Table 25. Estimation of boundary layer signature concentrations
computed using surface soil concentration and soilair partition
coefficients above land mines.
Median
Estimated
surface
Median
boundary
conc.
Ks/a
layer conc.
(g/kg)
Chemical
(L-air/kg-soil)
(pg/L)
a. TMA-5
4.48 106
9.4 101
2,4,6-TNT
4.2
1.04 105
1.5 102
2,4-DNT
15.5
1.89 106
9.0 100
2-ADNT
17.0
1.55 106
1.1 101
4-ADNT
16.7
b. PMA-1A
4.48 106
8.5 101
2,4,6-TNT
3.8
1.04 105
3.0 102
2,4-DNT
31.6
1.89 106
2.3 101
2-ADNT
43.6
1.55 106
2.9 101
4-ADNT
44.3
for the surface soils near TMA-5 mines, the median
other hand, a sensor could be engineered that samples
values for 2,4-DNT, 2-ADNT, and 4-ADNT in surface
surface soil particles, a much greater mass of ERCs
soils near the PMA-1A were a factor of 2 higher. These
would be accessible. For example, if 1 g of surface soil
higher surface concentrations may be a result of the
containing the median concentration of signatures found
shallower burial of the PMA-1A mines compared to
above a TMA-5 were sampled, the mass of 15.5 ng of
the TMA-5s and the resulting shorter transit time to
2,4-DNT, with similar masses of the two ADNTs, would
reach the surface.
be available for the sensor, compared with the mass of
While equilibrium is never really achieved between
signature present in 1 L of boundary layer air. This is a
surface soils and the atmospheric boundary layer
thousand-fold increase in the mass of signature that
because of vapor diffusion and air movement, the
could be supplied to a sensor. Thus, the option of
assumption of equilibrium allows us to compute maxi-
developing a concept based on particle sampling should
mum (equilibrium) values to compare the concentra-
be given serious consideration.
tions of the various ERCs that could develop. If we
make this assumption, we can estimate boundary layer
LITERATURE CITED
concentrations using the median surface soil concen-
trations presented in Table 24, and the soilair partition
coefficients presented in Table 22. This was done for
American Society for Testing and Materials (1985)
surface soils near the TMA-5 and PMA-1A mines (Table
Standard test method for classification of soils for en-
25). Estimates of atmospheric boundary layer concen-
gineering purposes, D 2487-83. 1985 Annual Book of
trations range from 0.85 pg/L for 2,4,6-TNT to 300
ASTM Standards 04.08. American Society for Testing
pg/L for 2,4-DNT above the PMA-1A mine. For the
and Materials, West Conshohocken, Pennsylvania, p.
TMA-5, the predicted boundary layer concentration of
395408.
2,4-DNT is 160 times the prediction for 2,4,6-TNT; for
Bauer, C.F., S.M. Koza, and T.F. Jenkins (1989) Liq-
the PMA-1A, the 2,4-DNT concentration is predicted
uid chromatographic method for determination of
to be 350 times that for 2,4,6-TNT. Likewise, for the
explosives residues in soil: Collaborative study. Jour-
PMA-1A, the concentration of 2,4-DNT is predicted to
nal of the Association of Official Analytical Chemists,
be about 10 times that for 2-ADNT and 4-ADNT.
73: 541552.
The volume of the atmospheric boundary layer that
develops with near equilibrium concentrations of ERCs,
Total. In Methods of Soil Analysis, Part 2. Chemical
however, is probably very small (much less than 1 L),
and Microbiological Properties. Agronomy Monograph
so the total mass of signature that is available to a
No. 9, second edition. Madison, Wisconsin: America
vapor sensor at any given time is probably no greater
Society of Agronomy--Soil Science Society of
than a few picograms of mostly 2,4-DNT. If, on the
America,
36
to contents
Previous Page
