Abstract. Ambient particulate matter (PM) can contain a mix of
different toxic species derived from a wide variety of sources. This study
quantifies the diurnal variation and nocturnal abundance of 16 polycyclic
aromatic hydrocarbons (PAHs), 10 oxygenated PAHs (OPAHs) and 9 nitrated PAHs
(NPAHs) in ambient PM in central Beijing during winter. Target compounds
were identified and quantified using gas chromatography–time-of-flight
mass spectrometry (GC-Q-ToF-MS). The total concentration of PAHs varied
between 18 and 297 ng m−3 over 3 h daytime filter samples and from 23
to 165 ng m−3 in 15 h night-time samples. The total concentrations of
PAHs over 24 h varied between 37 and 180 ng m−3 (mean: 97±43 ng m−3).
The total daytime concentrations during high particulate loading
conditions for PAHs, OPAHs and NPAHs were 224, 54 and 2.3 ng m−3,
respectively. The most abundant PAHs were fluoranthene (33 ng m−3),
chrysene (27 ng m−3), pyrene (27 ng m−3), benzo[a]pyrene (27 ng m−3), benzo[b]fluoranthene (25 ng m−3), benzo[a]anthracene (20 ng m−3) and phenanthrene (18 ng m−3). The most abundant OPAHs were
9,10-anthraquinone (18 ng m−3), 1,8-naphthalic anhydride (14 ng m−3) and 9-fluorenone (12 ng m−3), and the three most abundant
NPAHs were 9-nitroanthracene (0.84 ng m−3), 3-nitrofluoranthene (0.78 ng m−3) and 3-nitrodibenzofuran (0.45 ng m−3). ∑PAHs and
∑OPAHs showed a strong positive correlation with the gas-phase
abundance of NO, CO, SO2 and HONO, indicating that PAHs and OPAHs can
be associated with both local and regional emissions. Diagnostic ratios
suggested emissions from traffic road and coal combustion were the
predominant sources of PAHs in Beijing and also revealed the main source
of NPAHs to be secondary photochemical formation rather than primary
emissions. PM2.5 and NPAHs showed a strong correlation with gas-phase
HONO. 9-Nitroanthracene appeared to undergo a photodegradation during the
daytime and showed a strong positive correlation with ambient HONO
(R=0.90, P < 0.001). The lifetime excess lung cancer risk for those
species that have available toxicological data (16 PAHs, 1 OPAH and 6 NPAHs)
was calculated to be in the range 10−5 to 10−3 (risk per million
people ranges from 26 to 2053 cases per year).
A G4MP2 theoretical study on the gas phase enthalpies of formation for various polycyclic aromatic hydrocarbons (PAHs) and other C~10~ through C~20~ unsaturated hydrocarbons
