Environmental Engineering Reference
In-Depth Information
table 10.3
(continued)
Sediment
MMHg
(ng g
1
, dry
weight)
% Hg as
MMHg
in solid
phase
% Hg as
MMHg
in pore
water
Pore water
MMHg
(ng L
1
)
MMHg
benthic fl ux
(ng m
2
day
1
)
Location
References
Putuxent River
Estuary
(Maryland)
0.1-0.8
0.1-0.5
0.03-0.2
0.5-6
Benoit et al., 1998
South Florida
coast and
estuaries
0.001-0.5
0.01-6.1
Kannan et al., 1998
Lavaca Bay
(Texas)
0.03-13
0.01-2.8
0.7-250
1.5-92
330-1500
Bloom et al., 1999;
Gill et al., 1999
San Francisco
Bay (California)
0.06-2.4
0.03-1.2
Conaway et al.,
2003; Marvin-
DiPasquale et al.,
2003
San Francisco
Bay Delta
(California)
0.02-14
0.1-10
0.1-13
0.5-
100
20-180
Choe et al., 2004;
Heim et al., 2007
Bering Sea
0.06-0.6
0.02-0.7
Kannan and
Falandysz, 1998
Guanabara Bay
(Brazil)
1.1-11
0.2-6.3
Kehrig et al., 2003
South China
Sea
0.01-0.05
0.02-0.27
Kannan and
Falandysz, 1998
Deep sea
sediments of
Mediterranean
Sea
0.08-3.2
0.2-4.2
2.2-64.7
5-25
0.6-6.9
a
Ogrinc et al., 2007
note: Values were estimated visually from plots when data were not provided explicitly in a table or in the text.
a. Only diffusive component of benthic fl uxes were calculated and reported.
in off-axis deep-sea sediments, where advective fl uxes are
generally minor (Wolf and Chilingarian, 1992).
Benthic fl uxes of MMHg, like sediment MMHg concen-
trations and % total mercury as MMHg, display seasonal
and diurnal patterns. Bioirrigation, bioturbation, and other
sediment processes play an important role in controlling
rates of MMHg release to overlying waters (Covelli et al.,
2008; Gill et al., 1999; Hammerschmidt and Fitzgerald,
2008; Hammerschmidt et al., 2004). MMHg fl uxes from
sediments are sometimes higher when overlying waters
are low in oxygen, potentially because of increased MMHg
production at the sediment-water interface (Covelli et al.,
1999, 2008; Gill et al., 1999; Mason et al., 1999). However,
the opposite has been reported in other cases, presumably
due to decreased bioirrigation and bioturbation by infauna
during low oxygen conditions (Hammerschmidt and
Fitzgerald, 2008; Hammerschmidt et al., 2004, 2008; Hines
et al., 2006; Mason et al., 2006).
Benthic fl uxes of MMHg reported for estuary and nearshore
sediments are listed in Table 10.3. These fl uxes range from
-330 to
2370 ng m
-2
d
1
, demonstrating that sediments can
act as a source or sink for MMHg, although they are most
often an important source of MMHg to overlying waters.
For areas where data on the different sources of MMHg to
coastal environments exist and allow for a comparison, the
production and fl ux of MMHg from coastal sediments repre-
sents the largest source of MMHg to coastal waters (Balcom
et al., 2008; Hammerschmidt et al., 2004; Horvat et al.,
1999). For example, benthic fl uxes are estimated to repre-
sent ~67% of MMHg inputs to the water column of Long
Island Sound (Hammerschmidt et al., 2004) and 25% in the
New York/New Jersey Harbor Estuary (Balcom et al., 2008).
Similarly, in the San Francisco Bay Delta the effl ux of MMHg
from sediment was estimated to be roughly equal to riverine
inputs of MMHg during the dry season and one third of
riverine inputs during the wet season (Choe et al., 2004).
