Environmental Engineering Reference
In-Depth Information
Table 4
Concentrations in water (ng L
−1
), sediment (ng g
−1
), and atmosphere (ng m
−3
) in six
hydrographic regions of San Francisco Estuary
Water Sediment Air
UHg
T
FHg
T
UMMHg FMMHg DGM Hg
T
MMHg Hg
0
Region (ng L
−1
) (ng L
−1
) (ng L
−1
) (ng L
−1
) (ng L
−1
) (ng g
−1
) (ng g
−1
) (ng m
−3
)
Rivers/Delta 2-10 0.4-2 0.04-0.3 0.02-0.08 0.04-0.2 20-500 0.02-0.08
Northern
0.4-90
0.1-30
0.1
0.008-0.4
0.2-0.5
30-600
0.06-0.4
Estuary
Central Bay 0.3-10 0.08-0.6 0.02-0.06
0.02-0.1 0.01-0.04 10-400
0.0-0.7
2
South Bay
0.4-40
0.1-10
0.02-0.2
0.01-0.08 0.02-0.1 100-800
0.08-2
2
Southern
6-70
0.1-4
0.08-0.5
0.3
0.1-0.2
70-800
0.2-2
Sloughs
Estuary
2-70
0.1-30
0.1-0.4
0.2
0.5-2
100-1000
0.6-3
Interface
Total mercury in unfiltered water (UHg
T
), total mercury in filtered water (FHg
T
), monomethylmer-
cury in unfiltered water (UMMHg), monomethylmercury in filtered water (FMMHg), dissolved
gaseous mercury (DGM), total mercury in sediment (Hg
T
), monomethylmercury in sediment
(MMHg), and mercury vapor in air (Hg
0
).
Sources:
Data from Choe and Gill (2003), Choe et al. (2003), Conaway et al. (2003), and Conaway
(2005).
concentrations found in and near wetlands (Choe et al. 2004; Marvin-DiPasquale
et al. 2003) and in the central delta (Heim et al. 2007). Table 4 lists the concentration
of mercury species in various matrices around the estuary.
Both Hg(II) and MMHg are highly particle reactive, with partition coefficients
(
K
d
) of 10
4.0
-10
6.5
commonly measured in the estuary (Choe and Gill 2003; Choe
et al. 2003; Conaway et al. 2003). As a result, much of the advective transport of
mercury into and within the estuary occurs via particulate phases (Choe and Gill
2003; Choe et al. 2003; Conaway et al. 2003; Domagalski 2001; Roth et al. 2001)
as mercury-sulfide minerals, adsorbed to particles, or associated with organic mat-
ter (Roth et al. 2001; Slowey et al. 2005b).
A
Sediment: The Importance of Sediment Processes
A key area in linking mercury sources to ecological effects and human health is its
biogeochemistry in estuarine sediments. Using samples from San Francisco
Estuary, Olson and Cooper (1974, 1976) were the first to demonstrate that estuarine
sediments were an important site for the methylation of Hg(II). Studies of microbial
mercury methylation and demethylation potential in sediments from various
environments throughout the estuary and delta (Marvin-DiPasquale and Agee 2003;
Marvin-DiPasquale et al. 2003; Mehrotra and Sedlak 2005; Topping et al. 2004)
have subsequently illustrated the role of wetlands as hotspots of mercury methyla-
tion as well as the importance of Hg(II) speciation and bioavailability, microbial
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