Abstract
The concentrations of water-soluble humic-like substances (HULIS) in particulate matter collected on the Nishiwaseda Campus of Waseda University in Shinjuku, Tokyo, were determined by the DEAE-UV method in March, May, July, October, and December 2012. Particulate matter less than 10 µm (SPM: suspended particulate matter) was collected by a high-volume air sampler every 12 hours (6 : 00–18 : 00 and 18 : 00–6 : 00). The HULIS concentration in SPM was lower in the summer than in the autumn and winter. The fulvic acid fraction was about 90% of the water-soluble HULIS in SPM throughout the year. There were relatively high correlations between the HULIS concentration and the concentrations of NO2 and CO throughout the year, suggesting that HULIS was mostly of combustion origin like automobiles in the urban area. Comparing humic acid and fulvic acid, the magnitude of the concentration variation was higher in fulvic acid than in humic acid and it was suggested that humic acid has a more stable constructure. In addition, it was revealed that the concentration of fulvic acid tends to be influenced by artificial and burning sources. The behavior of the HULIS concentration was similar to OX in the summer and this indicated that HULIS was also generated by the secondary formation in addition to the primary sources. The high concentration and correlation between the concentration of levoglucosan (r=0.867), which is a tracer of cellulose in biomass burning, and HULIS in the autumn revealed that the increase in HULIS in the autumn was due to biomass burning.
