We report an investigation of the photolysis kinetics of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution, frozen in ice, and at air-ice interfaces. Measurements of PAH photolysis rates in aqueous solution and at air-ice interfaces as a function of lamp power show that the kinetics depend nonlinearly on photon flux. In both media, the rates do not increase when lamp powers are above 0.1 W, which corresponds to total photon fluxes lower than 10(13) photon cm(-2) s(-1) in the actinic region. This suggests that extrapolating laboratory-measured rates to expected atmospheric photon fluxes may not yield accurate lifetimes for some species. In the plateau region of the photon flux dependence, anthracene located within the ice matrix (or in liquid pockets or veins in the ice) undergoes photolysis at a similar rate to that in room temperature aqueous solution, but the rate of anthracene photolysis at air-ice interfaces is five times greater. This indicates that in order to accurately predict the lifetimes of aromatic pollutants in snow and ice, the quasi-liquid layer (QLL) must be treated separately from bulk ice.

[1] Springtime ozone depletion events have been linked to elevated levels of bromine in the polar boundary layer. It has also been suggested that iodine may play an important role in boundary layer chemistry. However, the mechanism(s) for initial halogen activation is not well understood. We report results of experiments using glancing-angle laser-induced fluorescence (LIF) and glancing-angle Raman spectroscopy to investigate the heterogeneous reaction of gas-phase ozone with bromide and iodide ions at the surface of frozen salt solutions. The results suggest that halides that have been excluded to the ice surface during the freezing process react in the dark and under non-acidified conditions to produce molecular halogen species. At environmentally relevant bromide concentrations, the reaction proceeds ∼60 times more rapidly at ice surfaces than at the surface of aqueous solutions. At an ozone concentration of ∼8 × 10 15 molec cm −3 , and sea water concentrations of bromide and iodide, we estimate uptake coefficients g(Br − ) = (1.3 ± 0.5) × 10 −8 and g(I − ) = (1.6 ± 0.5) × 10. We estimate that at atmospheric ozone concentrations, the uptake coefficients will be approximately a factor of ten greater.Citation: Wren, S. N., T. F. Kahan, K. B. Jumaa, and D. J. Donaldson (2010), Spectroscopic studies of the heterogeneous reaction between O 3 (g) and halides at the surface of frozen salt solutions,

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Objectives: To assess the benefits associated with radioactive seed localization (RSL) in comparison to conventional wire localization (WL) for nonpalpable breast lesions. Methods: Radioactive seed localization was initiated at our institution in July 2013. Retrospective review of all WL performed between June 2012 and July 2013 (2013) and all RSL performed during June 2015 and July 2016 (2016). Patients who received neoadjuvant therapy or did not undergo their planned surgeries and WL performed in 2016 were excluded. The following data were collected: final pathology, resection margins for malignant lesions, time to surgery, seed migration, and number of localized lumpectomies performed by each surgeon. Results: A total of 292 WL procedures (288 women) in 2013 and 194 RSL procedures (186 women) in 2016 were eligible for the study. All WLs were inserted the day of surgery. Mean time from RSL insertion to surgery was 4.0 ± 2.8 days (range: 1-17 days). There was no difference in specimen size for malignant lesions (6.8 ± 2.8 cm for WL and 6.9 ± 2.9 cm for RSL; P = .5). Specimen radiographs were obtained in 233 (80%) of 292 WL compared to 194 (100%) of 194 RSL ( P < .001). For malignant lesions, positive margins were present in 34 (17.2%) of 198 with WL compared to 15 (10.3%) of 146 with RSL ( P < .001). Close margins (≤1 mm) were present in 31 (15.6%) of 198 with WL compared to 1 (0.6%) of 146 with RSL ( P < .001). The seed fell out of the specimen during surgery in 6 (3.1%) of 194. No seed loss was recorded. The surgeons (n = 4) who transitioned to RSL increased the number of surgeries per month from a mean of 4.4 ± 2.6 in 2013 to 6.9 ± 3.5 in 2016, equivalent to a 41% increase ( P = .003). Conclusions: The use of RSL, as compared to conventional WL, resulted in a reduction in the number of pathologically involved surgical margins and was associated with an increased number of surgeries. Furthermore, RSL can be performed up to 14 days prior to surgery, which may improve scheduling flexibility in the radiology department.

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