| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
|
| Initial Amendment Date: | May 1, 2020 |
| Latest Amendment Date: | May 1, 2020 |
| Award Number: | 2030112 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Sylvia Edgerton
sedgerto@nsf.gov (703)292-8522 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | May 1, 2020 |
| End Date: | April 30, 2021 (Estimated) |
| Total Intended Award Amount: | $94,495.00 |
| Total Awarded Amount to Date: | $94,495.00 |
| Funds Obligated to Date: |
|
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
160 ALDRICH HALL IRVINE CA US 92697-0001 (949)824-7295 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
B-35 Rowland Hall Irvine CA US 92697-2025 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | Atmospheric Chemistry |
| Primary Program Source: |
|
| Program Reference Code(s): |
|
| Program Element Code(s): |
|
| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
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.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The COVID-19 pandemic offered an opportunity to study the impact of reduced activity levels on the air quality of the Los Angeles (LA) Basin. The Los Angeles Air Quality Campaign (LAAQC-2020) was carried out in the spring and summer of 2020 at the California Institute of Technology (Caltech) in Pasadena, about 15 km northeast of downtown LA. We collected whole air samples three times a day from April 16 to July 19, 2020 (314 canisters) and from September 5 to 19 (87 canisters), for a total of 401 samples. The data set also includes four diurnal profiles of 24-hourly samples per day, two on a Sunday (6/14/2020 and 9/6/2020) and the other two on weekdays (Monday 6/15/2020 and Wednesday 9/16/2020). However, the September samples were heavily impact by wildfire emissions and for this reason were not used in our data analysis to assess the VOC composition in the LA basin. All samples were analyzed within 7 days of sample collection using a multi-column/detector gas chromatographic system at the laboratory of the University of California, Irvine. The analyzed compounds comprise carbon monoxide (CO), methane and a wide variety of volatile organic compounds (VOCs) including selected sulfur compounds, halocarbons, selected alkyl nitrates and hydrocarbons. We focus on the variation of VOC levels from the beginning of the campaign in April, 2020 when California was already under a “stay at home” order, to the end of the first sampling period in July, 2020 when California transitioned to “Phase 3” which allowed the reopening of higher risk work places. We also evaluate the OH reactivity during the study, a measure of the potential of VOCs and other gases to form ozone. In addition, we use data collected at Mt Wilson, a sampling site in the Angeles National Forest about 30 km northeast of downtown LA, to better understand the effect of seasonality on the measured gases. The key findings are as follows:
(1) While the stay-at-home orders were expected to lead to a reduction in VOC levels as a result of reduced traffic emissions, levels of most VOCs stayed fairly similar between April/May (low traffic) and June/July (high traffic). (An exception is the biogenic tracer isoprene, which was expected to increase during the summer months). While we saw some evidence of increased emissions of selected VOCs associated with vehicular emissions, the results from the LAAQC-2020 campaign appear to support recent studies that suggest a decrease of the importance of VOCs emitted by mobile sources in Los Angeles compared to other emissions sources, namely volatile chemical products (VCPs) and biogenic sources. Specifically, the analysis of the composition of different classes of VOCs showed higher fractions of alkenes and aromatics (mostly associated with vehicular emissions) during the high traffic period, though the results were not statistically significant and some of these species are also associated with emissions from VCPs.
(2) The OH reactivity also stayed generally similar between the low traffic and high traffic periods. This again suggests that traffic was not the major factor affecting most VOCs.
(3) Year-round sampling at Mt Wilson suggests that known seasonality of the measured VOCs did not play a strong role in their observed behavior.
The campaign strongly highlights that VOC levels in urban areas are highly affected by a number of competing factors that make it difficult to establish the causal role of traffic emissions in VOC levels and ultimately tropospheric ozone formation. Moreover, we note that the campaign did not fully cover a “back to normal” situation in the LA basin as COVID-19 restrictions were still partially in place when the sampling ended.
Last Modified: 05/21/2021
Modified by: Donald R Blake
Please report errors in award information by writing to: awardsearch@nsf.gov.
