上海中心城区二氧化氮在线测量比对研究

An intercomparison study of online NO_2 measurement from ambient air in the vicinity of Shanghai City

对比了基于腔衰减相移光谱技术(CAPS)、化学荧光法(CL)和非相干宽带腔增强吸收光谱技术(IBBCEAS)3种不同方法在线测量NO_2浓度的仪器,并于2017年5月10日—6月10日采用3台仪器对上海中心城区大气环境NO_2进行监测,验证了IBBCEAS实验装置的稳定性、灵敏度、检测下限等关键特性,证明可以实现复杂环境下大气痕量气体高精度在线监测.IBBCEAS装置与其它两种仪器监测数据的一致性较好,监测过程中上海市中心NO_2日浓度变化范围为3~63 ppbv.各仪器测量结果之间的线性关系图表明,3种方式对NO_2浓度监测较为准确,偏差普遍在10 ppbv.根据早晚高峰车流量增加情况分析可以看出,NO_2高浓度污染主要来自于车辆排放.另外发现,受局地污染源的影响,NO_2浓度随时间推移而增加.

This article presents the measurement comparison of online NO2 monitoring carried out using three different instruments viz. cavity attenuated phase shift spectrometer（ CAPS）, chemiluminescence（ CL） NOx monitor and incoherent broadband cavity enhanced absorption spectrometer（ IBBCEAS）,that were setup in the laboratory at Shanghai Academy of Environmental Sciences,from May 10 to June 10,2017. The data from IBBCEAS experimental technique was verified with that obtained from CAPS and CL. The key features like the stability and sensitivity of IBBCEAS with low detection limits makes it ideal to carry out high-precision online monitoring of atmospheric trace gases in the complex environment of downtown Shanghai.The data obtained from IBBCEAS is in good agreement with that of the other two instruments. One of the important observations made during the measurements was that the daily variation of NO2 was in the range of 3 - 63 ppbv in the center region of Shanghai. The linear correlation diagram between the instruments proves that the IBBCEAS is also suitable for monitoring NO2 concentration,with a relative error of - 10 ppbv. The peak concentration of NO2 in the data analysis has been observed during the time of heavy traffic,indicating that the main source of NO2 maybe from vehicular combustion.Also,it was found that the NO2 concentration,at times,was influenced by other local pollution sources.