Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), two groups of struc-turally related chlorinated aromatic hydrocarbons, generally referred to as “dioxins” are of great concern due to their extreme toxicity and presence in all compartments of the environment. Since they occur at very low levels, their analysis is complex and challenging, and there is a need for cost-efficient, reliable and rapid analytical alternatives to the expensive methods in-volving use of gas chromatography high-resolution mass spectrometry (GC-HRMS). It is im-portant to routinely monitor food and feed items to detect contaminations at an early stage. For the regulation of dioxins and dioxin-like PCBs in food and feed according to current legis-lation, large numbers of samples have to be analysed. Furthermore, soils at many industrial sites are also contaminated with dioxins and need remediation. In order to optimize the cost-efficiency of reclamation activities it is important to acquire information about the levels and distribution of dioxins in the contaminated areas. The aim of the studies underlying this thesis was to investigate the potential of comprehen-sive two-dimensional gas chromatography with a micro-electron capture detector (GC × GC-µECD) as a cost-effective method for analysing dioxins and dioxin-like PCBs in food, feed, fly ash and contaminated soils. Quantification studies of dioxins and dioxin-like PCBs were con-ducted and results were compared with GC-HRMS reference data. Generally, there was good agreement between both the congener-specific results and data expressed as total toxic equiva-lents (TEQs). The developed GC × GC-µECD method meets the European Community (EC) requirements for screening methods for control of dioxins and dioxin-like PCBs in food and feed. The presented results also indicate that GC × GC-µECD has potential to be used as a routine method for the congener-specific analysis of 2,3,7,8-PCDD/Fs and dioxin-like PCBs in matrices such as food and feed, fly ash and soil. However, to fully exploit the potential of the GC × GC-µECD technique, it should be combined with a fast and cost-efficient sample preparation procedure. Therefore, a number of certified reference materials (CRMs) were extracted using a new shape-selective pressurized liquid extraction technique with integrated carbon fractionation (PLE-C), and the purified extracts were analysed for PCDD/Fs using GC × GC-µECD. The results compared well with the certified values of a fly ash and a sandy soil CRM, but they were much too high for a com-plex clay soil CRM. It was concluded that this combination of techniques was very promising for screening ash and highly permeable soils. Further assessments and method revisions are still required before GC × GC-µECD can be used on a routine basis, and available software packages need to be refined in order to accelerate the data-handling procedures, which currently restrict the sample throughput.

Brominated organic compounds (BOCs) of both natural and anthropogenic origin are abundant in the environment. Most compounds are either clearly natural or clearly anthropogenic but some are of either mixed or uncertain origin. This thesis aims to identify some naturally produced BOCs and to develop a method for analysis of the bromine isotopic composition in BOCs found in the environment. Polybrominated dibenzo-p-dioxins (PBDDs) in the Baltic Sea are believed to be of natural origin although their source is unknown. Since marine sponges are major producers of brominated natural products in tropical waters, BOCs were quantified in a sponge (Ephydatia fluviatilis) from the Baltic Sea (Paper I). The results showed that the sponge does not seem to be a major producer of PBDDs in the Baltic Sea. In this study, mixed brominated/chlorinated dibenzo-p-dioxins were however discovered for the first time in a background environment without an apparent anthropogenic source. The use of nuclear magnetic resonance spectroscopy (NMR) is unusual in analytical environmental chemistry due to its sample requirements. Preparative capillary gas chromatography was used to isolate a sufficient amount of an unidentified BOC from northern bottlenose whale (Hyperoodon ampullatus) blubber (Paper II) to enable NMR analysis for identification of the compound. The bromine isotopic composition of BOCs may give information on the origin and environmental fate of these compounds. The first steps in this process are the development of a method to determine the bromine isotope ratio in environmentally relevant BOCs (Paper III) and measuring the bromine isotope ratio of several standard substances to establish an anthropogenic endpoint (Paper IV). / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

