ABSTRACT
Metals naturally occur and are present in the soils, air, and water of all urban watersheds. Although metal contamination is brie¡y mentioned in Chapter 7, we emphasize metals in this chapter for a variety of reasons. First, metals are common and important contaminant constituents in urban streams and stream sediment. Second, as noted in Chapter 7, metals are commonly produced as by-products of many types of industrial, commercial, and even residential developments. Third, metals are released into the environment. This is particularly true in southeast Michigan, which developed as the focal point for the automotive industry in the country and where metals are used as pigments in paints, as rust inhibitors, metal plating, and in raw materials. Fourth, metals are interesting to study because they are subject to a number of reactions in soil and sediment including sorption and precipitation and are greatly in¡uenced by the redox conditions in these environments. Fifth, metals can be used to inexpensively screen for contamination at old industrial sites (brownœelds), without knowing the site history. For example, the USEPA lists 14 metals (Sb, As, Ba, Be, Cd, Cr, Cu, Pb, Hg, Ni, Se, Ag, Th, and Zn) as part of their 129 most common pollutants (USEPA 2003). These metals can all be analyzed simultaneously and inexpensively using ICP-MS (inductively coupled plasma mass spectrometry), as opposed to the higher cost and longer time required to randomly test for the presence of hundreds of organic compounds at an undocumented brownœeld site.
