Polycyclic aromatic hydrocarbon (PAH)
contamination has raised
great environmental concerns, while the effects of low-molecular-weight
organic compounds (LMWOCs) on PAH photodegradation at amorphous silica
(AS)/air interfaces have been largely ignored. In this study, the
phototransformation of anthracene (ANT) at amorphous silica (AS)/air
interfaces was investigated with the addition of LMWOCs. ANT removal
was attributed to •OH attacking and the energy transfer
process via 3ANT*. Light irradiation induced the fractured
SiO• or Si• generation
on AS surfaces, which could react with absorbed H2O and
O2 to generate •OH and further yield
a series of hydroxylated products of ANT. The presence of citric acid
and oxalic acid improved •OH generation and enhanced
ANT removal by 1.0- and 2.2-fold, respectively. For comparison, the
presence of catechol and hydroquinone significantly decreased ANT
removal and produced coupling products. The results of density functional
theory calculations suggest that persistent free radicals (PFRs) on
AS surfaces from catechol or hydroquinone after •OH attacking prefer to cross-couple with ANT via C–C bonding
rather than self-couple. Dianthrone and cross-coupling products might
possess higher ecotoxicity, while hydroxylated products were less
ecotoxic than their parent compounds based on Ecological Structure
Activity Relationships (ECOSAR) estimation. The results of this study
revealed the potential ecotoxicity of PAH-adsorbed particulates coexisting
with LMWOCs and also provided a new insight into PAH transformation
through PFR pathways.
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