The accumulation of polychlorinated biphenyls (PCBs) into humans was described using CoZMoMAN, a mechanistic multimedia fate and transport model coupled to a human food chain model. Model results demonstrated that concentration-age relationships for population cross-sections and individuals over time are not equivalent and that, under steady-state conditions, the lipid-normalized concentration of PCBs in an individual does not monotonically increase with age. By considering the decades-long emission history of PCBs in the model simulations, it was shown that an individual’s concentration mostly depends upon when she/he was born relative to the peak in emissions. Similarly, the two most influential factors controlling the shape of cross-sectional concentration-age trends obtained in human biomonitoring studies are the time lapse between the peak in emissions and sample collection and chemical elimination half-life. As a result, it should be possible to deduce information on these two factors from the shape of cross-sectional concentration-age trend. Reproductive behaviours (parity, age at birth, breastfeeding) were shown to potentially have a significant impact on exposure (and can contribute substantially to the observed variability in biomonitoring studies) though the mother’s reproductive history has a greater influence on the prenatal and postnatal exposures of her children than it does on her own cumulative lifetime exposure. A case study of the influence of dietary transitions in a hypothetical Arctic community demonstrated that dietary transitions are an important factor underlying the variability in PCB body burdens within and between subpopulations in addition to partially explaining the observed temporal trends. Comparison of PCB partitioning to various lipid materials suggested that 1) triolein is a good surrogate for human storage lipids; 2) liposomes are not an appropriate surrogate for human storage tissues; and 3) that partitioning into human MCF-7 cells is dominated by the storage lipids rather than by membrane lipids. Finally, a new bioenergetically-balanced bioaccumulation (3B) fish model is presented. Comparison of results from the 3B model with that of existing models revealed that feeding and growth rates used by previous fish bioaccumulation models were not bioenergetically consistent. Differences in biomagnification factors with fish size and temperature as a result of differing energetic requirements demonstrated the importance of the assumptions regarding growth rate and feeding rate.

This thesis focuses on the development of quantitative structure-activity relationship (QSPR) models for physicochemical properties, e.g., vapor pressure and partitioning coefficients. Such models can be used to estimate environmental distribution and transformation of the pollutants or to characterize solvents properties. Here, chemoinformatics was used as an efficient tool for modeling to produce safe chemicals based on green chemistry principles. Experimental determinations are only available for a limited number of the chemicals; however, theoretical molecular descriptors can be used for modeling of all organic compounds. In this thesis, we developed and validated a global and local QSPR model for vapor pressure of liquid and subcooled liquid organic compounds, in which perfluorinated compounds (PFCs) as outliers appeared in the model due to their molecular properties. Subsequently, after the update of the previous model, the vapor pressure of perfluorinated compounds (PFCs) for which no reliable experimental data are available was successfully predicted. At the same time, we used partitioning between n-octanol/water (Kow) and water solubility (Sw) to investigate the similarities and differences between linear solvation energy relationship (LSER) and partial least square projection to latent structures (PLS) models. Further, we developed QSPR model for prediction of melting points and boiling points of PFCs using multiple linear regression (MLR), PLS and associative neural networks (ASNN) approaches, meanwhile, the applicability domain of PFCs was also investigated. Experimental, semi-empirical and theoretical quantitative structure-retention relationship (QSRR) models were used to accurately predict retention factors (logk) in reversed-phase liquid chromatography (RPLC). These models are useful to characterize solvents for determination of the behavior and interactions of molecular structure and develop chromatographic methods. In both of QSPR and QSRR models using the PLS method, the first and second components captured main information which is related to van der Waals forces and polar interactions, and their results coincide with those from LSER. The results showed that the models of physicochemical properties and retention factors (logk) in chromatographic system can be successfully developed by the PLS method. PLS models were able to predict physicochemical properties of organic compounds directly from theoretical descriptors without prior synthesis, measurement or sampling. Further, the PLS method could overcome colinearity in data sets, and it is therefore a rapid, cheap and highly efficient approach

