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.     

Environmental odours assessment from waste treatment plants: dynamic olfactometry in combination with sensorial analysers "electronic noses"

After an overview about the criteria of odour nuisance in different technical laws, about electronic noses analysers and about dynamic olfactometry, in the present paper the authors describe an application of dynamic olfactometry in combination with the determinations of electronic noses. The coordination of the two approaches permits optimisation of the advantages offered by both methods to the measurable and objective evaluation of the odour nuisance from waste treatment plants and chemical plants.     

Interlinked temporal changes in environmental conditions, chemical characteristics of sediments and macrofaunal assemblages in an estuarine intertidal sandflat (Seto Inland Sea, Japan)

Five field surveys were conducted in an estuarine intertidal sandflat of the Seto Inland Sea (Japan) between April 1994 and April 1995. Chlorophyll a, pheopigments, total organic carbon and acid-volatile sulphides (AVS) of surface and subsurface sediments, and macrofaunal assemblages were investigated in parallel at 15 stations. Monthly hydrological data of low-tide creek water adjacent to the flat were used as a complementary environmental characterisation of the study area. Strong temporal changes were found among sampling dates, most remarkably in autumn with a major increase of algal detritus and AVS, a sharp reduction in macrofaunal abundances and species richness, and a massive mortality of the clam Ruditapes philippinarum. This dystrophic event was preceded by a photoautotrophic and hypertrophic spring–summer characterized by abundant fresh (i.e., living) algal material, including microphytobenthos and macroalgae (Ulva sp.). In summer, abundant macrofaunal assemblages reached the highest biomass values (455 g wet weight m⁻² or 60.6 g ash free dry weight m⁻²), with a major contribution of filter-feeding bivalves Musculista senhousia and R. philippinarum. These are among the highest values reported in the literature for sedimentary shores. From autumn, there was a progressive recolonisation of macrofauna, initiated by few opportunistic polychaetes (e.g., Cirriformia tentaculata and Polydora sp.), apparently promoting a fast sediment recovery in winter, and followed by new bivalve recruits in the next spring. This study provides the first evidence of significant and interlinked within-year changes in chemical characteristics of sediments and macrofaunal assemblages in an estuarine intertidal flat at a small spatial scale (i.e., tens of meters). This demonstrates the high temporal variability of species–environment relations in these systems and a close relationship in seasonally driven trophodynamic processes among primary producers and benthic consumers. We conclude that a thorough parallel evaluation of the temporal changes in chemical characteristics of sediments should be taken into account in assessing the year-round distribution and changes of intertidal macrofauna, particularly in eutrophic, estuarine intertidal flats.An erratum to this article can be found at     

Validation and global uncertainty of a gas chromatographic with mass spectrometry method for fenamidone analysis in grapes and wines

Fenamidone is an imidazolinone fungicide recently introduced in viticulture practices. This work reports the validation and assessment of global uncertainty of a gas chromatographic with mass spectrometry method to analyze fenamidone in grapes and wines. This method consists in a simple and fast liquid-liquid extraction step followed by chromatographic determination. Limits of detection for fenamidone in grapes and wines were, respectively, 0.05 mg/kg and 0.06 mg/L, precision was below 9.4% and average recovery was 89 +/- 5%. In the concentration range from 0.05 to 1.00 mg/kg (or mg/L) of fenamidone, global uncertainty calculated following the EURACHEM/CITAC rules, and also by the Horwitz function, was below 25%. The EURACHEM/CITAC global uncertainty budget used gave lower estimates than those obtained from the Horwitz function.     

Comparative study based on sediment characteristics and macrobenthic communities in two Italian lagoons

The aims of this study were to analyse sediment characteristics and macrobenthic assemblages in two very close Italian coastal lagoons (Lesina and Varano) and to assess the different behaviour between the two basins and the relationship between sediment matrix and benthic organisms within and between the two lagoons. The comparative study was performed in July 2007 at 13 sampling sites in Lesina lagoon and 15 sites in Varano basin for sediment grain size, total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and macrobenthic structure analyses. Both lagoons were generally dominated by fine-grained sediments (clay and silt components). The average contents of TOC and TN measured in Lesina was higher than in Varano (3.31% vs 2.52% for TOC and 5,200 μg·g^???1 vs 3,713 μg·g^???1 for TN); in contrast, the TP was lower (540 μg·g^???1 vs 620 μg·g^???1). Based on macrobenthic community patterns, the central zone in Varano lagoon and the eastern area in Lesina lagoon were characterised by the lowest abundance (168.7 ind·m^???2 and 503.2 ind·m^???2, respectively) and by the lowest number of species, as highlighted by the diversity indices (Shannon–Wiener, H ^′ range was 0.47–1.45 for Lesina and 0.00–1.68 for Varano; Margalef species richness, d range was 0.00–1.67 for Lesina lagoon and 0.00–2.38 for Varano basin). Ordination diagrams suggested an influence of marine and freshwater inputs on the sediment distribution in Varano lagoon and on macrobenthic assemblages in Lesina lagoon.     

