Iron Mobilization in Mineral Dust : Can Anthropogenic SO 2 Emissions Affect Ocean Productivity ?

In order for Fe contained in aeolian dust to act as a micronutrient for oceanic phytoplankton it must be first mobilized or dissolved. We propose that significant Femobilization can occur in mineral dust from East Asia as a result of the incorporation of SO2 from pollutant emissions into the advecting dust plumes and the subsequent acidification of the dust by heterogeneous SO2 oxidation. To test this acid-mobilization hypothesis, we consider a dust plume that originated from the gobi deserts and advected over the Yellow Sea in March of 2001. Data collected during the TRACE-P field campaign confirm that this plume contained high concentrations of both dust and SO2. Measurements within the plume of significant concentrations of gaseous HNO3 suggest that the dust particles were highly acidified (i.e., pH< 2). At these pH’s, approximately 1– 2% of the Fe contained in a deliquescent mineral dust particle would be mobilized within the nominal 3–5 day lifetime of the particle. These results suggest that there may be a link between the rate of C-fixation in so-called High-Nitrate-Low-Chlorophyll regions of the ocean and the rate of SO2 emissions from East Asia.