The photochemical aging of soot in
the aqueous phase could have
an important influence on water environments such as fog water and
wet aerosols in the atmosphere, as well as lakes and oceans. In this
study, we systematically investigated the photochemistry of soot in
the aqueous phase. Soot releases dissolved black carbon into the aqueous
phase during photoreactions, which is attributed to the phototransformation
of the nonpolar unsaturated C–H species in soot to polar carbonyl-containing
species. More importantly, we found that soot suspensions, particularly
those of the dissolved part of soot, were effective photosensitizers
for the generation of singlet oxygen (1O2).
The 1O2 apparent quantum yield of the dissolved
part reached 33 ± 2% under 377 nm irradiation, which is an order
of magnitude higher than those of most types of well-studied dissolved
organic matter in water. As a result, soot could impact the environmental
fate of coexisting organic contaminants, such as the photodegradation
of bisphenol A. This study will not only give insight into the photochemistry
of soot in the liquid phase but also reveal the significant implications
of soot photoaging in the aqueous phase by the release and degradation
of organic matter.