Environmental Engineering Reference
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example 3-hydroxybenzoic acid at Ex/Em = 314/423 nm, 3-hydroxycinnamic acid
at Ex/Em = 310/407 nm, and methyl salicylate at Ex/Em = 366/448 nm (Mostofa
et al. 2010 ). This may produce an increase of humic acid fluorescence. Weak light
intensity may prolong the lifetime of humic acid and its aromatic photoproducts,
which may result in a fluorescence increase. On the other hand, intense and pro-
longed irradiation may decompose humic acid and its photoproducts rapidly
(Corin et al. 1996 ), which causes a decrease in fluorescence.
Photodegradation of Aromatic Amino Acids and Protein
Photodegradation experiments have shown a decrease in tryptophan-like fluores-
cence (peak T) of 5-59 % in river waters, 7-88 % in lake waters, 37-45 % in estu-
arine waters, and 54 ± 6 % in sea waters (Table 4 ) (Stedmon et al. 2007a ; Mostofa
et al. 2010 , 2011 ; Winter et al. 2007 ; Moran et al. 2000 ). Similarly, the decrease
in tyrosine-like fluorescence intensity upon irradiation was 19-100 % in lakes,
26 ± 9 % in sea waters and 4-36 % for standard tyrosine dissolved in Milli-Q
water. A photolytically-induced increase of tyrosine like fluorescence (1-68 %)
was also observed in some lake waters (Table 4 ) (Stedmon et al. 2007a ; Winter
et al. 2007 ). A decrease of fluorescence upon irradiation has also been observed
as 63 % for standard tryptophan at 1 mg L 1 in milli-Q water and 10 h, 23 % for
3 mg L 1 and 3 h, and 20 % for 5 mg L 1 and 3 h (Table 4 ) (Mostofa et al. 2011 ).
Some amino acids including tryptophan are degradable by photoinduced processes
due to their high chemical reactivity (Yamashita and Tanoue 2003a ; Rosenstock
et al. 2005 ). The decrease in tryptophan-like fluorescence intensity was lower
(59 %) compared than that of fulvic acid (80 %) in rivers (Mostofa et al. 2007b ).
Therefore, protein- or tryptophan-like components are photolytically degradable
but they are less susceptible to photoinduced degradation compared to fulvic acid
in natural waters.
Photodegradation of FWAs and Other Substances in Aqueous Media
The FWAs (DAS1 and DSBP) and household detergents are present in sig-
nificant amount in some polluted rivers, lakes, coastal sea waters and sedi-
ments (Mostofa et al. 2005a , 2010 , 2011 ; Poiger et al. 1999 , 1996 ; Komaki
and Yabe 1982 ; Managaki and Takada 2005 ; Kramer et al. 1996 ; Stoll et al.
1998 ; Stoll and Giger 1998 ; Baker 2002 ; Yamaji et al. 2010 ). The observed
fluorescence intensity losses of FWAs or detergent components after up to
10 days irradiation have been 12-81 % in rivers, 34 % in drain samples, and
60-94 % in Milli-Q water (Table 4 ) (Mostofa et al. 2005a , 2010 , 2011 ). It
has been shown that losses in fluorescence intensity of peak W are 76-81 %
during 6-10 days irradiation in river water (Table 4 ). In the case of distyryl
biphenyl (DSBP), the decrease in fluorescence intensity is 94 % for 1 mg L 1
and 10 h, 73 % for 3 mg L 1 and 3 h, 60 % for 5 mg L 1 and 3 h; and 31 %
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