Production of molecular iodine and triiodide in the frozen solution of iodide: implication for polar atmosphere

Transcription

1 SUPPORTING INFORMATION Production of molecular iodine and triiodide in the frozen solution of iodide: implication for polar atmosphere Kitae Kim,, Akihiro Yabushita,, Masanori Okumura, Alfonso Saiz-Lopez, Carlos A. Cuevas, Christopher S. Blaszczak-Boxe, # Dae Wi Min, Ho-Il Yoon, Wonyong Choi,* School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang , Korea Korea Polar Research Institute (KOPRI), Incheon , Korea Department of Molecular Engineering, Kyoto University, Kyoto , Japan Department of Molecular and Material Sciences, Kyushu University, Kasuga, Fukuoka , Japan Atmospheric Chemistry and Climate Group, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain # Department of Physical, Environmental and Computer Sciences Medgar Evers College-City, University of New York, Brooklyn, NY 11235, USA * To whom correspondence should be addressed. wchoi@postech.edu; Fax:

2 Dye laser Nd 3+ :YAG laser fluorescence lamp Valve HRM NaI ice Valve HRM PMT detector Coolant outlet Coolant inlet Figure S1. Schematic diagram of the experimental setup of a photochemical reactor cell coupled with CRDS. HRM and PMT stand for high reflective mirror and photomultiplier tube, respectively.

3 log r = log [ H + ] log r log r = 1.12 log [ I - ] log r = 1.42 log [ O 2 ] log [ H + ] log [ I ] log [ O 2 ] 0 Figure S2. The rate law determination of reaction 1. The slope of the plot of (log r) vs. log [conc.] determines the order for each reactant. That is, the order for [H + ] is determined to be 0.5 and that for [I - ] and [O 2 ] is determined to be 1.0 and 1.5, respectively. Therefore, the following rate law is derived: d[i 3 ] (mol L 1 s 1 ) = r = [I ] 1 [O dt 2 ] 1.5 [H + ] 0.5

4 50 40 Aq Ice [I 3 - ] ( M) o C -10 o C -20 o C -30 o C Figure S3. Iodide photooxidation to triiodide at different temperature. Experimental conditions: [I - ] 0 = 1 mm, after 2 h UV irradiation, ph = 3

5 Abs [I - ] = 0.1 M (air) [I - ] = 0.1 M (O 2 ) Transmittance of Pyrex filter Transmittance Wavelength (nm) Figure S4. UV-visible absorption spectrum of CT complex (I O 2 ) in pure oxygen-saturated aqueous solution. The transmittance of the pyrex filter employed for photoexperiments was also shown (red solid line) for comparison.

6 Figure S5. Model simulations of the experimental results. Utilizing CON-AIR to exemplify the release of I 2 (g) at initial I - concentrations relevant to Antarctica. We have therefore conducted a modelling exercise to reproduce the range of I 2 production in the CDRS reactor for the range of [I - ] o = 1 to 10 M used in the experiments. The irradiation conditions used in the model are typical of surface irradiances at 75 South during the austral springtime. 28 The modelled I 2 concentrations are in blue circles. Then, we extrapolated to environmentally relevant 43 concentrations [I - ] o = 10 nm (highlighted in sky blue in the inset) using a line of best linear fit (r 2 = 0.989). Figure shows that a linear function perfectly fits the range of iodide conditions under which the I 2 flux was experimentally derived (Fig. 5b in the main manuscript). This shows that the model, and the derived I 2 flux, is consistent throughout the range of iodide values used in the laboratory experiments and those observed in real polar conditions.

7 Table S1. QLL Reactions and Rate Constants 28,29 No. Reactions Rate Constants 1. HOI + I - + H + I 2 + H 2 O M -2 s -1 /(volumetric) 2 2. I 2 + H 2 O HOI + I - + H + 0 s HOI + Br - + H + IBr + H 2 O M -2 s -1 /(volumetric) 2 4. IBr + H 2 O HOI + Br - + H s HOI + Cl - + H + ICl + H 2 O M -2 s -1 /(volumetric) 2 6. ICl + H 2 O HOI + Cl - + H s HOBr + Br - + H + Br 2 + H 2 O M -2 s -1 /(volumetric) 2 8. Br 2 + H 2 O HOBr + Br - + H s HOBr + Cl - + H + BrCl + H 2 O M -2 s -1 /(volumetric) BrCl + H 2 O HOBr + Cl - + H s BrCl + Br - Br 2 Cl M -1 s -1 /(volumetric) 12. Br 2 Cl - BrCl + Br s Br 2 Cl - Br 2 + Cl s Br 2 + Cl - Br 2 Cl M -1 s -1 /(volumetric) 15. BrCl + Cl - BrCl BrCl 2 - BrCl + Cl s M -1 s -1 /(volumetric) 17. HOBr + I - IBr + OH M -1 s -1 /(volumetric) 18. HOCl + Cl - + H + Cl 2 + H 2 O e (-3508 / T) M -2 s -1 /(volumetric) Cl 2 + H 2 O HOCl + Cl - + H e (-8012 / T) s HOCl + Br - + H + BrCl + H 2 O M -2 s -1 /(volumetric) BrCl + H 2 O HOCl + Br - + H + 0 s HOCl + I - + H + ICl + H 2 O e (-900 / T) M -2 s -1 /(volumetric) ICl + H 2 O HOCl + I - + H + 0 s O 2 + 4H + + 6I - 2H 2 O + 2I M -2 s -1 /(volumetric) I- + I 2 I M -1 s -1 /(volumetric) K = 700

8 Table S2. Henry Constants of iodine species 28,29 Species Henry Constants IO e (5862(1/T 1/To)) M atm -1 HOI e (5862(1/T 1/To)) M atm -1 I e (4431(1/T 1/To)) M atm -1 ICl e (5600(1/T 1/To)) M atm -1 IBr e (5600(1/T 1/To)) M atm -1

9 Table S3. Kinetic experiments for the rate constant determination for the reaction 1: O 2 (aq) + 4H + + 6I - 2H 2 O + 2I 3 - [H + ] 0 [ I - ] 0 [O 2 ] r(d[i - 3 ]/dt) 10 6 k k 10 2 (mol -2 L 2 min -1 ) (mol -2 L 2 s -1 ) *Initial concentrations ([H + ] 0, [I - ] 0, [O 2 ] 0 ) in [mol L -1 ]; r in [mol L -1 min -1 ] Average rate constant: k = 1.29 (±0.24) [mol -2 L 2 min -1 ] or k = 2.16(±0.40) 10-2 [mol -2 L 2 s -1 ]