Metal-contaminated soil remediation by using sludges of the marble industry: toxicological evaluation

The major risks due to metal pollution of sediments consist of leaching to groundwater and potential toxicity to animals and/or plants. The objective of this study was to evaluate by means of an ecotoxicological approach the effects of the addition of cutting marble sludges on the mobile metal fraction of sediments polluted with heavy metals. The study was carried out on two sediments derived from mining activities in Portman Bay (SE, Spain) polluted by heavy metals. These sediments were mixed with sludges left after the cutting of marble. The results obtained by leaching experiments showed that the addition of marble cutting sludge, consisting mainly of carbonates, to a heavy-metal polluted sediment produces a decrease of available metal forms. The carbonate content seems to play a role in chemical stabilisation of metals and in a decrease of toxicity of sediments. The leached solutions have a non-toxic effect. The mild remediation by addition of sludge has moreover effects to long term.     

Understanding the North–South knowledge divide and its implications for policy: a quantitative analysis of the generation of scientific knowledge in the environmental sciences

The paper investigates the scientific knowledge divide in the environmental sciences between developed and developing countries and explores the implications and impacts on both science and policymaking. Quantitative data analysis of more than 6400 scientific papers published in 1993–2003 yield evidence for a growing divide in authorship, publication rates, and location of scientific research in nine environmental journals with high impact factor ratings. In addition to this severe imbalance in publication rates between developed and developing countries, we also find a research bias toward certain eco-climatic zones. More than 80% of papers are published in and about temperate and cold eco-climatic zones. Only 13% of the papers in our study are based on research in the dry sub-tropical and tropical zones, although these eco-climatic zones account for more than 52% of the world's land area. Based on these results, we discuss how the limited empirical source and focus of environmental research undermine the claims of universality of environmental science and what consequences this may have on policymaking processes at different levels. Finally, we briefly explore some short- and long-term strategies to address the knowledge divide.     

Short- and long-term importance of small sharks in the diet of the rare deep-sea shark Dalatias licha

Knowing the trophic ecology of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on deep-sea and threatened shark species is limited. Here, by combining analyses of individual stomach contents and stable isotope values, we examined the trophic ecology (dietary composition and trophic position) of the kitefin shark Dalatias licha, a deep-sea shark considered as near threatened globally and as data deficient in the Mediterranean Sea. Results revealed the importance of small sharks in the diet of the kitefin shark at short- and long-term scales, although fin-fish, crustaceans and cephalopods were also found. Predation on sharks reveals the high trophic position of the kitefin shark within the food web of the western Mediterranean Sea. Stable isotope values from liver and muscle tissues confirmed our results from stomach content analysis and the high trophic position.     

The intercoder agreement when using the Driving Reliability and Error Analysis Method in road traffic accident investigations

Many different classification schemes have been used in the analysis of road traffic accidents but the agreement between coders using the same classification scheme is rarely tested and/or reported. As a high intercoder agreement is a prerequisite for a study’s validity, this is a serious shortcoming. The aim of the present study was, therefore, to test the intercoder agreement of the Driving Reliability and Error Analysis Method (DREAM) version 3.0 by letting seven coders from different European countries analyse and classify the causes of the same four accident scenarios. The results showed that the intercoder agreement for genotypes (contributing factors) ranges from 74% to 94% with an average of 83%, while for phenotypes (observable effects) it ranges from 57% to 100% with an average of 78%. The results also showed that weaknesses in classification schemes, methods, training of coders as well as in presentation of accident information can be identified by testing the intercoder agreement.     

