Reclamation of acid waters using sewage sludge

An exhausted sand quarry which had filled with acid water (pH 3) from the oxidation of pyrite was treated with calcium hydroxide to neutralize the water (pH 8), and sewage sludge to prevent further ingress of acid. The water remained neutral for 2 years, an appreciable quantity of base being generated by the reduction of sulphate to sulphide in the anoxic sediment formed by the sewage sludge. After this time the water reverted to acid conditions, chiefly because the lake was too shallow to retain the sewage sludge over a sufficiently large area of its bed. Incubation experiments showed that the sewage sludge had a large capacity for sulphate reduction, which was equally efficient in acid or neutral waters and that the areal rate of consumption was sufficiently fast to neutralize all incoming acid, if at least 50% of the lake bed was covered with sludge. Throughout the course of the field investigations there was no foul smell and the lake was quickly colonized by phytoplankton, macrophytes and insects. Although nutrients associated with the sewage sludge stimulated photosynthesis and so caused the generation of additional organic matter, they were exhausted within two years. To ensure permanent reclamation, phosphate fertilizer could be added once the initial supply has been consumed. Neutralization removed trace metals from the system, presumably due to formation of insoluble oxyhydroxide and carbonates. The solubility of aluminium was apparently controlled by a basic aluminium sulphate (jurbanite).     

Application of the headspace CO2 method (ISO 14 593) to the assessment of the ultimate biodegradability of surfactants: results of a calibration exercise

In the recent review of the control of marketing surfactants used in detergents, the EU decided to increase the severity of the testing procedure by using the criterion of ultimate biodegradability (mineralization) rather than primary biodegradation (removal of the parent molecule) to ensure that possible harmful organic metabolites do not reach the environment. The relatively new ISO headspace CO2 test, considered to be an improvement on the OECD 301B (Sturm CO2) test was chosen. The method was subjected to a ring test by 11 laboratories using one of each of four classes of surfactants plus a poorly degradable reference surfactant; all laboratories satisfactorily applied the method. The necessary addition of silica gel to the medium containing the cationic surfactant, known as a class to be more inhibitory than other classes, was confirmed as a technique for avoiding inhibition of the inoculum. The biodegradability of the surfactants was in general agreement with results reported in the literature and the often reported variable values of % inorganic carbon (IC) produced of the theoretical was found. The anionic and cationic surfactants were readily biodegradable (%IC > 60), the non-ionic surfactant was well below the pass value, while the amphoteric was borderline. The IC production by the blank controls, one of the validity criteria, was about 0.3 mg C/100 ml test medium, equivalent to 3 mg C/l, as recommended in the ISO text. Mild conditions of pre-exposure of the inoculum to the test surfactant did not produce consistent worthwhile effects on either the percentage biodegradation or on its variability.     

A Knowledge-Based Approach to the Assessment of Watershed Condition

The Ecosystem Management Decision Support (EMDS) system is an application framework for knowledge-based decision support of ecological assessments. EMDS integrates geographic information system and knowledge base system technologies to provide an analytical tool for environmental assessment and monitoring. The basic objective of EMDS is to improve the quality and completeness of environmental assessments and the efficiency with which they are performed. The USDA Forest Service and the U.S. Environmental Protection Agency have cooperatively developed an EMDS knowledge base for watershed condition assessment. Specifically, this knowledge base evaluates watershed processes, patterns, general effects of human activity, and fisheries habitat suitability. Such assessments are based on spatially explicit input data concerning current conditions and reference conditions which are subsequently interpreted by user-defined "fuzzy" membership functions. In this paper we describe basic components of our knowledge base for assessing watershed condition and illustrate its application within northern Idaho and northwestern Montana.     

Population dynamics of Hawaiian seabird colonies vulnerable to sea-level rise

Globally, seabirds are vulnerable to anthropogenic threats both at sea and on land. Seabirds typically nest colonially and show strong fidelity to natal colonies, and such colonies on low-lying islands may be threatened by sea-level rise. We used French Frigate Shoals, the largest atoll in the Hawaiian Archipelago, as a case study to explore the population dynamics of seabird colonies and the potential effects sea-level rise may have on these rookeries. We compiled historic observations, a 30-year time series of seabird population abundance, lidar-derived elevations, and aerial imagery of all the islands of French Frigate Shoals. To estimate the population dynamics of 8 species of breeding seabirds on Tern Island from 1980 to 2009, we used a Gompertz model with a Bayesian approach to infer population growth rates, density dependence, process variation, and observation error. All species increased in abundance, in a pattern that provided evidence of density dependence. Great Frigatebirds (Fregata minor), Masked Boobies (Sula dactylatra), Red-tailed Tropicbirds (Phaethon rubricauda), Spectacled Terns (Onychoprion lunatus), and White Terns (Gygis alba) are likely at carrying capacity. Density dependence may exacerbate the effects of sea-level rise on seabirds because populations near carrying capacity on an island will be more negatively affected than populations with room for growth. We projected 12% of French Frigate Shoals will be inundated if sea level rises 1 m and 28% if sea level rises 2 m. Spectacled Terns and shrub-nesting species are especially vulnerable to sea-level rise, but seawalls and habitat restoration may mitigate the effects of sea-level rise. Losses of seabird nesting habitat may be substantial in the Hawaiian Islands by 2100 if sea levels rise 2 m. Restoration of higher-elevation seabird colonies represent a more enduring conservation solution for Pacific seabirds.     

