Abstract. Fine particulate matter (PM2.5) samples collected at Mount
(Mt.) Tai in the North China Plain during summer 2014 were analyzed for
dicarboxylic acids and related compounds (oxocarboxylic acids and α-dicarbonyls) (DCRCs). The total concentration of DCRCs was 1050±580
and 1040±490 ng m−3 during the day and night, respectively.
Although these concentrations were about 2 times lower than similar
measurements in 2006, the concentrations reported here were about 1–13 times
higher than previous measurements in other major cities in the world.
Molecular distributions of DCRCs revealed that oxalic acid (C2) was the
dominant species (50 %), followed by succinic acid (C4) (12 %)
and malonic acid (C3) (8 %). WRF modeling revealed that Mt. Tai was
mostly in the free troposphere during the campaign and long-range transport
was a major factor governing the distributions of the measured compounds at
Mt. Tai. A majority of the samples (79 %) had comparable concentrations
during the day and night, with their day–night concentration ratios between
0.9 and 1.1. Multi-day transport was considered an important reason for the
similar concentrations. Correlation analyses of DCRCs and their gas
precursors and between C2 and sulfate indicated precursor emissions and
aqueous-phase oxidations during long-range transport also likely play an
important role, especially during the night. Source identification indicated
that anthropogenic activities followed by photochemical aging accounted for
about 60 % of the total variance and were the dominant source at Mt. Tai.
However, biomass burning was only important during the first half of the
measurement period. Measurements of potassium (K+) and DCRCs were about
2 times higher than those from the second half of the measurement period. The
concentration of levoglucosan, a biomass burning tracer, decreased by about
80 % between 2006 and 2014, indicating that biomass burning may have
decreased between 2006 and 2014.