Environmental Engineering Reference
In-Depth Information
in river water mixed with DSBP during 12 h summer irradiation (Poiger et
al.
1999
; Mostofa et al.
2011
). For diaminostilbene (DAS1) it has been
observed a 93 % decrease at 1 mg L
−
1
initial concentration and 10 h irradia-
tion under a solar simulator; and a 12 % decrease in river water mixed with
DSBP during 12 h summer irradiation (Table
4
) (Poiger et al.
1999
; Mostofa
et al.
2011
). Photoinduced degradation can also decrease 53 % of DAS1 and
81 % of DSBP contents in lake surface waters (Stoll et al.
1998
). Irradiation
experiments for the standard DSBP and DAS1 using a solar simulator indi-
cate that the fluorescence intensities of FWAs are rapidly decreased, by 40 %
for DSBP and 45 % for DAS1 after of 30 min irradiation, but with no shift
of their Ex/Em wavelengths (Mostofa et al.
2005a
). It is estimated in field
observations that the observed removal of FWAs during transport (12 h resi-
dence time) is 31 and 12 % for DSBP and DAS 1, respectively, corresponding
to half-lives of 0.9 and 2.7 days, respectively, under cloudless summer skies
(Poiger et al.
1999
). In another study, a mass balance calculation and DSBP/
DAS1 ratio shows that ~95 % of DSBP and ~55 % of DAS1 supplied in sew-
age were decomposed photolytically by natural sunlight in inflowing riv-
ers and in lake, while sedimentation to the lake bottom was insignificant for
DSBP and reached ~35 % for DAS1 (Yamaji et al.
2010
). More intense pho-
todegradation of FWAs, especially the more photodegradable DSBP, has been
observed in Lake Biwa, Japan, than in Lake Greifensee, Switzerland, possibly
because of the longer residence time of water in the larger Lake Biwa (Yamaji
et al.
2010
). A FWAs-salinity diagram in the Tamagawa Estuary shows fairly
conservative behavior of the FWAs with ~20 % and ~10 % removal of DSBP
and DAS1, respectively, which is thought to be caused by photodegradation
(Hayashi et al.
2002
). The DSBP/DAS1 ratio also shows a decreasing trend
from sewage effluents to rivers and to the Tokyo Bay, indicating selective
photodegradation of DSBP (Hayashi et al.
2002
). These results suggest that
DSBP is more susceptible to photoinduced degradation than DAS1 in natural
waters.
For commercial household detergent, the decrease in fluorescence intensity of
detergent component (C-like, component 1) is 88 % at peak C-region and 70 % at
peak A-region in Milli-Q water during the 3 h of direct sunlight irradiation, under
noon summer clear sky conditions (Table
4
) (Mostofa et al.
2010
). The detergent
component (T
UV
-like) does not decompose photolytically, rather an increase in flu-
orescence is detected such as 4 % in sewerage drainage samples and 9 % in com-
mercial detergents samples dissolved in Milli-Q water (Table
4
) (Mostofa et al.
2010
). In sewerage-impacted rivers, the fluorescence intensity of the detergent-like
component (peak W) was significantly lower (28 %) at noon time (12:00-13:00
p.m.) than before sunrise (Mostofa et al.
2005a
). This indicates that detergent-like
compounds may have been decomposed photolytically by natural sunlight dur-
ing the water transport (Mostofa et al.
2005a
). In summary, FWAs and household
detergents are highly susceptible to photoinduced degradation upon irradiation
in the laboratory as well as in field observations (Table
4
) (Mostofa et al.
2005a
;
Baker
2002
).
