The concentration of greater than 1 ..mu..m coal fly ash particles in Lake Michigan surface waters was found to be 10/sup 5/ to 10/sup 6/ per liter. With an expected residence time of one year, this concentration implies a flux to the sediment of 10/sup 6/ to 10/sup 7/ particles/cm/sup 2//yr, or about 10/sup -6/ to 10/sup -5/ g/cm/sup 2//yr. The release of trace elements from fly ash and sediment has been studied using Chelex-100 resin to simulate leaching at high dilutions in natural media. Mn, Pb and Zn, but not Fe, are released more readily from Lake Michigan sediment than from fly ash