Inter- and Intralake Distributions of Trace Organic Contaminants in Surface Waters of the Great Lakes

Abstract

Concentrations of organochlorine pesticides, polychlorinated biphenyls (PCBs), and chlorobenzenes (di- to hexa-) were determined on large volume surface water samples collected throughout Lakes Ontario, Erie, Huron, and Superior in the spring of 1986. Analysis of variance revealed that all trace organic contaminants exhibited significant (p<0.05) differences between lakes. Chlorobenzenes, being derived from ongoing manufacturing and usage, exhibited highest concentrations in the lower lakes while those compounds whose principal source is atmospheric deposition displayed no discernable distribution patterns. Lake Ontario could be considered the most heavily impacted of the lakes as it ranked highest in mean concentration for all chlorobenzenes, PCBs, Undone, endrin, and p,p’-DDE. Determinants of large-scale spatial patterns of contaminants varied between lakes. Minor north-south gradients in contaminant concentrations in Lake Superior appeared largely a function of differences in atmospheric loading. In contrast, large gradients were evident in Lake Erie, a result of numerous tributary point sources, particularly in the western basin. Spatial distribution of contaminants in Lake Huron resulted primarily from inputs from Saginaw Bay, the Serpent/Spanish rivers, and the Black River/Lake Michigan at the Straits of Mackinac. The Niagara River was the most important determinant of spatial patterns of contaminants in Lake Ontario, especially with respect to the chlorobenzenes. Dramatic increases in the concentrations of chlorobenzenes were observed between eastern Lake Erie and the Niagara River plume in Lake Ontario.