Environmental Engineering Reference
In-Depth Information
Oldman Lake, Glacier NP
Matcharak Lake, GOTA-NPP
2000
1975
1950
1925
1900
Cd
Cd
Ni
Ni
1875
Hg
Hg
1850
0 0100
150
200
250
-50
-25
0
25
50
75
100
% Enrichment
% Enrichment
PJ Lake, Olympic NP
Mills Lake, RNP
2000
1975
1950
1925
1900
Cd
Cd
Ni
Ni
1875
Hg
Hg
1850
0
100
200
300
400
0
50
100
150
200
% Enrichment
% Enrichment
FIGURE 1.3
Four examples of the enrichment in Hg deposition found in lake cores in the Western United States. Oldman Lake is in Glacier
National Park, Montana; Matcharak Lake is in Gates of the Arctic National Park and Preserve, Alaska; PJ Lake is in Olympic National Park,
Washington; and Mills Lake is in Rocky National Park, Colorado. (
Source:
Landers et al., 2008).
found that 68% of the deposition is anthropogenic, with
31% coming from outside North America. As primary
anthropogenic sources emit some mercury in forms that can
be deposited locally (RGM and PHg) (Pacyna and Pacyna,
2002), the issue of source attribution encompasses multiple
spatial scales (Seigneur et al., 2004; Selin et al., 2007).
enhanced Hg extraction is thought to have increased the
total atmospheric burden of Hg by about a factor of 3, which
has resulted in a nearly threefold increase in deposition to
the land and ocean. But, it should be noted that the observa-
tional record of Hg in the atmosphere is relatively short, so
no clear pattern of change has been found (Ebinghaus et al.,
2009). Increased concentrations in the surface ocean and
land surface have accordingly increased emissions back to
the atmosphere. Thus, the total amount of mercury cycling
through the land surface, surface oceans, and atmosphere,
has increased signifi cantly (Selin et al., 2008; Sunderland
et al., 2009). The burden of total mercury in the deep
oceans has also increased, but by a much smaller factor. The
smaller increase in deep ocean concentrations is largely a
result of the much greater reservoir of Hg and slower mixing
and turnover times. This produces a lag in uptake on the
order of decades to centuries in the surface waters and deep
ocean, respectively (Sunderland and Mason, 2007).
The Modern Mercury Cycle
The modern, industrial cycle of mercury differs from the
preindustrial cycle (Figure 1.2) because of the extraction
and mobilization of Hg from deep reservoirs. (Deep res-
ervoirs are defi ned as reservoirs that are physically below
the surface ocean and land surface which contain a large
mass of mercury relative to the mass that cycles through
the land, air, and water, on an annual basis). Anthropogenic
activities have greatly increased the mobilization of Hg (e.g.,
coal combustion and mining) from deep reservoirs. This
