Effect of different types of elemental sulfur on bioleaching of heavy metals from contaminated sediments

The application of two different types of elemental sulfur (S0) was studied to evaluate the efficiency on bioleaching of heavy metals from contaminated sediments. Bioleaching tests were performed in suspension and in the solid-bed with a heavy metal contaminated sediment using commercial sulfur powder (technical sulfur) or a microbially produced sulfur waste (biological sulfur) as substrate for the indigenous sulfur-oxidizing bacteria and thus as acid source. Generally, using biological sulfur during suspension leaching yielded in considerably better results than technical sulfur. The equilibrium in acidification, sulfur oxidation and metal solubilization was reached already after 10-14 d of leaching depending upon the amount of sulfur added. The metal removal after 28 d of leaching was higher when biological sulfur was used. The biological sulfur added was oxidized with high rate, and no residual S0 was detectable in the sediment samples after leaching. The observed effects are attributable to the hydrophilic properties of the biologically produced sulfur particles resulting in an increased bioavailability for the Acidithiobacilli. In column experiments only poor effects on the kinetics of the leaching parameters were observed replacing technical sulfur by biological sulfur, and the overall metal removal was almost the same for both types of S0. Therefore, under the conditions of solid-bed leaching the rate of sulfur oxidation and metal solubilization is more strongly affected by transport phenomena than by microbial conversion processes attributed to different physicochemical properties of the sulfur sources. The results indicate that the application of biological sulfur provides a suitable means for improving the efficiency of suspension leaching treatments by shortening the leaching time. Solid-bed leaching treatments may benefit from the reuse of biological sulfur by reducing the costs for material and operating.     

Safety Evaluation for a Biodiesel Process Using Prion-Contaminated Animal Fat as a Source (6 pp)

Background Due to the bovine spongiform encephalopathy (BSE), specified risk material (SRM) as well as animal meat and bone meal (MBM) are banned from the food and feed chain because of a possible infection with pathogenic prions (PrPSc). Nowadays, prions are widely accepted to be responsible for TSE(transmissible spongiform encephalopathies)-caused illnesses like BSE and scrapie, and especially for the occurrence of the new variant of CJD in humans. Presently, SRM and MBM are burnt under high temperatures to avoid any hazards for humans, animals or the environment. The aim of this study was to evaluate a method using animal fat separated from Category I material which includes SRM and the carcasses of TSE-infected animals, or animals suspected of being infected with TSE, as a source for producing biodiesel by transesterification, analogous to the biodiesel process using vegetable oil. Methods For this purpose, animal fat was spiked with scrapie-infected hamster brain equivalents – as representative for a TSE-infected animal – and the biodiesel manufacturing process was downscaled and performed under lab-scale conditions. Results and Discussion The results analysed by Western blotting showed clearly that almost each single step of the process leads to a significant reduction of the concentration of the pathogenic prion protein (PrPSc) in the main and side-products. Conclusion The data revealed that the biodiesel production, even from material with a high concentration of pathogenic prions, can be considered as safe. Recommendations and Outlook The obtained results indicated that biodiesel produced from prion-contaminated fat was safe under the tested process conditions. However, it has to be pointed out that the results cannot be generalized because a different process control using other conditions may lead to different results and then has to be analysed independently. It is clear that the production of biodiesel from high risk material represents a more economic usage than the combustion of such material.     

On the stock–recruitment relationships in fish population models

The framework of this article is modeling applied to fisheries. It aims at relating some classical stock–recruitment curves to a dynamic structured model, consisting of the adults stages of the stock and a pre-recruits stage (i.e., eggs, larvae, juveniles). The main result is that no functional stock–recruitment relationship can be found, unless further restrictive assumptions are added to the model (slow–fast dynamics and uniformity). Among the curves thus obtained is the Beverton–Holt curve, but not Ricker's.     

