Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

Von Neumann: non solo architetto

Opera biografica su John von Neumann che punta a considerare tutti i suoi contributi alla comunità scientifica (come logico, matematico, fisico, economista) oltre a quelli più noti come informatico.

Proposta di traduzione dall'italiano al tedesco di una selezione di testi tratti dall'opera di Matteo Marani "Dallo scudetto ad Auschwitz": "Von der italienischen Fussballmeisterschaft nach Auschwitz"

La seguente tesi si prefigge lo scopo di far conoscere a un pubblico di lingua tedesca l'avvincente storia di Arpad Weisz, l'allenatore ebreo-ungherese del Bologna durante il periodo nazi-fascista. La parte centrale e' composta dalla traduzione dall'italiano al tedesco di una selezione di testi tratti dall'opera di Matteo Marani "Dallo scudetto ad Auschwitz" e oltre alla traduzione, la tesi si compone inoltre di un introduzione, di una parte teorica in cui vengono esplicate brevemente le caratteristiche del processo traduttivo insieme alle varie tipologie testuali e infine vi e' il commento alla traduzione, il quale espone le strategie utilizzate per risolvere i problemi traduttivi incontrati durante il lavoro.

Wilfred Von Oven, “Un «nazista» in Argentina”: primi risultati di una ricerca sulla figura dell’addetto stampa personale di Joseph Goebbels

L'elaborato si incentra sulla figura di Wilfred Von Oven (1912-2008), addetto stampa personale di Joseph Goebbels che, a guerra finita, si trasferì in Argentina, dove lavorò come giornalista e visse fino alla morte. Il ritratto di Von Oven che viene presentato si basa su due principali documenti: un'intervista in lingua spagnola realizzata per la televisione argentina e conservata nell'Archivio Storico dell'Istituto Luce Cinecittà a Roma e la sua autobiografia in lingua tedesca, consultata presso la sede di Francoforte della Biblioteca Nazionale Tedesca. A partire da queste fonti, e da altri documenti, l'elaborato ricostruisce la biografia di Von Oven e analizza tratti della sua personalità e mentalità, con particolare riferimento alle posizioni nazionalsocialiste e revisioniste del suo pensiero. L'elaborato, in mancanza di documentazione in lingua italiana su Wilfred Von Oven, si propone di presentare i primi risultati di una ricerca su questo personaggio storico, ricerca che non può dirsi conclusa dati i molti punti interrogativi che rimangono intorno ad alcuni aspetti della vita e della mentalità di Von Oven.

Wie Kinder kommunizieren: Die geheime Sprache von Bildern und Spielen

“Un bambino è un libro da leggere[...]” L’aforisma del poeta e scrittore austriaco Peter Rosegger introduce perfettamente il presente elaborato, il cui scopo è quello di capire il linguaggio segreto delle immagini e dei giochi dei bambini. Il lavoro, infatti, chiarirà come interpretare le immagini infantili e come scoprirne i significati nascosti; inoltre verranno approfonditi i diversi giochi effettuati dai bambini, perché anche questi rappresentano un’importante forma di comunicazione. Per questo, nell’elaborato, verrà attribuito un ruolo di primo piano alla comunicazione non verbale. L’intenzione del presente elaborato è quella di portare l’attenzione del lettore sulle immagini e sui giochi utilizzati dai bambini, in quanto forme di comunicazione che trasmettono messaggi più chiari e veritieri della lingua stessa. Di seguito verranno riportati molti esempi che renderanno più comprensibile l’argomento. L’elaborato è composto da tre macrosezioni: nella prima verrà trattata la prima forma di comunicazione, prestando particolare attenzione al significato del pianto e del sorriso; nella seconda ci si occuperà del linguaggio segreto delle immagini realizzate dai bambini e dell’interpretazione di queste ultime; la terza e ultima sezione, invece, affronterà il linguaggio segreto del gioco attraverso l’analisi di tre giochi conosciuti e significativi.

I contratti internazionali: proposta di traduzione italiano-tedesco di un contratto di concessione di vendita

Gegenstand der vorliegenden Masterarbeit ist die Übersetzung eines Alleinvertriebsvertrages zwischen einem italienischen Hersteller und einem deutschen Vertragshändler aus dem Italienischen ins Deutsche. Die Entscheidung für dieses Thema hat zwei Gründe: die Leidenschaft für das Recht und für die Rechtsübersetzung und die Möglichkeit, ein übliches Szenario in der heutigen Realität der Handelsbeziehungen zwischen Italien und Deutschland aufzuzeigen. Die Arbeit besteht aus sechs Kapiteln, an die sich drei Anhänge anschließen: Der erste enthält ein mit SDL MultiTerm erstelltes Termbase mit den aus übersetzerischer Sicht wichtigsten Termini, die im italienischen Vertrag gefunden wurden. Der zweite beinhaltet den Originaltext auf Italienisch. Der dritte Anhang schließlich besteht aus dem Fragebogen, der zwecks Analyse der Tendenz bezüglich der Abfassung und/oder Übersetzung internationaler Verträge erstellt und internationalen Anwaltskanzleien vorgelegt wurden, sowie die Antworten seitens der kontaktierten Kanzleien. Das erste Kapitel beinhaltet eine kontrastive Analyse betreffend die allgemeine Disziplin der Verträge in Italien und in Deutschland, mit der die Ähnlichkeiten und die Unterschiede zwischen den zwei Rechtsordnungen herausgearbeitet werden. Dieser Teil bietet auch einen Überblick über die Kategorie der Alleinvertriebsverträge, zu der der Originaltext gehört. Das zweite Kapitel behandelt das Thema der internationalen Verträge; insbesondere werden die hauptsächlichen Probleme bei der Abfassung dieser Verträge, sowie die zahlreichen Versuche im Bereich der Harmonisierung des europaischen und internationalen Privatrechts und die Ergebnisse des Fragebogens vorgestellt. Das dritte Kapitel enthält eine Einführung in die Rechtsübersetzung: Nach einer Beschreibung der Kompetenzen eines Rechtsübersetzers und der Merkmale der Rechtssprache werden die besonderen Faktoren, die die Übersetzung von Rechtstexten beeinflussen können, sowie die Unterscheidung zwischen Übersetzungsmethoden und -verfahren erläutert. Das vierte Kapitel beschäftigt sich mit der Analyse des Ausgangstexts im Hinblick auf die Ebenen der Makrostruktur, des Wortschatzes und der Morphosyntax. Nach der Übersetzung des Vertrages ins Deutsche werden im sechsten Kapitel die Übersetzungsschwierigkeiten und die Veränderungen vorgestellt, die bei der Übersetzung vorgenommen wurden.