TY - JOUR
T1 - Iron dissolution and speciation in atmospheric mineral dust
T2 - Metal-metal synergistic and antagonistic effects
AU - Hettiarachchi, Eshani
AU - Reynolds, Richard L.
AU - Goldstein, Harland L.
AU - Moskowitz, Bruce
AU - Rubasinghege, Gayan
N1 - Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/8
Y1 - 2018/8
N2 - Under acidic atmospheric conditions, iron leached from atmospheric mineral dust may influence the distribution of bioavailable iron at a global scale. However, the effects of non-Fe-containing minerals on iron dissolution remain unknown. This work describes metal-metal synergistic and antagonistic effects on iron dissolution that go beyond aggregation and ionic strength effects in mineral dust mixtures. In this study, we investigated iron mobilization by proton-promoted dissolution in natural mineral dust samples from the Kalahari Desert (SZ1) and Australian Red Dawn event (RO), along with one iron oxide proxy, hematite. The total iron dissolution in natural dust samples highly corresponds with the respective amount of Ti, rather than their particle sizes or Fe contents. The dust sample with high Ti content, SZ1, also showed a higher fraction of dissolved Fe(II), under dark conditions. These observations are in good agreement with the dissolution data for hematite artificially mixed with metal oxides. Total iron dissolution in hematite, mixed with TiO2, is 1.5- and 2-fold higher compared to that of just hematite under dark and light conditions, respectively. However, dissolution of hematite is suppressed when mixed with Al2O3 and CaO. Under dark conditions, furthermore, dissolved Fe(II) fraction is enhanced for hematite when mixed with TiO2 compared to that of other mixtures or hematite alone. Yet, dissolved Fe(II) is lower in hematite mixed with TiO2 under light conditions compared to that of hematite alone, suggesting photo-oxidation of Fe(II) by reactive oxygen species, such as OH radicals.
AB - Under acidic atmospheric conditions, iron leached from atmospheric mineral dust may influence the distribution of bioavailable iron at a global scale. However, the effects of non-Fe-containing minerals on iron dissolution remain unknown. This work describes metal-metal synergistic and antagonistic effects on iron dissolution that go beyond aggregation and ionic strength effects in mineral dust mixtures. In this study, we investigated iron mobilization by proton-promoted dissolution in natural mineral dust samples from the Kalahari Desert (SZ1) and Australian Red Dawn event (RO), along with one iron oxide proxy, hematite. The total iron dissolution in natural dust samples highly corresponds with the respective amount of Ti, rather than their particle sizes or Fe contents. The dust sample with high Ti content, SZ1, also showed a higher fraction of dissolved Fe(II), under dark conditions. These observations are in good agreement with the dissolution data for hematite artificially mixed with metal oxides. Total iron dissolution in hematite, mixed with TiO2, is 1.5- and 2-fold higher compared to that of just hematite under dark and light conditions, respectively. However, dissolution of hematite is suppressed when mixed with Al2O3 and CaO. Under dark conditions, furthermore, dissolved Fe(II) fraction is enhanced for hematite when mixed with TiO2 compared to that of other mixtures or hematite alone. Yet, dissolved Fe(II) is lower in hematite mixed with TiO2 under light conditions compared to that of hematite alone, suggesting photo-oxidation of Fe(II) by reactive oxygen species, such as OH radicals.
KW - Bioavailable iron
KW - Iron dissolution
KW - Mineralogy effects
KW - Photochemistry
KW - Redox cycling
KW - Titanium dioxide
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U2 - 10.1016/j.atmosenv.2018.06.010
DO - 10.1016/j.atmosenv.2018.06.010
M3 - Article
AN - SCOPUS:85048709795
SN - 1352-2310
VL - 187
SP - 417
EP - 423
JO - Atmospheric Environment
JF - Atmospheric Environment
ER -