Development and Evaluation of a Fluctuating Plume Model for Odor Impact Assessment

For environmental odor nuisance, it is extremely important to identify the instantaneous concentration statistics. In this work, a Fluctuating Plume Model for different statistical moments is proposed. It provides data in terms of mean concentrations, variance, and intensity of concentration. The 90th percentile peak-to-mean factor, R90, was tested here by comparing it with the experimental results (Uttenweiler field experiment), considering different Probability Distribution Functions (PDFs): Gamma and the Modified Weibull. Seventy-two percent of the simulated mean concentration values fell within a factor 2 compared to the experimental ones: the model was judged acceptable. Both the modelled results for standard deviation, σC, and concentration intensity, Ic, overestimate the experimental data. This evidence can be due to the non-ideality of the measurement system. The propagation of those errors to the estimation of R90 is complex, but the ranges covered are quite repeatable: the obtained values are 1–3 for the Gamma, 1.5–4 for Modified Weibull PDF, and experimental ones from 1.4 to 3.6.

Modelling Exposure from Airborne Hazardous Short-Duration Releases in Urban Environments

When considering accidental or/and deliberate releases of airborne hazardous substances the release duration is often short and in most cases not precisely known. The downstream exposure in those cases is stochastic due to ambient turbulence and strongly dependent on the release duration. Depending on the adopted modelling approach, a relatively large number of dispersion simulations may be required to assess exposure and its statistical behaviour. The present study introduces a novel approach aiming to replace the large number of the abovementioned simulation scenarios by only one simulation of a corresponding continuous release scenario and to derive the exposure-related quantities for each finite-duration release scenario by simple relationships. The present analysis was concentrated on dosages and peak concentrations as the primary parameters of concern for human health. The experimental and theoretical analysis supports the hypothesis that the dosage statistics for short releases can be correlated with the corresponding continuous release concentration statistics. The analysis shows also that the peak concentration statistics for short-duration releases in terms of ensemble average and standard deviation are well correlated with the corresponding dosage statistics. However, for more reliable quantification of the associated correlation coefficients further experimental and theoretical research is needed. The probability/cumulative density function for dosage and peak concentration can be approximated by the beta function proposed in an earlier work by the authors for continuous releases.

Simple solutions for the concentration fluctuations of a passive scalar

<p>The dispersion dynamics of a contaminant released in the atmosphere is crucial for risk assessments and environmental analyses. Yet, because of the unsolved problem of turbulence, analytical solutions physically-derived are currently limited to the Gaussian models for the mean concentration field. In this work, we have obtained simple solutions for the concentration statistics of a passive scalar released from a punctual source. The main result is a novel analytical solution for the passive scalar variance, which is obtained from the contaminant transport equation. We have verified this solution against wind-tunnel data, and further adopted it in a simple stochastic model to provide closed relationships for the temporal statistics of concentration (e.g., the mean duration and occurrence of the peak events). These results may serve as a rapid and practical way to estimate the intensity and duration of the concentration fluctuations of a pollutant released in the atmosphere.</p>

Cluster identification

Purpose This paper aims to contribute to the approaches based on traditional industry concentration statistics for identifying clusters by complementing them with the techniques of exploratory spatial data analysis (ESDA). Design/methodology/approach Using a sample with 34,500 observations retrieved from the social information annual report released by Brazil Ministry of Labor and Employment, the methodology was designed to make a comparison between the application of industry concentration statistics and ESDA statistics. Findings As the results show, the geographic distribution measures proved to be fundamental for longitudinal studies on regional dynamics and industrial agglomerations, and the local indicator of spatial association statistic tends to overcome the limitation of the industry concentration approach. Research limitations/implications In the period considered, due to economic, structural and circumstantial questions, activities linked to the transformation industry have been losing ground in the value creation process in Brazil. In this sense, the study of other industries may generate other types of insights that should be considered in the process of regional development. Originality/value This paper offers a critical analysis of empirical approaches and methodological advances with an emphasis on the treatment of special effects: spatial dependence, spatial heterogeneity and spatial scale. However, the regional dynamic presents a temporal dimension and a spatial dimension. The role of space has increasingly attracted attention in the analysis of economic changes. This work has identified opportunities for incorporating spatial effects in regional analysis over time.

Correction: Galešić, M., et al. New Screening Tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries. Water 2018, 10, 639

The authors wish to make the following correction to their paper [...]

New Screening tool for Obtaining Concentration Statistics of Pollution Generated by Rivers in Estuaries

Rivers represent an essential pathway for waterborne transport, and therefore estuaries are critical coastal areas for a pollution hazard that might lead to eutrophication and general water quality deterioration. When addressing these problems, the decision makers and coastal managers often need additional skills and specialists, so they engage consultants in developing models and providing potential solutions. Different stakeholders’ interests present a challenge in the implementation process of proposed solutions. Nevertheless, if the relevant institutions were presented with a screening tool, enabling them with a certain level of solution ownership, potentially more involvement would occur. There are numerous intertwined physical processes present in the estuary ecosystem, including river discharge, tidal forces, wind-induced stress and water density variations. This research utilizes an analytical model based on ensemble averaging and near-field approximation of the advective-diffusion equation for the case of continuous, steady, conservative solute transport in a stratified, river-dominated estuary. Such an approach significantly reduces the costs and time needed to obtain enough measured data required for common statistical analysis or the need for a more complex numerical model. The developed methodology is implemented into a simple software named CPoRT (Coastal Pollution Risk Tool) within a recently conducted research project funded by European Social Fund.

Concentration Statistics for Conservative Solute Transport in River Estuaries

When addressing water quality issues in coastal zone management, rivers are considered to be among the most significant pathways for waterborne solute transport. On the other hand, estuaries are some of the most productive environments on Earth and multiple interests from different stakeholders put additional pressure on such an ecosystem. Estuaries are thus among the most critical areas for pollution hazard and a lot of research is being conducted in order to ensure their sustainable development. The flow in an estuary is characterized by a mixing process, which results from a combination of small-scale turbulent diffusion and larger-scale variation of mean advective velocities. Scalar concentration in such turbulent flows is a random variable, which requires a statistical approach. This thesis focuses on the development of two analytical methodologies for obtaining concentration statistics of a conservative contaminant generated by a steady river flow in a salt-wedge estuary. Analytically obtained concentration statistics, which include concentration moments, probability density function defined in point, spatially integrated moments, and expected mass fraction, significantly reduce the costs and time needed for obtaining the measured data. Although these analytical models lack the level of detail possessed by sophisticated numerical models, they can generate results within seconds and with little preprocessing. Therefore, the developed analytical models represent screening tools for obtaining concentration statistics of pollution in estuaries, and can be used by stakeholders of different backgrounds. While investigating various validation procedures for the developed analytical models, and using the case study of the Žrnovnica River estuary, near Split, Croatia, several new findings were obtained. For instance, a new model for mean velocity attenuation was proposed and verified. Furthermore, a new proxy concentration was tested and, combined with numerical modeling, it delivered qualitative verification of analytically obtained concentration statistics. The analytical model for point concentration statistics was implemented in a user-friendly computer application (CPoRT) and presented to different stakeholders as a screening tool. Finally, the most important scientific contributions of this thesis are the development of the semi-analytical approach for obtaining concentration statistics in a river-dominated estuary, application of proxy concentration using the salinity data and the introduction of the expected mass fraction as a significant novelty to address the pollution loading to coastal waters.