Urban films are ubiquitous coatings that form on virtually all exterior surfaces. They are formed as biogenic and anthropogenic emissions mix in the atmosphere and ultimately return to Earth’s surfaces as complex mixtures of organic and inorganic compounds. The films’ surface morphologies and chemical profiles result in unique physicochemical properties and reactivity which remain largely uncharacterized. Here, we present data that describe urban films’ physical and chemical morphology on the micro- and nano-scale. Passive air samplers are deployed at urban, suburban, and metropolitan locations for time scales from 1 to 52 weeks. Urban films are collected over these timeframes on silicon wafers, quartz crystals, and glass fiber filters for subsequent analysis of urban film morphology, absorbed mass, and composition, respectively. Analysis includes bright-field microscopy, scanning electron microscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry to provide the first reports of spatial and chemical morphology of urban films. We find that native urban films exhibit incredible physical and chemical heterogeneity; particle sizes range from sub-micrometer to tens of micrometers. Chemical domains of hydrocarbons, lipids, salts, metals, and other organic and inorganic substituents are identified on similar size scales for each collection site studied. The sorption of water and selected other volatiles is quantified on the films via quartz crystal microbalance analysis to provide initial estimates of possible urban film loading rates as they participate in the fate and transport of persistent organic species and environmental pollutants.

Native urban films’ spatial and chemical heterogeneity reported by microscopy and SIMS analysis

255th National Meeting (2018)

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