| 1. |
- Hultin, Kim, 1976-
(författare)
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Primary Marine Aerosol Production : Studies using bubble-bursting experiments
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aerosol particles affect the Earth’s climate, although their impact is associated with large uncertainties. Primary marine aerosol represents a significant fraction of the global aerosol budget considering the Earth’s 70-percentage coverage by oceans. They are produced when bubbles burst at the ocean surface and can consist of sea salt, organic matter and bacteria. An experimental approach was here used to investigate the primary marine aerosol production from the bubble-bursting mechanism using water from four different geographical locations. The main findings include: Similar and stable aerosol number size distributions at all locations, centered close to 0.2 μm. Largely varying aerosol organic fractions, both with size and location. Clear tendency for increased water temperature to negatively influence the aerosol production. No covariance between surface water chlorophyll α and aerosol production on a 10-minute time scale, although decreased aerosol production was observed at times of elevated phytoplankton activity on longer time scales. Mainly external mixtures of sea salt and organics was observed. A high tendency for colony-forming marine bacteria to use bubble-bursting to reach the atmosphere. A clear diurnal cycle in aerosol production was found for both laboratory produced aerosol and in-situ aerosol fluxes, probably biologically driven. The first near coastal sea spray fluxes with limited fetch and low salinity. While the primary marine aerosol spectral shape is stable, emission concentration varies with environmental parameters. Above that, the organic fraction of the aerosol varies largely between locations. This shows that observations of primary marine aerosol emissions not necessarily can be applied to large time- or spatial scales.
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| 2. |
- Posselt, Malte, 1987-
(författare)
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Transformation of Micropollutants in the Hyporheic Zone
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hyporheic zones (HZs) are reactive transition regions between rivers and aquifers which are thought to play an important role in the attenuation of micropollutants. Micropollutants are chemical substances such as pharmaceuticals, industrial chemicals or personal care products that are found in trace concentrations in the environment and that can be harmful to organisms. This thesis aimed to narrow the knowledge gap on the environmental fate of wastewater-derived polar organic micropollutants in the aquatic environment, with a specific emphasis on the hyporheic zone.In Paper I an efficient workflow was developed for the in-situ characterization of polar organic micropollutants and their transformation products (TPs) in the hyporheic zone at high spatial and temporal resolution and with minimal disturbance of natural flow paths. A low volume sampling device was combined with a newly developed high throughput-direct injection-UHPLC-MS/MS method. Application in the field revealed significant differences in micropollutant concentrations that varied over small time- and spatial scales. In Paper II the results of a comprehensive field study performed in the urban lowland river Erpe in Berlin, Germany, are presented. The work provided data on in-situ attenuation behavior of 24 micropollutants and TPs, along with novel insights into the spatially- and temporally varying environmental factors which play a major role in controlling in-stream attenuation of micropollutants. Paper III describes a novel, multi-flume experiment designed to investigate the influence of hyporheic exchange flow and sediment bacterial diversity on dissipation half-lives of 31 micropollutants and associated TPs. Attenuation and transformation of most substances increased significantly with bacterial diversity; fewer compounds responded to both bacterial diversity and hyporheic exchange flow. In addition to the discovery of several novel TPs, a number of bacterial strains were identified that might be associated with micropollutant degradation. In Paper IV the fate of metformin in the hyporheic zone was examined using large-scale (100m) recirculating flumes to perform realistic yet well-controlled experiments. In addition to determining dissipation half-lives in surface and pore water, the formation of novel TPs was investigated via suspect screening and bacterial communities were characterized using microbiological analyses. Data from these experiments indicate that dunes and macrophytes promote hyporheic exchange flow and create reactive environments with steep and varying biogeochemical gradients, which enhanced the degradation of metformin.Collectively, the fate of 33 parent compounds and 37 transformation products was assessed in field and mesocosm experiments described in this thesis. Additionally, 29 suspected TPs were tentatively identified. Higher bacterial diversity in the hyporheic zone and more intense hyporheic exchange flows significantly enhanced biodegradation of organic micropollutants. A number of known and novel TPs were discovered under diverse conditions, many of which showed signs of environmental persistence, providing further evidence for inclusion of TPs in contaminant risk assessments and regulatory frameworks. This work highlights the importance of considering both small- and reach-scale temporal and spatial variability for a mechanistic understanding of attenuation in in-stream studies.
