Does Sea Spray Aerosol Contribute Significantly to Aerosol Trace Element Loading? A Case Study From the U.S. GEOTRACES Pacific Meridional Transect (GP15). Issue 8 (8th August 2022)

• Record Type: Journal Article
• Authors: Marsay, Chris M.; Landing, William M.; Umstead, Devon; Till, Claire P.; Freiberger, Robert; Fitzsimmons, Jessica N.; Lanning, Nathan T.; Shiller, Alan M.; Hatta, Mariko; Chmiel, Rebecca; Saito, Mak; Buck, Clifton S.
• Is Part Of: Global biogeochemical cycles. Volume 36:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-08
• Subjects: aerosols -- trace elements -- GEOTRACES -- sea spray aerosol -- Pacific Ocean; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2022GB007416
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Atmospheric deposition represents a major input for micronutrient trace elements (TEs) to the surface ocean and is often quantified indirectly through measurements of aerosol TE concentrations. Sea spray aerosol (SSA) dominates aerosol mass concentration over much of the global ocean, but few studies have assessed its contribution to aerosol TE loading, which could result in overestimates of "new" TE inputs. Low‐mineral aerosol concentrations measured during the U.S. GEOTRACES Pacific Meridional Transect (GP15; 152°W, 56°N to 20°S), along with concurrent towfish sampling of surface seawater, provided an opportunity to investigate this aspect of TE biogeochemical cycling. Central Pacific Ocean surface seawater Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Pb concentrations were combined with aerosol Na data to calculate a "recycled" SSA contribution to aerosol TE loading. Only vanadium was calculated to have a SSA contribution averaging >1% along the transect (mean of 1.5%). We derive scaling factors from previous studies on TE enrichments in the sea surface microlayer and in freshly produced SSA to assess the broader potential for SSA contributions to aerosol TE loading. Maximum applied scaling factors suggest that SSA could contribute significantly to the aerosol loading of some elements (notably V, Cu, and Pb), while for others (e.g., Fe and Al), SSA contributions largely remained <1%. Our study highlights that a lack of focused measurements of TEs in SSA limits our ability to quantify this component of marine aerosol loading and the associated potential for overestimating new TE inputs from atmospheric deposition. Plain Language Summary: Sea spray aerosol (SSA) generated by breaking waves and bursting bubbles can dominate the particle population in the marine atmosphere. We investigated whether this mechanism could mobilize significant amounts of trace elements (TEs)—nutrient and pollutant elements present in the surface ocean in very low concentrations. Previous studies have suggested that TEs could become enriched on SSA during its formation, relative to their concentrations in seawater, and this could make the process a more significant source for aerosol concentrations of some elements. But for others, the SSA contribution is always likely to be insignificant. Our calculations based on sea salt and TE aerosol concentrations in the atmosphere and dissolved TEs in the surface ocean suggest that SSA does not contribute significantly to total aerosol TE loading, with the possible exception of vanadium, which has relatively higher concentrations in seawater than the other elements considered. This study highlights that this process remains poorly quantified due to limited direct measurements. Key Points: Sea spray aerosol (SSA) concentration was quantified along a meridional Pacific Ocean transect during low mineral aerosol conditions Sea spray‐derived aerosol trace elements (TEs) are negligible unless significant enrichment occurs during formation; only vanadium is >1% SSA contributions to aerosol TEs of >100% calculated by applying enrichments from earlier studies suggests these are not widely applicable