Freshwater Critical Loads in Wales

The Steady State Water Chemistry (SSWC) modeland the Diatom model have been used to calculate criticalloads for acidity using annual mean chemistry for 102 acidupland streams in Wales sampled as part of the Welsh AcidWaters Survey (WAWS) in 1995. Diatom critical loads werelower than SSWC values reflecting the higher effective[ANC]_limit of the Diatom model compared to the[ANC]_limit of zero used in the SSWC model. The WAWSstream sites were all located within 41 10 × 10 km squares andeach square was assigned the lowest critical load value fromamongst the sites located within it. Comparison with valuesassigned under the UK national critical loads mappingprogramme (UKCLMAP) showed that WAWS critical loads were lowerthan UKCLMAP values in approximately 40% of squares.Differences in critical load class were variable, but exceeded2 keq ha^-1 yr^-1 in up to a maximum of seven squares.It cannot be assumed, therefore, that reducing acid depositionto the currently mapped UKCLMAP critical load will protect allstreams occurring within a given 10 × 10 km grid square inWales. The limited number of sample sites means that even inthose squares where all WAWS sites will be protected, theremay be other, more acid sensitive freshwaters with lowercritical loads. This has important implications for theinterpretation and use of critical loads data for regional andlocal environmental planning.     

Investigating the Uncertainties in the Simple Mass Balance Equation for Acidity Critical Loads for Terrestrial Ecosystems in the United Kingdom

The Simple Mass Balance (SMB)equation has been developed and used as one ofthe principal methods for calculating criticalloads of acidity for forest ecosystems. Criticalloads have formed the basis for informing policyrelated to the control and abatement of emissionsof acidifying pollutants. The SMB equationrelies on a variety of assumptions and dataderived from a variety of sources. Each of thesecomponent constituents has a potential source oferror depending on the method(s) used for theirderivation and the value(s) assigned. The resultis the possibility of generating a range ofcritical load values for a single ecosystem. This paper summarises the SMB equation, examinesthe uncertainties in deriving input values andreviews other works on the key assumptions.     

The costs,benefits, and limitations of organizational level stress interventions

Models of organizational stress posit that a number of undesirable employee states and behaviors, such as lower levels of well‐being and performance, and higher levels of absence and turnover are caused by organizational stress. It is often suggested that organizational level interventions which aim to reduce stress, such as job redesign, will therefore reduce or eliminate these states and behaviors. This suggestion is, however, based on two unsupportable assertions. The first is that these states and behaviors are caused by organizational stress. While there is some limited evidence for the role of stress, the quality of this evidence is severely compromised by numerous methodological and conceptual problems. The second assertion is that organizational level interventions aimed at changing some of these states and behaviors will actually have an effect, and that these effects will be uniformly positive. However, the available evidence suggests that these interventions often have little or no effect, and where they do have effects, these may be both positive and negative., The implications of this analysis for future work on organizational level stress interventions are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Honeybees use a Lévy flight search strategy and odour-mediated anemotaxis to relocate food sources

The availability of food resources changes over time and space, and foraging animals are constantly faced with choices about how to respond when a resource becomes depleted. We hypothesise that flying insects like bees discover new food sources using an optimal Lévy flight searching strategy and odour-mediated anemotaxis, as well as visual cues. To study these searching patterns, foraging honeybees were trained to a scented feeder which was then removed. Two new unrewarding feeders, or ‘targets’, were then positioned up- and downwind of the original location of the training feeder. The subsequent flight patterns of the bees were recorded over several hundred metres using harmonic radar. We show that the flight patterns constitute an optimal Lévy flight searching strategy for the location of the training feeder, a strategy that is also optimal for the location of alternative food sources when patchily distributed. Scented targets that were positioned upwind of the original training feeder were investigated most with the numbers of investigations declining with increasing distance from the original feeder. Scented targets in downwind locations were rarely investigated and unscented targets were largely ignored, despite having the same visual appearance as the rewarding training feeder.     

Spatial sampling for a rabies vaccination schedule in rural villages

Environmental and Ecological Statistics - Efforts are being made to contain rabies in Tanzania, reported in the southern highland regions, since 1954, and endemic in all districts in Tanzania...