Disinfection of secondary effluents using tin oxide anodes.

Direct current applied to a tin oxide anode submersed in water has the potential to generate hydroxyl radicals, a strong chemical oxidant. Tin oxide anode systems, which may represent a viable alternative disinfectant, were investigated for the disinfection of secondary effluents. Coliform bacteria in the effluent were effectively inactivated in a bench-scale tin oxide disinfection system. The number of anodes in the tin oxide disinfection system influenced the steady-state concentration of hydroxyl radicals and, consequently, the contact time necessary to achieve a specified dose. The life expectancy of the anodes was greater than 30 days and no appreciable loss of tin was observed over a 5-day period. A preliminary estimate of the capital and operating costs of a pilot- or full-scale tin oxide disinfection system designed to meet a discharge requirement of 23 most probable number/100 mL at a 3 785-m3/d (1-mgd) facility was comparable to UV and chlorination/dechlorination facilities. Based on this preliminary assessment, tin oxide disinfection systems are a promising alternative disinfectant for secondary effluents.     

A Landscape Approach for Detecting and Evaluating Change in a Semi-Arid Environment

Vegetation change in the American West has been a subject of concern throughout the twentieth century. Although many of the changes have been recorded qualitatively through the use of comparative photography and historical reports, little quantitative information has been available on the regional or watershed scale. It is currently possible to measure change over large areas and determine trends in ecological and hydrological condition using advanced space-based technologies. Specifically, this process is being tested in a community-based watershed in southeast Arizona and northeast Sonora, Mexico using a system of landscape pattern measurements derived from satellite remote sensing, spatial statistics, process modeling, and geographic information systems technology. These technologies provide the basis for developing landscape composition and pattern indicators as sensitive measures of large-scale environmental change and thus may provide an effective and economical method for evaluating watershed condition related to disturbance from human and natural stresses. The project utilizes the database from the North American Landscape Characterization (NALC) project which incorporates triplicate Landsat Multi-Spectral Scanner (MSS) imagery from the early 1970s, mid 1980s, and the 1990s. Landscape composition and pattern metrics have been generated from digital land cover maps derived from the NALC images and compared across a nearly 20-year period. Results about changes in land cover for the study period indicate that extensive, highly connected grassland and desertscrub areas are the most vulnerable ecosystems to fragmentation and actual loss due to encroachment of xerophytic mesquite woodland. In the study period, grasslands and desertscrub not only decreased in extent but also became more fragmented. That is, the number of grassland and desertscrub patches increased and their average patch sizes decreased. In stark contrast, the mesquite woodland patches increased in size, number, and connectivity. These changes have important impact for the hydrology of the region, since the energy and water balance characteristics for these cover types are significantly different. The process demonstrates a simple procedure to document changes and determine ecosystem vulnerabilities through the use of change detection and indicator development, especially in regard to traditional degradation processes that have occurred throughout the western rangelands involving changes of vegetative cover and acceleration of water and wind erosion.     

High levels of genetic subdivision in peripherally isolated populations of the atherinid fish Craterocephalus capreoli in the Houtman Abrolhos Islands,Western Australia

The atherinid fish Craterocephalus capreoli Rendahl is abundant in the Houtman Abrolhos Islands, 70 km off the Western Australia coast and 250 km south of the southern limit of the range of the species along the mainland. Electrophoretic examination of 7 allozyme loci at 17 sites in the Houtman Abrolhos revealed a substantially lower level of polymorphism than found in an earlier study of the species in its mainland distribution, with many of the uncommon alleles and some common ones missing. There is a very high degree of genetic subdivision among the populations in the Houtman Abrolhos, measured by a mean F _ST of 0.437 over a distance of 35 km. This F _ST (standardized variance in allelic frequencies) is six times that found previously among populations along the mainland coast over distances up to 850 km. The subdivision of populations in the Houtman Abrolhos is similar within one island group on a scale up to 12 km, and between two groups that are separated by 15 km of deep water. Significant differences in allelic frequencies were found between populations from the open shore and enclosed lagoons less than 800 m apart, but the overall levels of subdivision were similar for the two types of environment. Previous work had shown high levels of genetic subdivision in the Houtman Abrolhos for a gastropod with direct development. The results for C. capreoli demonstrate that the archipelago favours subdivision even for a species with potentially much greater mobility and different life history.     

Estimating the risk of insect species invasion: Kohonen self-organising maps versus k-means clustering

Previous work on the estimation of the invasiveness of insect pest species used a single Kohonen self-organising map (SOM) to quantify the invasion potential of each member of a set of species in relation to a particular geographic region. In this paper that method is critically compared to an alternative approach of calculating the invasive potential of insect pest species as an outcome of clustering of regional species assemblages. Data clustering was performed using SOM and k-means optimisation clustering and multiple trials were performed with each algorithm. The outcomes of these two approaches were evaluated and compared to the previously published results obtained from a single SOM. The results show firstly, due to the inherent variation between trials of the algorithms used, that multiple trials are necessary to determine reliable risk ratings, and secondly, that k-means clustering can be considered a more appropriate algorithm for this particular application, as it produces clusters of higher quality, as determined by objective cluster measures, and is far more computationally efficient than SOM.     

Planning for persistence in marine reserves: a question of catastrophic importance.

