4 research outputs found
Contemporary Mobilization of Legacy Pb Stores by DOM in a Boreal Peatland
We examined how different landscape
areas in a catchment containing
a northern ombrotrophic peatland and upland mineral soils responded
to dramatic decreases in atmospheric deposition of lead (Pb). Pb concentrations
in the outflow stream from the peatland measured from 2009β2015
indicated continued mobilization and export of Pb derived from historic
inputs to the bog. In contrast, Pb concentrations in surface peat
and runoff from upland mineral soils have declined in response to
reductions in atmospheric deposition. Relative to the early 1980s,
Pb concentrations in the streamflow decreased only βΌ50%, while
Pb in surface peat and upland subsurface runoff decreased by more
than 90%. Water level fluctuations in the slow-accumulating peat have
allowed dissolved organic matter (DOM) to continue mobilizing Pb deposited
in the peatland decades earlier. Strong correlations between dissolved
organic carbon (DOC) and Pb concentrations in outflow from the peatland
and in bog porewaters demonstrate Pb mobility related to DOM production.
Peat stores of Pb in 2016 were less than or equal to those reported
in the early 1980s despite the dry mass inventory increasing by 60β80%.
Much of the loss in Pb stored in peat can be accounted for by stream
runoff from the peatland
Long-Term Experimental Manipulation of Atmospheric Sulfate Deposition to a Peatland: Response of Methylmercury and Related Solute Export in Streamwater
Changes in sulfate (SO42β) deposition
have been linked to changes in mercury (Hg) methylation in peatlands
and water quality in freshwater catchments. There is little empirical
evidence, however, of how quickly methyl-Hg (MeHg, a bioaccumulative
neurotoxin) export from catchments might change with declining SO42β deposition. Here, we present responses
in total Hg (THg), MeHg, total organic carbon, pH, and SO42β export from a peatland-dominated catchment as
a function of changing SO42β deposition
in a long-term (1998β2011), whole-ecosystem, control-impact
experiment. Annual SO42β deposition to
half of a 2-ha peatland was experimentally increased 6-fold over natural
levels and then returned to ambient levels in two phases. Sulfate
additions led to a 5-fold increase in monthly flow-weighted MeHg concentrations
and yields relative to a reference catchment. Once SO42β additions ceased, MeHg concentrations in the outflow
streamwater returned to pre-SO42β addition
levels within 2 years. The decline in streamwater MeHg was proportional
to the change in the peatland area no longer receiving experimental
SO42β inputs. Importantly, net demethylation
and increased sorption to peat hastened the return of MeHg to baseline
levels beyond purely hydrological flushing. Overall, we present clear
empirical evidence of rapid and proportionate declines in MeHg export
from a peatland-dominated catchment when SO42β deposition declines
Long-Term Experimental Manipulation of Atmospheric Sulfate Deposition to a Peatland: Response of Methylmercury and Related Solute Export in Streamwater
Changes in sulfate (SO42β) deposition
have been linked to changes in mercury (Hg) methylation in peatlands
and water quality in freshwater catchments. There is little empirical
evidence, however, of how quickly methyl-Hg (MeHg, a bioaccumulative
neurotoxin) export from catchments might change with declining SO42β deposition. Here, we present responses
in total Hg (THg), MeHg, total organic carbon, pH, and SO42β export from a peatland-dominated catchment as
a function of changing SO42β deposition
in a long-term (1998β2011), whole-ecosystem, control-impact
experiment. Annual SO42β deposition to
half of a 2-ha peatland was experimentally increased 6-fold over natural
levels and then returned to ambient levels in two phases. Sulfate
additions led to a 5-fold increase in monthly flow-weighted MeHg concentrations
and yields relative to a reference catchment. Once SO42β additions ceased, MeHg concentrations in the outflow
streamwater returned to pre-SO42β addition
levels within 2 years. The decline in streamwater MeHg was proportional
to the change in the peatland area no longer receiving experimental
SO42β inputs. Importantly, net demethylation
and increased sorption to peat hastened the return of MeHg to baseline
levels beyond purely hydrological flushing. Overall, we present clear
empirical evidence of rapid and proportionate declines in MeHg export
from a peatland-dominated catchment when SO42β deposition declines
Long-Term Experimental Manipulation of Atmospheric Sulfate Deposition to a Peatland: Response of Methylmercury and Related Solute Export in Streamwater
Changes in sulfate (SO42β) deposition
have been linked to changes in mercury (Hg) methylation in peatlands
and water quality in freshwater catchments. There is little empirical
evidence, however, of how quickly methyl-Hg (MeHg, a bioaccumulative
neurotoxin) export from catchments might change with declining SO42β deposition. Here, we present responses
in total Hg (THg), MeHg, total organic carbon, pH, and SO42β export from a peatland-dominated catchment as
a function of changing SO42β deposition
in a long-term (1998β2011), whole-ecosystem, control-impact
experiment. Annual SO42β deposition to
half of a 2-ha peatland was experimentally increased 6-fold over natural
levels and then returned to ambient levels in two phases. Sulfate
additions led to a 5-fold increase in monthly flow-weighted MeHg concentrations
and yields relative to a reference catchment. Once SO42β additions ceased, MeHg concentrations in the outflow
streamwater returned to pre-SO42β addition
levels within 2 years. The decline in streamwater MeHg was proportional
to the change in the peatland area no longer receiving experimental
SO42β inputs. Importantly, net demethylation
and increased sorption to peat hastened the return of MeHg to baseline
levels beyond purely hydrological flushing. Overall, we present clear
empirical evidence of rapid and proportionate declines in MeHg export
from a peatland-dominated catchment when SO42β deposition declines