Accurate measurements of the trace nitrogenous atmospheric species amines (NR3) and nitrous acid (HONO) are essential to understanding their chemistry and potential influence on new particle formation and oxidation capacity in the atmospheric boundary-layer, respectively. Ambient Ion Monitor – Ion Chromatography (AIM-IC) methods developed in this work have provided quantitative online observations of atmospheric amines in the gaseous and condensed phases with detection limits of pptv and ng m-3 at hourly time resolution. Size-resolved particle observations demonstrated maximum amine mass loadings in 320 – 560 nm particles, and an increase in importance relative to ammonium for the smallest particles measured (56 – 180 nm). In particular, the size-resolved samples analysed in this work indicate that bulk aerosol measurements may not be appropriate for modelling the atmospheric processes that govern the incorporation of amines and ammonia in to atmospheric particles. Measurements of HONO made during the two intensive field campaigns (NACHTT, CalNex) and a lab study provided a new perspective on the interactions of this trace compound with ground surfaces. Integrated atmospheric column measurements of HONO and NO2 during NACHTT provided clear evidence that the ground surface dominates HONO production and loss at night. Simultaneous measurements of the gas and particle phases made by the AIM-IC system during CalNex demonstrated the potential for reactive uptake of HONO on mineral dust/soil as a nocturnal sink. Similarly, the potential for nitrite salts to react with strong acids, displacing HONO during the day was suggested by this dataset. Lab study results showed that HONO is taken up irreversibly on carbonate salts and real soil extracts. Relative humidity-dependent reactive uptake coefficients were derived. Subsequent release of HONO by displacement reactions with HNO3 and HCl was also confirmed. Together, these field and lab studies have produced a new picture of HONO surface interactions by providing i) a more explicit description of a nocturnal sink of HONO that could act as a surface reservoir and ii) a new mechanism for daytime HONO formation that does not require NO2.

Accurate measurements of the trace nitrogenous atmospheric species amines (NR3) and nitrous acid (HONO) are essential to understanding their chemistry and potential influence on new particle formation and oxidation capacity in the atmospheric boundary-layer, respectively. Ambient Ion Monitor – Ion Chromatography (AIM-IC) methods developed in this work have provided quantitative online observations of atmospheric amines in the gaseous and condensed phases with detection limits of pptv and ng m-3 at hourly time resolution. Size-resolved particle observations demonstrated maximum amine mass loadings in 320 – 560 nm particles, and an increase in importance relative to ammonium for the smallest particles measured (56 – 180 nm). In particular, the size-resolved samples analysed in this work indicate that bulk aerosol measurements may not be appropriate for modelling the atmospheric processes that govern the incorporation of amines and ammonia in to atmospheric particles. Measurements of HONO made during the two intensive field campaigns (NACHTT, CalNex) and a lab study provided a new perspective on the interactions of this trace compound with ground surfaces. Integrated atmospheric column measurements of HONO and NO2 during NACHTT provided clear evidence that the ground surface dominates HONO production and loss at night. Simultaneous measurements of the gas and particle phases made by the AIM-IC system during CalNex demonstrated the potential for reactive uptake of HONO on mineral dust/soil as a nocturnal sink. Similarly, the potential for nitrite salts to react with strong acids, displacing HONO during the day was suggested by this dataset. Lab study results showed that HONO is taken up irreversibly on carbonate salts and real soil extracts. Relative humidity-dependent reactive uptake coefficients were derived. Subsequent release of HONO by displacement reactions with HNO3 and HCl was also confirmed. Together, these field and lab studies have produced a new picture of HONO surface interactions by providing i) a more explicit description of a nocturnal sink of HONO that could act as a surface reservoir and ii) a new mechanism for daytime HONO formation that does not require NO2.

