M. Dickman et G. Rygiel, Municipal landfill impacts on a natural stream located in an urban wetlandin regional Niagara, Ontario, CAN FIELD-N, 112(4), 1998, pp. 619-630
In 1989, the 400 km long Niagara Escarpment was designated an Ecological Bi
osphere Preserve Area by UNESCO. Landfills on top of the escarpment were th
e subject of study in terms of their potential impacts on the streams and f
orest vegetation on the escarpment slopes below. Surprisingly little has be
en published on the impacts of these landfills on urban streams and wetland
s. In the present study, a forested hillside stream (Leawood Creel;) was ch
osen because its headwaters were located immediately below a municipal land
fill which is perched on the brow of the Niagara Escarpment. High iron and
zinc concentrations in the study creek, compared to nearby unimpacted creek
s, were interpreted as an indication that leachate from the Glenridge Landf
ill had previously contaminated Leawood Creek Iron concentrations in the se
diments of the study creek averaged 26 000 ppm and zinc reached a concentra
tion of 310 ppm. Both zinc and iron are common constituents of the numerous
metal objects deposited in the landfill. The Leawood Creek study stream fl
ows at an average rate of 3.2 L sec(-1). Because the Creek is spring-fed, i
t flows continuously throughout the year. During the study period (January
to June 1991), the biota in the lower portion of the creek differed substan
tially from the upper (escarpment) as did the iron bacterium (Gallionella)
which was absent from the lower section of the creek Gallionella discoloure
d 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 con
tained 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) an
d sludge worms (tutificids) were found in any abundance in this spring-fed
creek. Thus, pollution-sensitive stream invertebrates such as scuds, mayfli
es and caddisflies have been replaced by pollution tolerant sludge worms, n
ematodes, snails and blood worms.