Large-scale catastrophic events, although rare, lie generally beyond the control of local management and can prevent marine reserves from achieving biodiversity outcomes. We formulate a new conservation planning problem that aims to minimize the probability of missing conservation targets as a result of catastrophic events. To illustrate this approach we formulate and solve the problem of minimizing the impact of large-scale coral bleaching events on a reserve system for the Great Barrier Reef, Australia. We show that by considering the threat of catastrophic events as part of the reserve design problem it is possible to substantially improve the likely persistence of conservation features within reserve networks for a negligible increase in cost. In the case of the Great Barrier Reef, a 2% increase in overall reserve cost was enough to improve the long-run performance of our reserve network by >60%. Our results also demonstrate that simply aiming to protect the reefs at lowest risk of catastrophic bleaching does not necessarily lead to the best conservation outcomes, and enormous gains in overall persistence can be made by removing the requirement to represent all bioregions in the reserve network. We provide an explicit and well-defined method that allows the probability of catastrophic disturbances to be included in the site selection problem without creating additional conservation targets or imposing arbitrary presence/absence thresholds on existing data. This research has implications for reserve design in a changing climate.     

Iodine uptake,storage and translocation mechanisms in spinach (Spinacia oleracea L.)

Environmental Geochemistry and Health - Iodine is an essential micronutrient for human health; phytofortification is a means of improving humans’ nutritional iodine status. However, knowledge...     

Earthworms and in vitro physiologically-based extraction tests: complementary tools for a holistic approach towards understanding risk at arsenic-contaminated sites

The relationship of the total arsenic content of a soil and its bioaccumulation by earthworms (Lumbricus rubellus and Dendrodrilus rubidus) to the arsenic fraction bioaccessible to humans, measured using an in vitro physiologically-based extraction test (PBET), was investigated. Soil and earthworm samples were collected at 24 sites at the former arsenic mine at the Devon Great Consols (DGC) in southwest England (UK), along with an uncontaminated site in Nottingham, UK, for comparison. Analysis of soil and earthworm total arsenic via inductively coupled plasma mass spectrometry (ICP-MS) was performed following a mixed acid digestion. Arsenic concentrations in the soil were elevated (204–9,025 mg kg⁻¹) at DGC. The arsenic bioaccumulation factor (BAF) for both earthworm species was found to correlate positively with the human bioaccessible fraction (HBF), although the correlation was only significant (P ≤ 0.05) for L. rubellus. The potential use of both in vitro PBETs and earthworms as complementary tools is explored as a holistic and multidisciplinary approach towards understanding risk at contaminated sites. Arsenic resistant earthworm species such as the L. rubellus populations at DGC are presented as a valuable tool for understanding risk at highly contaminated sites.     

A pilot study on iodine in soils of Greater Kabul and Nangarhar provinces of Afghanistan

A robust and rapid methodology for the determination of iodine by inductively coupled plasma mass spectrometry in environmental samples is presented. Data were initially obtained for the validation of the analytical measurements, using 17 commercially available soil reference materials. The methodology was then tested on soil and water samples collected in Afghanistan where iodine deficiency and its effects are reportedly prevalent. Sample collections were conducted in Greater Kabul; the iodine in agricultural soils was determined to be in the range of 1.6–4.2 mg/kg and that in water drawn for drinking and irrigation was found to range from 9.9 to 22.7 μg/L. Samples were also collected in a second region, Nangarhar province, which is located to the east of Kabul, where goitres in the local population had been reported. The iodine content in soils and water at this location was 0.5–1.9 mg/kg and 5.4–9.4 μg/L, respectively. The organic content of soils in Kabul was found to be in the range of 1.9–4.2%; in Nangarhar, organic content ranged from 1.7 to 4.5%. All of the Afghan soils were slightly alkaline at pH 7.6–8.2.     

Treatment of uncertainty and developing conceptual models for environmental risk assessments and radioactive waste disposal safety cases

The common approach to performing quantitative risk assessments in the contaminated land industry in the UK lacks a formal methodology for the treatment of the full range of uncertainties and for documenting decisions regarding the development of conceptual models and the selection of computer codes. The approach presented here represents an alternative, more detailed, and systematic approach for developing conceptual models and addressing uncertainties when undertaking contaminated land risk assessments. It is intended that the advantages of this approach are recognised by practitioners in the contaminated land industry and adopted, where appropriate, to help improve the quality of contaminated land risk assessments. The identification of features, events, and processes (FEPs) has been applied to safety assessments of deep geological and near-surface disposal of radioactive wastes. One of the primary benefits of using this approach is in the development of conceptual models. The approach identifies the FEPs that need to be addressed during the development of conceptual models and in the selection of suitable computer codes that can be used to represent the conceptual models. This approach has been applied by BNFL at the low-level radioactive waste disposal site at Drigg in Cumbria and is currently being adopted for a contaminated land study at the Sellafield site, also in Cumbria. This paper presents the advantages of using FEPs in the development of conceptual models and the treatment of uncertainties. The paper also discusses the application of this approach to contaminated land studies and provides an example to demonstrate the application of the approach. BNFL's approach at the Drigg site involves the identification of components (features) and phenomena (events and processes) that govern interactions and dependencies between the components by arranging them in a matrix format.