The thermal formation of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), and naphthalenes (PCNs) is a major problem in waste incineration. Ideally, rather than relying on air cleaning systems and treatment techniques, their formation should be minimized or, if possible eliminated. The work presented in this thesis was conducted to obtain a deeper understanding of the thermal formation of PCDDs, PCDFs, PCBs, and PCNs during incineration using a 5 kW laboratory scale incinerator and two artificial wastes that were designed to reflect regional differences in waste composition. The first part of the thesis focuses on the validation of a recently-developed flue-gas sampling probe with enhanced cooling capabilities. Artifact formation of PCDDs and PCDFs can occur during the sampling of hot flue gases if the cooling is insufficient. The new probe was successfully used to collect samples at 700 °C without biasing the measured POP levels. The thermal formation of PCDDs, PCDFs, PCBs, and PCNs in the post-combustion zone of the incinerator was then studied by collecting flue gas samples at 400 °C, 300 °C, and 200 °C during the incineration of the two artificial wastes. Highly chlorinated POPs were formed in larger quantities when burning the waste with the higher content of metals and chlorine, which suggests that high metal levels in the waste favor the chlorination of less chlorinated POPs or otherwise facilitate the formation of highly chlorinated polyaromatics, possibly via the condensation of highly chlorinated phenols. The concentrations of these pollutants and the abundance of highly chlorinated homologues increased as the flue gas cooled. Fly ash particles play an important role in thermal POP formation by providing essential elements (carbon, chlorine, etc.) and catalytic sites. The chemical and mineralogical properties of fly ash samples were studied by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy/Energy Dispersive X-ray (SEM/EDX), and X-ray photoelectron spectroscopy (XPS) to determine their impact on thermal POP formation. Orthogonal Partial Least Squares (OPLS) modeling was used to identify correlations between the observed POP distributions and the physicochemical data. This investigation provided new insights into the impact of fly ash chemistry on thermal POP formation. In addition, the POP isomer distribution patterns generated during waste combustion were examined. These patterns are used to “fingerprint” mechanisms of POP formation. It was found that wastes containing large quantities of metals and chlorine favored the formation of highly chlorinated homologues including the very toxic 2,3,7,8-congeners. The data suggest that reducing fly ash emissions might increase the SO2 content of the flue gas and thereby suppress the Deacon process and the formation of harmful highly chlorinated aromatic species.

Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating POPs. South Africa signed and ratified the treaty, and it became international law on 17 May 2004. POPS are highly stable, toxic, hydrophobic and lipophilic compounds, with the ability to accumulate in biological tissues. Previous research had shown that dioxin-like POPS are present in the aquatic environments of South Africa, with the highest concentrations of these substances measured in industrialised areas of South Africa. The present study aimed at investigating the extent of polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzo-furan (PCDF) and polychlorinated biphenyl (PCB) pollution in the Vaal Triangle, by targeting aquatic sediments and biota. Sediment samples were collected from the Blesbok Spruit, Taaibos Spruit, Leeu Spruit and Suikerbosrand River, and fish tissue samples were collected from Blesbok Spruit and Suikerbosrand River, to determine bio-accumulation. The samples were extracted with organic solvents, cleaned-up and fractionated. Raw extracts and fractions were analysed with the H4IIE-luc reporter gene bio-assay. This bio-assay is a rapid, sensitive and relatively cost-effective method, which measures the effects of dioxin-like compounds on rat hepatoma cells, transfected with firefly luciferase gene. Selected samples were analysed with gas chromatographylmass spectrometry (GCIMS) to confirm results. Only one site had quantifiable amounts of dioxin-like substances in the sediment, measured to be 52.35 ng/kg [Effective Concentration 50 (EC 50)]. This value exceeds many of the European and USA quality guidelines, proposed for sediments. No dioxin-like substances were found in fish tissues. The absence of PCDD/Fs and PCBs in aquatic sediments and fish tissues from the Vaal Triangle area might be due to the climatic conditions of the area, dilution effects in streams, and degradation of these compounds by UV-radiation and microbial organisms. