Distribution, Bioavailability and Speciation of Mercury
191
defined to be the percentage of heavy metals mobilized by digestive model juices.
Due to the minor importance of absorption on the gastric stage (Ewers and
Schlipkoter 1991), the relative mobilization in this stage (in percent) is called the
mobilization degree.
5.1.1
Results and Discussion
Topsoil samples recovered from the contaminated area show percentages of HCIsoluble mercury less than 1-2% of aqua regia-extracted Hg (total Hg), if total
concentrations are less than 70 mg/kg. At higher concentrations of total Hg the
mobilization degree, however, widens dramatically within a range of 5 to almost
20%, whereas there is no strict correlation between HCI-soluble Hg and total Hg
(Fig. 5). This might result from the existence of different Hg-binding forms.
Especially for higher total Hg concentrations, we can assume that a large portion
of the original pure inorganic salt still exists. These mercury chloride residues
have not been subjected to any kind of transformation to yield a stronger affinity
to mineral and organic material yet.
Table 2 shows the results from extracts with aqua regia, the mobilization (mg/
kg) and mobilization degree (%) from the saliva-stomach (gastric) stage as well
as the mobilization on the saliva-stomach-duodenum (gastrointestinal) stage and
the absorption availability from a total of 17 soil samples. Hg concentrations
between 19.8 and 609 mg/kg were determined in the soil samples. The
mobilization in the gastric stage ranged between 0.05 and 109 mg/kg with
mobilization degrees between 0.25 and 17.9%.
In the gastrointestinal stage, the mobilization of mercury ranged between < 0.2 mg/kg and 43 mg/kg with absorption availabilities between less
than 0.1 and 7.1%.
In the gastric stage, the mobilization was found to be relatively high and can be
compared with the elution of soil samples with 0.07 N hydrochloric acid (Fig. 5).
20
18
16
~ 14
l:' 12
"
!!
-- j jtlit __ -
1
0 Hg-HCI
-
• Gastric Stage
x Glistrointestinal
. . .
....
" 10
::;;
..,
- 0
~ 8
:;;
6
0
::;;
I -
4
2
0
,;~.~ . . ~ . . ~!.;. P<~
-0
•
.~. ~o -
o
o
1
10 Hg(total) in Soil (mg/kg) 100
1000
Fig. 5. Percentages of mobilizable mercury by Hel elution and by digestive juices on tbe gastric stage
as well as on the gastrointestinal stage
191
defined to be the percentage of heavy metals mobilized by digestive model juices.
Due to the minor importance of absorption on the gastric stage (Ewers and
Schlipkoter 1991), the relative mobilization in this stage (in percent) is called the
mobilization degree.
5.1.1
Results and Discussion
Topsoil samples recovered from the contaminated area show percentages of HCIsoluble mercury less than 1-2% of aqua regia-extracted Hg (total Hg), if total
concentrations are less than 70 mg/kg. At higher concentrations of total Hg the
mobilization degree, however, widens dramatically within a range of 5 to almost
20%, whereas there is no strict correlation between HCI-soluble Hg and total Hg
(Fig. 5). This might result from the existence of different Hg-binding forms.
Especially for higher total Hg concentrations, we can assume that a large portion
of the original pure inorganic salt still exists. These mercury chloride residues
have not been subjected to any kind of transformation to yield a stronger affinity
to mineral and organic material yet.
Table 2 shows the results from extracts with aqua regia, the mobilization (mg/
kg) and mobilization degree (%) from the saliva-stomach (gastric) stage as well
as the mobilization on the saliva-stomach-duodenum (gastrointestinal) stage and
the absorption availability from a total of 17 soil samples. Hg concentrations
between 19.8 and 609 mg/kg were determined in the soil samples. The
mobilization in the gastric stage ranged between 0.05 and 109 mg/kg with
mobilization degrees between 0.25 and 17.9%.
In the gastrointestinal stage, the mobilization of mercury ranged between < 0.2 mg/kg and 43 mg/kg with absorption availabilities between less
than 0.1 and 7.1%.
In the gastric stage, the mobilization was found to be relatively high and can be
compared with the elution of soil samples with 0.07 N hydrochloric acid (Fig. 5).
20
18
16
~ 14
l:' 12
"
!!
-- j jtlit __ -
1
0 Hg-HCI
-
• Gastric Stage
x Glistrointestinal
. . .
....
" 10
::;;
..,
- 0
~ 8
:;;
6
0
::;;
I -
4
2
0
,;~.~ . . ~ . . ~!.;. P<~
-0
•
.~. ~o -
o
o
1
10 Hg(total) in Soil (mg/kg) 100
1000
Fig. 5. Percentages of mobilizable mercury by Hel elution and by digestive juices on tbe gastric stage
as well as on the gastrointestinal stage