摘要:
对北京中关村地区大气中PAN的监测结果表明:在强日照条件下,PAN浓度随汽车等排放和NO2浓度的增加而增加,高PAN浓度水平与高O3浓度相关联;夏季的PAN浓度明显高于春季.模拟实验的结果证实:C3H6是大气中重要的PAN前体物,在一定范围内,其浓度越高,PAN浓度越大;C2H4生成PAN是困难的,H2O2的存在对C2H4反应生成PAN有促进作用;大气中SO2的存在可降低PAN的生成速率.在400nm光照条件下,PAN光解迅速;而其热解则需较高温度,在室温下其热解的半衰期达17.3b,这对说明大气中PAN的长距离传输和深夜PAN的存在是重要的.
关键词:
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大气
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PAN
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监测
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模拟实验
Abstract:
PAN(peroxyaoetyl nitrate)was prepared by Gaffneys method for calibration of gas chromatograph used for ambient air monitoring as determined by Fourier Transform Infrared spectrosoopy. Concentrations of PAN in atmosphere were measured in Haidian region of Beijing, China, during March 20-June 12, 1990. The observed range of gaseous PAN concentration was 1.3-6.8 ppbv. High values of gaseous PAN were determined in summer, whereas the lower in spring. The concentration of PAN are generally associated with NO2 and O3 under high SR. From diurnal variations of PAN, the maximum value up to 6.8ppbv was recorded at time 12:00-14:00 on June 9, 1990, and the minimum was less than 1 ppbv during night. Indoor smog chamber experiments were conducted to assess the productions of PAN from several systems. The results are shown as follows: in propene-NOx-dry air systems, the peik concentration of PAN depends mainly upon the initial concentration of hydrocarbon[HC]0. High content of SO2 in the systems was strongly associated with low PAN concentration. In ethylene-NOx-dry air systems, PAN takes approximately hours of time to reach the maximum and then maintains at low level. The formation of PAN can be promoted in the presence of H2O2.
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