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating POPs. South Africa signed and ratified the treaty, and it became international law on 17 May 2004. POPS are highly stable, toxic, hydrophobic and lipophilic compounds, with the ability to accumulate in biological tissues. Previous research had shown that dioxin-like POPS are present in the aquatic environments of South Africa, with the highest concentrations of these substances measured in industrialised areas of South Africa. The present study aimed at investigating the extent of polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzo-furan (PCDF) and polychlorinated biphenyl (PCB) pollution in the Vaal Triangle, by targeting aquatic sediments and biota. Sediment samples were collected from the Blesbok Spruit, Taaibos Spruit, Leeu Spruit and Suikerbosrand River, and fish tissue samples were collected from Blesbok Spruit and Suikerbosrand River, to determine bio-accumulation. The samples were extracted with organic solvents, cleaned-up and fractionated. Raw extracts and fractions were analysed with the H4IIE-luc reporter gene bio-assay. This bio-assay is a rapid, sensitive and relatively cost-effective method, which measures the effects of dioxin-like compounds on rat hepatoma cells, transfected with firefly luciferase gene. Selected samples were analysed with gas chromatographylmass spectrometry (GCIMS) to confirm results. Only one site had quantifiable amounts of dioxin-like substances in the sediment, measured to be 52.35 ng/kg [Effective Concentration 50 (EC 50)]. This value exceeds many of the European and USA quality guidelines, proposed for sediments. No dioxin-like substances were found in fish tissues. The absence of PCDD/Fs and PCBs in aquatic sediments and fish tissues from the Vaal Triangle area might be due to the climatic conditions of the area, dilution effects in streams, and degradation of these compounds by UV-radiation and microbial organisms. / Thesis (M. Environmental Science (Water Science))--North-West University, Potchefstroom Campus, 2007.

Farmed Southern Bluefin Tuna (SBT) (Thunnus maccoyii) is an important export product for South Australia (SA). It is exported to Japan, China, Korea and the United States for the sushi and sashimi markets. The primary purpose of SBT farming in SA is to fatten wild-caught juvenile fish (2-4 years of age with initial mean weights between 12-20 kg) over a period of approximately five months by feeding a selection of baitfish types. Farmers, farm managers and consumers of SBT all have an interest in managing chemical residues that have the potential to biomagnify in the fatty tissue of the farmed SBT fillets. Of particular interest are chemical residues of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins / dibenzofurans (PCDD/Fs). This research presents the investigations and experimental validation of a predictive model that can be used to address the levels of residues in the fillets of farmed SBT at harvest from feeding (as the source) when applied to SBT aquaculture. An additional industry-focussed aim of this research was to determine if a Longer Term Holding (LTH) farming period, with a duration of an extra 12 months after a typical farming period of approximately five months, could produce SBT with higher condition index (CI) and lipid content, while keeping levels of PCBs and PCDD/Fs low, compared to the typical farming period. The justification for this research is that an adequate quantitative model is essential to help industry achieve targeted concentrations in the final fillet product by making scientific-based decisions on baitfish selection (baitfish strategies for the feeding of SBT), and longer term, to confidently demonstrate to local markets and importing countries that Australia is actively managing levels of PCBs and PCDD/Fs in farmed SBT, to ensure a high quality and safe product is delivered to the consumer. The novelty of this research is underpinned by four integrated stages, and the criteria for an adequate model established. The important criteria included: accurate predictions versus observed data demonstrated through the analysis of residual plots, potential physiological interpretation of model coefficients, parsimony – the model should be as simple as possible (but no simpler) and that the model should be easy to use. Firstly, a logical starting point was the development of a risk framework for residues in SBT. The developed framework was based on conventional principles of microbiological risk assessment highlighted in Codex Alimentarius. The risk framework consists of five governing principles: hazard identification, hazard characterisation, exposure assessment, risk characterisation and model validation. The advantages of the risk framework is that it provides a systematic research approach and permits information to be handled unambiguously, especially