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| 3. |
- Hader, John D., 1992-
(författare)
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Forecasting chemical exposure in a changing world
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exposure to anthropogenic chemicals in natural and built environments is a threat to humans and other species. Now and through the 21st Century, the world will experience a large number of global changes, including anthropogenic climate change, shifts in demographics, agricultural expansion, socioeconomic development, and an increasing number and volume of chemicals on the market. All of these forcings have potentially important ramifications for how humans and other species are exposed to chemicals. A better understanding of global change forcings and their impacts on chemical exposures could help identify local, regional, and international chemical management techniques that could help avert harmful changes in exposure in the coming decades. Overall, this thesis aims to understand how exposure to chemicals may change in the future against the backdrop of rapidly changing natural and built environments. Five studies have been conducted in pursuit of this aim, including a literature review, two exposure modelling studies, and the development of an industrial chemical spill risk screening tool for sewage treatment plants. The current lack of knowledge around chemical emission rates is a key information gap for the ability to forecast how global change forcings might change the emissions of chemicals in agricultural environments, especially through the use of wastewater, biosolids, and veterinary pharmaceuticals. Consensus, high-throughput exposure modelling in the context of changing climate, indoor microenvironments, and dietary patterns showed changes in intake fraction up to a factor of 2, driven most notably by changing precipitation patterns and human diet. Global-scale modelling of chemical exposure with shifting socioeconomic and dietary patterns showed that socioeconomic development may lead to a larger fraction of global emissions occurring in rapidly industrialising regions with high population density (e.g., sub-Saharan Africa and India) leading to a larger fraction of the global burden of chemical exposure being borne by these historically low chemical-emitting regions. In the context of rapid urbanization, the upstream chemical risk assessment tool we developed for sewage treatment plants showed, in a case study in Sweden, that fewer than 1% of chemicals posed a risk to plant operations, but the risk from roughly 40% of chemicals could not be quantified due to lack of available toxicity data. Overall, this thesis shows that the use of numerical modelling and data analysis can elucidate key factors that determine exposure of humans and other species to chemicals in a rapidly changing environment. Where and how much chemical is emitted in the future, and what humans will be eating, are key factors determining population-level exposure to chemicals that should be considered in future decision making. Better information reporting for chemical emissions in agricultural environments and chemical toxicity towards sewage treatment plants are key data gaps that need to be closed to improve prospective exposure assessment. To help facilitate more effective chemical management at the international level, this thesis also presents an initial harmonized list of key terms used within exposure science, as robust and effective communication is urgently needed to solve the global problem of chemical pollution and exposure in a rapidly changing environment.
