- Title
- Beyond the obvious: understanding the environmental health implications of polycyclic aromatic compounds (PACs)
- Creator
- Idowu, Oluyoye Damilola
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The ecological and human health consequences of the presence of polar polycyclic aromatic hydrocarbons (PAHs) in the environment has not received adequate attention. Despite their widespread presence in the environment, they remain excluded during the remediation of contaminated environmental media and various human and environmental risk assessment efforts. This implies a serious underestimation of risk potentials of contaminated sites as focus is usually on legacy contaminants, and particular parent PAHs, in the case of organic contaminants. This PhD investigation is the first comprehensive study on the potential risks of polar PAHs within the Australian context. It is also one of the few studies, globally, to carry out wide-ranging examinations of the presence and fate of polar PAHs in the aquatic environment. It contains a compilation of studies on polar PAH presence in soil and potential cancer risk through incidental soil ingestion, source and presence in sediments, bioaccumulation to a model aquatic organism and fate in an aquatic environment; all from the standpoint of human and/or environmental risk assessments. The concentration profiles of parent PAHs and their polar derivatives including oxygenated PAHs (oxyPAH), nitrated PAHs (NPAHs) and, nitrogen, sulphur and oxygen heterocyclic PAHs (N/S/O-heterocyclic PAHs or HPAHs) in the city of Newcastle, a well-known industrial heritage city of Australia, were assessed. In addition, excess lifetime cancer risk (ELCR) from incidental ingestion of soils were computed for the investigated soil types (residential, recreational and industrial soils) using a standard deterministic approach. Concentrations of polar PAHs were generally lower than that of parent PAHs with positive correlation (r = 0.5, p < 0.01) observed between ∑PAHs and ∑polar PAHs implying possible similar sources and spatial association. The most abundant oxyPAHs, NPAHs and HPAHs were 9-fluorenone, 2-nitrofluorene and carbazole, respectively. The computed ELCR values ranged from 8.2*10-7 (industrial soils) to 2.3*10-6 (residential soils), indicating acceptable cancer risks. An assessment of parent and polar PAH concentrations in the sediments of the largest saltwater Lake in the southern hemisphere (Lake Macquarie), was carried out on 31 sediment samples along the pollution prone western shoreline. In addition, the sources of the PAHs in the estuarine sediments were investigated through the deployment of multiple source apportionment methods such as diagnostic ratios, compositional analysis and principal component analysis (PCA). Sediment concentration results revealed the highest values for high molecular weight (HMW) PAHs compared to low molecular weight (LMW) PAHs and highest PAH concentrations were recorded for oxyPAHs compared to parent and other polar PAHs. Sediment PAHs of Lake Macquarie were predominantly pyrogenic according to the apportionment methods utilised. Principal component analysis identified three groupings of PAHs with component 1 accounting for highest data variation (40.2%) and dominated by oxyPAHs and NPAHs. Carbazole, a heterocyclic PAH and a signature contaminant of coal combustion and coal tar/tar oil contamination, was also a prominent contributor to sediment PAH concentrations. The bioaccumulated fractions of polar PAHs and their parent analogues in the tissues of the Sydney rock oyster, Saccostrea glomerata, a model aquatic bio-indicator organism was investigated for a polluted south-east Australian estuary. Sediment and water samples were collected from 33 sites across the estuary and oyster samples at two locations from within ~ 2 km of the estuary mouth. All samples were analysed to determine PACs’ concentration and distribution patterns. Hierarchical cluster analysis (HCA), used to explain the spatial distribution of PAHs in water, sediment and oyster tissues, showed a clustering into two groups in each case, and concentrations were generally similar. Computed biota-sediment accumulation factors (BSAFs) on lipid-normalised oyster concentrations revealed that while ∑oxyPAHs (0.002) and ∑HPAHs (0.094) exhibited low accumulation from sediment to oyster tissues (BSAF < 1), ∑PAHs (42.5) and ∑NPAH (1.8) accumulated at high levels (BSAF > 1). We carried out in-field quantitative biomonitoring of the bioavailable fractions of parent PAHs and polar PAHs in the tissues of S. glomerata sourced from the same site as the previous study. Approximately 200 oysters were relocated to a relatively isolated waterway for the depuration study. Translocated oysters were tested 24 and 72 h after deployment and subsequently at Day 7, 14, 28, 52 and 86. Control oysters sourced from Camden Haven River were also monitored for concentration changes at the time of translocation (time 0), after 28 days and at the end of the study. Lipid-normalised concentration changes indicated that PAHs and NPAHs, as well as 9-FLO (oxyPAH), had elimination rate constant (k2) values significantly different from zero (p < 0.05) implying that PAHs, NPAHs and 9-FLO were significantly eliminated from oyster tissues during the 86-day period. All other oxyPAHs and HPAHs showed no clear depuration, with their concentrations remaining similar. The totality of the investigations on polar PAHs carried out during the PhD study has added, in no small dimension, to the body of knowledge about these transformation products of parent PAHs. Overall, the information in this thesis will be useful to all stakeholders for the better appreciation of the potential risks inherent in the presence of polar PAHs in environmental media such as soil, sediment and water.
- Subject
- polar polycyclic aromatic hydrocarbons; aquatic environment; soil; environmental fate; environmental health risk; human health risk; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1508394
- Identifier
- uon:56122
- Rights
- Copyright 2020 Oluyoye Damilola Idowu
- Language
- eng
- Full Text
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