Geoscience Reference
In-Depth Information
Table 14.2 Estimated trace
element concentrations in soil
solutions (based on Senesi
and Loffredo
2005
; Sauve
and Parker
2000
)
Element
Soil solution lg/L
As
0.5-60,000
Cd
0.01-5,000
Cr
2-500
Cu
5-10,000
Ni
0.5-5,000
Pb
0.5-500
Se
1-100,000
Zn
1-100,000
14.3 Surface-Induced Interactions of Inorganic
Contaminants
Metal ion complexation to natural organic components in the solid phase is a major
example of abiotic interactions of inorganic contaminants in the subsurface.
Through these interactions, initial metal ion relationships of the original compounds
are changed and contaminant retention, persistence, and transport in the environ-
ment exhibit different behaviors. As mentioned previously (see Part I), subsurface
organic compounds that form complexes with toxic metal ions include natural humic
substances (about 80 %), additional organic substances of biological origin (such as
aliphatic and amino acids, polysaccharides, and polyphenols), and xenobiotic
organic chemicals released on the land surface by accident or intentionally.
Potentially toxic compounds in the subsurface, such as Cd
2+
,Pb
2+
,orHg
2+
,
which are generally found in very low concentrations, are considered ''soft cat-
ions'' (Buffle
1988
). These ions have strong affinity to intermediate and soft
ligands and therefore bond to them covalently. ''Borderline'' cations, which
embrace transition metals such as Cu
2+
and Zn
2+
, exhibit affinity for the soft
cations as well as for alkaline earth compounds. The order of donor atom affinity
for soft metals is O \ N \ S. Functional groups present in subsurface organic
matter that
show affinity
for ''soft'' and ''borderline'' metals are shown in
Table
14.2
.
References
Armstrong DE, Chester G, Harris RF (1967) Atrazine hydrolysis in soil. Soil Sci Soc Am Proc
31:61-66
Brown CB, White JL (1969) Reactions of 12-triazines with soil clays. Soil Sci Soc Am Proc
33:863-867
Buffle
J (1988) Complexation
reactions
in aquatic systems:
an analytical
approach.
Ellis
Horwood, Chichester, England
Chaussidon J, Calvet R (1965) Evolution of amine cations adsorbed on montmorillonite. J Phys
Chem 69:265-268
