Trace metal fractional solubility in size-segregated aerosols from the
tropical eastern Atlantic Ocean
Abstract
Soluble and total trace metals were measured in size fractionated
aerosol samples collected over the tropical eastern Atlantic Ocean. In
samples that were dominated by Saharan dust, the size distributions of
total iron, aluminium, titanium, manganese, cobalt and thorium were very
similar to one another and to the size distributions of soluble
manganese, cobalt and thorium. Finer particle sizes (<
~3 µm) showed enhanced soluble concentrations of iron,
aluminium and titanium, possibly as a result of acid processing during
atmospheric transport. The difference in fine particle solubility
between these two groups of elements might be related to the hyperbolic
increase in the fractional solubility of iron, and a number of other
elements, during the atmospheric transport of Saharan dust, which is not
observed for manganese and its associated elements. In comparison to
elements whose solubility varies during atmospheric transport, the
stability of thorium fractional solubility should reduce uncertainties
in the use of dissolved concentrations of this element in seawater as a
proxy for dust deposition.