Heavy metal contamination in highway soils. Comparison of Corpus Christi, Texas and Cincinnati, Ohio shows organic matter is key to mobility

Abstract.

Heavy metal content of roadside soil samples from along the interstate highway systems in Corpus Christi, Texas and Cincinnati, Ohio was measured to assess the degree of contamination such soils contain and the likelihood that this contamination can be remobilized. High values of Ba, Cu, Pb, and Zn can be attributed to anthropogenic effects related to motor vehicles, whereas Cr and Ni variations are best ascribed to natural processes. The anthropogenic substances are strongly correlated to the amount of organic matter in the soil. Sequential extraction experiments, however, show that this organic matter is not extractable by agents that normally solubilize soil organic matter, so these metals are bound to an insoluble form of organic matter that is itself probably anthropogenic. The insolubility of the heavy metals and Ba indicates that these constituents are not likely to move in solution to water supplies, but they would still be subject to physical remobilization by roadway maintenance or even by grass mowing. Inhalation of small dust particles poses a potential health hazard to highway maintenance workers that needs to be assessed.