Photochemical Transformations of Trace Persistent Organic Pollutants in Snow and Ice

Polar snowpacks have been established as active matrices for chemical processing of atmospheric species such as molecular halogens, volatile organics and ozone. It has previously been demonstrated that photochemical transformations of anthropogenic persistant organic pollutants (POPs) in ice occur under laboratory conditions, but there is little in the published literature regarding these processes. In the study described here, we consider the effect of near ultraviolet radiation on trace amounts of various organochlorine compounds in ice; the compounds selected are of interest because of their known presence in polar regions and their detrimental effect on organisms in polar ecosystems. Both direct photochemical transformations and indirect photo-oxidation by OH radical were investigated. To differentiate between pure liquid-phase, solid phase and interfacial processes, experiments were conducted on POPs in aqueous solution, ice and crushed ice/snow at various temperatures. In all cases, the degradation of the POP was monitored by the extraction of photolyzed samples followed by GC analysis. On the basis of these degradation studies, some reactive systems were selected for more detailed investigation. Reaction products were identified from irradiated samples by SPME with GCMS analysis. On the basis of the kinetic studies and identified reaction products, mechanisms for selected photochemical transformations are proposed. Potential implications of these transformations for environmental partitioning and interactions of the selected POPs will be discussed.