California Air Resources Board

Scope of Work

Background

Air toxics have been a significant concern in California for decades, particularly in priority communities where they are often found at elevated levels[1]. At levels above certain thresholds, exposure to air toxics, including those designated as Toxic Air Contaminants (TACs) by the state of California and Hazardous Air Pollutants (HAPs) by the federal government, can cause severe health impacts, including cancer, respiratory diseases, and developmental issues. They are emitted from a variety of sources, such as (1) stationary sources like industrial facilities, power plants, dry cleaners, and hospitals; (2) mobile sources, including on-road vehicles, agricultural and construction machinery, aircraft, and marine vessels; and (3) area-specific sources like residential burning, consumer products, and agricultural operations. Natural events such as wildfires also contribute.

California has developed an Air Toxics Program to reduce emissions of TACs and HAPs and to protect public health. This program operates under regulations such as the federal Clean Air Act and California-specific laws, including AB 2588 (Air Toxics "Hot Spots" Information and Assessment Act). CARB’s current air toxics monitoring network relies on traditional sampling methods, which provide limited temporal resolution and frequency, with data collected once every twelve days that yield a single 24-hour aggregated data point. This approach requires offline laboratory analysis to detect compounds. Due to its coarse temporal resolution and frequency, it cannot accurately evaluate short-term exposure risks.   

Real-time measurements of TACs/HAPs using advanced mass spectrometry–based technologies can potentially address these gaps by providing high-resolution datasets that improve our understanding of their concentrations and temporal trends, as well as facilitate short-term exposure analysis.

TAC/HAP sources also emit Volatile Organic Compounds (VOCs), referred to as “precursor VOCs” in this document. These precursor VOCs significantly contribute to the formation of secondary pollutants, including other TACs/HAPs (such as formaldehyde), criteria pollutants like ozone (O₃), and fine particulate matter (PM_2.5) through secondary organic aerosols (SOA). CARB’s current monitoring methods lack sufficient temporal resolution to identify and quantify precursor VOCs that inform secondary pollutant formation.

High-resolution datasets acquired from advanced mass spectrometry methods enable more accurate source characterization and improved estimation of secondary pollutant formation. Additionally, in situ hydroxyl radical (OH) reactivity measurements, along with these advanced measurements, significantly improve our ability to estimate the contribution from missing precursor VOCs and TACs/HAPs to secondary pollutant formation and to further address these research gaps. A major challenge in deploying such technologies is that, compared to conventional offline air toxics sampling, they are less established and require greater technical expertise and resources for field deployment. 

Therefore, a key aspect of this project is to successfully deploy advanced and emerging technologies that can be effectively applied to this research. Notable technologies under consideration include Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) and Chemical Ionization Mass Spectrometry (CIMS) for online measurements, and Thermal Desorption Gas Chromatography Time-of-Flight Mass Spectrometry (TD-GC-ToF-MS) for offline analysis. These techniques are recognized for their high sensitivity, precision, and broad compound coverage. Collectively, this integrated mass spectrometry approach enables the detection of hundreds of air toxics and precursor VOCs with lower measurement uncertainty.

Objectives

The primary objectives of this project are to (1) evaluate the feasibility of, and facilitate, the long-term deployment of advanced real-time mass spectrometry-based techniques to address key gaps in existing air toxics and VOC monitoring data and methods, particularly related to time resolution and compound coverage; (2) compare the performance of these advanced technologies against offline laboratory analysis; and (3) improve characterization of complex air toxics emission sources. CARB envisions this contract as a pilot project to support ongoing CARB and Air District efforts and to develop transferable Standard Operating Procedures (SOPs) and workflows that can be applied to future deployments for advanced VOCs and air toxics monitoring.

