HISTORY OF HEAVY METAL POLLUTION IN CINCINNATI: SEDIMENTS IN THE OLD MIAMI AND ERIE CANAL

The Miami and Erie Canal operated in Cincinnati, Ohio from 1825-1925. During the use of the canal, make-up water was supplied by a series of reservoirs, including Blair Pond and Mummert Pond located where Interstate 75 crosses over Clifton Avenue in the Mill Creek Valley. The fill in the former Mummert Pond was investigated to help reconstruct an urban sedimentation history for Cincinnati. Depth probing, auguring, grain size measurement, magnetic susceptibility, X-ray diffraction and X-ray fluorescence were used to analyze the sediment. The pond fill can be divided into three distinct horizons representing different time periods and sediment sources. Below 180 cm, there is a constant concentration of the heavy metals Cr+Cu+Pb+Zn of about 300 ppm, typical of background levels in the area. From 180 to 30 cm, there is a sharp increase upward in heavy metals to a high of 700 ppm. The surface layer reverts to the 300 ppm level.. Grain size shows a coarsening upward trend, with clays transitioning to silt above 180cm, and then to sand near the surface. Log Zr/TiO₂ plots indicate three distinct provenances: soil below 180cm has the same log Zr/TiO₂ as average glacial lake clays; the middle section has uniformly lower ratios; the surface sediment is higher than either of the other two. From these observations, the sediment section preserved in Mummert is interpreted as glacial lake clay below 180cm, Anthropocene canal pond deposits from 180cm to 30cm, and recent coarser slope outwash comprising the top few centimeters. The most striking feature of the profile is the upwards enrichment in metals. Chemical data from Mill Creek alluvium downstream of the site also shows high levels of the same metals, up to 1100 ppm at depth, dropping to 400 ppm at the surface. A maximum in the Mill Creek data occurs near a former overflow from the canal down to the creek, so discharges of waste from the canal may have polluted the creek or both were receiving waste from the same sources. The two sediment records reveal that Cincinnati was exposed to steadily increasing levels of heavy metal contamination in the hundred years after 1825.