Atmospheric Transport of Semivolatile Organic Contaminants across an Urban-Alpine Boundary

Current understanding of atmospheric transport of semivolatile organic contaminants (SVOCs) in alpine areas is limited due to complex meteorology and topography. Salt Lake City, Utah borders protected wilderness areas in the Wasatch Mountains, exhibiting a useful model system in which an urban source of SVOCs, including polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), is located directly adjacent to an alpine sink. Our objective was to investigate the impacts of topographical features on the transport and deposition of SVOCs across an urban-alpine boundary. To do so, we measured PAHs and PCBs in soils along a transect starting at the urban-mountain interface and extending into an alpine wilderness, crossing several prominent ridgelines. Concentrations of PAHs and PCBs in soils were heavily influenced by soil organic carbon content, air temperature, and proximity to the urban boundary. However, the role of source proximity was only revealed after normalizing concentrations in soil to organic carbon content and air temperature. Further, we present evidence of SVOC emission/deposition cycles driven by diurnal alpine winds that do not extend past topographical features. Our results illustrate the roles of multiple competing processes on SVOC transport in alpine systems and their importance at an urban-alpine boundary.