Environmental Engineering Reference
In-Depth Information
Total DOC
Hydrophilic DOC
Hydrophobic DOC
Metal concentration (mmol L
-1
)
+
, Ca
2
+
, Al
3
+
and Fe
3
+
Fig. 8
Effects of increasing concentrations of Na
on the total, hydro-
philic and hydrophobic DOC at three pH levels (2.1, 4.0 and 6.5) and an initial total DOC con-
centration of 1.0 mmol L
−
1
.
Data source
Kaiser (
1998
)
DOC-facilitated transport of elements (Reszat and Hendry
2007
). The ability of
actinide ions such as uranyl to form complexes with DOC is very variable depend-
ing on the occurrence of humic fractions (fulvic and humic acids) in DOM, which
undergo in turn large variations (5-80 %) in the aquatic environments (Mostofa et
al.
2009a
; Kim and Czerwinski
1996
; Giesy et al.
1986
; Kim et al.
1994
; Artinger
et al.
2002
; Crancon and van der Lee
2003
; Jackson et al.
2005
). Interestingly, the
complexation of U to DOM is kinetically controlled (Artinger et al.
2002
).
Studies on M-DOM complexation suggest that trace metals with high binding
strength are primarily distributed in the larger molecular size fractions, and met-
als with low binding strength are mostly distributed in the smaller molecular size
fractions (Wu et al.
2004b
; Shin et al.
2001
; Lakshman et al.
1993
; Midorikawa
and Tanoue
1996
,
1998
; Lin et al.
1995
; Rao and Choppin
1995
; Sekaly et al.
1998
; Sposito et al.
1982
). The larger molecular size fractions have a higher affin-
ity for metals such as Al, Cu, UO
2
(II), and Np(V) than smaller molecular size
fractions (Shin et al.
2001
; Lakshman et al.
1993
; Midorikawa and Tanoue
1998
;
Lin et al.
1995
; Midorikawa and Tanoue
1996
; Rao and Choppin
1995
; Sekaly
et al.
1998
; Sposito et al.
1982
). Kinetic studies show that strong affinity metals
