Environ. Sci. Technol. 2006, 40, 1372
2005, Volume 39, 6130-6137 Charlotte E. Jones and Lucy J. Carpenter*: Solar Photolysis of CH2I2, CH2ICl, and CH2IBr in Water, Saltwater, and Seawater. There are errors in the reported values of the absorption cross sections (Figure 2 and Appendix 1) and corresponding quantum yields (Table 3) of CH2I2, CH2IBr, and CH2ICl, due to the absorption cross sections being reported in base 10 rather than in base e and a calibration error on the Schimadzu PharmaSpec 1700 UV-vis spectrophotometer. The correct versions are shown below. The corrected values change the interpretation of the difference in gas and aqueous phase absorption cross sections (p 6132). The corrected aqueous phase absorption cross sections are increased relative to the gas-phase values and the differences are consistent with the (refractive index-dependent)
TABLE 3. Apparent Quantum Yields in Water, 0.5 M NaCl, and Seawater halocarbon
quantum yield in water
quantum yield in 0.5 M NaCl
quantum yield in seawater
CH2I2 CH2IBr CH2ICl
0.31 ( 0.04 0.29 ( 0.04 0.13 ( 0.01
0.31 ( 0.04 0.29 ( 0.05 0.15 ( 0.03
0.31 ( 0.05 0.26 ( 0.09 0.13 ( 0.04
a Yields in 0.5 M NaCl are based on photolysis rates from combined data sets given in Table 2; water and seawater quantum yields are from single data sets and therefore generally have larger errors.
Appendix 1. Absorption Cross-Sections for Dihalomethanes in 0.5 M NaCl Solution 10-20σ/cm2 λ/nm
CH2I2
CH2IBr
CH2ICl
390 385 380 375 370 365 360 355 350 345 340 335 330 325 320 315 310 305 300 295 290 285 280 275 270 265 260 255 250 245 240 235 230 225 220 215 210 205
0.00 0.00 0.00 0.00 0.00 0.00 2.10 7.90 16.65 32.70 55.86 91.20 137.06 193.91 257.04 317.95 376.90 427.11 467.05 490.47 502.58 501.40 480.60 430.00 352.36 270.83 214.77 202.34 221.02 240.43 240.76 227.60 236.42 292.81 401.84 590.36 909.82 760.58
0.00 0.00 0.00 0.00 0.00 0.07 0.13 0.20 0.39 2.00 2.91 3.71 5.30 9.53 15.47 22.46 31.57 42.37 56.57 75.64 102.54 136.65 176.91 219.71 260.60 285.81 286.44 259.54 214.62 166.53 134.32 136.02 197.67 351.70 591.32 765.27 774.59 723.32
0.00 0.00 0.00 0.00 0.00 0.09 0.18 0.27 0.53 1.06 1.86 2.92 4.52 6.64 9.21 12.49 16.56 21.88 28.96 39.68 55.45 76.44 101.42 127.91 150.85 163.07 161.39 148.01 127.46 103.72 81.23 61.47 45.26 34.72 33.22 54.92 171.04 275.74
Chako correction. The discussions on p 6132 and p 6135 regarding the much higher quantum yield of CH2I2 compared to those of CH2IBr and CH2ICl are erroneous; in fact, the corrected quantum yields (0.31 ( 0.05, 0.26 ( 0.09, and 0.13 ( 0.04 in seawater for CH2I2, CH2IBr, and CH2ICl, respectively), are now in the same relative order as the isophotoisomer quantum yields reported by Tarnovsky et al. (12). FIGURE 2. Absorption cross-sections of (a) CH2I2, (b) CH2IBr, and (c) CH2ICl. Thin gray lines correspond to the gas-phase absorption cross-sections (22, 23); thick black lines represent cross-sections of dihalomethanes dissolved in 0.5 M NaCl.
ES058022E 10.1021/es058022e Published on Web 01/07/2006
