Cities are severely affected by air pollution. Local emissions and urban structures can produce large spatial heterogeneities. We aim to improve the estimation of NO2, O3, PM2.5 and PM10 ...concentrations in 6 Italian metropolitan areas, using chemical-transport and machine learning models, and to assess the effect on population exposure by using information on urban population mobility. Three years (2013–2015) of simulations were performed by the Chemical-Transport Model (CTM) FARM, at 1 km resolution, fed by boundary conditions provided by national-scale simulations, local emission inventories and meteorological fields. A downscaling of daily air pollutants at higher resolution (200 m) was then carried out by means of a machine learning Random-Forest (RF) model, considering CTM and spatial-temporal predictors, such as population, land-use, surface greenness and vehicular traffic, as input. RF achieved mean cross-validation (CV) R2 of 0.59, 0.72, 0.76 and 0.75 for NO2, PM10, PM2.5 and O3, respectively, improving results from CTM alone. Mean concentration fields exhibited clear geographical gradients caused by climate conditions, local emission sources and photochemical processes. Time series of population weighted exposure (PWE) were estimated for two months of the year 2015 and for five cities, by combining population mobility data (derived from mobile phone traffic volumes data), and concentration levels from the RF model. PWE_RF metric better approximated the observed concentrations compared with the predictions from either CTM alone or CTM and RF combined, especially for pollutants exhibiting strong spatial gradients, such as NO2. 50% of the population was estimated to be exposed to NO2 concentrations between 12 and 38 μg/m3 and PM10 between 20 and 35 μg/m3. This work supports the potential of machine learning methods in predicting air pollutant levels in urban areas at high spatial and temporal resolutions.
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•Machine learning methods were applied to obtain pollutant concentration in urban areas.•Population weighted exposure was estimated using dynamic mobile phone location data.•Long term NO2, PM, and O3 daily concentrations were provided for 6 urban areas.•Differences among cities were found with spatial/geographical concentration gradients.
Bulk specific gravity, G^sub mb^, is of outstanding importance in bituminous mixes. Life cycle costs, contract requirements, and Quality Control/Quality Assurance procedures are strongly dependent on ...the effective G^sub mb^ obtained by suitable design and construction, and compliance with a number of boundary conditions. There are many ways to estimate G^sub mb^, and within-method variance is appreciable. The "transportability" of a G^sub mb^ determined according to a given standard to another standard is therefore a critical issue. Our objective was to study relationships between G^sub mb^ values determined using a given standard to G^sub mb^ estimates calculated by applying other standards. We derived a model, and conducted experiments using five different methods. The model evaluates the elementary volumes that contribute to differences among the five considered methods. A tendency toward a common maximum value is assumed. The results are analyzed and interpreted, and the conceptual framework validated. Useful relationships between specific gravities determined by different methods are derived and analyzed. Power-asymptotic curve analysis yielded an algorithm well-grounded in logic to solve the issue of G^sub mb^ transportability. PUBLICATION ABSTRACT
The role of atmospheric dispersion models is becoming increasingly relevant to assess air pollution urban population exposure for epidemiological studies. Estimating urban air quality is challenging, ...because of the intrinsic characteristics of cities atmospheric structure, such as high density of primary emissions and presence of local dispersion processes, that produce strong concentration gradients. Therefore, very high spatial resolution simulations may often be required to improve the accuracy of estimations.
The objective of this study is developing a microscale hybrid modelling system (HMS) to carry out, in a reasonable computational time, long-term simulations providing hourly concentration fields at building-resolving scale in extended urban areas in order to calculate annual indicators to evaluate exposure. The proposed system couples two atmospheric dispersion models suited for different scales: a Eulerian chemical transport model, FARM (Flexible Air quality Regional Model), accounting for dispersion phenomena due to regional and local emission sources, and a Lagrangian particle micro-scale dispersion model, PMSS (Parallel Micro Swift Spray), used to compute concentrations induced by vehicular traffic inside the city. The HMS has been applied on 12 × 12 km2 domain in Rome with a horizontal resolution of 4 m for calculating NO2 and PM10 concentrations for all year 2015. This study has been carried out in the frame of project BEEP (Big data in Environmental and occupational Epidemiology), that is an Italian research project in epidemiological field.
Results show that the combined use of the two models reproduces the spatial and temporal variability of the observed atmospheric pollutants with a good agreement. The statistical analysis performed on daily average concentrations proves that the HMS suits the standard acceptance criteria for urban dispersion model evaluation, with a FAC2 of 0.92 and 0.80 and a Fractional Bias of −0.03 and −0.2 for NO2 and PM10 respectively.
Furthermore, the implementation of an innovative kernel method to calculate concentrations in PMSS has made possible to reduce the computational time by 80%, leading to an average computational time of 3 h per simulated day on an HPC (High Performance Computing) system with 180 cores.
