Release of Arsenic from Volcanic Rocks through Interactions with Inorganic Anions and Organic Ligands |
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| Authors: | Barbara Casentini Maurizio Pettine Frank J Millero |
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| Institution: | (1) Water Research Institute, National Research Council, Via Salaria 29.300, C.P. 10, 00016 Monterotondo, Rome, Italy;(2) Marine and Atmospheric Chemistry, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA; |
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| Abstract: | The effects of a number of inorganic anions (F−, HCO3
−, B(OH)4−, Cl−, I−) and of the siderophore DFO-B on the release of As from volcanic rocks were investigated in batch experiments. While previously
reported field and laboratory data support a role of inorganic anions on As mobilization into aquifers, the role of siderophores
on As-induced mobilization was less investigated. Fluoride, bicarbonate and DFO-B have shown a significant influence on the
release of As from the rocks. Lava was mostly affected among the investigated rocks at pH 6 and 20°C by releasing 4% of its
initial As content in the presence of 0.01 M F−and 10% in the presence of 500 μM DFO-B. The effect of fluoride was larger at pH 6 than at pH 8.5 for all the rocks. In the
case of DFO-B, there was also a larger effect at pH 6 compared to pH 8 for the various rocks except tuff. Bicarbonate played
a role under alkaline conditions while its effect was negligible at pH 6. Anion exchange processes in the presence of fluoride
and bicarbonate and complexation processes in the presence of the siderophore DFO-B appear to be the major processes responsible
for the release of arsenic from the rocks. The siderophore DFO-B plays mainly an indirect role on the As release by complexing
Al, Fe and Mn, thus favoring the dissolution of the rocks and the consequent release of As bound to surface Al, Fe and Mn
oxy-hydroxides. These findings suggest that ionic interactions with fluoride, bicarbonate and siderophore may be a further
triggering factor in the mobilization of As from aquifer rocks. |
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