15 06 Godwin - International Mine Water Association · 2011-07-11 1 Predicting toxicity of future combined pit lakes at the former Steep Rock Iron Mine near Atikokan, Ontario Amy
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2011-07-11
1
Predicting toxicity of future combined pit lakes at the former Steep Rock Iron Mine
near Atikokan, Ontario
Amy L. Godwin1, Peter F. Lee1, Andrew G. Conly2 and Andrea R. Goold1
1Department of Biology2Department of Geology
LUMINX-LUEL-ATRC
Location
Hogarth
Caland
Errington
Robert’s
Hogarth Pit looking southeast, ca. 1970’s
Original Lake Level
History
Courtesy J. Baechler
The Issues
West Arm
Middle Arm/Hogarth
East Arm/Caland
Atikokan
Nature of the Pit Lakes
• Typical pH for both pit lakes is 7 to 8• Caland
– Stratified (only upper 20 m oxygenated)– Non-toxic (hosted a fish farm)
PREDICTIVE MODELING: · Growth inhibition tests using Lemna minor
Predictive Modeling: Growth inhibition testsGrowth inhibition tests were conducted using Lemna
minor• Static column experiments:
• Varying water ratios from the two pit lakes• Geological influence of wall rocks
• Resultant water represented future water quality of the• Resultant water represented future water quality of the merged pits as they fill:• Used in Lemna minor growth inhibition tests
• Analysis and Alternate Endpoints:– IC25 (ToxCalc v5.0)– Dry weights– Chlorophyll-a concentration– Frond surface area
• (total, by colour – dark green, light green, yellow (chlorotic), white (necrotic)
Predictive Water Quality
Crushed (1-2 mm) wall rock(amount =
24 in exposed surface area of pit wall rock@ outflow)
Mix of Hogarth &Caland water
Water:rock ratio (by mass) = 10:1
Predictive Water Quality
1
10
Column 1 Column 2 Col 3 umnCol 4 umnCol 5 umnC l 6o
nc
entr
atio
n N
orm
aliz
ed
to
Cal
and
200
6 W
ate
r
pH SO4
2- Ca+Mg Na+K TotalMetal
0.1
Col 6 umnCol 7 umnCol 8 umnCol 9 umnCol 10 umn
Hog06 EC25 range (see Section 5)
Co
Column 1 2 3 4 5 6 7 8 9 10
Hogarth (water sample depth) n/a 2 m 30 m 30 m 30 m 2 m 2 m 2 m n/a 30 m
Caland (water sample depth) 2m n/a 2 m 2 m 2 m 30 m 30 m 30 m 30 m n/a