1,720,957 research outputs found
Absolute risk analysis applied to contaminated sites
Full text linkLo strumento “Analisi di Rischio” per la valutazione dei siti contaminati è in uso da alcune decine di anni ed ha ricevuto un forte impulso negli USA con il Programma Superfund ed in Europa con l’emergere del problema del risanamento di un numero molto ampio di siti e con l’avvio di programmi di collaborazione internazionale.
La procedura di analisi di rischio può essere condotta in modalità diretta (forward mode) o inversa (backward mode). La modalità diretta permette di stimare il rischio sanitario per il recettore esposto, sia posto in prossimità del sito (on-site) che ad una certa distanza (off-site), conoscendo la concentrazione in corrispondenza della sorgente di contaminazione. Avendo invece fissato il livello di rischio per la salute ritenuto accettabile per il recettore esposto, la modalità inversa permette il calcolo della massima concentrazione in sorgente compatibile con la condizione di accettabilità del rischio.
L’Agenzia Italiana per la Protezione dell’Ambiente ed i Servizi Tecnici (ora ISPRA, già APAT) ha recentemente sviluppato delle linee guida che forniscono una procedura standard per l’applicazione dell’analisi di rischio ai siti contaminati. In particolare sono fornite delle indicazioni tecniche per l’esecuzione di un livello 2 di analisi di rischio; tale livello di analisi si basa su alcune assunzioni semplificative:
• il trasporto dei contaminanti viene descritto attraverso equazioni analitiche che però non sono state validate né attraverso un confronto con dati sperimentali né attraverso un confronto con i risultati forniti da modelli numerici.
• Non viene considerata l’attenuazione della contaminazione attraverso il fenomeno biodegradativo.
• La catena alimentare non viene considerata come possibile via di esposizione alla contaminazione.
Inoltre, quando il lavoro di dottorato è stato iniziato, la prima revisione delle linee guida fornite dall’APAT comprendeva unicamente la procedura per l’applicazione dell’analisi di rischio in modalità diretta.
Lo scopo del presenta lavoro di dottorato, che è stato sovvenzionato dall’APAT, è stato quello di implementare la procedura di analisi di rischio proposta nelle linee guida andando a sviluppare le tematiche viste precedentemente.
Nel capitolo 1, dopo un breve introduzione sui fondamenti dell’analisi di rischio, è stata sviluppata una procedura per il calcole delle concentrazioni soglia di rischio, cosi come richiesto dalla nuova legislazione italiana (D.M. 152/06)
Nel capito 2 sono state analizzate le procedure e le assunzioni sulla catena alimentare vegetale proposte da alcuni documenti tecnici e software, è stata quindi proposta una procedura standard da implementare nella struttura dell’analisi di rischio.
Nel capitolo 3 sono stati confrontati i risultati ottenuti dall’applicazione delle equazioni analitiche per il trasporto dei contaminanti, utilizzate nel livello 2 di analisi, con quelli forniti dai modelli numerici di trasporto. in particolare sono stati analizzati due fattori di trasporto:
• il fattore di lisciviazione, LF, che descrive il trasporto dei contaminanti nella zona insatura;
• il fattore di attenuazione laterale in falda, DAF, che descrive il trasporto dei contaminanti nella zona satura.
Nel capitolo 4 è stata studiata l’influenza del fenomeno biodegradativo in zona insatura sull’intrusione indoor dei contaminanti, in modo da capire quanto tale fenomeno sia influente nella volatilizzazione in ambienti confinati.
Infine, durante le attività di dottorato, è stato sviluppato un software di analisi di rischio basato sulle linee guida APAT integrato con un database contenente le caratteristiche chimico-fisiche e tossicologiche dei contaminanti.The instrument 'Risk Analysis' for the assessment of contaminated sites has been used for several years and has received a strong boost in the U.S. in the framework of the Superfund Program and in Italy has gained wider relevance after the introduction of new environmental legislation.
Risk analysis is currently the most advanced procedure for the evaluation of the degree of contamination of an area and to define the priorities and modalities of intervention in the site itself. The risk analysis procedure can be conducted in forward mode or backward mode. The forward mode allows estimating the health risk for the exposed receptor, whether located near the site (on-site) or at some distance (off-site), given the concentration at the source of contamination. Having instead set the level of risk to health considered acceptable to the exposed receptor, the backward mode allows the calculation of the highest concentration at the source compatible with the condition of acceptability of the risk, i.e. the so-called site-specific target level.
The Italian Agency for Environmental Protection (now ISPRA, formerly APAT) has recently issued a guideline document that provides a standard procedure for application of risk analysis to contaminated sites. This guideline document is based on a Tier 2 risk analysis approach, which is based on a series of simplifying assumptions:
• Contaminant transport is described through the analytical equations which are not validated with experimental data or with numerical model results.
• Attenuation of contaminant through biodegradation phenomena is not accounted for;
• Exposure to contaminants through the food chain is neglected.
Besides, when this thesis was started, the document included only the procedure for applying the risk analysis in forward mode.
The work performed within this PhD thesis, supported by APAT, was to upgrade the procedure for application of risk analysis to contaminated sites, including also the unresolved issues listed above.
In chapter 1, after a short background on the fundamentals of risk analysis, a procedure to obtain the threshold risk concentration, as requested by the new Italian legislation (D.M. 152/06) was developed.
In chapter 2 the assumption and the procedure suggested by several technical documents and software on the exposure through the food chain were analyzed and a standard procedure was suggested for implementation in the risk analysis framework.
In chapter 3 the results of the analytical equation selected for tier II risk analysis were compared with those provided by numerical transport models. The validation of the equations for Tier 2 risk analysis was performed on two key transport factors:
• The Leaching Factor, LF, which describes the contaminant transport through the vadose zone;
• The Dilution Attenuation Factor, DAF, which describes the contaminant transport through the acquifer.
In chapter 4 the influence of the vadose zone biodegradation related to the indoor vapour intrusion was studied in order to understand how this phenomena can influence the chemical volatilization to indoor environment.
Besides, in the framework of the PhD activities, a risk analysis software, based on the APAT guidelines, was developed and linked to a database of the chemical and toxicological properties of the contaminants, properly developed
Confronto tra modelli numerici e fattori di trasporto usati nell'analisi di rischio di livello 2.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
