During the latter 20th century, global urban areas, and by extension, road networks have rapidly expanded. Urban soils are often contaminated with potentially toxic trace metals due to multiple human activities, and the relatively high loadings of trace metals to urban ecosystems pose a significant risk to public and ecosystem health. However, metal dynamics in near-road areas are driven by the interactions of many processes, and consequently, few studies have comprehensively examined urban soil metal dynamics.
Examination of both anthropogenic and natural loadings of metals to urban areas and the interactions among processes (e.g., soil acidification, exchange reactions) reveal urban soil chemical dynamics. This dissertation documents findings resulting from a variety of approaches to clarify near-road and urban soil metal dynamics: 1) Soil acidification across regional gradients of road network density, climate, and geology in Southern California results in road construction material weathering (i.e., concrete) and significantly influences near-road soil metal dynamics. 2) Inputs of road material weathering offset calcium losses due to the flushing of soil exchange sites during road deicer pulses in Pittsburgh, Pennsylvania. Moreover, complicated soil water flowpaths documented in this transect create discontinuous and delayed down slope transport of sodium. 3) Two centuries of metal inputs to a Southwestern Pennsylvanian lake revealed an unexpectedly long period and complicated mix of trace metal contamination, accumulated from a historical sequence of industrial transitions. 4) Synthesis of roadside soil phosphorus concentration data from both the Southern California dataset and the Pittsburgh transect indicate near-road soil phosphorus accumulation at magnitudes near estimated phosphorus accumulations in global agricultural soils, suggesting that vehicular emissions are a significant, yet under characterized component of the global phosphorus cycle.
This research documents roadside soil metal dynamics and the role of historical metal inputs and ultimately will contribute to more effective management of road networks and urbanization
