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

Increases in PM2.5 levels in Houston are associated with a highly recirculating sea breeze

Local land-sea breezes play an important role in coastal air quality because they circulate air between coastal/urban and marine areas, potentially causing the accumulation of pollutants. This has been observed for the secondary photochemical pollutant ozone. However, particulate matter (PM) also warrants investigation. To understand the complicated interactions between coastal urban air quality and a local land-sea breeze, we analyzed historical monitoring data from Houston, Texas, which is the fourth most populous city in the United States. Using k-means clustering algorithms to analyze wind data from Houston, we successfully identified a sea breeze recirculation cluster. Additionally, we performed positive matrix factorization on PM2.5 (2.5 μm in diameter or smaller) composition data for 2010-2018 from Houston Deer Park #2 monitoring site, 5 km south of the industrialized Houston Ship Channel. The resulting eight factors indicated a variety of anthropogenic, natural, primary and secondary sources. Emphasizing the PM2.5 sources in each of the wind clusters for June, July, and August, we discovered that on southernly wind and sea breeze recirculation days, the PM2.5 concentrations are ∼30% higher than those under other wind patterns. Under southerly wind, 53% of PM2.5 was attributed to long-range transport of soil and 15% to aged and fresh sea salt. In contrast, on days identified as being impacted by a sea breeze, 60% of PM2.5 was attributed to anthropogenic emissions and only 15% to soil sources. Secondary organic aerosol from multiple sources also appeared to be important on sea breeze days.

Bacteria involved in the sulfur cycle in tarballs collected from the Alabama Gulf Coast

Tarballs are formed from released or discharged crude oil containing sulfur compounds. A considerable amount and variety of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) were identified in tarballs collected from the intertidal and supratidal zones of Alabama's Gulf beaches. Amplicon sequencing of the bacterial 16S rRNA gene showed that SRB were more abundantly distributed in the core than on the surface of tarballs, while no significant differences were observed in the distribution of SOB. To our best knowledge, this is the first report on the spatial distribution of diverse SRB and SOB in tarballs.