腔增强吸收光谱测量大气亚硝酸的车载走航观测应用

Application of cavity-enhanced absorption spectroscopy for cruise monitoring observation of ambient nitrous acid(HONO)measurements

本研究开发了一种基于非相干宽带腔增强技术(IBBCEAS)的大气亚硝酸走航测量装置.该装置实现了高时间分辨率的气态亚硝酸(HONO)与二氧化氮(NO_(2))在线测量.在对装置表征优化后,4 s的时间分辨率下,HONO的检测限可达到0.34×10^(-9),并基于卡尔曼滤波降噪方法,进一步可将其降低至0.11×10^(-9).在使用NO2气体的性能验证实验以及与走航车搭载的商业化NO_(2)分析仪的平行比对实验中,发现本研究所搭建的装置对NO2测量表现出良好的性能,与商业仪器的测量结果的相关性高达0.99.对比于液芯波导方法的气态亚硝酸分析仪(HONO-WLPAP),本研究所开发装置与其测量的HONO数据呈现较好的一致性,斜率为0.99,R^(2)为0.91,证明了本研究所开发装置的可靠性与准确性.利用所搭建的走航测量装置,结合搭载于走航车上的NO_(x)分析仪等商用装置,于2022年秋季在上海地区开展走航测试,包括城市中心区、城市外围、城市上风向背景区域、城市快速路、南部化工聚集区、长兴岛、临港、宝钢及外高桥等城市典型排放区域,并得到了各区域的HONO、NO_(2)、NO等污染物的排放比值与浓度特征.研究发现,除了外高桥重柴聚集区与农村点位外,其他区域的HONO/NO_(x)分布在1.0%±0.5%左右,HONO/NO则在2.0%±1.0%附近波动.

In this study,we developed an incoherent broadband cavity enhancement spectroscopy(IBBCEAS)-based cruise monitoring instrument for atmospheric nitrite.The instrument enabled the measurement of HONO and nitrogen dioxide(NO_(2))with high time resolution.The detection limit of HONO reached 0.34×10^(-9) at a time resolution of 4 s,and could be further reduced to 0.11×10^(-9) based on optimization using the Kalman filter denoising method.The performance verification experiments using NO2 and parallel comparison experiments with a commercial NO_(2) analyzer were carried out.The result showed that the instrument developed in this study exhibited good performance for NO_(2) measurements.The measurements of NO_(2) for our instrument correlated up to 0.99 with those from commercial analyzer.The measurements of HONO showed good agreement with the measured data by an HONO-WLPAP(waveguide-based liquid-core photoacoustic spectrometer)analyzer.The slope and R^(2) were 0.99 and 0.91,respectively,which highlights the reliability and accuracy for our instrument.The cruise monitoring experiment was conducted in the fall of 2022 in Shanghai covering typical emission areas of the city,including suburban areas,upwind background areas,urban expressways,southern chemical gathering areas,Changxing Island,Lingang,Baosteel,and Wai Gaoqiao.The emission ratios and concentration of HONO,NO_(2),NO in each area were also obtained by using our instrument and commercial NO_(x) analyzers.We found that the distribution of HONO/NO_(x) was around 1.0%±0.5%,while HONO/NO fluctuated at 2.0%±1.0%except for the Waigaoqiao heavy diesel aggregation area and suburban areas.