Environmental Considerations for Wet Mining Peatlands in Northwestern Ontario
Abstract
Signi cant changes in water quality were detected using a Before-After-Control-Impact
(BACI) experimental design. Porewater showed increases in pH, alkalinity, conductivity
(including Ca, Mg, K, Na), some metals (Sr, Ba, Mn, Fe) and total nitrogen (TN) in
the mined and restored plot. Change in surface water total mercury (THg) was linked
to total suspended solids (TSS) and limited to active phases of wet mining. The season
mining ceased, TSS and THg concentrations in impacted surface waters were similar to
reference site water (<5 mg L1 and <4 ng L1, respectively).
Experimentally derived 28 day dry weight Biota-Sediment Bioaccumulation Factors
(BSAFs) for THg using Lumbriculus variegatus exposed to site sediment ranged from 0.91
to 1.59, while indigenous benthos ranged from 1.2 to 6.8. The BSAFs for methylmercury
(MeHg) ranged from 9.92 to 67.4 and benthos from 21.8 to 106. A kinetic trial with
inorganic mercury (iHg) spiked sediment, showed tissue THg reached steady state (11.5 d,
model BSAF=3.12). Both tissue and sediment MeHg for the same trial showed linear
increases (model BSAF=8.38), suggesting an increase in MeHg concentration in sediment
would result in a corresponding MeHg increase in L. variegatus tissue.