Environmental Engineering Reference
In-Depth Information
2000
(b)
OR1: Irradiated samples
OR1: Dark samples
OR2: Irradiated samples
OR2: Dark samples
OR5: Irradiated samples
OR5: Dark samples
OR6: Irradiated samples
OR6: Dark samples
SRFA
SRHA
Tryptophan
DAS1
DSBP
1500
(a)
1600
1200
1200
900
800
600
400
300
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
200
200
(c)
(d)
150
150
100
100
50
50
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
Irradiation time (min)
Fig. 1
Production of H
2
O
2
(
a
,
b
) and ROOH (
c
,
d
) as a result of solar irradiation on the Ohta
River waters (sites OR1, OR2, OR5, and OR6) and on various standard substances, respectively,
in photo-experiments conducted using a solar simulator.
Data source
Mostofa and Sakugawa
(
2009
)
H
2
O
2
is highly variable in the presence of various standard organic substances in
aqueous media (Fig.
1
b), which suggests that the concentration of H
2
O
2
depends
on the nature of the DOM components. (v) The photoinduced generation of
H
2
O
2
increases with an increase in the contents of fulvic acid in photo-irradiated
samples under a solar simulator (Fig.
3
), which suggests that H
2
O
2
produc-
tion depends on the DOM amount. (vi) When photogenerated H
2
O
2
in unfiltered
river water is incubated in the dark, it is entirely decomposed in the first day of
incubation and it is not produced further during the incubation period (Fig.
2
b).
Therefore, microbial reactions may be more effective in consuming than in pro-
ducing H
2
O
2
in river water.
ROOH compounds typically show the following features in natural waters:
(i) The photoinduced generation of ROOH does not follow a regular trend of
increasing concentration with increasing irradiation time, in photoexperiments
conducted using a solar simulator; in contrast, produced ROOH is very low and
fluctuates heavily without any observable trends (Fig.
1
c, d). It is suggested that
ROOH compounds are readily decomposed in aqueous solution. (ii) The pho-
toinduced generation of ROOH compounds is typically higher in filtered than in
