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.

Phylogeny and phylogeography of the family Hyalidae (Crustacea: Amphipoda) along the northeast Atlantic coasts

The family Hyalidae comprises more than one hundred species, distributed worldwide. They are common and abundant in the littoral and shallow sublittoral habitats and they play an important role in the coastal food chain. Most studies about this family were dealing with taxonomy and ecology, while very little is known about phylogenetic relationship among genera and species. In the present study we aim to achieve the first approach of the phylogenetic patterns of this family in NE Atlantic Ocean and Mediterranean Sea, and to perform the first insight into the phylogeography Apohyale prevostii along both the North Atlantic coasts. In order to do that, eight species belonging to the genera Apohyale, Hyale, Serejohyale and Protohyale were investigated using the mitochondrial COI-5P barcode region. Specimens were collected along European and Moroccan Atlantic rocky shores, including Iceland, the British Isles, Macaronesia and in the Mediterranean Sea. Sequences of A. prevostii, from the NW Atlantic Ocean, available in BOLD and GenBank, were retrieved. As expected, phylogenetic analyses showed highly-divergent clades, clearly discriminating among different species clusters, confirming their morphology-based identifications. Although, within A. perieri, A. media, A. stebbingi, P. (Protohyale) schmidtii and S. spinidactylus, high genetic diversity was found, revealing putative cryptic species. The clade of A. prevostii and A. stebbingi appears well supported and divided from the other two congeneric species, and P. (Protohyale) schmidtii shows a basal divergence. The north-western Atlantic coasts were recently colonized by A. prevostii after the last glacial maximum from the European populations showing also a common haplotype in every population analysed. The use of the COI-5P as DNA barcode provided a good tool to underline the necessity of a revision of this emblematic family, as well as to discern taxonomically the possible new species flagged with this molecular device.

Bioconcentration of selected personal care products in Ruditapes philippinarum (Manila clam)

The Bioconcentration Factor (BCF) is the principal source of information used to assess and regulate the potential hazard and risk for a chemical that has the potential to bioaccumulate in the marine environment, according to the Marine Strategy Framework Directive (MSFD). The main objective of this thesis was to estimate the BCFs of two different emerging contaminants in Ruditapes philippinarum (Manila clam) under controlled laboratory conditions: the UV filter 4-methylbenzylidene camphor (4-MBC) commonly used in skincare products, and the artificial sweetener Acesulfame potassium (ACE-K) used as a food additive. Ruditapes philippinarum organisms were exposed directly to 4-MBC and ACE-K nominal concentration of 1, 10 and 100 μg L-1 during 10 days. Bioconcentration factors (BCFs) were estimated according to 3 different models for both compounds. The 4-MBC estimated BCFs fall in range of 61553 - 539143 L Kg-1, showing that this compound is very bioaccumulative and could also undergo biomagnification in the marine food chain. On the contrary, estimated ACE-K BCF is consistently lower, in order of 7 L Kg-1 for the nominal exposure concentration of 100 μg L-1. The low ACE-K BCF could be explained by its high solubility in water and thus a rapid metabolization by clams during the experiments. In summary, future research focusing on the marine environment is needed on these two emerging compounds.

Food waste along the supply chain. An analysis of nowadays food supply chain challenges in the italian and english contexts

Scopo. Lo scopo di questo studio è esaminare il problema degli sprechi nelle moderne food supply chain, così da consentire una piena comprensione delle principali cause di inefficienza sistemica nell’industria alimentare e individuare potenziali opportunità di miglioramento. Approccio e Metodologia. Per raggiungere gli obiettivi prefissati la presente trattazione si propone di implementare una ricerca empirica basata sull’analisi di due realtà industriali operanti nel settore alimentare. Nello specifico verranno studiate due aziende integrate rispettivamente nel contesto economico italiano e in quello inglese e operanti a due stadi diversi e complementari della filiera alimentare, quello della produzione e quello della distribuzione. Questo studio incrociato consentirà, auspicabilmente, di portare alla luce quegli elementi chiave necessari per una lettura chiara ed esaustiva delle maggiori sfide che le moderne supply chain si trovano a dover affrontare, in una prospettiva di minimizzazione degli sprechi e di accrescimento del valore per il consumatore. Risultati. I risultati che si prevede di ottenere dall’implementazione di questo studio sono fondamentalmente quattro: 1.Piena comprensione del concetto di spreco nell’industria alimentare. 2.Identificazione dei principali fattori chiave che dovrebbero essere attentamente monitorati con lo scopo di conseguire un’efficace riduzione degli sprechi lungo la filiera alimentare. 3.Analisi critica di quelle che sono le più utilizzate pratiche manageriali e operative nelle moderne aziende alimentari. 4.Individuazione dei potenziali sviluppi che potrebbero essere implementati attraverso l’utilizzo delle più recenti ICT in termini di efficienza della supply chain. Valore della Ricerca. Seppure mediante un’analisi prevalentemente di tipo qualitativo, questa trattazione si prefigge di fornire un contributo nell’ambito del food supply chain management che, data la rilevanza del problema relativo agli sprechi, risulta oggi più attuale che mai. L’originalità di questo studio risiede principalmente nelle fonti dei dati che ne hanno costituito le fondamenta: da un lato la ricerca teorica sviluppata nel Regno Unito, dove lo studio della supply chain è ormai da decenni approfondito nelle più importanti Università; dall’altro la ricerca empirica sviluppata sia presso una delle più importanti e moderne aziende alimentari italiane, che presso uno dei più famosi logistics service provider a livello mondiale.