Marine Submicron Aerosols from the Gulf of Mexico: Polluted and Acidic with Rapid Production of Sulfate and Organosulfates

Abstract

We measured submicron aerosols (PM1) at a beachfront site in Texas in Spring 2021 to characterize the “background” aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine “background” aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM1 mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf “background” aerosols were much more polluted; the average non-refractory (NR-) PM1 mass concentration was 3–70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured “background” sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Emission Ratios and Diurnal Variability of Volatile Organic Compounds and Influence of Industrial Emissions in Two Texas Cities

“…The instrumentations were housed in a Baylor University/University of Houston/Rice University-operated mobile air quality lab (MAQL2) during both campaigns. MAQL2 is a 35 m 3 insulated air-conditioned trailer with a ~10 m telescoping tower and inlet box that extends above the trailer during stationary measurements [15]. A heated sampling line set at 70 • C (Atmo-Seal Engineering Inc., Troy, MI, USA) was used for VOC measurements.…”

“…Total reactive nitrogen (NO y ) measurements were conducted using a modified Thermo Scientific Model 42C chemiluminescence analyzer with a 300 • C molybdenum converter at the sample inlet. Greater details about these measurements are presented in our previous publications [13][14][15]. The Baylor PTR-MS is operated in select ion mode; the PTR-MS data reported in this study are only for a select list of VOCs: isoprene (m/z 69), methyl vinyl ketone (m/z 73), benzene (m/z 79), toluene (m/z 93), and xylenes (m/z 107), measured in the H 3 O + mode.…”

“…BTX in Texas cities have likely been impacted by increasing population and changes in local industry and vehicle emission technology [12]. The Texas Commission on Environmental Quality (TCEQ) has recently funded a series of urban field campaigns to evaluate O 3 precursors, including volatile organic compounds (VOCs), such as BTX in Corpus Christi, San Antonio, and Houston, Texas [13][14][15]. However, each city will have its signature blend of emission sources and regional transport of pollutants.…”