Metals in sediments of the Great Lakes of North America determined by factor analysis

Metal data from eight sediment cores including 178 segments from Lakes Superior, Michigan, Huron, Erie, and Ontario were subjected to positive matrix factorization to extract characteristic loading and score plots for Pb, Cd, As, Zn, Cu, Ni, Co, and Cr. Lake Superior has significant concentrations of Cu, max 205 ppm, with notable contributions of Pb, Ni, and Cr from the Precambrian bedrock in the northern part. Lake Michigan shows distinct Pb input in the southern core and likely automotive input with max during 1966-1971 in both cores. Recent input of As since 2009 is reflected in Lake Huron, max 31.4 ppm, and both the western and eastern Lake Ontario, max 81 ppm, which may originate in part from Lakes in the Sudbury, area and from Lake Moira both in Ontario, Canada. Highway input of metals is shown in cores from Lakes Huron, Erie, and Ontario with maxima during 1970-1973. This is supported by Zn/Pb and Zn/Cu ratios which match literature values of 6.3 and 4.7, respectively, for highway runoff. Lake Ontario has large inputs of Ni and Zn, likely from local industries. Plots of Ag vs. time for Lake Ontario point to a maximum in the eastern part in 1971, which along with literature values for Ag in Ponar Grabs of eastern Lake Ontario suggest an Ag source near Rochester, NY.