The measurement method of NO with continuous analysers is specified for EU Ambient Air Quality Directive compliance reporting, which provides a consistent methodology and concurrent NO measurements (85/203/EEC-NO2). While the established method of measurement of NO, following conversion of NO to NO using a molybdenum-conversion process, has known interference uncertainties (due to conversion of other oxidised nitrogen (NO) chemicals, the consistency and traceability of compliance measurement is important. This study compared three continuous NO analyser instruments: a Thermo-NO molybdenum convertor chemiluminescence analyser (Model 42C, ThermoFisher Scientific Inc., MA, USA), a photolytic chemiluminescence analyser (T200UP, Teledyne Technologies Inc., San Diego, USA) and a Cavity Attenuated Phase Shift (CAPS) analyser (T500U, Teledyne Technologies Inc., CA, USA). The instruments were run for over a year at the Auchencorth Moss long-term peatland monitoring site (Southeast Scotland) which is a low NO atmosphere away from sources. NO and NH chemicals were also measured concurrently. This study concludes that there is a strong artefact in molybdenum catalyst chemiluminescent instruments as a result of unselective catalysis of airborne NO compounds that causes an overestimate of NO measured in the atmosphere. The observed artefact in concentration measurements is likely to be observed at the entire UK scale as almost the entirety of the rural air network relies on molybdenum catalyst instruments. We therefore recommend that molybdenum catalyst instruments should be phased out and replaced in air quality monitoring networks with molecule specific (spectroscopy) instrumentation (equivalent in cost, such as those described in this study) that do not suffer from the same measurement artefacts.

中文翻译：

---

评估农村空气质量网络中二氧化氮测量中钼催化转化的偏差

使用连续分析仪测量 NO 的方法是为欧盟环境空气质量指令合规报告指定的，它提供了一致的方法和并发的 NO 测量 (85/203/EEC-NO2)。虽然使用钼转化过程将 NO 转化为 NO 后，现有的 NO 测量方法存在已知的干扰不确定性（由于其他氧化氮 (NO) 化学品的转化，合规性测量的一致性和可追溯性非常重要。这研究比较了三种连续 NO 分析仪：Thermo-NO 钼转换器化学发光分析仪（型号 42C，ThermoFisher Scientific Inc.，马萨诸塞州，美国）、光解化学发光分析仪（T200UP，Teledyne Technologies Inc.，圣地亚哥，美国）和 Cavity衰减相移 (CAPS) 分析仪（T500U，Teledyne Technologies Inc.，加利福尼亚州，美国）。该仪器在 Auchencorth Moss 长期泥炭地监测站点（苏格兰东南部）运行了一年多，该站点的 NO 浓度较低，远离本研究得出的结论是，由于空气中 NO 化合物的非选择性催化作用，钼催化剂化学发光仪器中存在强烈的伪影，导致大气中测得的 NO 值被高估。由于几乎整个农村空气网络都依赖于钼催化剂仪器，因此在浓度测量中观察到的人为现象很可能在整个英国范围内观察到。因此，我们建议在空气质量监测网络中逐步淘汰钼催化剂仪器，并用不会遭受相同测量伪影的分子特定（光谱）仪器（成本相当，如本研究中描述的仪器）取代。