Silica reduces the toxicity of aluminium to a tropical freshwater fish (Mogurnda mogurnda)

The toxicity of aluminium (Al) to fish in acidic waters has been well documented. It was therefore expected that Al toxicity would be significant in fish communities in Gadjarrigamarndah (Gadji) Creek, a seasonally flowing stream in tropical northern Australia. This creek receives acidic groundwater containing elevated concentrations of Al from earlier land irrigation of treated mine tailings water from the former Nabarlek uranium mine. It was hypothesised that Al toxicity was reduced by high levels of silica (Si) in the water, and the subsequent formation of Al-silicate complexes. This prompted a laboratory assessment of the toxicity of Gadji Creek water to sac-fry of the native fish, Mogurnda mogurnda, followed by more detailed investigation of the toxicity of Al and the influence of Si in reducing Al toxicity. No mortality of M. mogurnda sac-fry was observed in two toxicity tests using Gadji Creek water collected in August 1997 and September 1998. The majority of Al (80-95%) was calculated to be complexed with humic substances and sulfate, with < 1% being complexed with silicate. Assessment of the influence of silica on the acute toxicity of Al in the absence of natural organic complexants (i.e. in reconstituted freshwater, pH 5) revealed that Si reduced Al toxicity. As the molar ratio of Si:Al was increased, the percent survival of M. mogurnda sac-fry increased until there was no significant (P > 0.05) difference from the controls. However, speciation modelling again predicted that little (< 3%) Al complexed with silicate, with the speciation and bioavailability of Al remaining constant as the molar ratio of Si:Al increased. Therefore, the original hypothesis that Al-silicate complexes in solution reduced the toxicity of Al to M. mogurnda could not be supported. This potential mechanism, and an alternative hypothesis, that Si competes with Al for binding sites at the fish gill surface, requires further investigation.     

A Comparative Analysis of the Vegetation and Topsoil Cover Nutrient Status between Two Similarly Rehabilitated Ash Disposal Sites

The aim of this paper is to compare the rehabilitation result between two ash disposal sites with regard to its vegetation establishment and soil nutrient status. The study areas were situated in close proximity, in the Mpumalanga coalfield, South Africa. Although both areas received a similar amelioration treatment and were seeded with similar seed mixture the vegetation composition were significantly different. Both areas were poor in essential nutrients, this probably being one of the most limiting factors for vegetation establishment. No serious phytotoxic conditions, as is frequently experience with coal ash, could be identified. A regular monitoring and low level maintenance program is therefore proposed to improve the sustainability of the vegetation. The study proposed that results form such evaluations be used to identify performance standards for rehabilitated derelict land.     

Washing away poverty: Water, democracy and gendered poverty eradication in South Africa

This article discusses ways in which the South African Government and grassroots organizations envisage and implement democracy achieved since 1994 in the field of water resources management. The focus is on the democratic, political and economic freedom and equality in resource rights for poor black women, who are central to poverty eradication. While the new water policy and law provide an enabling framework for achieving these goals, implementation on the ground encounters both new opportunities and constraints. This is illustrated by several cases of establishing South Africa's new water management institutions: catchment management agencies and water user associations. The important nexus between state‐led democratization of water resources management and bottom‐up grassroots movements is also discussed. The article concludes that the Government's affirmative and targeted intervention is indispensable for redressing gender inequalities and eradicating poverty.     

The time-varying factors influencing the recycling rate of products

In Europe targets have been laid down by EU legislation for the recycling rate of end-of-life vehicles to be achieved within the nearby future. It is illustrated in this paper that the definition of the recycling rate and the realisation of the imposed targets are very much dependent on different parameters such as the changing lifetime of the product and product design. It may seem obvious that the recycling rate is determined by various time-varying factors, however, this paper endeavours to describe and quantify the role of these factors on the recycling rate over time by the use of a dynamic systems model. This model permits the prediction of the recycling rate as a function of the numerous presented parameters, changing design scenarios etc. In addition, different definitions of the recycling rate will be presented and discussed. This will lead to a better understanding of the parameters affecting the recycling system and a more precise understanding of the recycling targets and their realisation as imposed by EU legislation. This paper focuses on cars, but the discussion and the definitions derived are equally valid for any end-of-life product.     

