The elemental signature of transported Asian dust at Mauna Loa observatory

Dust storms in Asia's interior deserts loft immense quantities of continental crust that are blown over the North Pacific Ocean every year. The transported mineral aerosol is first lofted and then experiences mixing and fallout during the transport. Its elemental signature is no longer that of bulk soil. The concentration for many elements is greater in transported crust compared to bulk soil due to a difference in mineralogy of the small crustal particle. Small particles are defined as those below 100 mu m in diameter. The elements Al, Mg, Ca and Na do not experience an internal concentration change with particle size. Many of the elements in the MLO mineral aerosol have concentrations that are greater than 1.5 times that of bulk soil. Iron, an important biological agent, has twice the concentration in the MLO mineral aerosol than in bulk soil. The elemental to Al concentration ratios observed are consistent, implying that the transported crustal material is below 20 mu m in diameter.