Modelling Tracer Dispersion from Landfills

Several wind tunnel experiments of tracer dispersion from reduced-scale landfill models are presented in this paper. Different experimental set-ups, hot-wire anemometry, particle image velocimetry and tracer concentration measurements were used for the characterisation of flow and dispersion phenomena nearby the models. The main aim of these experiments is to build an extensive experimental data set useful for model validation purposes. To demonstrate the potentiality of the experimental data set, a validation exercise on several mathematical models was performed by means of a statistical technique. The experiments highlighted an increase in pollutant ground level concentrations immediately downwind from the landfill because of induced turbulence and mean flow deflection. This phenomenon turns out to be predominant for the dispersion process. Tests with a different set-up showed an important dependence of the dispersion phenomena from the landfill height and highlighted how complex orographic conditions downwind of the landfill do not affect significantly the dispersion behaviour. Validation exercises were useful for model calibration, improving code reliability, as well as evaluating performances. The Van Ulden model proved to give the most encouraging results.     

Trisomy 15 mosaicism owing to familial reciprocal translocation t(1;15): implication for prenatal diagnosis

We describe a 4-year-old female child with severe global mental retardation, myoclonic epilepsy, proximal hypotonia and dysmorphisms, whose prenatal diagnosis following amniocentesis revealed a constitutional female karyotype carrying a t(1;15)(q10;p11) familial reciprocal translocation. Post-natal high-resolution karyotype, Fluorescence in situ hybridization (FISH) screening for subtelomeric rearrangements, VNTR search for UPD15 in the blood and fibroblast, and WCP1 and 15 in the mother, failed to provide an explanation for the complex clinical phenotype of the proband. Since the pachytene configuration of the translocated chromosomes defines a high probability of 3:1 segregation, an extensive workup was undertaken to look for a possibly cryptic mosaicism. Four percent of the cells with trisomy 15 was found in the peripheral blood lymphocytes examined by classical cytogenetic technique and interphase FISH analysis. The clinical features associated with cryptic trisomy 15 mosaicism and the problems concerning prenatal diagnosis and genetic counselling for carriers of translocations at high risk of 3:1 segregation are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Prediction of syngas quality for two-stage gasification of selected waste feedstocks

This paper compares the syngas produced from methane with the syngas obtained from the gasification, in a two-stage reactor, of various waste feedstocks. The syngas composition and the gasification conditions were simulated using a simple thermodynamic model. The waste feedstocks considered are: landfill gas, waste oil, municipal solid waste (MSW) typical of a low-income country, the same MSW blended with landfill gas, refuse derived fuel (RDF) made from the same MSW, the same RDF blended with waste oil and a MSW typical of a high-income country. Energy content, the sum of H2 and CO gas percentages, and the ratio of H2 to CO are considered as measures of syngas quality. The simulation shows that landfill gas gives the best results in terms of both H2+CO and H2/CO, and that the MSW of low-income countries can be expected to provide inferior syngas on all three quality measures. Co-gasification of the MSW from low-income countries with landfill gas, and the mixture of waste oil with RDF from low-income MSW are considered as options to improve gas quality.     

Cryo-comminution of plastic waste

Recycling of plastics is a big issue in terms of environmental sustainability and of waste management. The development of proper technologies for plastic recycling is recognised as a priority. To achieve this aim, the technologies applied in mineral processing can be adapted to recycling systems. In particular, the improvement of comminution technologies is one of the main actions to improve the quality of recycled plastics. The aim of this work is to point out suitable comminution processes for different types of plastic waste. Laboratory comminution tests have been carried out under different conditions of temperature and sample pre-conditioning adopting as refrigerant agents CO2 and liquid nitrogen. The temperature has been monitored by thermocouples placed in the milling chamber. Also different internal mill screens have been adopted. A proper procedure has been set up in order to obtain a selective comminution and a size reduction suitable for further separation treatment. Tests have been performed on plastics coming from medical plastic waste and from a plant for spent lead batteries recycling. Results coming from different mill devices have been compared taking into consideration different indexes for representative size distributions. The results of the performed tests show as cryo-comminution improves the effectiveness of size reduction of plastics, promotes liberation of constituents and increases specific surface size of comminuted particles in comparison to a comminution process carried out at room temperature.     

Characterisation of a reference site for quantifying uncertainties related to soil sampling

The paper reports a methodology adopted to face problems related to quality assurance in soil sampling. The SOILSAMP project, funded by the Environmental Protection Agency of Italy (APAT), is aimed at (i) establishing protocols for soil sampling in different environments; (ii) assessing uncertainties associated with different soil sampling methods in order to select the "fit-for-purpose" method; (iii) qualifying, in term of trace elements spatial variability, a reference site for national and international inter-comparison exercises. Preliminary results and considerations are illustrated.     

Precaution,uncertainty and causation in environmental decisions

What measures of uncertainty and what causal analysis can improve the management of potentially severe, irreversible or dreaded environmental outcomes? Environmental choices show that policies intended to be precautionary (such as adding MTBE to petrol) can cause unanticipated harm (by mobilizing benzene, a known leukemogen, in the ground water). Many environmental law principles set the boundaries of what should be done but do not provide an operational construct to answer this question. Those principles, ranging from the precautionary principle to protecting human health from a significant risk of material health impairment, do not explain how to make environmental management choices when incomplete, inconsistent and complex scientific evidence characterizes potentially adverse environmental outcomes. Rather, they pass the task to lower jurisdictions such as agencies or authorities. To achieve the goals of the principle, those who draft it must deal with scientific casual conjectures, partial knowledge and variable data. In this paper we specifically deal with the qualitative and quantitative aspects of the European Union's (EU) explanation of consistency and on the examination of scientific developments relevant to variability and uncertain data and causation. Managing hazards under the precautionary principle requires inductive, empirical methods of assessment. However, acting on a scientific conjecture can also be socially unfair, costly, and detrimental when applied to complex environmental choices. We describe a constructive framework rationally to meet the command of the precautionary principle using alternative measures of uncertainty and recent statistical methods of causal analysis. These measures and methods can bridge the gap between conjectured future irreversible or severe harm and scant scientific evidence, thus leading to more confident and resilient social choices. We review two sets of measures and computational systems to deal with uncertainty and link them to causation through inductive empirical methods such as Bayesian Networks. We conclude that primary legislation concerned with large uncertainties and potential severe or dreaded environmental outcomes can produce accurate and efficient choices. To do so, primary legislation should specifically indicate what measures can represent uncertainty and how to deal with uncertain causation thus providing guidance to an agency's rulemaking or to an authority's writing secondary legislation. A corollary conclusion with legal, scientific and probabilistic implications concerns how to update past information when the state of information increases because a failure to update can result in regretting past choices. Elected legislators have the democratic mandate to formulate precautionary principles and are accountable. To preserve that mandate, imbedding formal methods to represent uncertainty in the statutory language of the precautionary principle enhances subsequent judicial review of legislative actions. The framework that we propose also reduces the Balkanized views and interpretations of probabilities, possibilities, likelihood and uncertainty that exists in environmental decision-making.