Atmospheric processing outside clouds increases soluble iron in mineral dust

Zongbo Shi, Michael D. Krom, Steeve Bonneville, Liane G. Benning

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)
175 Downloads (Pure)

Abstract

Iron (Fe) is a key micronutrient regulating primary productivity in many parts of the global ocean. Dust deposition is an important source of Fe to the surface ocean, but most of this Fe is biologically unavailable. Atmospheric processing and reworking of Fe in dust aerosol can increase the bioavailable Fe inputs to the ocean, yet the processes are not well understood. Here, we experimentally simulate and model the cycling of Fe-bearing dust between wet aerosol and cloud droplets. Our results show that insoluble Fe in dust particles readily dissolves under acidic conditions relevant to wet aerosols. By contrast, under the higher pH conditions generally relevant to clouds, Fe dissolution tends to stop, and dissolved Fe precipitates as poorly crystalline nanoparticles. If the dust-bearing cloud droplets evaporated again (returning to the wet aerosol stage with low pH), those neo-formed Fe nanoparticles quickly redissolve, while the refractory Fe-bearing phases continue to dissolve gradually. Overall, the duration of the acidic, wet aerosol stage ultimately increases the amount of potentially bioavailable Fe delivered to oceans, while conditions in clouds favor the formation of Fe-rich nanoparticles in the atmosphere.
Original languageEnglish
Pages (from-to)1472-1477
JournalEnvironmental Science & Technology
Volume49
Issue number3
Early online date9 Jan 2015
DOIs
Publication statusPublished - 3 Feb 2015

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