Reactive nitrogen species (N_r), defined here as all N-containing compounds except N₂ and N₂O, have been shown to be important drivers for indoor air quality. Key N_r species include NO_x (NO + NO₂), HONO and NH₃, which are known to have detrimental health effects. In addition, other N_r species that are not traditionally measured may be important chemical actors for indoor transformations (e.g. amines). Cooking and cleaning are significant sources of N_r, whose emission will vary depending on the type of activity and materials used. Here we present a novel instrument that measures the total gas-phase reactive nitrogen (tN_r) budget and key species NO_x, HONO, and NH₃ to demonstrate its suitability for indoor air quality applications. The tN_r levels were measured using a custom-built heated platinum (Pt) catalytic furnace to convert all N_r species to NO_x, called the tN_r oven. The measurement approach was validated through a series of control experiments, such that quantitative measurement and speciation of the total N_r budget are demonstrated. The optimum operating conditions of the tN_r oven were found to be 800 °C with a sampling flow rate of 630 cubic centimetres per minute (ccm). Oxidized nitrogen species are known to be quantitatively converted under these conditions. Here, the efficiency of the tN_r oven to convert reduced N_r species to NO_x was found to reach a maximum at 800 °C, with 103 ± 13% conversion for NH₃ and 79–106% for selected relevant amines. The observed variability in the conversion efficiency of reduced N_r species demonstrates the importance of catalyst temperature characterization for the tN_r oven. The instrument was deployed successfully in a commercial kitchen, a complex indoor environment with periods of rapidly changing levels, and shown to be able to reliably measure the tN_r budget during periods of longer-lived oscillations (>20 min), typical of indoor spaces. The measured NO_x, HONO and basic N_r (NH₃ and amines) were unable to account for all the measured tN_r, pointing to a substantial missing fraction (on average 18%) in the kitchen. Overall, the tN_r instrument will allow for detailed survey(s) of the key gaseous N_r species across multiple locations and may also identify missing N_r fractions, making this platform capable of stimulating more in-depth analysis in indoor atmospheres.

中文翻译：

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新兴研究者系列：测量和确定室内总活性氮预算的仪器：描述和现场测量

活性氮物质 (N _{r )，此处定义为除 N 2}和 N ₂ O之外的所有含氮化合物，已被证明是室内空气质量的重要驱动因素。关键的 N _r物种包括 NO _x (NO + NO ₂ )、HONO 和 NH ₃，已知它们对健康有不利影响。此外，传统上未测量的其他 Nr_物种可能是室内转化的重要化学参与者（例如胺）。烹饪和清洁是 N _{r的重要来源}，其排放量将根据活动类型和使用的材料而有所不同。在这里，我们展示了一种新型仪器，用于测量总气相活性氮 (tN _r ) 预算和关键物种 NO _x、HONO 和 NH ₃，以证明其适用于室内空气质量应用。tN _r水平是使用定制的加热铂 (Pt) 催化炉测量的，该炉将所有 N _r物质转化为 NO _x，称为 tN _r炉。通过一系列对照实验验证了测量方法，例如总 N _{r的定量测量和形态分析}预算得到证明。_{发现 tN r}烘箱的最佳操作条件为 800 °C，采样流量为每分钟 630 立方厘米 (ccm)。已知氧化的氮物质在这些条件下被定量转化。_{此处，tN r烘箱将还原的 N r}物质转化为 NO _x的效率在 800 °C 时达到最大值，NH ₃的转化率为 103 ± 13%，选定的相关胺类转化率为 79–106%。_{观察到的还原 N r}物质转化效率的可变性证明了催化剂温度表征对 tN _{r的重要性}烤箱。该仪器已成功部署在商业厨房中，这是一个水平快速变化的复杂室内环境，并证明能够在较长时间的振荡（> 20 分钟）期间可靠地测量 tN _r预算，典型的室内空间. 测得的 NO _x、HONO 和碱性 N _r（NH ₃和胺类）无法解释所有测得的 tN _r，表明厨房中存在大量缺失部分（平均 18%）。总的来说，tN _r仪器将允许对多个位置的关键气态 N _r物种进行详细调查，并且还可以识别缺失的 N _r分数，使该平台能够激发对室内大气的更深入分析。