Identification
and Composition of Emerging Quaternary
Ammonium Compounds in Municipal Sewage Sludge in China
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Abstract
Quaternary ammonium compounds (QACs)
have raised considerable attention
due to their wide commercial applications and recent discovery of
unknown persistent analogues in aqueous environment. In this work,
the occurrence and distribution of alkyltrimethylammonium (ATMAC),
benzylakyldimethylethylammonium (BAC) and dialkyldimethylammonium
(DADMAC) homologues were investigated in fifty-two municipal sewage
sludge samples. ATMAC C10–18, BAC C8–18 and paired DADMAC
C8:8-C18:18 as well as emerging homologues such as ATMAC-20, 22 and
mixed DADMAC-16:18 and 14:16 were present. Furthermore, paired DADMAC-20:20
and mixed DADMAC-14:18, 18:20 were identified for the first time by
nontarget qualitative strategies. A triple quadruple mass spectrometer
quantification method was also initially verified with the aid of
laboratory synthesized standards for the analysis of the mixed DADMACs
with no certificated commercial standards currently available. The
total concentrations of ATMACs, BACs and DADMACs were in the range
of 0.38–293, 0.09–191 and 0.64–344 μg/g
dry weight, respectively, and particularly, mixed DADMACs constituted
39 ± 7% of total DADMAC concentrations. The concentrations and
profiles of individual homologues further suggested different QAC
applications and fate in China. Significant correlations were also
found among the concentrations of various QAC homologues as well as
wastewater treatment plant (WWTP) characteristics (total organic carbon
contents and daily treatment volumes)