Determination of spatially-resolved porosity, tracer distributions and diffusion coefficients in porous media using MRI measurements and numerical simulations

This work is focused on measuring the concentration distribution of a conservative tracer in a homogeneous synthetic porous material and in heterogeneous natural sandstone using MRI techniques, and on the use of spatially resolved porosity data to define spatially variable diffusion coefficients in heterogeneous media. The measurements are made by employing SPRITE, a fast MRI method that yields quantitative, spatially-resolved tracer concentrations in porous media. Diffusion experiments involving the migration of H(2)O into D(2)O-saturated porous media are conducted. One-dimensional spatial distributions of H(2)O-tracer concentrations acquired from experiments with the homogeneous synthetic calcium silicate are fitted with the one-dimensional analytical solution of Fick's second law to confirm that the experimental method provides results that are consistent with expectations for Fickian diffusion in porous media. The MRI-measured concentration profiles match well with the solution for Fick's second law and provide a pore-water diffusion coefficient of 1.75×10(-9)m(2)s(-1). The experimental approach was then extended to evaluate diffusion in a heterogeneous natural sandstone in three dimensions. The relatively high hydraulic conductivity of the sandstone, and the contrast in fluid density between the H(2)O tracer and the D(2)O pore fluid, lead to solute transport by a combination of diffusion and density-driven advection. The MRI measurements of spatially distributed tracer concentration, combined with numerical simulations allow for the identification of the respective influences of advection and diffusion. The experimental data are interpreted with the aid of MIN3P-D - a multicomponent reactive transport code that includes the coupled processes of diffusion and density-driven advection. The model defines local diffusion coefficients as a function of spatially resolved porosity measurements. The D(e) values calculated for the heterogeneous sandstone and used to simulate diffusive and advective transport range from 5.4×10(-12) to 1.0×10(-10)m(2)s(-1). These methods have broad applicability to studies of contaminant migration in geological materials.     

Monitoring anthropogenic sewage pollution on mangrove creeks in southern Mozambique: a test of Palaemon concinnus Dana, 1852 (Palaemonidae) as a biological indicator

Tropical coastal ecosystems, such as mangroves, have a great ecological and socioeconomic importance for adjacent systems and local populations, but intensive environmental impact monitoring is still lacking, mainly in East Africa. This study evaluated the potential anthropogenic disturbance on Palaemon concinnus population structure and fitness. Palaemon concinnus populations from one peri-urban (domestic sewage impacted) and two pristine mangrove creeks were studied by sampling nearly 100 shrimps per location every 15 days for 12 months. The shrimps at the peri-urban location were larger, experienced longer reproductive periods, presented higher proportion of ovigerous females and better embryo quality when compared with shrimps inhabiting pristine locations. Physiological indices (RNA/DNA ratio) were similar between shrimps at pristine and peri-urban mangroves. However, a higher level of parasitation by a Bopyridae isopod, Pseudione elongata indicated some degree of stress on the host at the peri-urban mangrove, with potential effects on the host population dynamics.     

Domestic waste composting facilities: a review of human health risks

In the management of municipal solid waste (MSW), the sorting-composting approach presents many advantages. However, since MSW contains a number of chemical and biological agents, the compost should not be necessarily a harmless product. These contaminants may expose different populations to health hazards, ranging from the composting plant workers to the consumers of vegetable products grown in soils treated with compost. Recent information concerning health risks derived from occupational exposure to organic dusts, bioaerosols and microorganisms in MSW composting plants is here reviewed. An evaluation of the potential health risks of volatile organic compounds (VOCs) released during composting is also included. Taking into account the potential biological and chemical risks, an exhaustive control of the workers employed in MSW composting facilities is clearly recommendable. Moreover, because the compost derived from the organic fraction of MSW can contain a number of metals and persistent organic pollutants, as well as microbial and fungi toxins, any compost that may mean a health risk for the population should not be commercialized.     

Multi-compartmental environmental surveillance of a petrochemical area: levels of micropollutants

Since 2002, the chemical/petrochemical industrial zone of Tarragona County (Catalonia, Spain) is being annually monitored. As part of the environmental surveillance program, in this study the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), polycyclic aromatic hydrocarbons (PAHs), and metals (As, Cd, Cr, Hg, Mn, Pb and V) were determined in soil and vegetation samples collected in 4 areas of Tarragona County (chemical, petrochemical, urban/residential, and unpolluted). Moreover, the airborne concentrations of the same micropollutants were determined in each area. In soil samples, significant higher levels of PCNs and higher concentrations of PCDD/Fs and PAHs were found in the urban zone. PCDD/F levels in vegetation samples significantly decreased from 2002. The concentrations of Cr in soil samples, as well as V levels in vegetation samples collected in the vicinity of an oil refinery were significantly higher than those found in the unpolluted zones. A significant and progressive increase in V concentrations was also noted. The current results clearly indicate that the petrochemical industry is still being an important focus of inorganic pollution for the surrounding environment. In air, the higher amount of the 7 carcinogenic PAHs suggests a relatively greater impact on the petrochemical and urban areas. The temporal trend of the global pollution was also studied an Integral Risk Index was applied.     

