Pyrogenic iron: The missing link to high iron solubility in aerosols

Area of Science:

• Oceanography
• Atmospheric Chemistry
• Biogeochemistry

Background:

• Atmospheric deposition of iron (Fe) influences marine biological productivity.
• High aerosol Fe solubility compared to soil particles remains a subject of debate, with several proposed hypotheses.
• Understanding iron solubility is critical for marine ecosystem dynamics.

Purpose of the Study:

• To statistically analyze aerosol Fe solubility using multiple models and field observations.
• To identify the primary sources of highly soluble aerosols.
• To assess the discrepancy between model estimations and field data in the Southern Ocean.

Main Methods:

• Statistical analysis of aerosol Fe solubility data.
• Compilation of observations from multiple field campaigns.
• Comparison of four different models with empirical data.

Main Results:

• Pyrogenic aerosols identified as the main source of high Fe solubility at low concentrations.
• Field data from the Southern Ocean show a wider range of Fe solubility than models suggest.
• Models underestimate labile Fe concentrations by a factor of 15 in the Southern Ocean.

Conclusions:

• Pyrogenic Fe-containing aerosols are significant contributors of bioavailable atmospheric iron to the open ocean.
• Accurate assessment of aerosol Fe solubility is vital for predicting marine productivity.
• These findings highlight the importance of considering pyrogenic sources in marine biogeochemical models and climate change predictions.