Analysis of foundation sliding of an arch dam considering the hydromechanical behavior

This paper presents the application of a methodology which can be used to assess arch dam foundation stability,using the discrete element method (DEM) and the code 3DEC.A global three-dimensional model...     

Social preferences and economic valuation for water quality and river restoration: the Segura River,Spain

The Water Framework Directive (WFD) aims at improving the ecological status of the water bodies in Europe. In this context, some rivers are currently being restored and, in accordance with this Directive, the restoration actions have to be evaluated from a socio‐economic approach. This work applies the Choice Modelling method to the WFD provisions for river restoration. This method proves to be useful for the economic valuation of the restoration measures, as well as a very important tool for people's public participation. In this sense, the water quality improvement has been defined as a priority action from a social point of view. Moreover, the method used has provided answers to both basic questions included in the WFD: the calculation of the economic value of the Segura River's ecological flow, the decrease of which would pose an environmental cost, and the estimation of the environmental income generated by this river.     

Performance characteristics of the anaerobic baffled reactor

An anaerobic sludge blanket process, termed the anaerobic baffled reactor (ABR), has been developed and shows promise for industrial wastewater treatment. It combines the advantages of high stability and reliability with a high void volume. The risk of clogging and sludge bed expansion with resulting high microbial losses is reduced and there is no need for special gas collection or biological solids separation systems. Organic loadings as high as 36 g COD l^?1day^?1 have been achieved with COD removal rates of more than 24 g COD l^?1 day^?1 and methane production rates exceeding 6 volumes per day per unit volume of reactor. The hypothesis, that the ABR may be adequately modeled as a fixed-film reactor, has been supported. Therefore, a unified approach, based on fundamentals of bacterial kinetics and mass transport, appears useful for modeling this and similar systems. Pilot plant studies are necessary to determine the scaling factors of the system as well as the overall efficiency and costs.     

Bioreactivity of municipal solid waste landfill leachates-Hormesis and DNA damage

The issue of domestic waste is recognised as one of the most serious environmental problems facing the nation. With the UK producing 35 million tonnes of municipal solid waste per annum, an understanding of the ranges of toxicity of landfill emissions is crucial to determine the degree of concern we should have about the potential effects these waste sites could have upon nearby populations and the surrounding environment. The aim of this study was to evaluate the bioreactivity of landfill leachates in terms of their capacity to damage ROS-sensitive bacteriophage plasmid DNA and induce toxicity in a commercial photobacterium toxicity assay, based on the light emission of Vibrio fischeri bacteria (ROTAS). The bacterial assay revealed widespread biostimulation and a hormesis response in the bacteria, with alpha-, beta- and gamma-response curves observed following exposure to the different landfill leachates. Different biological mechanisms lead to variations in bioreactivity, as seen in the plasmid DNA scission and ROTAS assays.     

Effects of chelates on plants and soil microbial community: comparison of EDTA and EDDS for lead phytoextraction

Most studies on chelate-induced phytoextraction have focused on EDTA-mediated Pb phytoextraction. But EDTA and the formed EDTA-Pb complexes have low biodegradability and high solubility in soil, resulting in an elevated risk of adverse environmental effects. EDDS is an easily biodegradable chelating agent that has recently been proposed as an environmentally sound alternative to EDTA. Consequently, a greenhouse experiment, using a completely randomized factorial design with four replications, was carried out to compare the potential of EDTA and EDDS for chelate-induced Pb phytoextraction with Cynara cardunculus, as well as to investigate the toxicity of these two chelates to both cardoon plants and soil microorganisms. The effects of chelate addition on soil microbial communities were studied through the determination of a variety of biological indicators of soil quality such as soil enzyme activities, basal and substrate-induced respiration, potentially mineralizable nitrogen, and community level physiological profiles. EDTA was much more efficient than EDDS for the enhancement of root Pb uptake and root-to-shoot Pb translocation. In a soil polluted with 5000 mg Pb kg(-1), as a result of the addition of 1 g EDTA kg(-1) soil, a value of 1332 mg Pb kg(-1) DW shoot was obtained. EDDS application resulted in a shoot Pb accumulation of only 310 mg kg(-1)DW. Plants treated with EDDS showed lower values of biomass than those treated with EDTA. EDDS proved to be rapidly degraded, and less toxic to the soil microbial community in control non-polluted soils. Pb-polluted EDDS-treated soils showed significantly higher values of basal and substrate-induced respiration than those treated with EDTA. Although EDDS had a lower capacity to enhance Pb phytoextraction than EDTA, it has the advantage of rapid biodegradation.     

