Physical and Chemical Morphology of Passively Sampled Environmental Films

Abstract

This work presents spatially resolved physical and chemical surface characterization of passively sampled environmental films developed in urban, suburban, and metropolitan locations. Environmental surface films are important mediators of atmospheric particulate matter (PM) and persistent organic pollutants (POPs) fate and transport. The films are developed via dry deposition onto silicon wafer substrates for time scales ranging from 1 to 52 weeks. Spatial and chemical morphologies of the films are analyzed by bright-field, scanning electron, and atomic force microscopies. Surface feature sizes span 6 orders of magnitude, from the millimeter to nanometer regimes, indicative of super- and sub-micrometer PM as well as conformal films of nanoscale PM and semivolatile molecules. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging data are analyzed to report the films’ chemical morphology and speciation which include a range of organic and inorganic species. Increases in surface coverages (ca. 5%...