Environmentally active surface films

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Project Period: 
Project Investigator(s): 
S.K. Shaw, J.S. Grant, Department of Chemistry, The University of Iowa

This research will address an emerging avenue for pollutant fate and transport in the active surface film. Surface films are composed of organic (waxy) and inorganic (salty) species which combine in dynamic, heterogeneous matrixes on nearly all impervious surfaces. The films work as ‘environmental sponges’ by mediating fate and transport of volatile and semi-volatile organic pollutants (OP), ultimately affecting human and environmental health. Our goal is to assign culpability of surface films’ physical morphology (roughness) and chemical maturity (oxidation state) to their participation in OP absorption and release. We propose to develop and expose proxy films to metered doses of known environmental maturation agents (i.e. UV radiation and ozone) and quantify the films’ morphology and interaction with OP as a function of film maturity. We predict the films’ heterogeneous character and dynamic behavior will significantly impact OP adsorption (and absorption), and that this behavior will trend with film hydrophobicity.

Project Results: 

Researchers conducted detailed studies of environmental films that form on solid surfaces both indoors and outdoors.  The films can act as a sponge for 'persistent organic pollutants', which are chemicals that harm humans and human environments.  By better understanding the chemistry of these films, what chemicals may be absorbed or released can be better predicted, and when (i.e. hot, windy days or during rain-storms).  This will support better air and water quality monitoring and predictions.

The study had three primary findings.

  1. Environmental films exhibit a large degree of heterogeneity
  2. Chemical profile exhibits fatty acids, triglycerides, saccharides, paraffins, metals, and inorganics such as phosphate, nitrate, and sulfate
  3. Water sorption differs between sampling sites, suggesting differing chemical profile and film hygroscopicity