1 research outputs found
Spatial and Temporal Assessment of Mercury and Organic Matter in Thermokarst Affected Lakes of the Mackenzie Delta Uplands, NT, Canada
We examined dated sediment cores from 14 thermokarst
affected lakes
in the Mackenzie Delta uplands, NT, Arctic Canada, using a case-control
analysis to determine how retrogressive thaw slump development from
degrading permafrost affected the delivery of mercury (Hg) and organic
carbon (OC) to lakes. We show that sediments from the lakes with retrogressive
thaw slump development on their shorelines (slump-affected lakes)
had higher sedimentation rates and lower total Hg (THg), methyl mercury
(MeHg), and lower organic carbon concentrations compared to lakes
where thaw slumps were absent (reference lakes). There was no difference
in focus-corrected Hg flux to sediments between reference lakes and
slump-affected lakes, indicating that the lower sediment Hg concentration
in slump-affected lakes was due to dilution by rapid inorganic sedimentation
in the slump-affected lakes. Sedimentation rates were inversely correlated
with THg concentrations in sediments among the 14 lakes considered,
and explained 68% of the variance in THg concentration in surface
sediment, further supporting the dilution hypothesis. We observed
higher S2 (algal-derived carbon) and particulate organic carbon (POC)
concentrations in sediment profiles from reference lakes than in slump
lakes, likely because of dilution by inorganic siliciclastic matter
in cores from slump-affected lakes. We conclude that retrogressive
thaw slump development increases inorganic sedimentation in lakes,
and decreases concentrations of organic carbon and associated Hg and
MeHg in sediments