Grantee Research Project Results

2023 Progress Report: Development of a reference method for open-path remote sensing of air toxics

EPA Grant Number: R840426
Title: Development of a reference method for open-path remote sensing of air toxics
Investigators: Stutz, Jochen , Pikelnaya, Olga , Polidori, Andrea , Low, Jason
Current 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, 2023 through April 30,2024
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 volatile 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 finalized the construction of the reference OP-ORS system. The instrument consists of three parts: 1) a fiber-based sending receiving telescope (1 m focal length, 250 mm diameter) which can be rotated in the vertical and horizontal with two high precision stepper motors. 2) A weather-proof case that contains all the other parts of the instrument, i.e. LED light source, spectrometer, detector, power supplies, and control computer. The case is temperature regulated and serves as the stand for the telescope. The case and telescope can be deployed anywhere in the field and only need 110V power to be fully operational. 3) An array of quartz corner-cube retroreflector with a custom clamp can be attached to existing structures in the field, including a stable meteorological tripod available at UCLA. The entire instrument can be transported in a small van and can be set up in a few hours, thus allowing straightforward deployments near BTEX fenceline monitoring systems in refineries.

In close collaboration between UCLA and South Coast AQMD we have refined our strategy for validation of the OP-ORS instrument. Our new design uses a 300 mm diameter, 1.5 m long open-ended pipe that we will fill with benzaldehyde. The pipe can be closed off on both ends thus allowing two different ways of introducing benzaldehyde: 1) we can flush the pipe with a benzaldehyde/air mixture; 2) we can introduce a small amount of liquid benzaldehyde and let it evaporate in the closed pipe. It should be noted that benzaldehyde is a fairly safe chemical with an absorption structure in the same wavelength range as the BTEX compounds and thus ideally suited for this experiment. Benzaldehyde concentrations in the pipe will be monitored by a direct internal optical absorption measurement and an independently calibrated automated gas-chromatograph (Auto-GC). A typical experiment consists of the following steps: 1) base-line measurements with all three analytical instruments, 2) close the pipe and introduce benzaldehyde, 3) mix and monitor the benzaldehyde concentrations, 4) open pipe covers and perform OP-ORS measurements in parallel to Auto-GC and internal absorption measurements. The validation setup has been built and we are performing the validation measurements in Summer 2024. The validation experiment follows the requirements of the project QAPP.

In summary, we have made good progress towards the goals of our project, partially making up the delays in the first project year due the long delivery times for crucial parts. We expect to reach our goals by the end of the project.

Future Activities:

We are currently testing the reference OP-ORS system on the UCLA campus. The validation experiments will be performed during Summer 2024 with the goal to build trust in the reference OP-ORS performance. The field test in a local refinery is scheduled for the Fall. We will continue to compile the details of the instrument as well as our experience in field operation/validation in a design document, as per the original workplan. We will present the results of the validation experiments and the first field deployment inside a refinery at the 2024 Fall Meeting of the American Geophysical Union in Washington, DC.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

air toxics monitoring, facility emission measurements, fenceline reference method

Relevant Websites:

N/A

Progress and Final Reports:

Original Abstract

The 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.