Collaborative Research: RAPID--Urban Air Quality during the Coronavirus (COVID-19) Shelter-In-Place Orders

在这个RAPID项目中，一个合作PI团队打算在加利福尼亚州洛杉矶地区收集时间敏感的大气样本，该地区历史上高水平的臭氧（O3）和细颗粒物（PM2.5）一直困扰着公众健康。通过利用与当前COVID-19就地安置命令相关的大气排放大幅减少的优势，一种自然实验已经出现，可以在独特有用的条件下进行观察。研究结果将有助于限制污染物浓度的预测模型，并指导监管机构制定缓解空气质量差的最佳战略。在COVID-19解除期间和之后，将通过在加州理工学院建立的屋顶采样平台上共同放置采样设备来收集气体和颗粒样本，在该平台上持续监测NOx， O3和PM2.5等基本参数。本研究的重点是含有1至15个碳原子（C1-C15）的挥发性到中间挥发性有机化合物（I/VOCs）的重要前体族化合物的详细化学形态。这些化合物通过许多不同的来源排放，包括化石燃料的生产和燃烧、化学产品的使用和生物生产力。它们的来源和反应不明确归因于现有的知识空白，这可能解释大城市中高于预期的臭氧水平，而在过去几十年里，大城市的前体排放普遍减少。在这里，将在运输相关的VOC和NOx排放量较低的时期确定I/VOC源和源标记。PIs实验室收集的样品的最先进的分析包括二维气相色谱（GC×GC）与飞行时间质谱（TOFMS）和多柱/检测器GC系统，具有5种不同类型的分离和检测组合。研究结果将(i)为在独特的低氮氧化物条件和不断变化的VOCs组合下O3和PM2.5生成的复杂机制提供新的见解，（ii）有助于约束大气化学和空气质量的预测模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this RAPID project, a collaborative PI team intends to collect time sensitive atmospheric samples in the Los Angeles, CA, area, where historically high pollutant levels of ozone (O3) and fine particulate matter (PM2.5) have plagued public health. By taking advantage of significant reductions in atmospheric emissions associated with current COVID-19 shelter-in-place orders, a natural experiment has presented itself that allows for observations to be made under uniquely useful conditions. Results will help constrain predictive models of pollutant concentrations and guide regulatory agencies in best strategies to mitigate poor air quality.Gaseous and particulate samples will be collected during and after the lifting of COVID-19 by co-locating sampling devices on Caltech’s established roof-top sampling platform, where continuous monitoring of essential parameters, including NOx, O3, and PM2.5, is ongoing. Focus in this study is on the detailed chemical speciation of the important precursor group of compounds denoted as volatile to intermediate volatility organic compounds (I/VOCs) containing 1 to 15 carbon atoms (C1-C15). These compounds are emitted through a number of different sources, including from fossil fuel production and burning, use of chemical products, and biological productivity. Their ill-defined sources and reactivities have been attributed to an existing gap in knowledge that could describe higher-than-expected O3 levels in megacities where precursor emissions have seen a general decrease in past decades. Here, I/VOC sources and source markers will be determined during a period when transportation associated emissions to VOCs and NOx are low. State-of-the-art analyses of collected samples at PIs’ laboratories include two-dimensional gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS) and a multi-column/detector GC system with 5 different types of separation and detection combinations. Results will (i) provide new insight into the intricate mechanisms of O3 and PM2.5 production under uniquely low NOx conditions and a changing mix of VOCs, and (ii) help constrain predictive models of atmospheric chemistry and air quality.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.