Evaluating urban PM10 pollution benefit induced by street cleaning activities

Despite their burden in urban particulate air pollution, road traffic non-exhaust emissions are often uncontrolled and information about the effectiveness of mitigation measures on paved roads is still scarce. The present study is aimed to evaluate the effectiveness of mechanical sweeping/water flushing treatments in mitigating urban road dust resuspension and to quantify the real benefit in terms of ambient PM₁₀ concentrations. To this aim a specific campaign was carried out in a heavily trafficked central road of Barcelona (Spain), a Mediterranean city suffering from a traffic-related pollution, both for a high car density and a frequent lack of precipitation. Several street washings were performed by means of mechanical sweepers and pressure water during night in all traffic lanes and sidewalks. PM₁₀ levels were simultaneously compared with four reference urban background air quality stations to interpret any meteorological variability. At the downwind measurement site, PM₁₀ concentrations registered a mean daily decrease of 8.8 μg m^?3 during the 24 h after street washing treatments. However 3.7–4.9 μg m^?3 of such decrease were due to the meteorological variability detected at the upwind site, as well as at two of the reference sites. This reveals that an effective decrease of 4–5 μg m^?3 (7–10%) can be related to street washing efficiency. Mitigation of road dust resuspension was confirmed by investigating the chemical composition of airborne-PM₁₀ filters. Concentrations of Cu, Sb, Fe and mineral matter decrease significantly with respect to concentrations of elemental carbon, used as tracer for exhaust diesel emissions. High efficiency of street washing in reducing road dust loads was found by performing periodic samplings both on the treated and the untreated areas.     

Measurement of machinery safety level: European framework for product control: Particular case: Spanish framework for market surveillance

Current brief aims to introduce the concept of safety in European industrial sectors, particularly in mechanics and machinery industry. It also highlights the importance to ensure an even level of machinery safety along the European Union, setting up the appropriate frame and procedures to keep it under control. An overview over market surveillance activities for machinery (regulations, main actors and their roles) first at Community level, and secondly an approach to one of the Member States is also introduced.     

Effectiveness of three bulking agents for food waste composting

Rather than landfilling, composting the organic fraction of municipal solid wastes recycles the waste as a safe and nutrient enriched soil amendment, reduces emissions of greenhouse gases and generates less leachate. The objective of this project was to investigate the composting effectiveness of three bulking agents, namely chopped wheat (Triticum) straw, chopped mature hay consisting of 80% timothy (milium) and 20% clover (triphullum) and pine (pinus) wood shavings. These bulking agents were each mixed in duplicates at three different ratios with food waste (FW) and composted for 10 days using prototype in-vessel composters to observe their temperature and pH trends. Then, each mixture was matured in vertical barrels for 56 days to measure their mass loss and final nutrient content and to visually evaluate their level of decomposition. Chopped wheat straw (CWS) and chopped hay (CH) were the only two formulas that reached thermophilic temperatures during the 10 days of active composting when mixed with FW at a wet mass ratio of 8.9 and 8.6:1 (FW:CWS and FW:CH), respectively. After 56 days of maturation, these two formulas were well decomposed with no or very few recognizable substrate particles, and offered a final TN exceeding the original. Wood shavings (WS) produced the least decomposed compost at maturation, with wood particles still visible in the final product, and with a TN lower than the initial. Nevertheless, all bulking agents produced compost with an organic matter, TN, TP and TK content suitable for use as soil amendment.     

Developing a framework for safety validation of multi-stakeholder changes in air transport operations

The high volume of air traffic over Europe is expected to double within the next 15 years. This requires changes in the airspace structure and in the organisation of air transport operations that involve multiple stakeholders. Changes, by regulation, require a sufficient safety validation, in order to show that the changed situation is safe and will remain safe during an applicable period. Many methods and techniques exist that can be used to support such safety validation process. However, for air transport operations, the stakeholders involved are numerous and diverse, and there are no guidelines on how to address their roles, responsibilities and goals during development and validation.This paper develops a safety validation framework that emphasises the active roles and collaboration of multiple stakeholders during the development phases of air transport operations. The framework is developed in three steps: First, established validation views from literature are identified and analysed to reveal open issues when it comes to their use for multi-stakeholder changes in air transport operations. Next, validation views emerging beyond the established ones are identified, and evaluated on whether they address the open issues. Finally, the strong points of established and emerging views are combined into a novel framework.