Backgrounds of students of behavior in relation to their attitude toward animal well-being

Knowledge of the backgrounds of students of behaviour working in the field of applied animal behavior science may help us to recognize their influence on conclusions reached in a particular study and on more general points of view. This recognition may result in a speed up of the progress in this science, to the benefit of science and animals. Some types are: (1) Eco-ethologists (ethologists of the hunters-type). They like to stalk healthy wild animals in their natural environment. They are less interested in the abnormal behavior of domestic animals under husbandry circumstances. (2) Behaviorists. These are psychologists that still think in a man-animal dichotomy. They are not interested in animals for their own sake but as models for human behavior. (3) Behavior physiologists. These biologists are not primarily interested in behavior. Because of the type of experiments they perform they have an aversity against animal protectionists. (4) Ethologists of the farmers type. These ethologists want to posses animals, collect animal species, take care of them and breed them. They are able to speak on approximately the same wavelength as farmers as well as animal protectionists. (5) Zootechnicians of the farmers type. These scientists want to make a living out of animals and like to take care for them. They are also able to speak at approximately the same wavelength as farmers and animal protectionists.     

An economic analysis of different types of formal and informal entrepreneurs, recovering urban solid waste in Bangalore (India)

The recycling sector in India, which consists of a comprehensive trade and production sector, is rather complex. Nevertheless, it creates important benefits for both the economy and the environment. In order to comprehend the system, a case study has been performed on the recycling sector (paper, plastic, glass and non-ferrous metal) in Bangalore (India), focussing on the market structure, the scale of operation, employment effects, constraints, and recent developments. It was found that this highly competitive and labour-intensive industry is largely dependent on cheap labour and the supply of solid waste from the local trade system. Its mostly informal nature results from the ‘unregisteredness’ of the materials. Consequently, government involvement is avoided as much as possible. With present growth rates, prospects of recycling in Bangalore are advancing. Yet, problems such as lack of supply and loss of quality emerge. Therefore, quality control and market conditions should be improved.     

Flanders’ urbanity — an outline

This article deals with Flanders’ urbanity. At the moment Flanders, a part of Belgium, is responsible for its own town and country planning. Nevertheless, today's picture of urbanity is, for the greatest part, the result of Belgian policy. The results are nothing to be proud of. In fact Flanders has no urbanity anymore, nor a real rurality. Everywhere in the countryside there are houses and other constructions; on the other hand and consequently the centres of cities and villages are in decay. The following text tries to draw, very briefly, the problems and the development of the problems in urban and rural Flanders. The roots have to be searched in the 19th century, especially in the constitution of Belgium, which is one of the most liberal on earth. The first part of the article is dealing with the history of urbanisation, whilst the second part deals with some recent evolutions in housing and housing policy, in employment and employment policy, in transport and transport policy. Finally, the third part is concerned with the town and country planning which has to structure the developments in spatial use for housing, industrial building and so on, but which has failed.     

Stages in Dutch regional policy: 1945–1984

This paper discusses the major developments in regional policy in the Netherlands by relating the policy instruments and locations to stages in the socio‐economic and political development of the Netherlands from 1945 onwards. It concludes that, at present, the spatial dimension of economic policy has lost importance, and the support for peripheral regions is restricted.     

South African gold mining taxation : An example of a resource rent tax

Theoretically, a resource rent tax is neutral in that it does not influence the allocation of resources. However, the application of such fundamental principles in the tax formula of the South African gold mining industry negates the neutrality principle. A progressive element in the tax rate encourages mining of submarginal ores - leads to misallocation of resources. However, it substantially reduces the financial risks of a mining company engaged in the extraction of a commodity characterized by price volability, such as gold, and permits economies of scale in mining and encourages conservation of a non-renewable resource. As long as prices increase faster than costs, the advantages of this system probably exceed the disadvantages. The choice of the threshold rate in such a tax system is critical. If it is too high it will encourage mining of submarginal ores, and if too low it does not recognize the peculiar risks of gold mining investments.     

Streambed Sediment Geochemical Controls on In-Stream Phosphorus Concentrations during Baseflow

A spatially extensive geochemical data set of stream water and bed sediment composition across the Tamar catchment in south-west England was analysed to identify the key bed sediment properties that control the in-stream dissolved reactive phosphorus (DRP) concentrations during baseflow conditions. Linear regression analysis of the streamwater DRP concentrations and the distribution coefficient K _d for DRP revealed that the former is positively correlated with total SiO₂ and Al₂O₃, and negatively correlated with K₂O. The primary control on these major element distributions is the dominant bedrock geology. The data suggest that streamwater DRP concentrations are mainly controlled by adsorption to clay minerals. Where P concentrations in streamwater were considerably elevated by inputs from point sources, DRP concentrations are also controlled by precipitation of hydroxyapatite.