北京市PM2.5水溶性有机物污染特征

用离子色谱技术对北京市2001~2002年大气PM2.5中7种水溶性有机物(WSOC)(甲酸、乙酸、甲磺酸、乙二酸、丙二酸、丁二酸、戊二酸)及12种无机离子(F-、Cl-、NO2-、NO3-、SO32-、SO42-、PO43-、Na 、NH4 、K 、Mg2 、Ca2 )的污染水平进行了同步测定.结果表明,SO42-、NO3-及NH4 为PM2.5中主要的水溶性物种,分别占PM2.5质量的10.6%、7.4%和5.7%;7种WSOC的浓度为0.011~0.118靏/m3,占PM2.5质量浓度的0.01%~0.1%,其中浓度最高的为乙二酸,其次为乙酸、丙二酸、丁二酸等;对PM2.5各化学组分浓度的季节变化特征的分析表明,PM2.5及OC的高浓度污染均出现在冬季采暖期,而WSOC则出现在夏季;对乙二酸与其他各组分进行相关性分析表明,乙二酸与SO42-、K 、NH4 、NO3-有较强的线性相关性(r=0.83,0.57,0.49,0.33),而与Cl-、Na 、Mg2 、Ca2 、EC、OC相关性较差(r=0.24, 0.22,0.12,0.05,0.13,0.10).由乙二酸季节变化特征及与其他物种相关性等特征初步推断,北京市PM2.5二元羧酸的主要来源为光化学反应而形成的二次污染物,而非来源于机动车、海盐或土壤的一次排放.

Pollution character of PM2.5 water-soluble organic compounds in Beijing City

The pollution levels of 12 kinds of inorganic ions (F-, Cl-, NO2-, NO3-, SO32-, SO42-, PO43-, Na , NH4 , K , Mg2 , Ca2 ) and 7 kinds of WSOC (formate, acetate, methylsulfonate, oxalate, malonate, succinate, glutarate) in atmospheric PM2.5 of Beijing City in the year 2001~2002 were determined synchronously with ion chromatography (IC) technique. SO42-, NO3- and NH4 were the dominant water-soluble species occuping 10.6%, 7.4% and 5.7% of PM2.5 mass respectively. The concentrations of 7 kinds of WSOC were 0.011~0.118mg/m3 occupying 0.01%~0.1% of PM2.5 mass concentration, among which oxalate was the highest and acetate, succinate, malonate and formate were the next. Analysis of seasonal change character of the concentration of each chemical component of PM2.5 indicated that high concentrations pollution of PM2.5 and OC appeared in winter (during heating period) and that of WSOC was in summer. Analysis of interrelativity of oxalate with other component showed that oxalate had relatively high linear interrelativity with SO42- (r=0.83), K (r=0.57), NH4 (r=0.49) and NO3- (r=0.33), while had relatively poor with Cl- (r=0.24), Na (r=0.22), Mg2 (r=0.12), Ca2 (r=0.05), EC (r=0.13) and OC (r=0.10). Preliminary deduction was made from the characters of oxalate change and the interrelativity with other species that the main source of PM2.5 dicarboxylic acids in Beijing City was the secondary pollutants produced by the photochemical reaction, not the primary pollutants released from vehicles, sea-salts or soil.