The mineral make-up of iron-containing particles determines their solubility in sea water, according to a study published online in Nature Geoscience. Iron can stimulate biological productivity in many regions of the world ocean, but only if it exists in a readily dissolvable form.

Andrew Schroth and colleagues analysed the solubility and mineral make-up of iron in aerosols derived from arid soils, glacial weathering products and oil combustion products. Less than 1% of the iron in arid soils was soluble, whereas 2-3% of the iron in glacial products and over 77% of the iron in oil combustion products dissolved. Iron solubility was directly linked to the chemical form of the iron.

The authors suggest that changes in the distribution of deserts, glaciers and fossil-fuel combustion could have a pronounced effect on aerosol iron solubility, and therefore on biological productivity and the ocean carbon cycle.