Revegetation Strategies for Bauxite Refinery Residue: A Case Study of Alcan Gove in Northern Territory, Australia

Alumina extraction from bauxite ore with strong alkali produces waste bauxite refinery residue consisting of residue sand and red mud. The amount and composition of refinery residue depend on the purity of the bauxite ore and extraction conditions, and differs between refineries. The refinery residue is usually stored in engineered disposal areas that eventually have to be revegetated. This is challenging because of the alkaline and sodic nature of the residue. At Alcan Gove’s bauxite refinery in Gove, Northern Territory, Australia, research into revegetation of bauxite residue has been conducted since the mid-1970s. In this review, we discuss approaches taken by Alcan Gove to achieve revegetation outcomes (soil capping of refinery residue) on wet-slurry disposal areas. Problems encountered in the past include poor drainage and water logging during the wet season, and salt scalding and capillary rise during the dry season. The amount of available water in the soil capping is the most important determinant of vegetation survival in the seasonally dry climate. Vegetation cover was found to prevent deterioration of the soil cover by minimising capillary rise of alkalinity from the refinery residue. The sodicity and alkalinity of the residue in old impoundments has diminished slightly over the 25 years since it was deposited. However, development of a blocky structure in red mud, presumably due to desiccation, allows root penetration, thereby supplying additional water to salt and alkali-tolerant plant species. This has led to the establishment of an ecosystem that approaches a native woodland.     

Spatial analysis of land use impact on ground water nitrate concentrations

In spatial analyses of causes or health effects of environmental pollutants, small units of analyses are usually preferred for internal environmental homogeneity reasons but can only be done when fine resolution data are available for most units. Objectives of this study were to determine which land use practices were spatially associated with ground water nitrate concentrations across Prince Edward Island (PEI), Canada, and which spatial aggregation is the preferred unit of analyses. Nitrate concentrations were determined for 4855 samples from private wells. Validated field-by-field land use data were available. Average nitrate concentration and percentage of area for the 14 major land use categories in PEI were determined for each of three spatial aggregations: watersheds based on topography and hydrology; freeform polygon boundaries based on similar neighboring nitrate concentrations; and 500-m buffer zones around each well. Results showed that the percentages of potato, grain, and hay coverage were positive predictors of ground water nitrate concentrations. Percentage of blueberry was a marginally significant negative predictor in the watershed and freeform polygon models, and percentage of residential coverage was a positive predictor in the freeform polygon and buffer zone models. Spatial autocorrelation was present in the freeform polygon and buffer zone models even after land use was taken into account. In conclusion, analyses based on watersheds produced the best predictive model with the percentages of land cover of potato, hay, and grain being significantly associated with ground water nitrate concentrations, and the percentages of blueberry, clear-cut woodland, and other agriculture being marginally significant.     

Characterizing ammonia emissions from swine farms in eastern North Carolina: part 2--potential environmentally superior technologies for waste treatment

