Environmental Engineering Reference
In-Depth Information
2. Experimental
Two annular denuder-filter pack (AD-FP) systems were used for collecting of
water-soluble organic acids in gaseous and particulate phases at a suburban site in
Saitama, Japan. The AD-FP system consisted of a PM 2.5 cyclone (URG-2000-
30EN), followed by two KOH-coated annular denuders (URG-2000-30B) in
series, and a filter pack with a quartz filter (Pallflex 2500 QAT-UP) and a KOH-
impregnated quartz filter. The sampler was operated at a flow rate of 16.7 Lmin −1 .
The sampling was taken during July 29 to August 4, 2008 ( n = 48), with sampling
intervals of 00:00−05:45, 03:00−08:45, 06:00−11:45, 09:00−14:45, 12:00−17:45,
15:00−20:45, 18:00−23:45, 21:00−02:45.
The Aerodyne aerosol mass spectrometer (Q-AMS, Aerodyne Research Inc.)
was used to measure the compositions (water content, organics, sulfate, nitrate,
chloride and ammonium etc.) of submicron aerosols (PM 1 ) during July 29 to
August 4, 2008. The mass concentrations of hydrocarbon-like organic aerosol
(HOA) and oxygenated organic aerosol (OOA) were further separated, using m/z
57 (mostly C 4 H 9 + ) and m/z 44 (mostly CO 2 + ) as their tracers (Hagino et al., 2007).
Water-soluble dicarboxylic acids, ketocarboxylic acids, and dicarbonyls in
denuder and filter samples were analyzed by means of BF 3 / n -butanol derivatization
to their esters followed by a gas chromatography/mass spectrometer (Shimadzu
GCMS-QP 5050) determination (Kawamura and Yasui 2005). The target compounds
were identified by comparison of GC retention times with mass chromatograms
of authentic standards to contain quantities to 100, 250, 500, 1,000, 2,500, and
5,000 ng of each compound. These target compounds included seven saturated
n -dicarboxylic acids (C 2 : oxalic, C 3 : malonic, C 4 : succinic, C 5 : glutaric, C 6 : adipic,
C 7 : pimelic, and C 9 : azelaic acid), three unsaturated dicarboxylic acids (M: maleic,
F: fumaric, and Ph: phthalic acid), two ketocarboxylic acids (Pyr: pyruvic and
WC 2 : glyoxilic acid), and two dicarbonyls (Gly: glyoxal and MeGly: methylglyoxal).
3. Results and Discussion
In summer, the average total concentrations of target organic acids in gaseous and
particulate phase were 496.2 and 1,076.6 ng/m 3 , respectively. Oxalic acid (C 2 ), as
the final product of photochemical reaction, was the most abundant species in
gaseous and particulate phase. Longer chain n -dicarboxylic acids were less
abundant in gaseous phase, except for malonic acid (C 3 ) and azelaic acid (C 9 ). C 3 ,
glyoxilic (WC 2 ), and pyruvic acid (Pyr) have higher abundances in particulate
phase.
Daily variation of gaseous and particulate phase concentrations together with
OOA concentrations are showed in Fig. 1. Gaseous phase line showed multiple-
peaks, and appeared the maximum in the afternoon (12:00−18:00) during July
29−31 and in the morning (06:00−12:00) during August 1−4, 2008, possibly due
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