A large part of oceanic biological production is limited by the scarcity of dissolved iron. Mineral dust aerosols, processed under acidic atmospheric conditions, are the primary natural source of bioavailable iron to oceanic life. However, the mineralogical impact on atmospheric processing of Fe-containing mineral dusts as well as that on the phytoplankton growth is poorly understood. The current study focuses on the mineralogical influence on Fe solubility under atmospherically relevant conditions using natural dust samples collected from the Kalahari Desert and selected proxies for Fe-containing minerals, i.e. ilmenite (FeTiO3), hematite (Fe2O3), and hematite mixed with TiO2. Further, the growth of a marine diatom, Cyclotella meneghiniana, was evaluated with respect to these different Fe sources. The solubility experiments were conducted over 48 hours, with a daytime: nighttime ratio of 16h/8h, where the daytime was simulated with a Sol1 ABB solar simulator. At the end of the 48th hour, Ti-bearing mineral dust showed comparatively higher Fe solubility in aerated nitric acid solutions (pH 2) maintained at 25 °C. Ilmenite and hematite mixed with TiO2 produced 2037±123 μM/g and 2338±30 μM/g total dissolved Fe respectively whereas hematite alone produced only 1799±56 μM/g. In a different setup, fresh dust samples were allowed to interact with water vapor and gaseous nitric acid for 48 hours to simulate the atmospheric-acidic processing and the formation of deliquescence layer. Both fresh and processed dust were then added to Fe starved seawater inoculums of c. meneghiniana and allowed to grow under simulated light. The periodic chlorophyll absorbance measurements and the cell counts indicate higher diatom growth in the inoculums containing processed dusts compared to their respective fresh dust containing counterparts. Further, the diatom growth is relatively higher in inoculums containing higher Ti:Fe ratio compared to others without such a significant amount of Ti, indicating the mineralogy dependency of ocean Fe fertilization.

Mineralogy dependent atmospheric processing of mineral dust aerosols and their impact on the growth of marine diatoms

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.