Site Selection Criteria

CARB developed five main criteria to select a long-term monitoring site (referred to as the supersite in this document): (1) diversity of air toxics sources, (2) ability to leverage existing infrastructure, (3) opportunity for data comparability, (4) alignment with ongoing CARB and Air District efforts, and (5) overall budget feasibility. To expand specifically on criterion #2, sites requiring new shelter construction or extensive infrastructure upgrades would significantly increase costs, delay implementation, and reduce the resources available for conducting continuous monitoring and data analysis. As a pilot effort, the primary goal of this project is to maximize scientific outcomes through data collection and operational learning while minimizing deployment risks.

Following the development of the site selection criteria, CARB conducted a comprehensive evaluation of potential locations statewide and determined that the Wilmington-Carson-Long Beach area is the only region that fully satisfies all selection criteria. Other regions meet the selection criteria partially. For example, although the Bay Area has diverse air toxics emission sources, the Bay Area Air Quality Management District (BAAQMD) will require an infrastructure update to accommodate the required space. As another example, while the existing infrastructure in the San Joaquin Valley (SJV) could potentially accommodate the required space, previous research indicates that the SJV’s air toxic emissions are more heavily dominated by mobile and area sources, with relatively limited contributions from stationary industrial sources. However, the South Coast Air Basin’s (SoCAB) air toxics inventories show a broader mixture of point, area, on‑road, and off‑road sources, making it more chemically complex[2].

Wilmington-Carson-Long Beach is a designated AB 617 community in SoCAB with well-documented concerns regarding air toxics exposure. The area is influenced by highly diverse emission sources, including refineries, port-related activities, and dense mobile and stationary sources, making it an ideal location to evaluate the capabilities of advanced measurement technologies in resolving complex chemical mixtures. Another factor distinguishing Wilmington-Carson-Long Beach from other candidate locations is the ability to leverage the existing SCAQMD’s infrastructure and programs, including Rule 1180[3] and the planned MATES VI program. Candidate sites, such as the Rule 1180’s G Street location, offer sufficient space and power, and proximity to major air toxics sources (including the Phillips refinery), substantially reducing deployment time, cost, and risks. Locating the supersite in Wilmington-Carson-Long Beach will also provide a unique opportunity to compare high-time-resolution datasets generated under this contract with existing lower-time-resolution air toxics measurements collected by SCAQMD (e.g., BTEX, acetaldehyde, acrolein under Rule 1180) and with planned UV-DOAS and FTIR measurements under MATES VI.

Scope of Work

The contractor should develop a research plan and perform all tasks described below.

Task 1: Deployment of a PTR-ToF-MS for long-term and a CIMS for seasonal operations  

PTR-ToF-MS is known for its high sensitivity and precision in measuring precursor VOCs and air toxics in real time. Previous studies have demonstrated the successful application of PTR-ToF-MS across diverse locations and seasons, accurately quantifying a comprehensive suite of VOCs and air toxics[4]^,[5].

Under task 1, the contractor will deploy a PTR-ToF-MS at the supersite and operate it for ~1.5–2 years. The contractor will be responsible for all costs associated with the deployment at the supersite, and these costs must be included in the draft research proposal. The contractor will coordinate with SCAQMD to get approval for the supersite deployment in Wilmington-Carson-Long Beach.

In addition, a CIMS instrument will be deployed alongside the PTR-ToF-MS for continuous operation during summer and winter to identify and expand the list of measured air toxics (such as organic acids and other TACs/HAPs), thereby supporting the data analysis conducted under task 5.

Task 2: Develop standard operating procedures for PTR-ToF-MS

Under task 2, the contractor will generate Standard Operating Procedures (SOPs) and checklists outlining step-by-step guidance for deploying, calibrating, operating, maintaining, and troubleshooting the PTR-ToF-MS. These documents should include, but are not limited to, methods for streamlining deployment in real-world monitoring scenarios, as well as any constraints or risks that need to be evaluated prior to or during deployment.

To perform this task successfully, the contractor will identify ways to enhance the utility of these technologies, ensuring they provide robust, high-quality data across various field conditions while facilitating ease of operation.

