Environmental Engineering Reference
In-Depth Information
global warming (Freeman et al.
2001a
; Zhang et al.
2010
; Sinha et al.
2001
; Sobek
et al.
2007
; Rastogi et al.
2010
). The increase in temperature driven by solar radia-
tion is effective in inducing photoinduced and microbial processes of OM (includ-
ing DOM and POM) as well as in enhancing photosynthesis. This is consistent with
data from the Central England Temperature Record (Parker et al.
1992
), showing
that mean summer temperatures across England were 0.66 °C higher during the
1990s than in the preceding 30 years. Model studies predict that the production
of new DOM due to photosynthetic processes from winter to summer would vary
from 6 to 60 %, due to a large seasonal variation in light intensity (Anderson and
Williams
1998
; Bratback and Thingstad
1985
). The factors affecting the photosyn-
thesis in natural waters are discussed in detail in chapter
“
Photosynthesis in Nature:
A New Look
”.
6.7 Metal Ions Complexation and Salinity
Metal ions can complex the DOM functional groups (fulvic and humic acids of
vascular plant origin, autochthonous fulvic acids of algal or phytoplankton origin,
tryptophan, protein, algae and so on) and can induce structural changes (e.g. molec-
ular conformation or rigidity) and formation of aggregates. Complexation would
thus change the outer appearance of the molecule and its optical properties, such
as absorption properties of CDOM and fluorescence properties of FDOM, either
increasing or decreasing them (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
). Correspondingly, salinity can also
affect the DOM components in seawater, both structurally and optically, modifying
them in comparison to freshwater (Nakajima
2006
; Blough et al.
1993
; del Vecchio
and Blough
2002
; Boyd et al.
2010
). Complexation of metal ions and the effect
of salinity are extensively discussed in Chapters
“
Photoinduced and Microbial
6.8 Global Warming
Global warming may affect DOM in two ways: First, global warming could fur-
ther enhance atmospheric CO
2
, because of elevated net primary productivity
and increases root exudation of DOC in soil environments (Freeman et al.
2001b
,
2004
; Lavoie et al.
2005
; Fenner et al.
2007a
,
b
; Wolf et al.
2007
; Kang
et al.
2001
; Tranvik and Jasson
2002
; Monteith et al.
2007
; Evans et al.
2002
;
Dorodnikov et al.
2011
). This process ultimately leaches allochthonous DOM
