Grantee Research Project Results
2022 Progress Report: Real-Time Analysis of Aerosol-Phase Plastic Additives in a Coastal Marine Environment in California
EPA Grant Number: R840424Title: Real-Time Analysis of Aerosol-Phase Plastic Additives in a Coastal Marine Environment in California
Investigators: Slade, Jonathan H
Institution: University of California San Diego
EPA Project Officer: Chung, Serena
Project Period: May 1, 2022 through April 30, 2025
Project Period Covered by this Report: May 1, 2022 through April 30,2023
Project Amount: $399,464
RFA: Measurement and Monitoring Methods for Air Toxics and Contaminants of Emerging Concern in the Atmosphere (2021) RFA Text | Recipients Lists
Research Category: Early Career Awards , Air Quality and Air Toxics
Objective:
The research's main goal is to quantify emerging concern contaminants, such as plastic additives, personal care product additives, and antimicrobials, within sea spray aerosol (SSA) particles along the coastal region of San Diego, CA. This will be achieved using online extractive electrospray ionization (EESI-TOF) high-resolution mass spectrometry. We intend to identify relationships between aerosol mass concentrations of these contaminants and factors like season, time of day, air mass origin, wave height, and oceanic biological activity.
In the initial project year, our objectives encompassed: (1) calibrating an Aerodyne EESI-TOF mass spectrometer for direct quantification of contaminants in their native aerosol state, (2) standardizing the EESI-TOF measurement approach by introducing an internal aerosol standard to detect variations in instrument sensitivity in the field, and (3) conducting our inaugural field study.
Progress Summary:
Summarizing our achievements from the project's first year, we have (1) established a functional protocol for automated aerosol sampling, standardization, and sensitive detection of contaminants in the field using the EESI-TOF mass spectrometer, (2) progressed in quantifying contaminants during our inaugural field deployment, MATADOR (Measuring Airborne Toxics And Determining Oceanic Relationships), in Winter 2023 in San Diego, CA, and (3) delineated statistical connections between measured aerosol contaminant concentrations, SSA generation, and their reliance on factors like hydrophobicity (selective transfer in SSA), environmental parameters such as wave height, wind direction (air mass origin), and oceanic biological activity.
From our analysis of aerosols and seawater collected across multiple coastal sites in San Diego, CA prior to this study, a concentration gradient in contaminant levels has been identified, quantified offline using LC-MS2, in both aerosol and water—from the Tijuana River outflow to the farthest northern site, La Jolla, CA. In this investigation, benzoylecgonine, a cocaine metabolite, emerged as a representative marker for polluted SSA. We observed correlations between benzoylecgonine and the toxic sunscreen ultraviolet filter, octinoxate, the illicit drug, methamphetamine, and the rubber additive, dibenzylamine, in aerosol, indicating a common source within polluted SSA. A targeted semiquantitative analysis of 15 contaminant molecules displayed noticeable enrichment in aerosol relative to seawater, with enrichment levels escalating as hydrophobicity increased, parameterized by the octanol-water partitioning coefficient. Nonetheless, air-water interfacial adsorption also contributes to the enrichment process. Employing Global Natural Products Social (GNPS) molecular networking for non-targeted analysis of MS1 and MS2 mass spectra, 390 contaminants were identified in both aerosol and sea water samples. Trajectory analyses revealed statistically significant enhancements (p<0.05) in personal care product compounds in coastal aerosol during periods of marine influence, contrasting with land-influenced air masses. Plastic compounds, on the other hand, exhibited significantly higher concentrations in land and mixed land- and marine-influenced air masses compared to primarily marine-influenced air masses.
Our EESI-TOF was deployed during the Winter MATADOR field study on the Scripps Pier at SIO in La Jolla, CA, spanning from mid-February to mid-March 2023. Measurements occurred continuously, with aerosol filter samples and seawater collected in 11-hour cycles, covering both day and night periods throughout the study. A notable accomplishment was the development of a setup allowing single-point standardizations of the EESI-TOF using a standard aerosol, facilitating high-frequency sensitivity measurements. While still in its early stages, our measurements unveiled the following relationships: (1) all targeted contaminants measured by EESI-TOF exhibited positive correlations among themselves, (2) coastal aerosol contaminant levels displayed an exponential dependence on wave height akin to SSA number flux's dependence on wave height, and (3) aerosol contaminant levels showed positive correlations with aerosol volume and chloride concentration measured through an aerosol chemical speciation monitor, while demonstrating a negative correlation with aerosol number concentration.
Future Activities:
During the upcoming reporting period, activities will concentrate on four primary areas: (1) enhancing EESI-TOF detection sensitivity by employing near-ambient aerosol concentrations for standard calibration, (2) calibrating LC-MS2 and determining extraction efficiencies for both aerosol filter and seawater samples, (3) analyzing aerosol and seawater contaminants using LC-MS2 based on samples collected during the Winter 2023 study, and (4) executing two additional field studies in Summer 2023 and Winter 2024. These studies will facilitate the identification of diurnal and seasonal trends, along with confirming the structure of detected contaminants for comparison with EESI-TOF measurements. Our intent is to publish the findings based on our previous field measurements and the intercomparison between EESI-TOF and LC-MS2.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 8 publications | 2 publications in selected types | All 2 journal articles |
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Cooper AW, Rogers MM, Wiggin KJ, Slade JH. We need a “Keeling curve” approach for contaminants of emerging concern. Environmental Science & Technology 2023;57:10147–50. |
R840424 (2022) |
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Supplemental Keywords:
Plastics, additives, aerosol, marine, mass spectrometryRelevant Websites:
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.