In addition, the contractor will develop a list of target analyte compounds for PTR-ToF-MS and design a comprehensive data-collection protocol to obtain high-quality data on ambient air toxics and precursor VOCs, accounting for seasonal variations and meteorological influences.

Interim Deliverables

SOPs and checklists outlining the strategies followed for PTR-ToF-MS long-term deployment and operation, and a list of measured precursor VOCs and air toxics by PTR-ToF-MS.

Task 3: Compare PTR-ToF-MS with offline laboratory techniques

Under task 3, the contractor will set up a sampling system at the supersite to collect offline air samples at select intervals using canisters and cartridges, and perform subsequent laboratory analysis using advanced techniques such as TD-GC-ToF-MS and Gas Chromatography with Vacuum Ultraviolet detectors (GC-VUV). The TD-GC-ToF-MS technique is often regarded as the gold standard for accurately measuring VOCs for offline samples. The offline analysis results will then be compared to the online PTR-ToF-MS measurements. This approach will enable a robust intercomparison and provide critical insights into the performance, sensitivity, and reliability of PTR-ToF-MS, as well as its effectiveness in detecting a wide range of VOCs and air toxics, highlighting their capabilities and limitations.

If possible, the contract will also incorporate a comparison with existing collocated sampling, such as other offline measurements at the site.

Interim Deliverables

Documents/reports outlining performance, precision, and accuracy details (including QA/QC, detection limits, and uncertainties), as well as intercomparison results for advanced technologies in real-world scenarios.

Task 4: Conduct in situ OH reactivity measurements to constrain the contribution of missing VOCs

VOC measurements alone often fail to capture the total OH loss because many highly reactive species, particularly oxygenated VOCs (OVOCs) and other unidentified or poorly quantified compounds, are underestimated. This leads to a discrepancy between the calculated OH reactivity derived from measured VOCs and the total OH reactivity directly measured in the atmosphere. Performing direct OH reactivity measurements will provide an integrative constraint on VOC emissions, help identify missing reactive species, and improve our understanding of the oxidative capacity and its potential for secondary pollutant formation.

Under task 4, the contractor will utilize the deployed analytical system at the supersite to perform in situ measurements of OH reactivity during summer and winter, thereby quantifying the contributions of unidentified air toxics and precursor VOCs to secondary pollutant formation. The contractor will complement the VOC measurements by performing the OH reactivity measurements using novel methods, such as the comparative reactivity method[6], to collect a crucial dataset for an improved understanding of VOC-OH reactions, and the contribution of unknown VOCs to total reactive pollutants loading, which will provide a holistic measure of the oxidative burden.

Interim Deliverables

Documents/reports outlining the experimental setup and details of OH reactivity measurements using novel methods, such as the comparative reactivity method.

Task 5: Processing and analyzing the acquired datasets

The contractor will perform detailed processing and analysis of the acquired air toxics and precursor VOC datasets to identify a broad spectrum of compounds detected during monitoring, their temporal and seasonal variations, and assess their contribution to secondary pollutant formation. Using the collected data, the contractor will perform the positive matrix factorization (PMF) model to identify and characterize source categories affecting the supersite and their contributions to measured air toxics. In consultation with CARB, the contractor is also expected to perform PMF analysis on at least two weeks of the mobile monitoring datasets acquired by CARB’s Statewide Mobile Monitoring Initiatives (SMMI) in the vicinity of the supersite. This analysis will assess the robustness of applying PMF on a mobile monitoring dataset for source characterization. Additionally, contractors will perform a detailed analysis of the OH reactivity measurement datasets. The contractor will also provide recommendations for conducting exposure studies using the collected dataset.

Interim Deliverables

Regular updates on the progress of data analysis and results to CARB.