important for the niche SBT industry where chemical residue research is carried out for the first time. Secondly, because of a lack of available scientific data in context of this research, commercial-scale experimental field data for levels of PCBs and PCDD/Fs in typical farmed SBT as affected by feeding and growth were collected over 17 months at seven time intervals from Farm Delta Fishing Pty Ltd in 2005/06 (n = 50). Field data from another commercial company, Farm Alpha Fishing Pty Ltd, was collected over the typical farming period specific to this company, spanning 15 weeks at three time intervals in 2006, for validation work (n = 15). The data obtained from Farm Delta Fishing Pty Ltd revealed that whole weight of farmed SBT increased from 18.5 kg to 30.3 kg for a typical farming period, and subsequently to 41.0 kg by the end of the LTH farming period. A maximum mean CI of 24.0 ± 0.5 kg.m⁻³ and a maximum mean lipid content of 17.6 ± 0.5% was achieved at the third time interval of the typical farming period, for the baitfish types and ratios used as feed. There were no significant differences in the CI and lipid between the final harvests of the typical farming and LTH periods, i.e. even after an additional 12 months of farming. PCB and PCDD/F concentrations, however, increased between the final harvests of the typical farming and LTH periods. The data indicated that a typical farming period was sufficient to achieve a maximum CI and lipid content with lower concentrations of PCBs and PCDD/Fs in the fillets relative to the LTH farming period. For the third stage of this research, a quantitative model was synthesised and applied to the PCB and PCDD/F (2,3,7,8-TeCDF) data detected in farmed SBT fillets. Assimilation efficiencies for PCBs and 2,3,7,8-TeCDF in the fillets of SBT were obtained. An assimilation efficiency, or percentage retention (efficiency expressed as a percentage), in the fillet of SBT is a measure of the uptake of a chemical residue from food (baitfish) to the SBT fillet. For the WHO-PCBs, assimilation efficiencies based on SBT fillets ranged between 19.1 – 35.3 % with the exception of PCB 169. The highest assimilation efficiency of 35.3 %, with a range of 30.4 – 40.3 % (at the 95 % confidence level) was attributed to the most toxic PCB congener, PCB 126. An assimilation efficiency of 39.2 % was determined in SBT fillets for the congener 2,3,7,8-TeCDF, which was higher than the assimilation efficiencies determined for the WHO-PCB congeners. A residual plot as predicted value versus observed value indicated that the predictive model was neither under- or over-parameterised. However, when the predictive model was assessed against the data set from Farm Alpha Pty Ltd, the model over-predicted the actual PCB and PCDD/F concentrations. The over-prediction is attributed to possible overfeeding of SBT farmed by Farm Alpha Fishing Pty Ltd. From a food safety point of view, in the absence of ideal predictions because of a lack of ideal validation data sets, an over-prediction instead of under-prediction is preferred. In the fourth stage, the practical application of the predictive model was demonstrated. Because SBT fillets are retailed as tissue group-specific, i.e. akami (low fat), chu-toro (medium fat) and otoro (high fat) fillets, PCB and PCDD/F analyses were carried out on the three tissue groups for selected SBT (n = 7). Dietary modelling on SBT consumption in humans was carried out using findings from the predictive model and tissue-specific data. The baitfish strategy employed for the feeding of farmed SBT consequently affects dietary exposure to SBT consumers. Exposure to PCBs and PCDD/Fs is approximately seven times lower for the consumption of a skin-free, boneless akami fillet than for a comparable otoro fillet of the same size. This dietary exposure assessment accounted only for consumption of SBT tissue-specific fillets. The experimental field study and modelling work on PCB and PCDD/F concentrations in farmed SBT (fillets) outlined in this thesis importantly directs the need to re-evaluate a specific model to better cater for SBT farming practices where SBT fillets are produced for human consumption. Because conditions that normally pertain to commercial farming of wild-caught fish were studied, findings should be of interest to industries where other species of fish (for food) are farmed in sea-cages in the open ocean. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342453 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

