期刊
ATMOSPHERIC ENVIRONMENT
卷 36, 期 13, 页码 2099-2107出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S1352-2310(02)00230-3
关键词
oxalate; malonate; succinate; PM2.5; semi-volatile species; evaporation; sampling artifacts; gas-particle conversion; Hong Kong
The PM2.5 concentrations and the size distributions of dicarboxylic acids in Hong Kong were studied. Eleven sets of daily PM2.5 samples were obtained at a downtown sampling site during the period of 5-16 December 2000 using an R&P speciation PM2.5 sampler. About 6-12% of the total oxalic acid was found in the gas phase in some samples. A good correlation between succinate and sulfate (R-2 = 0.88) and a moderate correlation between oxalate and sulfate (R-2 = 0.74) were found. Sampling artifacts of oxalate, malonate and succinate were found to be negligible. A total of 18 sets of 48-96 h size distribution data on dicarboxylic acids, sulfate, nitrate and sodium at an urban site and a rural site from June 2000 to May 2001 were obtained using a Micro-Orifice Uniform Deposit Impactor. Data from both sites show similar size distribution characteristics of the dicarboxylic acids. The condensation mode of oxalate was usually observed at 0.177-0.32 mum. The location of the peak of the droplet mode of oxalate was associated with that of sulfate. When the peak of sulfate in the droplet mode appeared at 0.32-0.54 mum, the peak of oxalate sometimes appeared at 0.32-0.54 mum and sometimes shifted to 0.54-1.0 mum. When the peak of sulfate in the droplet mode appeared at 0.54-1.0 mum, the peak of oxalate sometimes appeared at 0.54-1.0 mum and sometimes shifted to 1.0-1.8 mum. Oxalate, succinate and sulfate found in the droplet mode were attributed to in-cloud formation. The slight shift of the oxalate peak from 0.32-0.54 to 0.54-1.0 mum or from 0.54-1.0 to 1.0-1.8 mum was ascribed to minor oxalate evaporation after incloud formation. The maximum peak of malonate sometimes appeared in the droplet mode and sometimes appeared at 3.1-6.2 mum. The formation of malonate is associated to the reactions between sea salt and malonic acid. (C) 2002 Elsevier Science Ltd. All rights reserved.
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