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研究报告

摘要：采用美国热电公司的NO-NO₂-NO_x分析仪(Model 42i TL)和NO_y分析仪(Model 42i NO_y),在2011年1月-10月期间,对北京城市大气中的NO、NO_x和NO_y进行了连续在线测量.两台仪器对NO的测量结果具有较高的一致性(r>0.998,p<0.01),说明两台仪器测量精度基本一致.将NO_y分析仪(Model 42i NO_y)采样口处安装和不安装颗粒物过滤膜两种条件下测量的NO_y结果与NO-NO₂-NO_x分析仪所测的NO_x结果分别进行了相关性分析([NO_y]=0.989×[NO_x],R²=0.993; [NO_y]=1.134×[NO_x],R²=0.959),得出以下两个结论: 1以颗粒态硝酸盐为代表的颗粒物是造成NO_x与NO_y偏差的主要原因,其所占比例在10%左右; 2目前Model 42i-TL所测NO_x的浓度水平较真实值偏高,其测量值更接近气态NO_y的浓度水平.为估算NO₂测值被高估的程度(以2011年8月6日-15日观测数据为例),用扣除部分气态NO_z物种(HONO、HNO₃、PAN、PPN)的修正方法,推论出在夏季NO₂被高估约7%(R²=0.968).

Abstract：An intercomparison of atmospheric measurements was conducted using the mainstream instruments of NO_x (Model 42i-TL NO-NO₂-NO_x) and NO_y (Model 42i NO_y analyzers), both by Thermo Fisher Scientific Inc., at an urban site in Beijing.During the study, concentrations of NO, NO_x and NO_y were continuously monitored from January to October 2011. Good correlation (r>0.998, p<0.01) of NO measurements produced by the two instruments was obtained, which confirms measurement accuracy of the two devices. By comparing the NO_y measurement results obtained under the conditions of attaching and removing a particulate filter from the sample inlet of the Model 42i NO_y analyzer with that of the NO_x measurements using the NO-NO₂-NO_x analyzer, the following correlation results are obtained: [NO_y]=0.989×[NO_x], R²=0.993 and [NO_y]=1.134×[NO_x], R²=0.959. Two conclusions are drawn from this study: 1 The difference between NO_x and NO_y is caused by particulate nitrate which accounts for around 10 percent of the total NO_x.2 Concentration of NO_x measured using the current Model 42i-TL analyzer is higher than its real values,and is closer to concentration of NO_y. Using the correction method of subtracting concentrations of the main NO_y components (e.g. HONO, HNO₃, PAN, PPN) from that of NO₂ (based on data collected during August 6-15, 2011), it could be concluded that concentration of NO₂ in summer are overestimated by 7 percent (R²=0.968).