Farmed Southern Bluefin Tuna (SBT) (Thunnus maccoyii) is an important export product for South Australia (SA). It is exported to Japan, China, Korea and the United States for the sushi and sashimi markets. The primary purpose of SBT farming in SA is to fatten wild-caught juvenile fish (2-4 years of age with initial mean weights between 12-20 kg) over a period of approximately five months by feeding a selection of baitfish types. Farmers, farm managers and consumers of SBT all have an interest in managing chemical residues that have the potential to biomagnify in the fatty tissue of the farmed SBT fillets. Of particular interest are chemical residues of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins / dibenzofurans (PCDD/Fs). This research presents the investigations and experimental validation of a predictive model that can be used to address the levels of residues in the fillets of farmed SBT at harvest from feeding (as the source) when applied to SBT aquaculture. An additional industry-focussed aim of this research was to determine if a Longer Term Holding (LTH) farming period, with a duration of an extra 12 months after a typical farming period of approximately five months, could produce SBT with higher condition index (CI) and lipid content, while keeping levels of PCBs and PCDD/Fs low, compared to the typical farming period. The justification for this research is that an adequate quantitative model is essential to help industry achieve targeted concentrations in the final fillet product by making scientific-based decisions on baitfish selection (baitfish strategies for the feeding of SBT), and longer term, to confidently demonstrate to local markets and importing countries that Australia is actively managing levels of PCBs and PCDD/Fs in farmed SBT, to ensure a high quality and safe product is delivered to the consumer. The novelty of this research is underpinned by four integrated stages, and the criteria for an adequate model established. The important criteria included: accurate predictions versus observed data demonstrated through the analysis of residual plots, potential physiological interpretation of model coefficients, parsimony – the model should be as simple as possible (but no simpler) and that the model should be easy to use. Firstly, a logical starting point was the development of a risk framework for residues in SBT. The developed framework was based on conventional principles of microbiological risk assessment highlighted in Codex Alimentarius. The risk framework consists of five governing principles: hazard identification, hazard characterisation, exposure assessment, risk characterisation and model validation. The advantages of the risk framework is that it provides a systematic research approach and permits information to be handled unambiguously, especially important for the niche SBT industry where chemical residue research is carried out for the first time. Secondly, because of a lack of available scientific data in context of this research, commercial-scale experimental field data for levels of PCBs and PCDD/Fs in typical farmed SBT as affected by feeding and growth were collected over 17 months at seven time intervals from Farm Delta Fishing Pty Ltd in 2005/06 (n = 50). Field data from another commercial company, Farm Alpha Fishing Pty Ltd, was collected over the typical farming period specific to this company, spanning 15 weeks at three time intervals in 2006, for validation work (n = 15). The data obtained from Farm Delta Fishing Pty Ltd revealed that whole weight of farmed SBT increased from 18.5 kg to 30.3 kg for a typical farming period, and subsequently to 41.0 kg by the end of the LTH farming period. A maximum mean CI of 24.0 ± 0.5 kg.m⁻³ and a maximum mean lipid content of 17.6 ± 0.5% was achieved at the third time interval of the typical farming period, for the baitfish types and ratios used as feed. There were no significant differences in the CI and lipid between the final harvests of the typical farming and LTH periods, i.e. even after an additional 12 months of farming. PCB and PCDD/F concentrations, however, increased between the final harvests of the typical farming and LTH periods. The data indicated that a typical farming period was sufficient to achieve a maximum CI and lipid content with lower concentrations of PCBs and PCDD/Fs in the fillets relative to the LTH farming period. For the third stage of this research, a quantitative model was synthesised and applied to the PCB and PCDD/F (2,3,7,8-TeCDF) data detected in farmed SBT fillets. Assimilation efficiencies for PCBs and 2,3,7,8-TeCDF in the fillets of SBT were obtained. An assimilation efficiency, or percentage retention (efficiency expressed as a percentage), in the fillet of SBT is a measure of the uptake of a chemical residue from food (baitfish) to the SBT fillet. For the WHO-PCBs, assimilation efficiencies based on SBT fillets ranged between 19.1 – 35.3 % with the exception of PCB 169. The highest assimilation efficiency of 35.3 %, with a range of 30.4 – 40.3 % (at the 95 % confidence level) was attributed to the most