Dispersion of Contaminants in Urban Regions and Beyond

Abstract

Cities are important sources of contaminants at the local, regional, and global scales. In urban areas, automobile traffic, leaching from building materials, urban runoff, and industrial sources are resulting in the occurrence of elevated concentrations of metals, including Ag, Cd, Cu, Pb, Pt, Rh, Sb, Sn, W, and Zn. Here, we show that in addition to local impacts, urban contamination extends beyond the urban boundary. Two examples are provided to show that atmospheric and water-based dispersion result in regional-scale contamination. In Stockholm, contaminants are found in sediments downstream from the urban center. Platinum-group elements (PGEs) are used as tracers of urban contamination and show that a significant fraction of contaminants emitted into the atmosphere can be transported at regional scales. The projected growth of cities will lead to an increase in pollution, especially in developing countries where environmental legislation is still lagging and material use is soaring. There is in general an urgent need to raise awareness and implement programs to reduce the environmental impact of urban activities.