Task 6: Summary, evaluation, and final report

The contractor will provide the CARB contract manager with a comprehensive draft final report (DFR) six months prior to the project's completion, detailing the research findings and their recommendations. This report should include a thorough analysis of the methods, data collected, and the effectiveness of the technologies evaluated, along with actionable suggestions for future applications and studies. The contractor will update the report to address feedback from CARB staff and the Research Screening Committee (RSC). By the end of the contract period, the contractor will submit the final report and the finalized dataset from the study. To ensure transparency and accessibility, CARB will publish detailed, publicly available project reports that outline the findings, methodologies, and their impacts on racial equity, making them accessible to diverse audiences. Additionally, interactive tools, webinars, and presentations can be used to share the project's findings, demonstrate equity-centered metrics, and highlight how the research outcomes contribute to identifying and mitigating the impacts of air toxics and precursor VOCs.

Project Deliverables

The project proposal shall include but not be limited to the following deliverables from the contractor:

At the Beginning of the Contract

• Participate in a kick-off meeting to give an overview of the project.
• Discuss with CARB to finalize field site locations, deployment strategies, and data collection approach.
• All researchers must undergo cultural competency training (e.g., implicit bias training and racial equity training). Training should be completed or scheduled within 30 days of contract execution.

During the Active Contract Period

• Submit Quarterly Progress Reports. These reports shall include plain-language summaries that can be posted publicly. CARB will provide the progress report template.
• Engage in frequent (e.g., monthly) consultation conference calls with CARB and key stakeholders.
• Submit Interim reports to keep CARB staff informed. Upon CARB staff's request, these reports are expected at the end of each task to ensure progress is being made.

Prior to Contract Close

• Submit all data, analyses, and analytical tools generated during this project.
• Produce plain-language fact sheets, including recommendations for preventative actions (if available). The fact sheets will be translated into Spanish.
• Satisfy the following requirements of the Draft Final Report (DFR):
  • DFR will be copy-edited, reviewed, and approved by the Principal Investigator.
  • Include a plain language summary in DFR
  • Include an equity implications section in DFR
  • If applicable, have the DFR reviewed by community representatives.
• Work with CARB to create plain-language outreach deliverables for the public, summarizing the project's results and impact.
• The Final Report submitted to CARB must be ADA-compliant.
• Participate in a virtual or in-person seminar to present the project findings.
• Peer-reviewed publications should be publicly available (please budget for this expense; submission-ready publications shall be reviewed by CARB staff).
• Additional deliverables shall be determined in consultation with CARB staff.

Timeline

This project is anticipated to be completed in 36 months from the start date. Cost shall not exceed $900,000.

Scoring Criteria

Responsiveness to the goals and objectives outlined in the proposal solicitation(15 points)

Proposers should demonstrate a clear understanding of the policy objectives and research needs that CARB aims to address with this project while highlighting their expertise on the subject. The proposal should present a clear research question or testable hypothesis, consider various aspects of the research need, and identify or acknowledge any potential biases. It should outline, in sufficient detail, the proposed approach to meeting the requirements of the Solicitation. The draft proposal must detail work that aligns with the objectives outlined in the Research Solicitation:

The primary objectives of this project are to (1) evaluate the feasibility of, and facilitate, the long-term deployment of advanced real-time mass spectrometry-based techniques to address key gaps in existing air toxics and VOC monitoring data and methods, particularly related to time resolution and compound coverage; (2) compare the performance of these advanced technologies against offline laboratory analysis; and (3) improve characterization of complex air toxics emission sources. CARB envisions this contract as a pilot project to support ongoing CARB and Air District efforts and to develop transferable Standard Operating Procedures (SOPs) and workflows that can be applied to future deployments for advanced VOCs and air toxics monitoring.

Policy relevance/benefits to the state(10 points)

Does the proposal describe how the project will provide data, information, and/or products to support CARB in achieving its mission?