toxic PCB congener, PCB 126. An assimilation efficiency of 39.2 % was determined in SBT fillets for the congener 2,3,7,8-TeCDF, which was higher than the assimilation efficiencies determined for the WHO-PCB congeners. A residual plot as predicted value versus observed value indicated that the predictive model was neither under- or over-parameterised. However, when the predictive model was assessed against the data set from Farm Alpha Pty Ltd, the model over-predicted the actual PCB and PCDD/F concentrations. The over-prediction is attributed to possible overfeeding of SBT farmed by Farm Alpha Fishing Pty Ltd. From a food safety point of view, in the absence of ideal predictions because of a lack of ideal validation data sets, an over-prediction instead of under-prediction is preferred. In the fourth stage, the practical application of the predictive model was demonstrated. Because SBT fillets are retailed as tissue group-specific, i.e. akami (low fat), chu-toro (medium fat) and otoro (high fat) fillets, PCB and PCDD/F analyses were carried out on the three tissue groups for selected SBT (n = 7). Dietary modelling on SBT consumption in humans was carried out using findings from the predictive model and tissue-specific data. The baitfish strategy employed for the feeding of farmed SBT consequently affects dietary exposure to SBT consumers. Exposure to PCBs and PCDD/Fs is approximately seven times lower for the consumption of a skin-free, boneless akami fillet than for a comparable otoro fillet of the same size. This dietary exposure assessment accounted only for consumption of SBT tissue-specific fillets. The experimental field study and modelling work on PCB and PCDD/F concentrations in farmed SBT (fillets) outlined in this thesis importantly directs the need to re-evaluate a specific model to better cater for SBT farming practices where SBT fillets are produced for human consumption. Because conditions that normally pertain to commercial farming of wild-caught fish were studied, findings should be of interest to industries where other species of fish (for food) are farmed in sea-cages in the open ocean. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342453 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

Farmed Southern Bluefin Tuna (SBT) (Thunnus maccoyii) is an important export product for South Australia (SA). It is exported to Japan, China, Korea and the United States for the sushi and sashimi markets. The primary purpose of SBT farming in SA is to fatten wild-caught juvenile fish (2-4 years of age with initial mean weights between 12-20 kg) over a period of approximately five months by feeding a selection of baitfish types. Farmers, farm managers and consumers of SBT all have an interest in managing chemical residues that have the potential to biomagnify in the fatty tissue of the farmed SBT fillets. Of particular interest are chemical residues of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins / dibenzofurans (PCDD/Fs). This research presents the investigations and experimental validation of a predictive model that can be used to address the levels of residues in the fillets of farmed SBT at harvest from feeding (as the source) when applied to SBT aquaculture. An additional industry-focussed aim of this research was to determine if a Longer Term Holding (LTH) farming period, with a duration of an extra 12 months after a typical farming period of approximately five months, could produce SBT with higher condition index (CI) and lipid content, while keeping levels of PCBs and PCDD/Fs low, compared to the typical farming period. The justification for this research is that an adequate quantitative model is essential to help industry achieve targeted concentrations in the final fillet product by making scientific-based decisions on baitfish selection (baitfish strategies for the feeding of SBT), and longer term, to confidently demonstrate to local markets and importing countries that Australia is actively managing levels of PCBs and PCDD/Fs in farmed SBT, to ensure a high quality and safe product is delivered to the consumer. The novelty of this research is underpinned by four integrated stages, and the criteria for an adequate model established. The important criteria included: accurate predictions versus observed data demonstrated through the analysis of residual plots, potential physiological interpretation of model coefficients, parsimony – the model should be as simple as possible (but no simpler) and that the model should be easy to use. Firstly, a logical starting point was the development of a risk framework for residues in SBT. The developed framework was based on conventional principles of microbiological risk assessment highlighted in Codex Alimentarius. The risk framework consists of five governing principles: