Environmental Engineering Reference
In-Depth Information
table 4.2
Mercury Isotope Variations Relative to NIST SRM 3133 in a Variety of Biologic and Sediment Reference Materials
CRM
Matrix
202
Hg (‰)
199
Hg (‰)
201
Hg (‰)
Reference
NIST SRM-1641d
Solution
0.03
0.10
ND
ND
Blum and Bergquist, 2007
UM-Almadén
Solution
0.54
0.08
ND
ND
Blum and Bergquist, 2007
0.52
0.07
ND
ND
Foucher et al., 2009
NRC DORM-2
Fish
0.18
1.07
0.88
Bergquist and Blum, 2007
0.15
0.06
1.11
0.01
0.89
0.06
This chapter
0.11
0.08
1.08
0.03
0.93
0.05
Malinovsky et al., 2008
BCR CRM-464
Fish
0.68
0.06
2.21
0.04
1.81
0.04
This chapter
NRC DOLT-2
Biologic
0.1
0.71
0.59
Bergquist and Blum, 2007
NRC DOLT-3
Biological
1.26
0.05
0.57
0.04
0.65
0.02
Malinovsky et al., 2008
NRC TORT-2
Biological
0.18
0.04
0.70
0.03
0.59
0.01
This chapter
IAEA-356
Sediment
0.32
0.04
ND
ND
Foucher et al., 2009
BCR CRM-580
Sediment
0.46
0.04
ND
ND
Foucher et al., 2009
NIST SRM-1944
Sediment
0.54
0.04
ND
ND
Foucher et al., 2009
NRC MESS-3
Sediment
2.50
0.28
ND
ND
Foucher et al., 2009
NRC PACS-2
Sediment
0.28
0.09
ND
ND
Malinovsky et al., 2008
ND
not detected.
or
resolved experimentally with existing technology. While
Schauble derives a purely mass-dependent behavior for
200
Hg, Ghosh et al.'s scale factor should cause some mass-
independent fractionation for
200
Hg as well, which has not
been observed so far, but may be too small to be detectable.
It appears that additional nuclear radii determinations
and calculations are required to resolve the remaining
differences or, alternatively, very precise isotope ratio mea-
surements must be conducted to decide which set of scale
factors is most accurate.
The Hg isotope system offers now a unique opportu-
nity to deconvolute mechanisms leading to MIF. It has not
one but two magnetic isotopes, both subject to NVE and
MIE. Plots of
xxx
Hg
δ
xxx
Hg
measured
δ
202
Hg
measured
f,
where f is an isotope-pair specifi c scaling factor.
The most commonly used equations are to calculate:
199
Hg
δ
199
Hg
measured
δ
202
Hg
measured
0.25,
200
Hg
δ
200
Hg
measured
δ
202
Hg
measured
0.50,
201
Hg
δ
201
Hg
measured
δ
202
Hg
measured
0.75,
204
Hg
δ
204
Hg
measured
δ
202
Hg
measured
1.49.
Table 4.3 precisely summarizes scale factors (based on the
δ
201
Hg should reveal the rela-
tive contribution of both effects. MIF caused by NVE alone
should show a slope between 0.366 (Schauble, 2007) and
0.457 (Ghosh et al., 2008). The challenge is to predict the
MIF caused by MIE. Whereas the latter authors speculate
that MIE fractionation will refl ect the ratio of the magnetic
moment of the two isotopes resulting in a ratio of
199
Hg versus
202
Hg system) for MDF as well as MIF caused by NVE,
derived by Schauble (2007) and by Ghosh et al. (2008).
Although both authors calculated similar factors, subtle
differences exist. Ghosh et al. predict no mass-independent
fractionation for
204
Hg, which is consistent with current
experimental results. Both authors develop scale factors for
odd Hg isotopes leading to signifi cant MIF, which is indeed
often observed for biologic materials. The differences
between odd isotope scale factors are small and cannot be
201
Hg/
1.11 (Korea Atomic Energy
Research Institute, 2000), this assumption is so far not
supported by any experimental or theoretical evidence.
199
Hg = 0.560225/0.5058852
