DEPOSITION OF TRACE-METALS IN URBAN AND RURAL-AREAS IN THE LAKE-MICHIGAN BASIN

Ambient concentrations measured in Chicago and in the rural area of Ka nkakee (Illinois) are presented for a wide range of trace metals assoc iated with fine (<2.5 mum) and coarse (2.5-10 mum) particles. Elements typically of crustal origin in the fine fraction were detected at sim ilar concentrations in both sites. However, crustal elements in the co arse fraction were found three to fifteen times higher than that assoc iated with fine fraction in both sites. Elements primarily of anthropo genic origin were found in similar concentrations in Chicago and Kanka kee, except for elements such as Cr which was detected at levels three to four times higher in Kankakee. Meteorological parameters, particle size distribution and surface characteristics are considered in a dyn amic model for calculating the deposition velocity for each particle s ize. The deposition velocities for fine particles is in the range from 0.25 to 0.46 cm/s in Chicago and from 0.18 to 0.25 cm/s in Kankakee, while for coarse particles the range is from 1.47 to 2.93 cm/s in Chic ago and from 0.87 to 1.71 cm/s in Kankakee. The deposition fluxes in C hicago are usually highest, except for Al which is deposited at highes t rates in Kankakee in both the fine 4.6 mug/m2-h and coarse 250 mug/m 2-h fraction. Finally, estimates of the total amount of trace metals a ccumulated on paved areas and potentially discharged into the sewer sy stems by storm water run-off in the urban and rural area are discussed .