hazard identification, hazard characterisation, exposure assessment, risk characterisation and model validation. The advantages of the risk framework is that it provides a systematic research approach and permits information to be handled unambiguously, especially important for the niche SBT industry where chemical residue research is carried out for the first time. Secondly, because of a lack of available scientific data in context of this research, commercial-scale experimental field data for levels of PCBs and PCDD/Fs in typical farmed SBT as affected by feeding and growth were collected over 17 months at seven time intervals from Farm Delta Fishing Pty Ltd in 2005/06 (n = 50). Field data from another commercial company, Farm Alpha Fishing Pty Ltd, was collected over the typical farming period specific to this company, spanning 15 weeks at three time intervals in 2006, for validation work (n = 15). The data obtained from Farm Delta Fishing Pty Ltd revealed that whole weight of farmed SBT increased from 18.5 kg to 30.3 kg for a typical farming period, and subsequently to 41.0 kg by the end of the LTH farming period. A maximum mean CI of 24.0 ± 0.5 kg.m⁻³ and a maximum mean lipid content of 17.6 ± 0.5% was achieved at the third time interval of the typical farming period, for the baitfish types and ratios used as feed. There were no significant differences in the CI and lipid between the final harvests of the typical farming and LTH periods, i.e. even after an additional 12 months of farming. PCB and PCDD/F concentrations, however, increased between the final harvests of the typical farming and LTH periods. The data indicated that a typical farming period was sufficient to achieve a maximum CI and lipid content with lower concentrations of PCBs and PCDD/Fs in the fillets relative to the LTH farming period. For the third stage of this research, a quantitative model was synthesised and applied to the PCB and PCDD/F (2,3,7,8-TeCDF) data detected in farmed SBT fillets. Assimilation efficiencies for PCBs and 2,3,7,8-TeCDF in the fillets of SBT were obtained. An assimilation efficiency, or percentage retention (efficiency expressed as a percentage), in the fillet of SBT is a measure of the uptake of a chemical residue from food (baitfish) to the SBT fillet. For the WHO-PCBs, assimilation efficiencies based on SBT fillets ranged between 19.1 – 35.3 % with the exception of PCB 169. The highest assimilation efficiency of 35.3 %, with a range of 30.4 – 40.3 % (at the 95 % confidence level) was attributed to the most toxic PCB congener, PCB 126. An assimilation efficiency of 39.2 % was determined in SBT fillets for the congener 2,3,7,8-TeCDF, which was higher than the assimilation efficiencies determined for the WHO-PCB congeners. A residual plot as predicted value versus observed value indicated that the predictive model was neither under- or over-parameterised. However, when the predictive model was assessed against the data set from Farm Alpha Pty Ltd, the model over-predicted the actual PCB and PCDD/F concentrations. The over-prediction is attributed to possible overfeeding of SBT farmed by Farm Alpha Fishing Pty Ltd. From a food safety point of view, in the absence of ideal predictions because of a lack of ideal validation data sets, an over-prediction instead of under-prediction is preferred. In the fourth stage, the practical application of the predictive model was demonstrated. Because SBT fillets are retailed as tissue group-specific, i.e. akami (low fat), chu-toro (medium fat) and otoro (high fat) fillets, PCB and PCDD/F analyses were carried out on the three tissue groups for selected SBT (n = 7). Dietary modelling on SBT consumption in humans was carried out using findings from the predictive model and tissue-specific data. The baitfish strategy employed for the feeding of farmed SBT consequently affects dietary exposure to SBT consumers. Exposure to PCBs and PCDD/Fs is approximately seven times lower for the consumption of a skin-free, boneless akami fillet than for a comparable otoro fillet of the same size. This dietary exposure assessment accounted only for consumption of SBT tissue-specific fillets. The experimental field study and modelling work on PCB and PCDD/F concentrations in farmed SBT (fillets) outlined in this thesis importantly directs the need to re-evaluate a specific model to better cater for SBT farming practices where SBT fillets are produced for human consumption. Because conditions that normally pertain to commercial farming of wild-caught fish were studied, findings should be of interest to industries where other species of fish (for food) are farmed in sea-cages in the open ocean. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342453 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

