Municipal landfill impacts on a natural stream located in an urban wetland in regional Niagara, Ontario

Abstract

In 1989, the 400 km long Niagara Escarpment was designated an Ecological Biosphere Preserve Area by UNESCO. Landfills on top of the escarpment were the subject of study in terms of their potential impacts on the streams and forest vegetation on the escarpment slopes below. Surprisingly little has been published on the impacts of these landfills on urban streams and wetlands. In the present study, a forested hillside stream (Leawood Creek) was chosen because its headwaters were located immediately below a municipal landfill which is perched on the brow of the Niagara Escarpment. High iron and zinc concentrations in the study creek, compared to nearby unimpacted creeks, were interpreted as an indication that leachate from the Glenridge Landfill had previously contaminated Leawood Creek. Iron concentrations in the sediments of the study creek averaged 26 000 ppm and zinc reached a concentration of 310 ppm. Both zinc and iron are common constituents of the numerous metal objects deposited in the landfill. The Leawood Creek study stream flows at an average rate of 3.2 L sec-1. Because the Creek is spring-fed, it flows continuously throughout the year. During the study period (January to June 1991), the biota in the lower portion of the creek differed substantially from the upper (escarpment) as did the iron bacterium (Gallionella) which was absent from the lower section of the creek. Gallionella discoloured the rocky substrate in the upper sections of the Creek near the landfill. Prior to the creation of the Glenridge Landfill in 1976, Leawood Creek contained numerous invertebrates including mayflies, amphipods (scuds), water pennies (Coleopterans), stoneflies and caddisflies. In 1991, after 15 years of operation, only snails, pollution tolerant blood worms (chironomids) and sludge worms (tubificids) were found in any abundance in this spring-fed creek. Thus, pollution-sensitive stream invertebrates such as scuds, mayflies and caddisflies have been replaced by pollution tolerant sludge worms, nematodes, snails and blood worms.