Grantee Research Project Results
2024 Progress Report: Development of a reference method for open-path remote sensing of air toxics
EPA Grant Number: R840426Title: Development of a reference method for open-path remote sensing of air toxics
Investigators: Stutz, Jochen , Polidori, Andrea , Low, Jason , Pikelnaya, Olga
Institution: University of California Los Angeles , South Coast Air Quality Management District
EPA Project Officer: Chung, Serena
Project Period: May 1, 2022 through April 30, 2025 (Extended to April 30, 2027)
Project Period Covered by this Report: May 1, 2024 through April 30,2025
Project Amount: $798,825
RFA: Measurement and Monitoring Methods for Air Toxics and Contaminants of Emerging Concern in the Atmosphere (2021) RFA Text | Recipients Lists
Research Category: Watersheds , Endocrine Disruptors , Environmental Engineering , Air Quality and Air Toxics
Objective:
The objective of this project is to develop an open-source reference instrument and methodology for operation, validation, and QA/QC of open-path optical remote sensing (OP-ORS) monitoring of volatime organic compounds (VOCs) and other air toxics. This work is essential to firmly establish OP-ORS as a reliable and trusted tool to monitor VOC and air toxic releases from industrial facilities and for community air quality monitoring of these compounds.
Progress Summary:
During this reporting period we have performed field tests of the new reference OP-ORS, built the hardware for our validation experiments, developed the protocols for the validation experiment, and performed first validation measurement.
OP-ORS field tests were performed on the University of California Los Angeles (UCLA) campus on a 1104 m long light path in the open atmosphere to ensure that all hardware components operate reliably over time periods of several weeks and to optimize the instrument software for fully automated operation. At the same time, we set up and optimized the spectral BTEX (benzene, toluene, ethylbenzene, and xylenes) and benzaldehyde retrievals for the OP-ORS system. The instrument performed as expected yielding measurement uncertainties in the sub-ppb range, which are sufficient for the planned use of the instrument to audit fenceline ultraviolet differential optical absorption spectroscopy (UV-DOAS) BTEX instruments.
In close collaboration between UCLA and South Coast AQMD we have built a 5-ft-long, 12-in-diameter gas reference cell (GRC) to validate the reference OP-ORS. The cell, which is placed in front of the OP-ORS, can be aligned such that the OP-ORS light path passes completely through it, and the OP-ORS can be operated in its normal mode. The GRC is equipped with an internation absorption spectroscopy (IAS) instrument that independently measures the benzaldehyde concentration in realtime. In addition, the air in the GRC can be sampled by a gas-chromatograph. These two measurements will provide the independent validation of the benzaldehyde measured by the OP-ORS. Small amounts of benzaldehyde can be introduced in the GRC either as a liquid or as gas-mixture to create mixing ratios in the range between 100 – 2000 ppb. We performed initial tests with the GRC to develop a measurement protocol for the OP-ORS validation experiments. First results comparing the OP-ORS operated on a 1104 m long open atmosphere absorption path with the IAS show excellent agreement, giving confidence that our protocol is adequate and that the OP-ORS is giving accurate data.
In summary, we have made good progress towards the goals of our project and expect to reach our goals by the end of the project.
Future Activities:
We will perform the final OP-ORS validations test in Summer 2025 and establish the accuracy of the instrument. This will be followed by a deployment of the OP-ORS at a refinery in the Los Angeles area, where we will run it in parallel to a fenceline path from UCLA’s Optical Tent. During this exercise we will first develop the protocol to validate fenceline instruments, and then test the protocol during a one to two weeklong validation experiment. A second deployment will be performed in Spring/Summer 2026, where South Coast AQMD and UCLA will independently run the OP-ORS and fenceline instrument, respectively, for a blind validation exercise. We will continue documenting the OP-ORS instrument, software and the various validation protocols.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
air toxics monitoring, facility emission measurements, fenceline reference methodRelevant Websites:
N/A
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.