Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)
Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)
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DOI：
10.5194/amt-12-6449-2019
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发表时间：
2019-12-09
影响因子：
3.8
通讯作者：
Bloss, William J.
中科院分区：
文献类型：
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作者：
Crilley, Leigh R.;Kramer, Louisa J.;Bloss, William J.
亚硝酸(HONO)是白天边界层白天自由基收支的关键决定因素，需要定量测量来了解OH自由基的丰度。因此，需要准确和精确地测量HONO；然而，在现场测量HONO是一种具有挑战性的化合物，特别是在化学复杂和高度污染的环境中。在本文中，我们报道了两种湿化学技术(市售的长程吸收光度计(LOPAP)和定制的仪器)和两台宽带腔增强吸收分光光度计(BBCEAS)在北京市区进行的HONO测量的比对工作。此外，我们报告了飞行时间化学电离质谱仪(ToF-CIMS)和选择离子流管质谱仪(SIFT-MS)与更成熟的技术(湿化学和BBCEAS)进行的HONO测量的比较。当前工作的关键发现是，所有仪器都同意HONO(r(2)>；0.97)的时间趋势和变异性，但它们在绝对浓度上显示出一些差异，湿化学方法总体上始终高于BBCEAS系统12%至39%。我们没有发现任何仪器存在系统性偏差的证据，但仪器检测极限附近的测量除外。HONO绝对浓度差异的原因尚不清楚，部分原因可能是空间差异，即仪器位置和/或进气口位置的差异，但这种观察结果可能更多是关联而不是偶然的。
Nitrous acid (HONO) is a key determinant of the daytime radical budget in the daytime boundary layer, with quantitative measurement required to understand OH radical abundance. Accurate and precise measurements of HONO are therefore needed; however HONO is a challenging compound to measure in the field, in particular in a chemically complex and highly polluted environment. Here we report an intercomparison exercise between HONO measurements performed by two wet chemical techniques (the commercially available a long-path absorption photometer (LOPAP) and a custom-built instrument) and two broadband cavity-enhanced absorption spectrophotometer (BBCEAS) instruments at an urban location in Beijing. In addition, we report a comparison of HONO measurements performed by a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) and a selected ion flow tube mass spectrometer (SIFT-MS) to the more established techniques (wet chemical and BBCEAS). The key finding from the current work was that all instruments agree on the temporal trends and variability in HONO (r(2) > 0.97), yet they displayed some divergence in absolute concentrations, with the wet chemical methods consistently higher overall than the BBCEAS systems by between 12% and 39 %. We found no evidence for any systematic bias in any of the instruments, with the exception of measurements near instrument detection limits. The causes of the divergence in absolute HONO concentrations were unclear, and may in part have been due to spatial variability, i.e. differences in instrument location and/or inlet position, but this observation may have been more associative than casual.