We hypothesized that the nucleating agent of fog and dew in arid regions leads to precipitation of the aqueous ions in solution of the dew, sourced from the dust. I have some data from atmospheric dew that I collected in the same region as some desert varnish that we did a chemical analysis on as well. Confirming MnO2 and Mn2O3 along with Fe2O3 and Fe(OH)2 are present in the desert varnish. Higher resolution isotopic data combined with more sample localities will improve this research. Therefore, what do you guys think of combining electron mircoprobe data from varnish thin sections with an ICP-MS analysis of atmospheric nanodroplets of water for their dissolved ions?
Research Proposal Trace Elements in Atmospheric Aerosols and the Origin of Des...
Yes, this one of the main theory for the varnish formation in arid desert environments: the leaching of mineral dust (e.g. clay minerals) at a lower pH in fog/rain and the subsequent precipitation on the rock substrate (though this is complex regarding the mechanism). We did measure varnishes from several regions, as well as dust collected on top and next to varnishes for comparison. However, we did not have the opportunity to collect fog/rain/dew in the deset environments, which is actually the third missing component which needs to be investigated now. So next to measuring the ions (and maybe their oxidation states by titration), you could consider to measure the pH and Eh of the solution as well. Do you have data yet? One could also consider to measure the pH/Eh on the varnish surface (and its change over the day before, during and after fog events) in comparison to the fog/rain itself, to observe if there is indeed the pH shift needed for the oxidation from Mn2+ to Mn4+. This work is quite important and would close the gap regarding the source...and maybe even the precipitation.
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