Due to the complex nature of ambient aerosols arising from the presence of myriads of organic compounds, the chemical reactivity of a particular compound with oxidant/s are studied through chamber experiments under controlled laboratory conditions. Several confounders (RH, T, light intensity, in chamber retention time) are controlled in chamber experiments to study their effect on the chemical transformation of a reactant (exposure variable) and the outcome [kinetic rate constant determination, new product/s formation e.g., secondary organic aerosol (SOA), product/s yield, etc.]. However, under ambient atmospheric conditions, it is not possible to control for these confounders which poses a challenge in assessing the outcome/s accurately. The approach of data interpretation must include randomization for an accurate prediction of the real-world scenario. One of the ways to achieve randomization is possible by the instrumental variable analysis (IVA). In this study, the IVA analysis revealed that the average ratio of fSOC/O3 (ppb−1) was 0.0032 (95% CI: 0.0009, 0.0055) and 0.0033 (95% CI: 0.0001, 0.0065) during daytime of Diwali and Post-Diwali period. However, during rest of the study period the relationship between O3 and fSOC was found to be insignificant. Based on IVA in conjunction with the concentration-weighted trajectory (CWT), cluster analysis, and fire count imageries, causal effect of O3 on SOA formation has been inferred for the daytime when emissions from long-range transport of biomass burning influenced the receptor site. To the best of our knowledge, the IVA has been applied for the first time in this study in the field of atmospheric and aerosol chemistry.

中文翻译：

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大气和气溶胶化学中的仪器变量分析

由于大量有机化合物的存在导致环境气溶胶的复杂性，因此在受控实验室条件下通过室内实验研究特定化合物与氧化剂的化学反应性。在室实验中控制几个混杂因素（RH、T、光强度、室保留时间）以研究它们对反应物化学转化（暴露变量）和结果 [动力学速率常数测定、新产品/秒形成例如、二次有机气溶胶 (SOA)、产品/秒收率等]。然而，在环境大气条件下，无法控制这些混杂因素，这对准确评估结果构成挑战。数据解释的方法必须包括随机化以准确预测真实世界的场景。工具变量分析 (IVA) 是实现随机化的一种方法。在这项研究中，IVA 分析显示，排灯节白天和后排灯节期间 fSOC/O3 (ppb-1) 的平均比率为 0.0032（95% CI：0.0009、0.0055）和 0.0033（95% CI：0.0001、0.0065）排灯节时期。然而，在剩余的研究期间，发现 O3 和 fSOC 之间的关系并不显着。基于 IVA 结合浓度加权轨迹 (CWT)、聚类分析和火灾计数图像，当生物质燃烧远程传输的排放影响受体位点时，已推断出 O3 对 SOA 形成的因果影响. 据我们所知，