Effects of Anthropogenic Particles on the Chemical and Geophysical Properties of Urban Soils, Detroit, Michigan

Abstract

A study was undertaken to assess the effects of anthropogenic particles on the pH, electrical conductivity (EC), and magnetic susceptibility (MS) of anthropogenic soils in Detroit, Michigan. The results showed that ^Au horizons of anthropogenic soils at residential demolition, industrial, and fly ash–impacted sites were distinguishable from A horizons of native soils (background level). Anthropogenic soils were higher by 1 pH unit or more, had an EC three to four times background level, and were characterized by an elevated MS that was up to 20 times background. Anthropogenic soils at residential demolition sites had a uniquely high EC signature, whereas those at industrial sites were distinguished by anomalously high MS. Fly ash–impacted soils differed from native soils but were similar to other anthropogenic soils. Analyses of reference artifacts suggest that the elevated pH of anthropogenic soils was caused by calcareous building material wastes, whereas elevated EC were the result of both calcareous and ferruginous wastes. Elevated MS were attributable to ferrimagnetic materials such as corroded iron nails, coal ash and cinders, and metalliferous slag. Analyses of “artificial soils” indicated that there were measurable effects on pH, EC, and MS even with low concentrations of anthropogenic microparticles (<5–10 wt %). These results support our hypothesis that urban soils contain anthropogenic particles that differ as a function of former land use. Hence, various types of anthropogenic soils and native soils have unique chemical and geophysical signatures. This suggests that EC and MS surveying methods may be used to remotely sense and map urban soils more effectively than using traditional methods alone.