Ce travail de thèse est axé sur l'élaboration de techniques de bioremédiation des sols contaminés par les Polluants Organiques Persistants (POP) en particulier sur deux familles de polluants : les Hydrocarbures Aromatiques Polycyliques et les dioxines (PCDD/F). La dégradation des POP présente deux obstacles majeurs à l'efficacité des traitements biologiques par voie fongique : la faible biodisponibilité des POP et la difficulté d'amorcer l'oxydation de molécules aussi stables chimiquement. Afin de lever ces verrous technologiques, nous proposons de coupler une oxydation chimique douce à l'oxydation biologique par les champignons telluriques saprotrophes et d'utiliser l'amidon pour améliorer la proximité spatiale entre le polluant et les réactifs d'oxydation. La première partie de ce travail de thèse consiste à fonctionnaliser de l'amidon de pomme de terre par la 1,4-butane sultone et l'anhydride 2-octén-1-ylsuccinique selon différentes conditions de synthèses. En comparaison avec l'amidon natif, un des produits obtenus, P9*, possède des propriétés surfactantes très intéressantes pour notre étude. En effet, P9* augmente la solubilité aqueuse de l'amidon par un facteur de 35 (22,60 g.L⁻¹) et stimulent 33 fois la solubilisation aqueuse du benzo[a]pyrène (BaP). Pour la seconde partie, l'utilisation d'un système d'étude simplifié où le champignon est cultivé en milieu minéral en conditions axéniques nous a permis de déterminer les paramètres (souche fongique, type et dose d'oxydant chimique) optimaux pour l'élaboration d'une méthode de dégradation des POP au laboratoire. Des études comparatives de dégradation du BaP sont donc réalisées in vitro par différents processus d'oxydation chimique (réaction de Fenton) et/ou biologique. Le couplage des deux procédés conduit à une dégradation du PaP de 40,0%. De plus, l'encapsulation du BaP par les nanosphères d'amidon P9* permet une dégradation du polluant de 64,6% par le réactif de Fenton. Deux souches fongiques (Penicillium brasilianum et Fusarium solani) sont ensuite utilisées pour des essais de dégradation conduits au laboratoire en microcosmes de sols historiquement contaminés par les PCDD/F. L'inoculation de la souche endogène P. brasilianum en présence de copeaux de carton comme agent structurant a conduit à une diminution de la toxicité des PCDD/F de 40,5% après seulement 2 mois d'incubation par rapport au sol témoin. Ce travail de thèse ouvre ainsi de nouvelles perspectives de techniques de remédiation des sols pollués par les POP à faible coût économique et respectueuses de l'environnement. / This thesis work deals with the development of bioremediation techniques for contaminated soils by Persistent Organic Pollutants (POPs) such as : Polycyclic Aromatic Hydrocarbons and dioxins (PCDD/F). The degradation of POPs has two main obstacles to efficient biological treatments by fungi : the low bioavailability of POPs and the difficulty of initiating the oxydation of molecules as stable as others. To overcome these technological barriers, we propose to couple a mild chemical oxidation to biological oxidation by saprotrophic telluric fungi and to use starch to improve the spatial proximity between the pollutant and oxidizing reagents. The first part of this study is to functionalize native potato starch by 1,4-butane sultone and 2-octenyl-1-succinic anhydride according to different synthesis conditions. In comparison with native starch, one of the processed products, P9*, has very interesting surfactant properties for our study. Indeed, P9* increases starch apparent aqueous solubility by a factor of 65 (22.60 g.L⁻¹) and stimulates 33-fold benzo[a]pyrene (BaP) aqueous solubilization. For the second part, the use of a simplified study system where the fungus is cultivated in mineral medium under axenic conditions allowed us to determine the best parameters (fungal strainsn type and dose of chemical oxydant) for the development of a POPs degradation method in the laboratory. Comparative studies of BaP degradation are therefore carried out in vitro by different processes of chemical (Fenton's reagent) and/or biologial oxidation. The coupling of the two processes leads to a BaP degradation of 40.0%. Moreover, the BaP encapsulation by starch nanospheres P9* allows a pollutant degradation of 94.6% by the Fenton reagent. Two fungal strains (Penicillium brasilianum and Funsarium solani) are then used for the degradation lab experiment in historically PCDD/F contaminated soil microcosms. the inoculation of the endogene strain P.brasilianum in presence of cardboard chips as a bulking agent led to a decrease in PCDD/F toxicity of 40.5% after only two months of incubation compared to the controm soil. This PhD work draws new perspectives for remediation techniques of contaminated soils by POPs that are cost-effective and environmentally friendly.