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| 4. |
- Liagkouridis, Ioannis, 1982-
(författare)
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Indoor emissions and fate of flame retardants : A modelling approach
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A significant number of consumer goods and building materials act as emission sources of flame retardants (FRs) in the indoor environment. As a result, FRs have become ubiquitous indoors raising concerns about human exposure and possible health implications. Once released indoors, FRs can escape to the outdoors where they can persist, be transported over long distances and present a threat to the environment. Despite the increasing number of studies reporting the occurrence of FRs in the indoor environment, the understanding of i) how and to what extent these chemicals are released from indoor sources, and ii) their subsequent fate indoors remains limited. The overarching objective of this thesis was to improve this understanding by assessing the indoor emissions and fate of FRs using a combination of multimedia modelling strategies and experimental/empirical approaches. Paper I identifies a number of knowledge gaps and limitations regarding indoor emissions and fate of FRs and the available modelling approaches. These include a limited understanding of the key emission mechanisms for low volatility FRs, uncertainties regarding indoor air/surface partitioning, poor characterization of dust and film dynamics and a significant lack of knowledge regarding indoor reaction/degradation processes. In Paper II we highlighted the serious scarcity in physicochemical property data for the alternative FRs and demonstrated the applicability of a simple QSPR technique for selecting reliable property estimates for chemical assessments. A modelling fate assessment indicated a strong partitioning to indoor surfaces and dust for most of the alternative FRs. Indications for POP (persistent organic pollutant)-like persistence and LRT (long-range transport) and bioaccumulative potential in the outdoor environment were also identified for many alternative FRs. Using an inverse modelling approach in Paper III we estimated 2 to 3 orders of magnitude higher emissions of organophosphate FRs (0.52 and 0.32 ng.h-1) than brominated FRs (0.083 μg.h-1 and 0.41 μg.h-1) in Norwegian households. An emission-to-dust signal was also identified for organophosphate FRs suggesting that direct migration to dust may be a key fate process indoors. No evidence of a direct source-to-dust transfer mechanism was seen in Paper IV where the chemical transfer between a product treated with an organophosphate FR and dust in direct contact was experimentally investigated. It was concluded though that direct contact between an FR source and dust can result in contamination hotspots indoors.
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| 5. |
- Sha, Bo, 1987-
(författare)
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Transport of perfluoroalkyl acids from the ocean to the atmosphere via sea spray aerosol
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perfluoroalkyl acids (PFAAs) are a subgroup of per- and polyfluoroalkyl substances (PFAS) that have been widely used in commercial and industrial applications. PFAAs are very persistent in the environment and some can bioaccumulate and have adverse health effects on human health. They have been detected ubiquitously in the abiotic environment, in biota and in humans. Long-range atmospheric transport (LRAT) is considered important for their global distribution. PFAAs are detected in the global oceans and they can be enriched in sea spray aerosol (SSA) due to their high surface activity. Thus, ocean-to-atmosphere transfer via sea spray aerosol emission is suggested to be one of the major sources of PFAAs to the atmosphere, yet the contribution of this source to PFAAs in air is not well-understood. The aim of this thesis is to improve the knowledge regarding the importance of SSA as a global source of PFAAs in the atmosphere. In Paper I, PFAA enrichment on SSA particles of different sizes was investigated via a series of laboratory experiments. A sea spray simulation chamber filled with sodium chloride solution (~35 g L-1) was used to generate SSA. The results showed that variation in PFAA water concentrations had little impact on the SSA enrichment factors (EFs). Furthermore, the results suggested that SSA production mechanisms result in different enrichment behaviors of individual PFAAs on <1 µm and >1µm SSA particles. Paper II provided clear field evidence that SSA can be an important source of PFAAs in the atmosphere. Significant positive correlations (p<0.05) were identified between the concentrations of PFAAs and SSA tracer ion (i.e. Na+) in aerosol samples collected at two Norwegian coastal sites during long-term air monitoring. Such correlations suggested that PFAAs transported via SSA can have a significant influence on their air concentrations in coastal areas. Aiming at bridging the gap between the lab and the field, in Paper III, a series of field experiments were conducted along a transect from ~50°N to ~50°S on the Atlantic Ocean. Changes in surface seawater temperature, salinity, conductivity and fluorescence during the field experiments revealed minor influences on EFs. However, the EFs derived from the field experiments were higher than the lab experiments in Paper I, which may be due to the different composition and properties of the chamber water in the two studies. It was concluded, however, that the variation of PFAA concentrations in the global oceans is the major contributor to the uncertainty in the estimation of PFAA ocean-to-air flux via SSA emission. Paper IV investigated mass-size distributions of PFAAs in aerosol samples collected near an industrial source and the associated LRAT potential of the PFAAs emitted. The results suggested that industrial sources can have regional influence on PFAA concentration in air. The information in Paper IV will help evaluate the relative importance of atmospheric sources of PFAAs at certain locations. This thesis contributes to a better understanding on the transport of PFAAs via SSA emission and on the sources of PFAAs to air in general.
