Environmental Engineering Reference
In-Depth Information
(Moran et al.
2000
; Raymond and Bauer
2001a
; Boyd and Osburn
2004
; Hummel
and Findlay
2006
); 133-453
μ
M C in Canada (Osburn et al.
2009
); 76-1427
μ
M
C in Europe (Abril et al.
2002
; Guéguen et al.
2002
; Huguet et al.
2010
; Baker
and Spencer
2004
; Stedmon et al.
2003
). DOC in estuaries is originated from both
autochthonous sources (algae or phytoplankton) and allochthonous sources such
as material of terrestrial plant origin.
DOM Contents in Coastal and Open Oceans
DOC concentrations are substantially higher (50-616
μ
M C) in coastal seawa-
ters than in the open ocean (40-117
μ
M C) (Table
2
) (Ogawa and Tanoue
2003
;
Mitra et al.
2000
; Chen and Gardner
2004
; Williams and Druffel
1987
; Opsahl and
Benner
1998
; Wang et al.
2004
; Zanardi-Lamardo et al.
2004
; Osburn et al.
2009
;
Blough et al.
1993
; Vodacek et al.
1995
; Ferrari et al.
1996
; Ferrari and Dowell
1998
; Del Castillo et al.
1999
,
2000
; Mostofa KMG et al., unpublished data).
DOC concentrations in coastal waters are generally regulated by terrestrial or riv-
erine input, zooplankton feeding and algal or phytoplankton production (Lee and
Wakeham
1988
; Lee and Henrichs
1993
; Mann and Wetzel
1995
; Hedges et al.
1997
). Increased biomass of primary producers also plays a major role in regulat-
ing the DOM contents in coastal areas (Ittekkot
1982
; Billen and Fontigny
1987
;
Bronk et al.
1998
). DOC concentrations in open oceans are relatively low and are
included in the range of 40-117
μ
M C at epilimnion and 30-90
μ
M C at hypolim-
nion (Table
2
) (Ogawa and Tanoue
2003
). DOC values appear to be relatively uni-
form in most of the oceans, whilst in coastal areas the DOM pool becomes much
more heterogeneous because of terrestrial inputs. In open oceans, the DOC con-
centrations in epilimnetic layers follow the order of Arctic Ocean (70-107
μ
M
C) > subtropical zone (~80
μ
M C) > tropical (equatorial) and temperate zones
(60-70
μ
M C) > subarctic and subantarctic regions (50-60
μ
M C) > Antarctic
region (40-60
μ
M C) (Ogawa and Tanoue
2003
). There are two main sources of
DOC in coastal oceans: allochthonous DOM of terrestrial origin and autochtho-
nous DOM of algal or phytoplankton origin. In open oceans, allochthonous DOM
contents are gradually decreased photolytically depending on the distance from
coastal areas, whilst autochthonous DOM is substantially increased (see the con-
tribution of DOM for detailed discussion). The three major sources of DOC in the
Arctic Ocean are in situ production (56 %), river run-off (25 %), and Pacific water
(19 %) (Kirchman et al.
1995
).
6 Factors Affecting DOM in Natural Waters
DOM contents and its dynamics are mostly dependent on two issues: origin and/
or input, as well as its consequent mineralization by various environmental fac-
tors that are associated with the watershed activities of natural waters. The river-
groundwater interface can act as a source or sink for DOM, depending on the
volume and direction of flow, DOC concentrations and biotic activity (Brunke
