Environmental Engineering Reference
In-Depth Information
ing in the formation of a species that can be viewed as diradicals, which
can then lead to the formation of thiazolones. In the case of Sea-Nine 211
the photoisomeration of the parent molecule yields 4,5-dichloro-3-
n
-octyl-
thiazolin-2-one. The mass spectra of 4,5-dichloro-3-
n
-octyl-thiazolin-2-one
was similar to Sea-Nine 211 and the fact that it appears at lower retention time
than Sea-Nine 211 supports the proposed structure, being less polar than
the starting molecule. N - C alkyl bond cleavage of 4,5-dichloro-3-
n
-octyl-
thiazolin-2-one and the oxidation of the alkyl group results in
n
-octanal.
Chromatographic data [34, 60] indicated the presence of three more com-
pounds that could not be identified but which were regarded as possible
transformation products because they were detected in all experiments and
their concentration increased and decreased as a function of the reaction
time. The evolution of chloride ions that reach only 63% of the stoichiometric
value after 30 h of simulated solar irradiation in distilled water clearly demon-
strates that chlorinated transient organics are present in the solution after
that time.
3.5
Diuron
Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is reported to be relatively
persistent in seawater [38], and considerably stable to hydrolysis. As far as the
degradation of diuron is concerned under UV irradiation conditions in nat-
ural seawater, photolysis appeared to be a very minor process [43]. A quite
long half-life of diuron has been reported, ranging from one month to one
year [43, 65]. Mazellier et al. [66] studied the photochemical behavior of di-
uron in the presence of different iron(III) species. The half-lives of diuron
when submitted to such process in the environment was estimated to be
1-2 h or a few days, depending on the concentration of iron(III). Faure and
Boule [67] calculated the quantum yields at a concentration of 10
-4
mol L
-1
,
and reported
Φ
(256 nm)
= 0.01.
Diuron photohydrolysis [68] occurs in the
meta
or
para
position with
respect to urea group, their proportion depending on the irradiation wave-
length [69]. According to Faure [70] and Jirkovsky et al. [69], who irradiated
solutions with the same lamps, the
meta
-hydroxylated product (1) is ap-
proximately nine times more concentrated than the
para
isomer (2). On the
contrary, when diuron was irradiated at the visible region using a light source
at 365 nm [67] the
para
-hydroxylated derivative was found to be the major
degradation product.
Diuron could be hydrolyzed in water leading to the formation of 3,4-
dichloroaniline. Although the latter has not been reported to be formed
during diuron photolysis, it is thought to be one of the most important bi-
otic and abiotic transformation products of the parent compound. For this
reason the photochemical fate of 3,4-dichloroaniline is also discussed in this
Φ
(254 nm)
=0.02and
