Environmental Engineering Reference
In-Depth Information
(a)
(b)
(c)
0.05
River waters (before irradiation)
Irradiated river waters (after 1 days)
Irradiated river waters (after 10 days)
Irradiated river waters (after 13 days)
0.012
0.06
0.04
0.009
0.04
0.03
0.006
0.02
0.02
0.003
0.01
0
0.00
0.00
250
400
550
700
250
400
550
700
250
400
550
700
Wavelengths (nm)
(d)
(e)
(f)
12
6
25
10
20
Irradiated river waters
Incubated dark samples
4
8
15
6
10
2
4
5
2
0
0
0
50
100
150
200
0
50
100
150
200
0
50
100
150
200
(g)
(h)
(i)
Irradiated river waters
Incubated dark river waters
110
40
200
190
90
35
180
170
70
30
160
50
25
150
0
50
100
150
200
0
50
100
15 0
200
0
50
100
15 0
200
Integrated solar intensity (MJm
-2
)
Fig. 1
Photoinduced and/or microbial mineralization of chromophoric dissolved organic matter
(CDOM) (
a
,
b
,
c
), fulvic acid-like fluorescence intensity at peak C (
d
,
e
,
f
), and dissolved
organic carbon (DOC) concentration (
g
,
h
,
i
) in the upstream waters of Kago and Nishi-Mataya
as well as in the downstream waters of Yasu River, respectively. Photoexperiments are conducted
under natural sunlight with integrated solar intensity (0, 22, 44, 92, 141, and 176 MJ m
−
2
) dur-
ing the irradiation period (0, 1, 4, 7, 10, and 13 days, respectively) and microbial experiments
are conducted on the filtered samples under dark condition. The quinine sulfate unit (QSU) is
estimated using the fluorescence of standard quinine sulfate solution for 1
μ
g L
−
1
=
1 QSU. The
error bar indicates the standard deviation between triplicate samples.
Data source
Mostofa et al.
(
2007
); Mostofa KMG et al. (unpublished)
Degradation takes place with simultaneous mineralization of dissolved organic car-
bon (DOC) (Fig.
1
g-i) in natural waters (Fig.
1
) (Vione et al.
2009
; Vahatalo et
al.
2000
; Mostofa et al.
2005
; Mostofa et al.
2007
; Moran et al.
2000
; Bertilsson
and Allard
1996
; Allard et al.
1994
; Mostofa et al.
2005
; Amador et al.
1989
;
Vähätalo and Wetzel
2004
; del Vecchio and Blough
2002
). The functional groups
in stream humic substances (fulvic and humic acids), with
14
C age
=
0 (Malcolm
1990
), are highly photosensitive/photoreactive, particularly in rivers (Mostofa
et al.
2005
,
2007
; Wu et al.
2005
). Photosensitivity sequentially decreases dur-
ing water transportation from source (stream water) to rivers and then to lakes or
coastal or marine waters on the basis of water residence time (Mostofa et al.
2005a
,
b
,
2007
; Malcolm
1990
; Kieber et al.
1990
; Mopper et al.
1991
; Miller and Zepp
1995
). The functional groups in DOM (either chromophores in CDOM or fluoro-
phores in FDOM) can efficiently absorb solar radiation in natural waters (Mostofa
and Sakugawa
2009
; Wu et al.
2005
; Zafiriou et al.
1984
; Mopper and Zhou
1990
;
