden/waste rock and economic resources. When complete data sets are compiled for specific metals, particular issues stand out with respect to sustainability—technological breakthroughs (e.g. flotation, carbon-in-pulp), new discoveries (e.g. uranium or U), price changes (e.g. Au, boom/bust cycles), social issues (e.g. strikes), etc. All of these issues are of prime importance in moving towards a semi-quantitative sustainability model of mineral resources and the mining industry. For the future, critical issues will continue to be declining ore grades (also ore quality and impurities), increased waste rock and associated liabilities, known economic resources, potential breakthrough technologies, and broader environmental constraints (e.g. carbon costs, water). For this latter area, many companies now report annually on sustainability performance—facilitating analysis of environmental sustainability with respect to production performance. By linking these two commonly disparate aspects—mining production and environmental/sustainability data—it becomes possible to better understand environmental sustainability and predict future constraints such as water requirements, greenhouse emissions, energy and reagent inputs, and the like. This paper will therefore present a range of fundamental data and issues which help towards quantifying the resource and environmental sustainability of mining—with critical implications for the mining industry and society as a whole.     

Enhanced biodegradation of pentachlorophenol in unsaturated soil using reversed field electrokinetics

This study investigated the use of electrokinetics in unsaturated soil to promote biodegradation of pentachlorophenol through increased contact between bacteria and contaminant. Soil microcosms, contaminated with approximately 100 mg kg⁻¹ pentachlorophenol (containing [¹⁴C]-PCP as a tracer), and inoculated with a specific pentachlorophenol-degrading bacterium (Sphingobium sp. UG30–1 × 10⁸ cfu g⁻¹) were subjected to constant and regularly reversed electric currents (10 mA). The former caused large pH and moisture content changes due to water electrolysis and electroosmotic effects, with subsequent negative impacts on biodegradation parameters including enzyme activity and contaminant mineralisation (as measured by ¹⁴CO₂ evolution rate). The reversed field caused little change in pH and moisture content and led to more rapid contaminant mineralisation, lower soil contaminant concentration in the majority of the microcosms and increased soil enzyme activity (with the exception of soil immediately adjacent to the anode). The presence of an electric field, if suitably applied, may therefore enhance contaminant biodegradation in unsaturated soil.     

Use of Sediment Risk and Ecological/Conservation Value for Strategic Management of Estuarine Environments: Sydney Estuary,Australia

Sediment mantling the floor of Sydney estuary contains a wide range of chemicals at highly elevated concentrations over extensive areas. Appropriate sediment management decisions are urgently required to prevent further degradation of sediment quality and to minimize resulting adverse ecological effects. The objective of the present work was to provide a systematic, estuary-wide assessment of sediment risk and ecological/conservation value throughout the harbor to guide sediment management decisions. Sediment risk is the likelihood of sediment chemistry causing adverse biological effects to bottom-dwelling animals and was conducted using national sediment quality guidelines (SQGs) for single contaminants and the mean SQG quotient approach to assess chemical mixtures. Sediment risk was negligible at the mouth of the estuary, but increased strongly landwards. The ecological/conservation value assessment was conducted to identify sites that warrant different levels of protection and was conducted using the value of ecological communities and priority waterway use. Consideration of these two parameters combined enabled the estuary to be prioritized for management attention. The prioritization and identification of appropriate management strategies were determined through the use of management matrices also based on sediment risk and ecological/conservation value. A computer package is being developed to provide managers with information on sediment risk, ecological/conservation value, the urgency and the type of management intervention required for any location in Sydney estuary, in real-time. This approach to estuarine management is unique and will greatly improve effective management of Sydney estuary, and other harbors in urgent need of management action and protection.     

Polybrominated diphenyl ethers and polybrominated biphenyls in Australian sewage sludge

This paper presents a brief review of the international scientific literature of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in sewage sludge and a survey of these compounds in sewage sludge from 16 Australian wastewater treatment plants (WWTPs). The SigmaPBDE mean concentration in the Australian study was 1137microgkg(-1) dry weight (d.w.) (s.d. 1116) and ranged between 5 and 4 230microgkg(-1)d.w. The urban mean of 1308microgkg(-1) (s.d. 1320) and the rural mean of 911microgkg(-1) (s.d. 831) are not statistically different and are similar to levels in European sludges. Principal components analysis was performed on the data set and revealed that 76% of the data variation could be explained by two components that corresponded to overall concentration of the pentaBDE and the decaBDE commercial formulations. An analysis of variance was performed comparing PBDEs levels at three WWTPs over the years 2005 and 2006, finding differences between treatment plants (BDE-47) but no significant difference in PBDE levels in the years 2005 and 2006. Low levels of BB-153 were detected in all samples of this survey (n=16); mean 0.6microgkg(-1)d.w. (s.d. 0.5). This compound has rarely been reported in any other study of sewage sludges undertaken outside Australia. This work highlights the need for a risk assessment of PBDEs in sewage sludge when used for land application, taking into account typical levels found in Australian sludges and soils.