Cholinesterases activities and lipid peroxidation levels in muscle from shelf and slope dwelling fish from the NW Mediterranean: its potential use in pollution monitoring

We selected muscle tissue from nine commercial fish species, seven teleosts and two elasmobranchs, frequently caught in the NW Mediterranean trawling grounds in two different habitats (the continental shelf at 53 m and the slope at 660 m) for cholinesterases (ChEs) characterisation and activities determination, as well as the measure of lipid peroxidation (LP) levels. Acethyl- (AChE), butyryl- (BChE) and propionyl- (PrChE) cholinesterase were chosen as exposure markers of neurotoxic chemicals/molecules and LP as an effect marker of oxidative damage. The use of diagnose inhibitors: eserine sulphate, iso-OMPA and BW284c51 confirmed the measurement of true ChEs as well as the presence of pseudocholinesterases. The present study has evidenced the existence of interspecies differences, especially between teleosts and elasmobranchs but not in relation to depth. Moreover, the good correlation observed between all ChEs in most of the studied fish, supports the use of AChE as neurotoxic marker in field pollution monitoring. The non-metric multidimensional scaling analysis identified the commercial species hake Merluccius merluccius, among teleosts, and the shark, Galeus melastomus, as more adequate sentinel species in commercial fishing grounds. AChE activity showed a relationship with the fish trophic level, while all ChEs revealed a relationship with the feeding habits (benthic, suprabenthic, pelagic) and the stomach fullness. BChE activity and LP levels were the only markers to show a relationship with their swimming capacity.     

Spatial location patterns of Spanish manufacturing firms*

In this paper, we evaluate the spatial location patterns of Spanish manufacturing firms in each industry. We use a distance‐based method, Ripley's K function, which allows us to treat space as continuous. With ‘complete spatial randomness’ as benchmark, every sector presents significant concentration whatever the distance considered. If we use the locations of all manufacturing firms as a benchmark, we find dispersion in some sectors and concentration in others, finding also differences in the spatial scale at which clustering occurs. Finally, the use of cities as a benchmark reveals that not only is ‘first nature’ among the location determinants of manufacturing firms but they also include the self‐reinforcing advantages of ‘second nature’. Resumen. En este artículo evaluamos los patrones de localización espacial de empresas de manufacturas en cada industria. Utilizamos un método basado en la distancia, la función K de Ripley, que nos permite tratar el espacio como un continuo. Tomando la ‘aleatoriedad espacial completa’ como cota de referencia, todos los sectores presentan una concentración significativa, independientemente de la distancia considerada. Si empleamos las localizaciones de todas las empresas manufactureras como cota de referencia, encontramos dispersión en algunos sectores y concentración en otros, así como diferencias en la escala espacial a la que ocurre la formación de conglomerados (clusters). Finalmente, el emplear ciudades como cota de referencia revela que entre los determinantes de localización de empresas manufactureras no solo está la ‘primera naturaleza’ sino que también se incluyen las ventajas de retroalimentación positiva de la ‘segunda naturaleza’.      

Persistent, bioaccumulative and toxic substances in fish: human health considerations

Fish are important dietary items that provide essential nutrients. Fish however, bioaccumulate monomethyl mercury (MMHg) and organo-halogenated pollutants (OHP) that are persistent bioaccumulative and toxic substances (PBTS). Unlike man-made OHP, MMHg is mainly of natural origin but background concentrations of aquatic systems are determined by the environmental Hg-methylating potential. Industrial activities can modulate environmental discharges and fish bioaccumulation of PBTS. Fish and seafood consumption are associated with human body load of PBTS, but farming practices that utilize fishmeal increase the terrestrial food chain resulting in farm-animal accumulation of PBTS. These substances are neurotoxic and endocrine active that can impact humans and wild life, but chemical characteristics of MMHg and OHP modulate interactions with animal tissues. MMHg is protein reactive with a faster metabolism (months) than OHP that are stored and slowly (years) metabolized in fat tissues. Except for brain-Hg, neither Hg nor OHP in tissues are markers of toxic effects; however, deficits in neurobehavioral test-scores of children have been shown in some fish-eating populations. These deficits are transient and within normal range, and are not prodromes of neurological diseases. Although population studies show that consumption of fish at current levels of contamination do not explain neurological disorders, endocrine activity remains controversial. Understanding risk of hazard caused by fish-PBTS consumption requires a wide range of expertise. We discuss chemical, toxic, metabolic, and ecological characteristics associated with PBTS in fish. There are proven health outcome derived from fish consumption, while risk of exposure to avoidable PBTS is a chance that can be minimized by societal actions.