Leaching assessment of concrete made of recycled coarse aggregate: Physical and environmental characterisation of aggregates and hardened concrete

Each year, millions of tonnes of waste are generated worldwide, partially through the construction and demolition of buildings. Recycling the resulting waste could reduce the amount of materials that need to be manufactured. Accordingly, the present work has analysed the potential reuse of construction waste in concrete manufacturing by replacing the natural aggregate with recycled concrete coarse aggregate.However, incorporating alternative materials in concrete manufacturing may increase the pollutant potential of the product, presenting an environmental risk via ground water contamination.The present work has tested two types of concrete batches that were manufactured with different replacement percentages. The experimental procedure analyses not only the effect of the portion of recycled aggregate on the physical properties of concrete but also on the leaching behaviour as indicative of the contamination degree. Thus, parameters such as slump, density, porosity and absorption of hardened concrete, were studied. Leaching behaviour was evaluated based on the availability test performed to three aggregates (raw materials of the concrete batches) and on the diffusion test performed to all concrete.From an environmental point of view, the question of whether the cumulative amount of heavy metals that are released by diffusion reaches the availability threshold was answered. The analysis of concentration levels allowed the establishment of different groups of metals according to the observed behaviour, the analysis of the role of pH and the identification of the main release mechanisms. Finally, through a statistical analysis, physical parameters and diffusion data were interrelated. It allowed estimating the relevance of porosity, density and absorption of hardened concrete on diffusion release of the metals in study.     

Correlation between physicochemical and ecotoxicological approaches to estimate landfill leachates toxicity

Leachates from municipal solid waste (MSW) landfills may contain a huge diversity of contaminants; these wastewaters should be considered as potentially hazardous complex mixtures, representing a potential environmental risk for surface and groundwater. Current MSW landfill wastes regulatory approaches deem exclusively on the physicochemical characterization and does not contemplate the ecotoxicological assessment of landfill leachates. However, the presence of highly toxic substances in consumer products requires reconsideration on the need of more specific ecotoxicological assessments. The main aim of this study was to evaluate the toxicity of different MSW landfill leachates using a battery of toxicity tests including acute toxicity tests with Daphnia magna and the anuran Xenopus laevis and the in vitro toxicity test with the fish cell line RTG-2. The additional objective was to study the possible correlation between physicochemical properties and the toxicity results obtained for untreated landfill leachates. The results showed that the proposed test battery was effective for the ecotoxicological characterization of MSW landfill leachates. A moderate to strong correlation between the measured physicochemical parameters and the calculated toxicity units was detected for all toxicity assays. Correlation factors of 0.85, 0.86 and 0.55 for Daphnia, Xenopus and RTG-2 tests, respectively, were found. The discriminant analysis showed that certain physicochemical parameters could be used for an initial categorization of the potential aquatic acute toxicity of leachates; this finding may facilitate leachates management as the physicochemical characterization is currently the most common or even only monitoring method employed in a large majority of landfills. Ammonia, alkalinity and chemical oxygen demand (COD), together with chloride, allowed a proper categorization of leachates toxicity for up to 75% of tested samples, with a small percentage of false negatives.     

Effects of zinc on the structure and growth dynamics of a natural freshwater phytoplankton assemblage reared in the laboratory

The response of a natural phytoplankton assemblage to different concentrations of Zn(2+) was evaluated by means of a static laboratory bioassay. Aliquots of surface water, taken in autumn from a non-polluted point of the Reconquista River (Buenos Aires, Argentia), were incubated in mineral nutrient media containing 2.5, 10 or 25 mg litre(-1) of Zn(2+) (as zinc chloride). The comparative structure and dynamics of the communities were followed through periodic physico-chemical and biological analyses of samples taken during 24 days of incubation. Under the experimental conditions of the bioassays, the existence of several Zn(2+) tolerant algal species was shown: the most important of them were Chlorella vulgaris Beij. (Chlorophyceae, Chlorococcales), Nitzschia palea (Kütz.) Smith and Gomphonema parvulum (Kütz.) Kütz. (Bacillariophyceae). It was also demonstrated that the algal responses to Zn(2+) were selectively concentration dependent: at 2.5 and 10 mg litre(-1) a stimulatory effect was observed in the diatoms; at 25 mg litre(-1), diatom toxicity occurred. In contrast, Chlorophyceae growth was stimulated at the maximal Zn level. In general, the diversity, richness and equitability of the community were adversely affected by Zn in a concentration-dependent fashion.