Rapid reaction of nanomolar Mn(II) with superoxide radical in seawater and simulated freshwater
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Abstract
Superoxide radical (O2−) has been proposed to be an important participant in oxidation−reduction reactions of metal ions in natural waters. Here, we studied the reaction of nanomolar Mn(II) with O2− in seawater and simulated freshwater, using chemiluminescence detection of O2− to quantify the effect of Mn(II) on the decay kinetics of O2−. With 3−24 nM added [Mn(II)] and <0.7 nM [O2−], we observed effective second-order rate constants for the reaction of Mn(II) with O2− of 6 × 106 to 1 × 107 M−1·s−1 in various seawater samples. In simulated freshwater (pH 8.6), the effective rate constant of Mn(II) reaction with O2− was somewhat lower, 1.6 × 106 M−1·s−1. With higher initial [O2−], in excess of added [Mn(II)], catalytic decay of O2− by Mn was observed, implying that a Mn(II/III) redox cycle occurred. Our results show that reactions with nanomolar Mn(II) could be an important sink of O2− in natural waters. In addition, reaction of Mn(II) with superoxide could maintain a significant fraction of dissolved Mn in the +III oxidation state.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Rapid reaction of nanomolar Mn(II) with superoxide radical in seawater and simulated freshwater |
| Series title | Environmental Science & Technology |
| DOI | 10.1021/es104014s |
| Volume | 45 |
| Issue | 7 |
| Year Published | 2011 |
| Language | English |
| Publisher | American Chemical Society |
| Description | 7 p. |
| First page | 2811 |
| Last page | 2817 |
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