Environmental Engineering Reference
In-Depth Information
An
Retardation
Mobilization
Figure 29.1
Humic substances (HS) influence the migration of actinides from two perspectives: (a) as mobile organomineral colloids and
complexes in aquatic environments (right panel); and (b) as immobile HS (e.g., humic coatings on mineral phases in soils—left panel) that
can retard actinide migration.
O
OH
OH
OH
COOH
N
O
OH
HOOC
HOOC
HOOCOH
O
OH
OH
O
OH
H
COOH
COOH
NH CH
2
O
Fe
2+
OH
O
O
OH
O
NH
NH
CH
2
NH
2
NH
O
-
OH
CH
3
NH
NH
2
O
O
-
O
OH
O
NH
H
3
C
NH
2
OH
OH
OH
CH
2
OH
NH
2
O
OCH
3
O
O
OH
O
H
OH
O
OH
O
O
CH
3
K
+
O
O
O
-
O
Fe
2+
H
O
CH
2
OH
NH
2
H
NH
2
O
-
OH
OH
OH
O
O
O
O
CH
3
Si
H
O
COOH
O
O
H
O
O
O
O
O
N
NH CH
2
NH
NH
CH
2
NH
HO
OH
O
-
CH
2
C
O
CH
2
CH
2
CH
2
Si
N
H
CH
2
O
CH
2
O
H
H
H
O
OH
O
O
N
OH
O
CH
2
CH
2
H
NH
O
O
Al
O
O H
HN
N
NO
2
Fe
Al
+
H
3
CO
O
H
O
OH
COOH
NH
2
O
O
HN
CH CH
2
O
OH
O
-
O
O
O
O
-
CH
2
OH
H
H
H
O
H
H
Si
O
Fe
2+
O
O
COOH
O
O
Fe
2+
O
H
H
OH
OH
O
-
O
O
CH
3
O
O
OH
H
3
CO
O
OH
OH
H
NH
2
O
-
H
O
H
CH
3
H
O
OH
CH
2
OH
CH
2
OH
H
H
CH
2
OH
HO
H
3
C
NH
OH
O
O
O
O
O
O
O
O
OH
O
O
O
O
O
OH
HO
NH
CH
2
CH
2
OH
O
OH
CH
2
OH
HO
CH
2
CH
2
O
N
OH
NO
2
OH
H
2
N
OH
O
O
O
Figure 29.2
Hypothetical structural fragment of soil humic substances (Kleinhempel, 1970). The fragment illustrates the extreme
structural heterogeneity of natural HS, which contain various oxygen-containing functional groups. The latter enables HS to engage redox,
complexation, and sorption interactions.