•Hybrid modelling approach to model air pollutant dispersion in an urban environment.•Long-term simulations over extended urban areas at building-resolving scale.•Combining micro-scale Lagrangian Particle Dispersion Model and Chemical Transport Model.•Innovative time-saving kernel method to compute concentrations at micro-scale.•Supporting advanced high-quality exposure assessment epidemiology studies.
Fuel Resistance of HMAs: Theory and Experiments Pratico, Filippo G; Ammendola, Rachele; Moro, Antonino
International Journal of Pavement Research and Technology,
07/2008, Letnik:
1, Številka:
3
Journal Article
Recenzirano
Fuel spillage on pavement during road transportation can cause deaths, great property damages, and a related decrease level of road safety. Therefore, as far as Hot Mix Asphalts (HMAs) are concerned, ...the choice of asphalt binders and a specific mix design are of paramount importance in disaster mitigation. In the light of above-mentioned facts, a new model for the analysis of the consequences of fuel spillage has been proposed and validated. The main objectives of the model were the expression of the loss mass (percentage) after soaking in the fuel and after brushing. The purposes of the research were to understand system response to changes in properties, to get a sense for which parameters of bituminous mix control its behavior, and finally to help design the experiments and choose mix type. Laboratory evaluation studies indicate that the formalized models seem to be effective in helping to predict the chemical resistance of HMAs. PUBLICATION ABSTRACT
Fire extinguishers must be maintained at regular intervals and many problems arise when fire-resistant dry powders need replacement. We analyze the potential of fire extinguisher powder (termed REP) ...as a filler in bituminous mixes. REP and REP-admixed bituminous mixes were subjected to chemical analysis, and the mechanical properties and environmental performances of the mixes were tested. Mixes with different REP contents were prepared. Mechanical performance was adequate and environmental compatibility was achieved. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined.
Lo scopo del lavoro è stato quello di sviluppare un profilometro per misure di tessitura stradale, al fine di studiarne la correlazione con il rumore di rotolamento. Il software di analisi è basato ...su una procedura che permette anche una stima dell’incertezza di misura. Sono state analizzate misure di tessitura e di rumore ottenuto col metodo CPX su diversi tipi di pavimentazione, e sono stati studiati alcuni modelli, tenendo conto del concetto di tessitura efficace. --- The purpose of this work was to develop a laser profilometer focused on the measurement of texture of road pavements, in order to study its correlation with rolling noise. The elaboration software is based on a procedure that yields information about uncertainties of measurements. The analysis has involved road texture measurements and rolling noise measured according to the CPX method on different pavements; several models have been studied, taking into account tyre envelopment of road texture.
Porous European mixes, PEMs, are porous asphalts which when compacted have an air void content usually in excess of 20%. PEMs points of strength are reduction of splash and spray, mitigation of ...outdoor noise, optimization of skid resistance at high speeds in wet conditions. Conversely, PEMs have quite low bearing properties, clogging, variation of volumetrics over the time, variation of noise, texture, friction, and permeability performance over the time. Furthermore, at the end of their lifecycle many issues arise: RAP variability, uncertainties on the potential for high percentage recycling, potential for recycling a surface layer back to a surface layer. Based on the abovementioned facts, objectives and scopes were then focused into the analysis of the feasibility of a two-layer porous asphalt (TLPA) by recycling from-PEM RAP, when highly variable rap stockpiles are involved. The following main issues were addressed: mitigating the clogging and its related consequences (acoustic and drainability performance over the time); preserving traditional (bearing properties, skid resistance) and premium (silentness, drainagebility) performance; recycling high percentages of from-PEM RAP. Materials selection was followed by mixtures production. Traditional and advanced tests on RAP and recycled mixes were carried out. RAP variability was examined and a method for facing its consequences was proposed. Mechanical performance was adequate and environmental compatibility was achieved. Functional performance resulted very promising. Results are encouraging about the possibility of achieving a satisfactory level of surface performance. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined.
Wear at the interface between flexible pavements and tires influences pavement life, pavement cycle costs, and tire consumption, and is a source of environmental harm. Wear-related processes evolve ...over time and are affected by a number of boundary conditions, such as interface fluids, water and fuels. We develop a model explaining and predicting mass losses in flexible pavements under carefully controlled conditions, and with estimation of the related environmental costs. We also employed an accelerated loading test. Under normal conditions, the environmental impact of pavement wear is not greatly influenced by mix type or volumetrics. Indeed, the presence of hazmat materials, traditional, dense mixes have an environmental impact that is appreciably lower than that of porous European mixes.
The goal of this paper is confined to the derivation of an equation for the analysis of the phenomenon of water flows along an asphalt pavement. By referring to the general theory for the percolation ...of water in rigid porous materials, we propose the theoretical derivation of models for some tests on asphalts. In order to validate the formalized models and to analyze the relationships among the main indicators introduced, in-field experiments were designed and performed. As our main results, we develop a model for tests on asphalts and validate it partially by means of our experimental results.
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