Publication Date:
2017-11-01
Description:
The fractional solubility of aerosol-derived trace elements deposited to the ocean surface is a key parameter of many marine biogeochemical models. Yet, it is currently poorly constrained, in part due to the complex interplay between the various processes that govern the solubilisation of aerosol trace elements. In this study, we used a sequential two-stage leach to investigate the fractional solubility of a suite of aerosol trace elements (Al, Ti, Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb) from samples collected during three GEOTRACES cruises to the North Atlantic Ocean. Regardless of the leaching protocol used (mild versus strong leach), the same trends were observed. These were that trace elements from aerosols from 1) North Africa were always the least soluble, and the most homogeneous (e.g. Fe was 0.36 ± 0.12 % and 6.0 ± 1.0 % soluble in North African and 6.5 ± 5.5 % and 17 ± 11 % soluble in non-African aerosols following leaches with ultra-high purity water, and 25 % acetic acid, respectively), 2) aerosols from the most remote locations were generally the most soluble, but had the most spread in the values of fractional solubility and 3) primarily pollution-derived TEs (Ni, Cu, Zn, Cd and Pb) were significantly enriched above crustal values in aerosols, even in samples of North African origin. We present aerosol trace element solubility data from two sequential leaches that provides a solubility window, covering a conservative, lower limit to an upper limit, the maximum potentially soluble fraction, and demonstrate why this lower limit of solubility may underestimate aerosol TE solubility in some regions. The leaching technique that yields the upper limit can also be used to estimate trace element solubility from suspended particulate matter (SPM). Therefore, facilitating direct comparison with SPM leached using the same technique, thereby introducing some degree of standardisation between aerosol and SPM trace element solubility studies which may help inform of in-water processes that modify the solubility, and thus bioavailability, of atmospheric particles following deposition to the surface ocean.
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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