Geochemical distribution of trace metals and organochlorine contaminants of a Lake Ontario shoreline marsh

Abstract

As part of a water quality study on Rattray Marsh, a suburban marsh located on the Lake Ontario shoreline at Mississauga, Ontario, a sedimentary geochemistry study was initiated. In general, Cu, Zn, Pb and Hg were higher in concentration than in local soils, but lower than Lake Ontario recent sediments. Over the past century, an approximate two-fold increase in the sedimentary levels of Cu, Zn, Co, Cr and Ni occurred, while Cd increased nearly 4 ×, and Pb, 8 ×. No correlation was found between metals and organic carbon, and the metals appear to be associated with silts and clays as evidenced by (1) factor analysis of geochemical data, (2) higher concentrations in areas of the marsh subjected to high sediment deposition, and (3) analysis of a suspended sediment sample from Sheridan Creek, the main tributary basin of the marsh. Organochlorine contaminants include p,p1-DDE,p,p1-DDD,p,p1-DDT, a-chlordane, PCB, mirex and HCB.