1. Air toxics and VOC monitoring: Will support long-term deployment and operation of advanced air toxics and VOCs monitoring technologies, and thereby will improve current methods and data.
2. Assembly Bill 617: Will provide high-time-resolution air toxics and VOCs datasets in a designated AB 617 community.
3. Assembly Bill 2588: Will support AB2588 through the identification of a broad range of air toxics and VOCs and a detailed source characterization of air toxics emissions near complex source areas.
4. California Air Toxics Assessment (CATA) and State Implementation Plan (SIP): The collected high-time-resolution datasets can be used as an input in CATA modeling efforts to inform CARB’s California Toxics Inventory (CTI) and hence, guide SIP.
5. Airborne Toxic Control Measures (ATCM): The collected datasets will provide air toxics and VOCs emission patterns, source characterization, and seasonal variability, and hence will inform ATCM.

Previous work (15 points)

Do the researchers have relevant experience in this area? Is the team composed of a multi-disciplinary team of experts? Do they discuss how they will build on previous relevant work funded by CARB, other state agencies, and any other appropriate organizations? If community engagement is included, the relevant research partner should describe prior experience in community engagement and provide letters of support, references or a community impact statement detailing how their previous work has benefitted communities. Five points will be reserved for project teams that meet at least one of the following criteria:

1. The project team is multi-disciplinary.
2. The project team includes members from various universities, non-academic institutions, or community-based organizations.
3. The project team includes one or more members who will contribute significantly to the project (e.g., a principal investigator, co-principal investigator, or co-investigator, contributing 25% or more of their time) who have not worked with CARB in the past 5 years.

Technical merit (25 points)

Describe the technical strengths and/or weaknesses of the pre-proposal. Proposers should demonstrate the logic and feasibility of the methodology and technical approach, outline the sequence and relationships of major tasks, and explain how the work will be carried out. The proposal should also explain how the proposed methods are robust and how the results will be validated. Consider how well the draft proposal addresses these areas:

1. Is the proposed measurement approach appropriate? Are the technologies being considered suitable, and will the proposed analysis yield relevant results?
2. Does the proposed work address all the deliverables outlined in the “Deliverables” section? If not, the proposal should not be considered for funding.
3. The review team will select only one draft proposal for development into a full proposal. If this draft proposal shows potential, what areas or topics should be prioritized or further explained in the full proposal?

Level and quality of effort to be provided(15 points)

Does the proposal allocate time and resources effectively to ensure the study objectives are met? Is the supervision and oversight sufficient to keep the project on schedule? Is the distribution appropriate for activities such as research, evaluation, analysis, data reduction, computer simulation, report preparation, meetings, and travel?

Cost effectiveness (20 points)

Is the cost appropriate for the proposed work? Does the proposed work appear feasible within the requested budget? Projects that include co-funding should be evaluated more favorably.

Scoring Criteria Scoring Guidance

91-100 points. Exceptionally strong. The submission is technically strong, meets stated research objectives, is cost-effective, and has a high potential to be successfully completed.

81-90 points. Strong. The submission is technically sound.

71-80 points. Mixed. The submission has either strong technical merit or strong policy significance, but not both.

61-70 points. Weak. The submission is not sufficiently linked to the needs of the Board and offers limited technical merit.

60 points or below. Unacceptable. The submission is not linked to the interests or needs of the Board and lacks technical merit.

[1]Bill Text - AB-617 Nonvehicular air pollution: criteria air pollutants and toxic air contaminants

[2]MATES VI; annual-air-toxics-report-2024.pdf; https://acp.copernicus.org/articles/22/10937/2022/?

[3]Rule 1180 - Refinery Community and Fenceline Air Monitoring

[4]https://acp.copernicus.org/articles/16/3979/2016/

[5]https://ww2.arb.ca.gov/measurements-vocs-socab-chemical-characterization-and-impacts-potential-ozone-and-pm-formation

[6]https://acp.copernicus.org/articles/12/7269/2012/