Pacific Ocean aerosols: Deposition and solubility of iron, aluminum, and other trace elements

Abstract

The deposition of aerosols to the open ocean and the mechanisms controlling trace element solubility are important factors in the biogeochemical cycling of biolimiting elements, including iron, with implications for the global carbon cycle. During 2004–2006, 24-hour integrated aerosol samples were collected on two Climate Variability and Predictability (CLIVAR)-CO2 Repeat Hydrography cruises in the Pacific Ocean. The cruise sections traversed the North Pacific Ocean along 30°N (Section P02) and the eastern Pacific along 150°W (Section P16). This dataset includes analyses of aerosol particle chemistry as well as iron, aluminum, and manganese solubility in ultrapure deionized water and iron solubility in filtered surface seawater, measured using a rapid, flow-through extraction technique. The atmospheric concentrations of soluble aerosol iron were not significantly different using these extraction solutions (Wilcoxon signed rank, p=0.076). However, aerosol iron fractional solubility was higher in ultrapure deionized water than in filtered surface seawater (Wilcoxon signed rank, p=0.009). The median fractional solubility of aerosol iron in ultrapure water was 9.2% (3.2–29.1%) and 6.4% (0.5–81.1%) in seawater. Soluble aerosol Fe(II) accounted for 1.7% of the total aerosol Fe and 26.2% of the seawater soluble aerosol iron. The fractional solubility of aerosol iron did not increase with distance from Asian source regions nor was solubility related to the concentration of aerosol Fe in the atmosphere.