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| 6. |
- Bui, Tuong Thuy, 1987-
(författare)
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Assessing human exposure to phthalates, alternative plasticizers and organophosphate esters
- 2017
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Phthalate esters (PEs) and organophosphate esters (OPEs) are common indoor pollutants frequently detected in environmental (dust, air), personal (hand wipes, diet) and human matrices (urine, serum etc.). In this thesis, mathematical models were used to establish links between intake and body burden for a comprehensive dataset based on a Norwegian study population. Also, the relative importance of different PE uptake pathways was assessed and discussed. Furthermore, the suitability of human nails as an alternative, non-invasive biomonitoring matrix for PEs was investigated. Additionally, information regarding alternative plasticizers to PEs was collected and presented extensively. Results showed that for PEs (paper II), daily intakes based on external exposure media agree with back-calculations using urinary metabolite concentrations, leading to the conclusion that human exposure for the general adult population is well understood and that the most important uptake routes were captured. Overall intake levels are comparable or lower than level presented in recent comprehensive studies and hazard quotients were well below 1 (low risk). As expected, diet was found to be the most important uptake route for all PEs. For lower molecular weight PEs, inhalation becomes a strong contributing pathway whereas for higher molecular weight PEs, dust ingestion was also important. Daily intake based on hand wipes was found to be much lower than the estimated total dermal intake based on air, dust and personal care products, questioning the relevance of hand wipes to represent total dermal exposure. Human nails were found to be unsuitable for replacing urine as a biomonitoring matrix for PEs as internal intake (from blood) cannot explain measured nail concentrations and uptake from air is too slow to reach observed concentrations within a realistic time frame (paper III). Hence, the kinetic links between intake and nail concentrations could not be established. Although exposure to traditional PEs is decreasing, use and body burden of some alternatives are increasing (paper I). Fortunately, most alternative plasticizers have favorable toxicological properties, resulting in low risk for humans. In contrast to PEs, OPEs still remain a group of poorly studied substances in terms of human exposure (paper IV). Due to lack of information regarding human metabolism, reliable links between intake and concentrations in serum and urine could not be established. Modelling results showed that concentrations in serum, and to some extent, urine, were underestimated for 2 compounds. It is likely that a combination of missing intake and suboptimal biomarkers were the cause for this under-prediction. Because of this, further studies regarding human metabolism should be performed for OPEs and potentially more specific biomarkers identified in the future. For PEs, there is a need for more comprehensive datasets to study exposure for high risk groups such as infants and children. Furthermore, dermal uptake remains poorly understood and the uptake of PEs into human nails should be studied in more detail to establish the kinetic links between exposure and body burden.
