Environmental Engineering Reference
In-Depth Information
or terrestrial material from soils, (ii) autochthonous or surface water-derived of
algal or phytoplankton origin, and (iii) syhthetic organic substances of man-made
or industrial origin. DOM in natural waters is composed of a heterogeneous mix-
ture of organic compounds with molecular weights ranging from less than 100 to
over 300,000 Daltons (Hayase and Tsubota
1985
; Thurman
1985a
; Ma and Ali
2009
). On the other hand, POM is composed of plant debris, algae, phytoplank-
ton cell, bacteria, and so on (Mostofa et al.
2009a
). Humic substances (fulvic and
humic acids) of terrestrial origin are the dominant DOM fractions in freshwater
and coastal seawater (Mostofa et al.
2009a
). On the other hand, autochthonous
fulvic acids (or marine humic-like) of algal or phytoplankton and bacterial origin
are the key DOM fractions in lakes and oceans (Mostofa et al.
2009a
,
b
; Coble
1996
,
2007
; Parlanti et al.
2000
; Amado et al.
2007
; Zhang et al.
2009
). In addi-
tion, among the major classes of DOM components there are carbohydrates, pro-
teins, amino acids, lipids, phenols, alcohols, organic acids and sterols (Mostofa
et al.
2009a
).
DOM can display physical properties such as the absorption of energy from
ultraviolet (UV) and photosynthetically available radiation (PAR) (Kirk
1976
;
Morris et al.
1995
; Siegel and Michaels
1996
; Morris and Hargreaves
1997
;
Tranvik
1998
; Bertilsson and Tranvik
2000
; Laurion et al.
2000
; Markager and
Vincent
2000
; Huovinen et al.
2003
; Sommaruga and Augustin
2006
; Hayakawa
and Sugiyama
2008
; Effler et al.
2010
), chemical properties such as complex for-
mation with trace metal ions (Mostofa et al.
2009a
,
2011
; Lead et al.
1999
; Wang
and Guo
2000
; Koukal et al.
2003
; Mylon et al.
2003
; Wu et al.
2004
; Lamelas
and Slaveykova
2007
; Lamelas et al.
2009
; Fletcher et al.
2010
; Reiller and Brevet
2010
; Sachs et al.
2010
; Da Costa et al.
2011
), the ability to maintain acidity and
alkalinity (Mostofa et al.
2009a
; Oliver et al.
1983
; Wigington et al.
1996
; Pace
and Cole
2002
; Hudson et al.
2003
; Kopá
ek et al.
2003
), the occurrence of redox
and photo-Fenton reactions (Voelker and Sulzberger
1996
; Voelker et al.
1997
,
2000
; Kwan and Voelker
2002
; Jeong and Yoon
2004
; Wu et al.
2005
; Vione et al.
2006
; Nakatani et al.
2007
), as well as the ability to control the cycling of nutri-
ents such as NH
4
ć
, and PO
4
3
−
in natural waters (Bronk
2002
; Zhang et al.
2004
,
2008
; Kim et al.
2006
; Vähätalo and Järvinen
2007
; Li et al.
2008
).
DOM can photolytically generate strong oxidants such as superoxide radi-
cal (O
2
+
+
, NO
3
•
−
•
), which also
play a role in its photoinduced decomposition in natural waters (Mostofa and
Sakugawa
2009
; Vione et al.
2006
,
2010
; Zellner et al.
1990
; Zepp et al.
1992
;
Moran et al.
2000
; Farias et al.
2007
; Mostofa et al.
2007a
; Minakata et al.
2009
).
Correspondingly, DOM can undergo photoinduced and microbial degradation
processes, which can produce a number of degradation products such as dis-
solved inorganic carbon (DIC), CO
2
, CH
4
, CO, low molecular weight (LMW)
DOM, organic acids. These compounds are very important in the aquatic envi-
ronments (Jones and Amador
1993
; Miller and Zepp
1995
; Lovley and Chapelle
1995
; Lovley et al.
1996
; Moran and Zepp
1997
; Miller
1998
; Conrad
1999
;
Johannessen and Miller
2001
; Ma and Green
2004
; Xie et al.
2004
; Johannessen
et al.
2007
; Yoshioka et al.
2007
; Brandt et al.
2009
; Rutledge et al.
2010
; Omar
), hydrogen peroxide (H
2
O
2
), and hydroxyl radical (HO