This thesis explored new methods for understanding the fate and transport of halogenated organic contaminants in the environment. A theoretical method of hazard assessment of chemical mixtures containing large numbers of components was developed and its application illustrated using polychlorinated alkanes, toxaphene, and halogenated dibenzo-para-dioxins and furans. Partitioning properties predicted by high-throughput quantitative structure property relationships were used to locate mixture constituents on plots displaying equilibrium phase distribution in various environmental compartments and the potential for bioaccumulation and long range transport. Potentially hazardous components were identified graphically for more detailed assessments. The applicability of XAD-resin based passive air samplers (XAD-PAS) for studying neutral polyfluoroalkyl substances (nPFAS) in the atmosphere was tested empirically. XAD-PASs have sufficiently high uptake capacity to yield temporally averaged nPFAS concentrations over period as long as a year. When applied as part of the Global Atmospheric Passive Sampling network, nPFAS were found to be truly global contaminants.

This thesis explored new methods for understanding the fate and transport of halogenated organic contaminants in the environment. A theoretical method of hazard assessment of chemical mixtures containing large numbers of components was developed and its application illustrated using polychlorinated alkanes, toxaphene, and halogenated dibenzo-para-dioxins and furans. Partitioning properties predicted by high-throughput quantitative structure property relationships were used to locate mixture constituents on plots displaying equilibrium phase distribution in various environmental compartments and the potential for bioaccumulation and long range transport. Potentially hazardous components were identified graphically for more detailed assessments. The applicability of XAD-resin based passive air samplers (XAD-PAS) for studying neutral polyfluoroalkyl substances (nPFAS) in the atmosphere was tested empirically. XAD-PASs have sufficiently high uptake capacity to yield temporally averaged nPFAS concentrations over period as long as a year. When applied as part of the Global Atmospheric Passive Sampling network, nPFAS were found to be truly global contaminants.

No description available.

The accumulation of polychlorinated biphenyls (PCBs) into humans was described using CoZMoMAN, a mechanistic multimedia fate and transport model coupled to a human food chain model. Model results demonstrated that concentration-age relationships for population cross-sections and individuals over time are not equivalent and that, under steady-state conditions, the lipid-normalized concentration of PCBs in an individual does not monotonically increase with age. By considering the decades-long emission history of PCBs in the model simulations, it was shown that an individual’s concentration mostly depends upon when she/he was born relative to the peak in emissions. Similarly, the two most influential factors controlling the shape of cross-sectional concentration-age trends obtained in human biomonitoring studies are the time lapse between the peak in emissions and sample collection and chemical elimination half-life. As a result, it should be possible to deduce information on these two factors from the shape of cross-sectional concentration-age trend. Reproductive behaviours (parity, age at birth, breastfeeding) were shown to potentially have a significant impact on exposure (and can contribute substantially to the observed variability in biomonitoring studies) though the mother’s reproductive history has a greater influence on the prenatal and postnatal exposures of her children than it does on her own cumulative lifetime exposure. A case study of the influence of dietary transitions in a hypothetical Arctic community demonstrated that dietary transitions are an important factor underlying the variability in PCB body burdens within and between subpopulations in addition to partially explaining the observed temporal trends. Comparison of PCB partitioning to various lipid materials suggested that 1) triolein is a good surrogate for human storage lipids; 2) liposomes are not an appropriate surrogate for human storage tissues; and 3) that partitioning into human MCF-7 cells is dominated by the storage lipids rather than by membrane lipids. Finally, a new bioenergetically-balanced bioaccumulation (3B) fish model is presented. Comparison of results from the 3B model with that of existing models revealed that feeding and growth rates used by previous fish bioaccumulation models were not bioenergetically consistent. Differences in biomagnification factors with fish size and temperature as a result of differing energetic requirements demonstrated the importance of the assumptions regarding growth rate and feeding rate.

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed May 6, 2009). Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 158-183). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.