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| 7. |
- Gomis, Melissa Ines, 1987-
(författare)
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From emission sources to human tissues: modelling the exposure to per- and polyfluoroalkyl substances
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Produced since the 1950’s, per- and polyfluoroalkyl (PFASs) substances are persistent, bioaccumulative and toxic compounds that are ubiquitous in the environment. Being proteinophilic with a tendency to partition to protein-rich tissues, PFASs have been found in human serum worldwide and in wildlife with a predominance of long-chain perfluoroalkyl carboxilic acids (C7-C14 PFCAs) and perfluoroalkyl sulfonic acids (C6-C9 PFSAs). Due to rising concern regarding their hazardous properties, several regulatory actions and voluntary industrial phase-outs have been conducted since early 2000s, shifting the production towards other fluorinated alternatives. This thesis explores the human exposure to long-chain PFASs and their alternatives using different modelling methods and aims to 1) link comprehensively the past and current industrial production with the human body burden and 2) assess the potential hazardous properties of legacy PFASs replacements, on which information is very limited. In Paper I, the historical daily intakes in Australia and USA were reconstructed from cross-sectional biomonitoring data of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) andperfluorohexanesulfonic acid (PFHxS). The results indicate that humans experienced similar exposure levels and trends to PFOS and PFOA in both regions, suggesting a common historical exposure possibly dominated by consumer products. The model could not be fitted to PFHxS concentration in serum. In Paper II, the relative contribution of indirect (i.e. subsequent metabolism of precursors into legacy PFASs) versus direct exposure was evaluated on occupationally exposed ski wax technicians. The indirect exposure contributed by up to 45% to the total body burden of PFOA. In Paper III, the physicochemical properties, the persistence and the long-range transport of fluorinated alternatives were predicted using different in silico tools. Findings suggest that fluorinated alternatives are likely similar to their predecessors, in terms of physicochemical properties and environmental fate. Finally, Paper IV compares the toxic potency of PFOS, PFOA and their alternatives as a function of external and internal dose. While alternatives are less potent than their predecessors when considering the administered dose, they become similarly potent when the assessment is based on levels in the target tissue. This thesis demonstrates that pharmacokinetic models are effective tools to comprehensively reconnect the body burden to the exposure of phased-out chemicals. More importantly, the studies on fluorinated alternatives raise the necessity to provide more information and data on the potential hazard of these novel and emerging products.
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| 8. |
- Johansson, Jana, 1985-
(författare)
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Sources, transport and fate of perfluoroalkyl acids in the atmosphere
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Perfluoroalkyl acids (PFAAs) are man-made chemicals which have been observed in the global environment, even in locations far away from where they are emitted. These persistent substances are taken up in humans and biota and may have toxic effects. Knowledge about how PFAAs are dispersed in the environment is needed to discern strategies to manage their sources and to evaluate the efficacy of adopted legislation. This thesis aimed to increase our understanding of the sources of PFAAs to the atmosphere and how PFAAs are transported in air. The results of Paper I demonstrated that gaseous perfluorooctanoic acid (PFOA) sorbs to typical glass fibre filters (GFFs) used in high-volume air sampling of PFAAs. As a consequence, the fraction of gaseous PFOA present in sampled air is underestimated, while the fraction of PFOA associated with aerosols is overestimated. Replacing GFFs with filters deactivated through silanisation and siliconisation did not eliminate this sampling artefact and is therefore not recommended as a means to determine the gas-particle partitioning of PFAAs. In Paper II, monitoring of the mass of PFOA transferred from water solutions of pH 0.2-5.5 demonstrated that the acid dissociation constant of linear PFOA and the four most ubiquitous branched PFOA isomers is around or below 1. Furthermore, the results demonstrated that the presence of counter ions and organic matter in water retarded, rather than enhanced, the volatilisation of PFOA. Therefore, volatilisation of all isomers of PFOA from environmental waters is expected to be negligible. To further study the transfer of PFAAs from environmental waters to air, Paper III simulated the process of sea spray generation in the laboratory. Strong enrichment of PFAAs was observed from bulk water to the surface microlayer and to aerosols. The enrichment increased with PFAA chain length, indicating that this process is of greater importance for more surface active substances. The highest enrichment was observed in aerosols < 1.6 µm, which can travel over long distances if not rained out. Based on the measured aerosol enrichment factors we estimated that approximately 70 metric tonnes of PFAAs are aerosolised from the global oceans yearly and that 3% of this mass is deposited in terrestrial environments. Paper IV reported the occurrence of branched PFOA isomers in deposition sampled in five geographical locations. The presence of these isomers demonstrated that atmospheric transformation of fluorotelomer alcohols is not the only ongoing source of PFAAs to air. We hypothesised that, additionally, both sea spray aerosols and direct emissions from manufacturing sources contributed to the contamination of the precipitation on different spatial scales. Although further research is required to determine the relative importance of different sources to the atmosphere locally and globally, this thesis has substantially advanced the state-of-the-science by i) demonstrating the significance of an air sampling artefact discussed as an uncertainty in the scientific literature over the past decade, ii) definitively ruling out volatilisation from environmental waters as a source of PFOA to air, iii) demonstrating transfer of PFAAs from seawater to air via sea spray aerosols and thus quantifying the environmental importance of this process, and iv) ultimately demonstrating that several types of sources of PFAAs impact the global atmosphere and thus PFAA contamination patterns in precipitation.
