Marine phytoplankton is the largest natural carbon dioxide sequestrators and Earth’s climate regulators. However, their growth is largely limited by the iron (Fe) scarcity of seawater. The Fe in wind-blown aerosols such as mineral dust and fly ash, therefore, is the primary Fe sources to the phytoplankton. Before deposition, these Fe-bearing aerosols chemically interact with acidic gases such as nitric acid (HNO3) and water vapor in the atmosphere producing soluble Fe. The concentration of HNO3 in the atmosphere vary greatly depending on the extent of industrialization. In the current study, the growth of a marine diatom Cyclotella meneghiniana is studied in the presence of mineral dust Fe sources; hematite (Fe2O3) and ilmenite (FeTiO3). Further, the impact of a common semiconductor nanoparticle TiO2 is evaluated in the presence of hematite. The Fe solubility of each Fe source in HNO3 solutions (pH 2) maintained at 25 °C is determined over 48 hours. Ilmenite and hematite mixed with TiO2 produce 2037±123 μM/g and 2338±30 μM/g total dissolved Fe respectively whereas hematite alone produces only 1799±56 μM/g suggesting the higher bioavailable Fe production from Fe sources with high Ti:Fe ratio. In a different setup, the minerals are allowed to interact with water vapor and gaseous HNO3 for 48 hours to simulate the atmospheric-acidic processing. Both fresh and processed minerals are then added to Fe-starving seawater inoculums of c. meneghiniana and allow to grow under simulated light. The periodic chlorophyll absorbance measurements and the cell counts indicate higher diatom growth in the inoculums containing processed minerals compared to their respective fresh minerals 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 synergy of Ti on ocean Fe fertilization.

Impact of Ti containing nanoparticles on ocean Fe fertilization: Laboratory investigation of the growth of marine diatom, Cyclotella meneghiniana

2019 Fall National Meeting

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