The need for developing environmentally superior and sustainable solutions for managing the animal waste at commercial swine farms in eastern North Carolina has been recognized in recent years. Program OPEN (Odor, Pathogens, and Emissions of Nitrogen), funded by the North Carolina State University Animal and Poultry Waste Management Center (APWMC), was initiated and charged with the evaluation of potential environmentally superior technologies (ESTs) that have been developed and implemented at selected swine farms or facilities. The OPEN program has demonstrated the effectiveness of a new paradigm for policy-relevant environmental research related to North Carolina's animal waste management programs. This new paradigm is based on a commitment to improve scientific understanding associated with a wide array of environmental issues (i.e., issues related to the movement of N from animal waste into air, water, and soil media; the transmission of odor and odorants; disease-transmitting vectors; and airborne pathogens). The primary focus of this paper is on emissions of ammonia (NH3) from some potential ESTs that were being evaluated at full-scale swine facilities. During 2-week-long periods in two different seasons (warm and cold), NH3 fluxes from water-holding structures and NH3 emissions from animal houses or barns were measured at six potential EST sites: (1) Barham farm--in-ground ambient temperature anaerobic digester/energy recovery/greenhouse vegetable production system; (2) BOC #93 farm--upflow biofiltration system--EKOKAN; (3) Carrolls farm--aerobic blanket system--ISSUES-ABS; (4) Corbett #1 farm--solids separation/ gasification for energy and ash recovery centralized system--BEST; (5) Corbett #2 farm--solid separation/ reciprocating water technology--ReCip; and (6) Vestal farm--Recycling of Nutrient, Energy and Water System--ISSUES-RENEW. The ESTs were compared with similar measurements made at two conventional lagoon and spray technology (LST) farms (Moore farm and Stokes farm). A flow-through dynamic chamber system and two sets of open-path Fourier transform infrared (OP-FTIR) spectrometers measured NH3 fluxes continuously from water-holding structures and emissions from housing units at the EST and conventional LST sites. A statistical-observational model for lagoon NH3 flux was developed using a multiple linear regression analysis of 15-min averaged NH3 flux data against the relevant environmental parameters measured at the two conventional farms during two different seasons of the year. This was used to compare the water-holding structures at ESTs with those from lagoons at conventional sites under similar environmental conditions. Percentage reductions in NH3 emissions from different components of each potential EST, as well as the whole farm on which the EST was located were evaluated from the estimated emissions from water-holding structures, barns, etc., all normalized by the appropriate nitrogen excretion rate at the potential EST farm, as well as from the appropriate conventional farm. This study showed that ammonia emissions were reduced by all but one potential EST for both experimental periods. However, on the basis of our evaluation results and analysis and available information in the scientific literature, the evaluated alternative technologies may require additional technical modifications to be qualified as unconditional ESTs relative to NH3 emissions reductions.     

The conservation status and trends of raptors and owls in Europe

To conserve biodiversity efficiently, an international framework is needed to ensure that national priorities take into account regional and global priorities. BirdLife International has published five comprehensive assessments of the global status of the world's birds and two evaluations of the status of Europe's birds at a continental level. This paper analyzes the results of these assessments in relation to Europe's 56 species of raptors and owls, 18% of which are of global conservation concern, and 64% of which have an unfavorable conservation status in Europe. The European Union (EU) holds half of the total estimated European breeding population of raptors and owls, and European Russia supports another third, but every European country has a responsibility for at least two species of European conservation concern. During the 1990s, more raptors increased than decreased in most EU member states, but the opposite was true in eastern Europe, where many of the most threatened species are concentrated. Given the popularity of these species with the public, and the political commitment to halt the loss of biodiversity by 2010, much more action is needed to monitor and conserve birds of prey.     

Black carbon-dominated PCDD/Fs sorption to soils at a former wood impregnation site

The influence of black carbon (BC) on the sorption of 17 native polychlorinated-p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was studied in five soil samples from a sawmill site where wood used to be impregnated with chlorophenol preservatives. The presence of BC caused measured total organic carbon (TOC)-water distribution ratios (K(TOC)) to be a median factor of 51 (interquartile range 18-68, n=85) higher than modeled amorphous organic carbon (AOC)-water distribution ratios (K(AOC)). K(TOC) was a factor of 73+/-27 above K(AOC) for PCDFs (n=10) and a factor of 20+/-13 (n=7) for PCDDs. The reason for this difference is probably that attaining a planar configuration after sorption to BC is less thermodynamically favorable for PCDDs than for PCDFs. BC-water distribution ratios were calculated from K(TOC), K(AOC) and BC contents, and ranged from 10(9.9) (2,3,7,8-Tetra-CDD) to 10(11.5) l kg(-1) (Octa-CDF). More than 90% of the PCDD/Fs in the soil was calculated to be BC-sorbed. Dissolved organic carbon (DOC)-water distribution ratios were measured to be in the same order of magnitude as K(AOC). This study shows that strong sorption to BC should be included when assessing ecotoxicological risk or modeling transport to groundwater of PCDD/Fs in soil.     

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.     

