Environmental Engineering Reference
In-Depth Information
and Gonser
1997
). The dynamics of lake DOM is greatly affected by specific
and regional factors such as pH of lake water, air temperature, solar radiation,
precipitation, sulfate deposition, DOC contents in the adjacent rivers, vegeta-
tion of the terrestrial ecosystem, and southern oscillation index (SOI) (Mostofa
et al.
2005a
,
2009b
; Hudson et al.
2003
). A complex balance of abiotic and biotic
processes controls the molecular composition of marine DOM to produce signa-
tures that are characteristic of different environments (Kujawinski et al.
2009
).
Therefore, the controlling factors affecting the origin and dynamics of both
allochthonous and autochthonous DOM in natural waters can be distinguished as:
(i) Types and nature of terrestrial plant material in soil; (ii) Land management
and natural effects (precipitation, flood and drought); (iii) Effect of temperature;
(iv) Microbial processes; (v) Photoinduced processes; (vi) Photosynthesis in
natural waters; (vii) Metal ions complexation and salinity; and (viii) Global
warming.
6.1 Types and Nature of Terrestrial Plant Material in Soil
Allochthonous DOM is originated in soil by microbial degradation of leachable
organic carbon, which varies depending on the types and nature of terrestrial plant
communities, soil types and other regional effects (Mostofa et al.
2009a
; Nakane
et al.
1997
; Uchida et al.
1998
,
2000
; Moore et al.
2008
; Tu et al.
2011
; Kindler
et al.
2011
; Duff et al.
1999
; Michalzik et al.
2001
; Rae et al.
2001
; Cronan and
Aiken
1985
; Frost et al.
2006
; Johnson et al.
2006
). The litter-rich surface soils
have relatively higher DOC concentration than the litter-lacking ones, which can
be distinguished because in the former case the
δ
13
C values of DOC are closer to
the
δ
13
C of litter than to the
δ
13
C of organic carbon in forest soil (Tu et al.
2011
).
In most temperate and boreal landscapes the DOC concentrations in inland waters
are regulated by a wide variety of watershed characteristics, including the quan-
tity and type of vegetation, watershed slope, and particularly the extent and nature
of wetlands (Kindler et al.
2011
; Allard et al.
1994
; Rae et al.
2001
; Xenopoulos
et al.
2003
; Frost et al.
2006
; Engstrom
1987
; Williamson et al.
2001
; Rice
2002
;
Canham et al.
2004
; Winn et al.
2009
).
DOC leaching from topsoils in the presence of different vegetation is largely
variable. Therefore, different values have been observed in the presence of grass-
lands (range 158-1425
μ
M C and mean: 667
μ
M C), croplands (range: 325-
1442
μ
M C and mean: 1000
μ
M C) and forests (range: 592-3592
μ
M C and
mean: 1917
μ
M C), but large variations have also been observed within land use
classes (Kindler et al.
2011
). Under Cerrado vegetation, total organic C (TOC)
concentrations (filtered < ca. 1
μ
m) found in the soil solution (ca. 417
μ
M C)
between 15 and 200 cm depth were lower than those usually found in the soil
of temperate forests (833-1667
μ
M C) (Michalzik et al.
2001
; Lilienfein et al.
2001
). TOC concentrations in the soil solution under
Pinus
are lower than under
Cerrado (Lilienfein et al.
2001
). In uplands, soils derived from coniferous forests
