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

在这个快速项目中，一个合作的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，那里的臭氧(O3)和细颗粒物(PM2.5)的污染物水平一直困扰着公众健康。通过利用与当前的新冠肺炎就地避难所订单相关的显著减少的大气排放，一项自然实验本身已经呈现出来，允许在独特有用的条件下进行观测。结果将有助于约束污染物浓度的预测模型，并指导监管机构采取最佳策略来缓解糟糕的空气质量。在新冠肺炎取消期间和之后，将通过在加州理工学院建立的屋顶采样平台上共置采样设备来收集气体和颗粒物样本，该平台正在持续监测基本参数，包括氮氧化物、臭氧和PM2.5。这项研究的重点是含有1-15个碳原子(C1-C15)的挥发性至中挥发性有机化合物(I/VOCs)的重要前体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，包括化石燃料生产和燃烧、使用化学产品和生物生产力。它们不明确的来源和反应性被归因于现有的知识差距，这可以描述超大城市的臭氧水平高于预期，这些城市的前体排放在过去几十年里普遍下降。在此，将在运输相关的VOCs和NOx排放量较低的期间确定I/VOC源和源标记。PIS实验室收集的样品的最先进分析包括二维气相色谱(GC×GC)和飞行时间质谱仪(TOFMS)，以及具有5种不同类型分离和检测组合的多柱/检测器GC系统。结果将(I)为在独特的低NOx条件和不断变化的VOCs组合下产生臭氧和PM2.5的复杂机制提供新的见解，以及(Ii)有助于限制大气化学和空气质量的预测模型。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.