Organic aerosol compositions and variations over Mt. Tai, North China Plain

Aerosol samples were collected at the summit (1534 m a.s.l.) of Mount Tai located in the North China Plain (36.25 N; 117.10 E) using high-volume air sampler and pre-combusted quartz fiber filters. Sampling was conducted on day/night basis in May 29 to June 28, 2006 during the biomass-burning season after the harvesting of wheat. The filter samples were analyzed for dicarboxylic acids, ketoacids and dicarbonyls using capillary gas chromatography (GC) and GC-MS employing water extraction and butyl ester derivatization. The samples were also analyzed for total carbon (TC: 5-90 ugm-3), total nitrogen (TN: 2-38 ugm-3), and their stable isotopic compositions using elemental analyzer (EA) and EA/isotope ratios mass spectrometer, respectively. Water-soluble organic carbon (WSOC: 1 to 37 ugm-3) was also measured. Saturated and unsaturated diacids (C2-C11, 200-6100 ngm-3) were detected in the mountain aerosols with a predominance of oxalic (C2) acid followed by malonic (C3) and succinic (C4) acids as well as C2-C9 w-oxocarboxylic acids, pyruvic acid and a-dicarbonyls (glyoxal and methylglyoxal). Maximum concentration of total diacids (>6000 ngm-3) was found to be several times higher than those reported on the ground levels of Chinese megacities. The temporal variation of diacids was found to be consistent with that of levoglucosan (biomass burning tracer).