Current Research:
South Tobacco Creek Project
A Major Research Initiative
The second major
research initiative to emerge from the South Tobacco Creek Project (STCP
background) has focused on tracking the movement of agricultural pesticides,
primarily herbicides, within the South Tobacco Creek watershed.
Thea Rawn, a
Ph.D. candidate in the Department of Soil Science at the University of
Manitoba, and under the guidance of Dr. Derek Muir of the Freshwater Institute
of Fisheries and Oceans Canada played a lead role. Rawn was responsible
for all sampling, analysis, evaluation, and data interpretation.
This project was established to operate from 1993 to 1996.
The Pesticide Research project's
objectives are:
- 1. To determine sources and pathways
of pesticides found in the runoff water from an agricultural watershed,
by focusing on pesticide traces found in field runoff, precipitation, and
air samples; and
- 2. To quantify the relative importance
of each of the atmospheric sources by monitoring changes in pesticide traces/concentrations.
Canadian water quality guidelines are derived by evaluating laboratory and field-based studies on the effects of pesticides on aquatic organisms. Limits are usually set at 10 to 100 times below the lowest concentrations which has been observed to cause chronic biological effects (i.e. effects on growth or reproduction). The most sensitive freshwater species (plants and animals) are used to establish the aquatic guideline.
The combined effects of several pesticides are not considered directly when setting the guideline limits, but this is taken into account by setting a margin of safety well below observed effects for a given chemical.
Monitoring the smallest trace levels of pesticides within Manitoba's waterways could greatly assist in understanding the relationships between these products and the environment. Unfortunately, most current monitoring programs are not designed to track pesticide levels well below the ug/L level. Another concern is that current monitoring efforts do not address the temporal fluctuation of pesticide traces. Accuracy problems occur when sampling does not coincide with pesticide application.
The pathways of
entry for these pesticide compounds are not well understood. For
example, we know most farmers within the Red River watershed use pesticides.
However, we can not confirm if the sources of specific pesticide compounds
are related to those pesticide levels which are detected in our waterways.
Time of application, method of application, point of origin, and mode of
transportation are all factors in the pathway equation. These important
factors and their complex interrelationships are all posing questions which
need to be answered.
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The best means of learning more about the movement of contaminants in water courses is to study changes at a measurable watershed level. While this is the ideal approach, very little accurate data exists in Manitoba, or elsewhere for that matter, regarding the timing of application for specific pesticides within a specific watershed. The Deerwood Association, in conjunction with its South Tobacco Creek Project partners, is now contributing to an increased understanding of these issues.
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