Is the diversity of epiphytic lichens a reliable indicator of air pollution? A case study from Italy

This work provided additional information for a better interpretation of lichen diversity values in biomonitoring studies of air pollution. The effects of 12 predictive variables were estimated for the Genova province (NW Italy) by means of a non-parametric model. The diversity of epiphytic lichens was strictly correlated with mean annual rainfall and mean annual temperature. Different variables were found to affect the lichen diversity in urban vs. forested areas. In urban areas, air pollutants, mainly SO2, are still the main limiting factor, even if under ameliorating conditions this relationship becomes less significant. In forested areas, harvesting and forest fires showed a predominant effect, suggesting the need to develop a more defined sampling protocol to estimate atmospheric pollution in such ecosystems.     

A stochastic Lagrangian micromixing model for the dispersion of reactive scalars in turbulent flows: role of concentration fluctuations and improvements to the conserved scalar theory under non-homogeneous conditions

Several reaction schemes, based on the conserved scalar theory, are implemented within a stochastic Lagrangian micromixing model to simulate the dispersion of reactive scalars in turbulent flows. In particular, the formulation of the reaction-dominated limit (RDL) reaction scheme is here extended to improve the model performance under non-homogeneous conditions (NHRDL scheme). The validation of the stochastic model is obtained by comparison with the available measurements of reactive pollutant concentrations in a grid-generated turbulent flow. This test case describes the dispersion of two atmospheric reactant species (NO and O₃) and their reaction product (NO₂) in an unbounded turbulent flow. Model inter-comparisons are also assessed, by considering the results of state-of-the-art models for pollutant dispersion. The present validation shows that RDL reaction scheme provides a systematic overestimation (relative error of ca. 85% around the centreline) in computing the local reactant consumption/production rate, whereas the NHRDL scheme drastically reduces this gap (relative error lower than 5% around the centreline). In terms of NO₂ production (or reactant consumption), neglecting concentration fluctuations determines overestimations of the product mean of around 100% and a NO₂ local production of one order of magnitude higher than the reference simulation. In terms of standard deviations, the concentration fluctuations of both the passive and reactive scalars are generally of the same order of magnitude or up to 1 or 2 orders of magnitudes higher than the corresponding ensemble mean values, except for the background reactant close to the plume edges. The study highlights the importance of modelling pollutant reactions depending on the instantaneous instead of the mean concentrations of the reactants, thus quantifying the role of the turbulent fluctuations of concentration, in terms of scalar statistics (mean, standard deviation, intensity of fluctuations, skewness and kurtosis of concentration, segregation coefficient, simulated reaction rate). This stochastic particle method represents an efficient numerical technique to solve the convection–diffusion equation for reactive scalars and involves several application fields: micro-scale air quality (urban and street-canyon scales), accidental releases, impact of odours, water quality and fluid flow industrial processes (e.g. combustion).     

Fate of azadirachtin A and related azadirachtoids on tomatoes after greenhouse treatment

The degradation of the main azadirachtoids on tomatoes was studied after greenhouse treatment. These experiments were carried out at 1 and 5× the concentration recommended by the manufacturer. In all experiments the deposition of azadirachtin A (AZA-A) was below the maximum residue level (MRL). Even if at the highest dose, AZA-A half-life time calculated as pseudo first order kinetic was 1.2 days in agreement with the recommended preharvest interval (PHI) of 3 days. Experiments with a model system showed that sunlight photodegradation is the main factor influencing the rate of disappearance of AZA-A after greenhouse treatment while tomato epicuticular waxes doubled the photodegradation rate of AZA-A in a commercial formulation.     

Effect of modified Fenton treatment on the thermal behavior of contaminated harbor sediments

This study presents the results of experimental Fenton-like treatments conducted on marine sediment slurries (2g sediment vs. 20 ml liquid). The sediment was collected in a harbor situated in a high density industrial area, characterized by a great hydrocarbon C>12 and PAHs contamination. The investigated parameters were: the H(2)O(2) dose, the reagent's pH and the effect of a phosphate salt and ferrous iron addition. To evaluate sediment's characteristics COD, particle size, thermogravimetric and differential thermal analyses were performed under N(2) and O(2) atmosphere while dissolved organic carbon and COD analyses were performed on the filtrate. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the organic carbon (up to 78% decrease of the 200-400 degrees C labile organic matter), to lower the COD of the sediment (60% COD removal maximum) and to increase the cumulated distribution undersize. In addition as the treated sediment showed easier-to-handle characteristics, reduced caking and lower aggregation capacity, the modified Fenton treatment could also be considered a pre-treatment of a successive thermal treatment.