Assessment of contamination and biomarker responses in two species of herons on the St. Lawrence river

This study was undertaken to validate potential biomarkers of exposure and effects due to chemical contaminants in breedingcolonies of the Great Blue Heron and the Black-crowned Night-Heron on the St. Lawrence River. Eggs and fledglings from both species were collected from many colonies along theRiver. The fledglings from colonies in freshwater and brackishwater were more contaminated by mercury and PCBs than those from estuarine and gulf colonies. With respect to fledglings ofthe two heron species, some morphometric and blood biochemicalmeasurements, including plasma thyroid hormones and retinol, were significantly different among colonies. Significant differences were also observed in liver retinoids, EROD and porphyrins among colonies. The results of this study suggestthat plasma retinoids and thyroid hormones are good biomarkersof exposure and effects, and are sufficiently sensitive to reflect local and regional variations in contamination. Along with the measure of contaminants in egg and plasma, they constitute non-invasive biomarkers which represent an importantcriteria for long term monitoring of wildlife species. It is concluded that the Great Blue Heron is an appropriate sentinelspecies in the surveillance network for the St. Lawrence River.     

Women at risk: gender and AIDS in Africa

AIDS in Africa is a gender, development and rights issue involving power and differential access to resources. The risk situations for women in stressed development contexts of war, destabilisation and displacement, and the many contexts of transactional sex, are poorly understood by policy makers and the medical community. The dominant epidemiological paradigm has focused on female 'prostitutes' in a number of African cities. The limitations of this approach are discussed, as are the different contextualised meanings of sexual exchange. The importance of women's experience of sexually transmitted diseases and HIV and their perceptions of risk are stressed, as is the need for non-judgmental services linked to primary and comprehensive health care, and for sensitive, qualitative research. It is argued that all women who engage in unprotected penetrative sex are at risk. Most health promotion messages, however, construct an image of women as prostitutes ('Avoid prostitutes') or seek to mobilise women as carers and educators of families and communities.     

Biodegradable Blends Based on Starch and Poly(Lactic Acid): Comparison of Different Strategies and Estimate of Compatibilization

Finding plastic substitutes based on sustainability, especially for short-term packaging and disposable applications has aroused scientific interest for many years. Starch may be a substitute for petroleum based plastics but it shows severe limitations due to its water sensitivity and rather low mechanical properties. To overcome these weaknesses and to maintain the material biodegradability, one option is to blend plasticized starch with another biodegradable polymer. To improve both the compatibility between the main phases and the performance of the final blend, different compatibilization strategies are reported in literature. However, the relative efficiency of each strategy is not widely reported. This paper presents three different strategies: in situ (i) formation of urethane linkages; (ii) coupling with peroxide between starch and PLA, and (iiii) the addition of PLA-grafted amylose (A-g-PLA) which has been elaborated ex situ and carefully analyzed before blending. This study compares the effect of each compatibilization strategy by investigating mechanical and thermal properties of each blend. Compatibilizing behavior of the A-g-PLA is demonstrated, with a significant increase (up to 60%) in tensile strength of starch/PLA blend with no decrease in elongation at failure.     

Evaluation of the exposure methodology for risk-benefit assessment of seafood consumption

This study evaluated the methodology of using existing, international data to calculate the intake of nutrients and contaminants via seafood consumption on a national level. This was done by combining French seafood consumption data with two different datasets. The results showed that a significant correlation was found between the results obtained by using different data sets and that a high percentage of the population was classified in the same category (above or below the intake reference values). As such, the general conclusion that can be drawn from the results: 'whether a part of the population does exceed the toxicological reference values for certain contaminants and whether a part of the population does not reach the recommended intake for certain nutrients' remains the same for the two approaches. Therefore, it can be concluded that the existing, international probability distributions are useful when aiming to perform a cost-effective risk benefit evaluation of seafood consumption on national or regional level. When this evaluation does indicate that more detailed results are needed because a certain health risk exists, it can be decided that it is worth to spend more time and money for the analyses of national samples in order to collect more detailed results.