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

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.

Automated summary

In Spring 2021, we conducted measurements of submicron aerosols (PM1) at a beachfront site in Texas to understand the composition and factors influencing the background aerosols advecting into Texas. Our observations revealed that the marine background aerosols from the Gulf of Mexico were highly processed and acidic, with sulfate being the most abundant component (57% of total PM1 mass). These aerosol characteristics were similar to those observed in other marine locations worldwide. However, the Gulf background aerosols were significantly more polluted compared to other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico were found to contribute to 78.3% of the total measured background sulfate in the air. During haze episodes, we observed elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid in the air mass from the Gulf. Our analysis suggests that aqueous oxidation of shipping emissions by peroxides might be an important pathway for the rapid production of acidic sulfate and organosulfates during these haze episodes under acidic conditions.