基于化学发光–光解转化法的大气氮氧化物精确测量原理与数值修正

Precise Measurement and Numerical Correction of Atmospheric Nitrogen Oxides Based on Photolytic Chemiluminescence

2017年夏季和冬季,将两台自主研发的蓝光光解转化–化学发光法(BLC-PCL)NOx分析仪与传统的钼转化法(MCL)NOx分析仪(Thermo 42i-TL)进行同期性能对比实验,详细阐述两种方法实现大气氮氧化物精确测量的原理,并重点讨论PCL法测量结果的光化学零点、水汽和光化学干扰的数值修正方法。数据显示,两种方法对NO的测量性能稳定(R2=0.994,斜率为0.98),MCL法对NO2的测量比PCL法偏高25%~30%。干扰的修正结果表明,观测期间水汽干扰可造成NOx信号被低估0.2%~13.2%;光化学干扰可导致NO信号被低估0~13.3%,还可导致NO2信号被高估0~8.8%。以上结果表明,在NOx的常规监测与数据处理中,对上述干扰的修正非常必要,为降低干扰,需要谨慎地设计光解转化效率、管路停留时间以及管路湿度控制等相关参数。

In summer and winter of 2017,two self-developed blue light converter-photolytic chemiluminescence(BLC-PCL)NOx analyzers and a traditional molybdenum-chemiluminescence(MCL)NOx analyzer(Thermo 42i-TL)were applied for atmospheric NOx monitoring.A performance comparison experiment for BLC-PCL and MCL NOx analyzers was carried out during the observation period,and the numerical correction methods for possible interferences was discussed in detail.Results show that the two methods have stable measurement performance for NO(R2=0.994,slope is 0.98).The measurement of NO2 by MCL is 25%–30%higher than that of PCL.Notably,water vapor interference can cause the NOx signals to be underestimated by 0.2%–13.2%;photochemical inter-ferences can lead to an underestimation of NO by 0–13.3%and an overestimation of NO2 by 0–8.8%.These re-sults highlight the necessity of numerical correction of such interferences and the importance to carefully design related parameters such as photolysis efficiency,pipeline residence time,and pipeline humidity control.