254
M.E. Farago
ceans and mollusks (Martin et al. 1981; McClurg 1984) were also found to be sensitive
to Hg(II).
I
I
Air
I
Deposition
I
DMHg
HgO
Hg2+
Pa rticulate
J
~
Hg2++MMHg
1
Removal via particles
I
1
Demethylation
I,
~
~
Production of HgO
~
Methylation of Hg2+
I
Thern'Iodlne
~
Hg2++MMHg
O:zmlnlmum
I
Removal via
I
particles
/
Hg2+ ~
HgO
t /
DMHg
~ MMHg
~
I ";I~:r- ~ftux
"
I
Fig. 13.4. Principal cycles and processes that affect the distributions of various mercury species in the
equatorial Pacific Ocean (from Mason and Fitzgerald 1991)
Table 13.3. Mean concentrations of mercury species found in different water masses on deep ocean
waters of the North Atlantic (56.6 oN, 25.5 OW); data from Mason et aI. 1995
Mixed layer
Thermocline
Intermed. water Deepwater
H9r
(pM)
1.55
4.25
3.15
1.7
(ngn
0.31
0.85
0.66
0.34
HgO
(pM)
0.89
0.07
0.3
0.56
(ng 1-1 )
0.18
0.014
0.06
0.11
Reactive Hg (pM)
0.95
0.94
0.75
1.03
(ng 1- 1)
0.19
0.19
0.15
0.21
DMHg
(pM)
<0.01
0.05
0.15
0.2
(ng ,- I)
0.01
0.03
0.04