A critical review of hydrological data collection for assessing preservation risk for urban waterlogged archaeology: A case study from the City of York, UK

Environmental change caused by urban development, possibly augmented by climate change, may result in accelerated decay of in situ archaeological resources. Damage may be related to changes in hydrological processes. Such archaeological resources have to be considered in environmental planning. In this paper we highlight the need for improved hydrological data from urban archaeological sites using the case study of the City of York, UK, arguably one of the most well studied and well preserved urban archaeological environments globally. We suggest that the quality of hydrological data collected during routine surveys and experimental work must be improved and standardised in order for us to produce reliable archaeological risk models for urban sites.     

Household wood heater usage and indoor leakage of BTEX in Launceston,Australia: A null result

A study has been conducted in Launceston, Australia, to determine within households with wood heaters the effect of leakage from the heater and flue on the indoor air concentrations of the pollutants: benzene, toluene, ethylbenzene and xylene (BTEX). The study involved three classes: 28 households without wood heaters, 19 households with wood heaters compliant with the relevant Australian Standard and 30 households with non-compliant wood heaters. Outdoor and indoor BTEX concentrations were measured in each household for 7 days during summer when there was little or no wood heater usage, and for 7 days during winter when there was widespread wood heater usage. Each participant kept a household activity diary throughout their sampling periods. For wintertime, there were no significant differences of the indoor BTEX concentrations between the three classes of households. Also there were no significant relationships between BTEX indoor concentrations within houses and several measures of the amount of wood heater use within these houses. For the households sampled in this study, the use of a wood heater within a house did not lead to BTEX release within that house and had no direct detectable influence on the concentrations of BTEX within the house. We propose that the pressure differences associated with the both the leakiness or permeability of the building envelope and the draught of the wood heater have key roles in determining whether there will be backflow of smoke from the wood heater into the house. For a leaky house with a well maintained wood heater there should be no backflow of smoke from the wood heater into the house. However backflow of smoke may occur in well sealed houses.The study also found that wood heater emissions raise the outdoor concentrations of BTEX in winter in Launceston and through the mixing of outdoor air through the building envelopes into the houses, these emissions contribute to increases in the indoor concentrations of BTEX in winter in all houses in Launceston.     

Sulfur processing in the marine atmospheric boundary layer: A review and critical assessment of modeling uncertainties

Sulfur is an extremely motile and vital element in the Earth's biogeochemical environment, one whose active redox chemistry maintains small reservoirs in the atmosphere and biosphere yet large fluxes through both. Essential for life, intimately linked to the climate state, and an important component of air quality, sulfur and its transport and processing in the atmosphere have been the subject of active research for several decades. This review article describes the current state of our understanding of the atmospheric sulfur cycle, focusing on the marine atmospheric boundary layer, with the aim of identifying the largest roots of uncertainty that most inhibit accurate simulation of sulfur cycling in the atmosphere. An overview of the emissions by phytoplankton and shipping, dispersion and entrainment in the marine boundary layer, and chemical processing by aerosols, clouds, and dry deposition is presented. Analysis of 20 contemporary modeling studies suggests that the greatest ambiguity in global sulfur cycling derives from (in descending order) wet deposition of aerosol sulfate, dry deposition of sulfur dioxide to the Earth's surface, and the heterogeneous oxidation of SO₂ in aerosols and clouds.     

Reflections: Resolving conflicting demands within disaster risk and recovery

This ‘reflection’ describes conflicting experiences, drawn from the author’s career in varied aspects of disaster risk management and recovery (1973–2016) delving into his memory, Ian Davis explores conflicts he has felt in four parallel roles he has adopted as architect, NGO board member, academic and the personal challenges he has faced working within the humanitarian sector. After describing these encounters, some practical solutions are suggested. The reflection concludes with a suggestion that at the root of these conflicts there is a need for people working in the humanitarian field to become more accountable in a downward direction towards those they seek to serve, who often lack power and influence. These include an architect’s clients, the beneficiaries of an NGO’s concern, an academic’s students or trainees and more broadly an ethical challenge that the author strives after, to regard his work as a vocation, highlighting the need for service to others rather than self-promotion.