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| 9. |
- Kong, Deguo, 1983-
(författare)
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Confronting new challenges in chemical assessment : emerging contaminants and climate change
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Both chemical-specific (e.g. physical-chemical properties) and environmental (e.g. climate) properties are required for model-based chemical exposure assessment. The physical-chemical property data for large numbers of “emerging chemicals” of concern are scarce and uncertain and their unusual structures and behaviour hinder the creation of hazard profiles. Climate change (CC) is expected to alter the transport and fate of chemicals in the environment, so from a long-term perspective it must be accounted for in chemical risk assessment. This thesis tackles the challenges (i) in developing hazard profiles for halogen-free flame retardants (HFFRs), which are emerging chemicals that are often ionogenic and can contain metallic and organic components in the same chemical structure, and (ii) in quantifying the effects of CC on the transport and fate of organic chemicals with a wide range of physical-chemical properties. The findings in Paper I suggest that the hazard profiles of HFFRs can be constructed, though they may be incomplete and associated with uncertainty as a result of data gaps and difficulties in developing models to describe their unique environmental chemistry. Paper II shows that the large uncertainties in physical-chemical properties dominate the variance in future forecasts of chemical concentrations and are far more important than variations in climate parameters due to CC. Paper III derives the CC/baseline scenario ratios of chemical concentrations, which vary widely with physical-chemical properties. Concentrations in the Baltic region are projected to change by factors of up to 3.0. Paper IV identifies significantly decreasing trends in measured atmospheric concentrations of many persistent organic pollutants, implying effectiveness of control actions. There is no evidence that CC has altered the temporal trends in long-term time series of chemicals based on the statistical analyses of the monitoring data.
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| 10. |
- Nfon, Erick, 1969-
(författare)
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Tools for Evaluating the Fate and Bioaccumulation of Organic Compounds in Aquatic Ecosystems
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The bioaccumulation of organic contaminants in aquatic ecosystems has been a key focus in environmental toxicology over the last decades. Bioaccumulation is a key concept in ecological risk assessments since it controls the internal dose of potential environmental contaminants. Information on the bioaccumulation of contaminants is used by regulatory authorities in the development of water quality standards, categorizing substances that are potential hazards and quantifying the risk of chemicals to human health. A basis for identifying priority chemicals has been the use of the octanol-water partition coefficient (KOW) as a criterion to estimate bioaccumulation potential. However, recognizing that the bioaccumulation process is not controlled by the hydrophobicity of a chemical alone, this thesis proposes a set of tools, incorporating chemical properties, environmental characteristics and physiological properties of organisms, to study the bioaccumulation of contaminants in aquatic ecosystems. In striving to achieve this objective, a tool based on an equilibrium lipid partitioning approach was used in Paper I to evaluate monitoring data for bioaccumulation of organic contaminants. In Papers II and III, mechanistic based modelling tools were developed to describe bioaccumulation of hydrophobic compounds in aquatic food webs. In Paper IV, the bioaccumulation of organic compounds in aquatic food chains was studied using stable isotopes of nitrogen. The mechanistic fate and food web models developed in this thesis provide regulators and chemical manufacturers with a means of communicating scientific information to the general public and readily applicable mechanistic fate and food web models that are easily modified for evaluative assessments purposes.
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