Mercury and Total Mercury in Boreal Upland Forests

Overview

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Key numbers

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The FLooded Upland Dynamics Experiment (FLU- duction (range = 120–1590 ng m)2 day)1) in all
northwest Ontario was designed to test the which time net demethylation (range = 360–1230
ada, as well as in Finland (Lodenius and others 60 and 27 times less OC than stored in the ELARP
and GHG production, whereas the total quantity of with 32-year mean July and January temperatures
OC flooded may affect the long-term duration of of 18.5 and )17.3C, respectively. Mean annual
To begin examining the link between OC min- with approximately 25% of this wet deposition
from the reservoir increased dramatically (Kelly majority of which was stored in trees (57%) and the
and others 1997). Continued background moni- fungal/humic (FH) layer of the soils (34%; Table 1).
Dominant vegetation Pinus/Ledum/Sphagnum (53%) Pinus/Betula Pinus/Vaccinium (73%)
Organic pillows (5%)
(Table 1). leatherleaf shrubs (Dyck and Shay 1999). The vast
(Table 1). A dense jack pine forest with tall birch
and herbs dominated the site. Approximately 80% dikes along low-lying contours of the sites followed
trees, whereas 16% was stored in the FH layer of oligotrophic lake. In areas where ﬂooding would
ridge-top. Approximately 73% of the site had tural walls were constructed in areas where
tained 30,900 kg C ha)1, with 64% and 28% Beginning in 1999 (Table 2), water was pumped
(Table 1). oligotrophic Roddy Lake (L468) through aluminum
Table 2. Physical Properties of the FLUDEX Upland Reservoirs
25% KOH in methanol (Horvat and others 1993) The amount of foliage mass in the forest canopy
80% and 110% recovery of certiﬁed values. Flett tors. Collectors were attached to trees just above
C, Medium C, and Low C sites, respectively). Cores were generally greater than 80% and greater than
centrations by a mean soil bulk density determined (Hall 2003).
density = 2.5, 3.0, and 2.0 g cm)2 in the High C, means of control valves and inline ﬂow meters.
hands–dirty-hands sampling protocol (St. Louis and September study period was 13% (425 mm), 54%
others 1996). MeHg water samples were frozen (580 mm), and 16% (399 mm) above the 32-year
using trace-metal-grade concentrated HCl to 1% of respectively. The volume of throughfall was deter-
(ANOVA; p = 0.92 and 0.93; n = 34 and 20 for calculated by summing the outputs for each
ha; Figure 1). However, because the NW inflow estimated as 95% of the total water column volume
wetland and the presence of wetlands in catch- interface) estimated as 5% of total water column
tions. Analytical error was less than 10% for both rinsed from two dowels at each station into plastic
19% and 10% of a consensus value obtained in a analyzed for MeHg at Flett Research Ltd. using the
about 18% when applying gauged runoff to similar analyzed for MeHg concentrations. Because quan-
pumping where the associated errors were 5%. culated by multiplying the concentration of grab
Table 3. Average concentrations (ng g)1) and Stores of (mg ha)1) of Methylmercury (MeHg) and Total
each September with either minnow traps (1999) (Table 3). Average THg concentrations were be-
trometry (Hendzel and Jamieson 1976) in the (37 and 39 mg ha)1, respectively; Table 3). THg
THg concentrations are approximately 30% higher C site (7580 mg ha)1; Table 3). For all sites, MeHg
than whole-body concentrations, therefore a con- and THg were predominantly stored in soils (81%–
version factor of 0.7 was applied to muscle THg 95% and 95%–98%, respectively). MeHg was pri-
Freshwater Institute, Winnipeg, MB). To determine in the Medium C site (Table 3). In the Medium
others 2001). The amount of THg present as MeHg 147 mg THg (Table 6) among reservoirs over the
in the High C site (1.1%) compared to the Medium between 87% and 98% of total MeHg inputs and

Methods (brief)

ada, as well as in Finland (Lodenius and others 60 and 27 times less OC than stored in the ELARP
leaves), mosses, lichens, and wood collected at the Figure 1. Location of study sites in relation to the
determined using cold vapor atomic ﬂuorescence
spectrometry (CVAFS) after overnight digestion in
concentrations were determined using CVAFS after terfall samples collected in duplicate at three sites
digestion in 7:3 (vol:vol) nitric:sulfuric acid, as de- within each reservoir (Matthews and others 2005).
Research Ltd. (Winnipeg, Manitoba, Canada) ana- the water level and litter was collected from the
lyzed plant tissues samples. containers monthly. Estimates of MeHg and THg
ing MeHg and THg concentrations in foliage by the lyzed by CVAFS after distillation (Horvat and others
multiplied by the total dry weight of each tissue in using CVAFS as described by Bloom and others
Storage of MeHg and THg in upland forest soils all water samples for MeHg and THg, with the
was calculated using concentrations measured in exception of bottom water samples which were
were collected using a stainless-steel barrel corer 90%, respectively.
lined with plastic sleeves and were typically 8–15 Surface water samples were taken concurrently
cm long. Cores were sectioned into surﬁcial litter/ with Hg water samples in Nalgene polypropylene
La Crosse Mercury Laboratories. MeHg samples 2001 using Onset Hobo data loggers.
were analyzed by CVAFS after distillation (Horvat Inputs. Inputs of MeHg and THg to the upland
Water at the end of the inﬂow pipe was sampled

Implications

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised