We fabricated a suite of polymeric electrospun nanofiber mats (ENMs) and investigated their performance as next-generation passive sampler media for environmental monitoring of organic compounds. Electrospinning of common polymers [e.g., polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polystyrene (PS), among others] yielded ENMs with reproducible control of nanofiber diameters (from 70 to 340 nm). ENM performance was investigated initially with model hydrophilic (aniline and nitrobenzene) and hydrophobic (selected PCB congeners and dioxin) compounds, generally revealing fast chemical uptake into all ENMs that was well described by a one compartment, first-order kinetic model. Typical times to reach 90% of equilibrium (t90%) were ≤ 7 days under mixing conditions for all ENMs, and < 0.5 days for the best performing materials under static (i.e., no mixing) conditions. Collectively, these short equilibrium timescales suggest that ENMs may be used in the field as an equilibrium-passive sampler, at least for our model compounds. Equilibrium partitioning coefficients (KENM-W, L kg−1) averaged 2 and 4.7 log units for the hydrophilic and hydrophobic analytes, respectively. PAN, PMMA and PS were prioritized for additional studies because they exhibited not only the greatest capacity for simultaneous uptake of the entire model suite (log KENM-W ~ 1.5 – 6.2), but also fast uptake. For these optimized ENMs, rates uptake into PAN and PMMA were limited by aqueous phase diffusion to the nanofiber surface, and the rate-determine step for PS was analyte specific. Sorption isotherms also revealed that the environmental application of these optimized ENMs would occur within the linear uptake regime. We examined ENM performance for the measurement of pore water concentrations from spiked soil and freshwater sediments. Soil and sediment studies not only yielded reproducible pore water concentrations and comparable values to other passive sampler materials, but also provided practical insights into ENM stability and fouling in such systems. Further, fast uptake for a suite of structurally diverse hydrophilic and moderately hydrophobic compounds were obtained for PAN and PS, with t90% ranging from 0.01 to 4 days with mixing and KENM-W values ranging from 1.3 to 3.2 log units. Our findings show promise for the development and use of ENMs as equilibrium-passive samplers for a range of organic pollutants across soil/sediment and water systems.

____________________________________________ Richard L. Valentine ____________________________________________ Syed Mubeen ii To my best friends, my siblings, my parents. I would not be here without you. iii ACKNOWLEDGEMENTS First and foremost, I would like to thank my advisor, David Cwiertny, who has been my mentor, guide, and advocate throughout my undergraduate and graduate coursework and research. Thank you for your constant encouragement and patience with me as I struggled to come into my own as an engineer. You have been and continue to be an inspiration with your positivity and your outrageous work ethic. To all of my lab mates -