Iodine compounds were measured above, below and within the sea ice of the Weddell Sea during a cruise in 2009, to make progress in elucidating the mechanism of local enhancement and volatilisation of iodine. I₂ mixing ratios of up to 12.4 pptv were measured 10 m above the sea ice, and up to 31 pptv was observed above surface snow on the nearby Brunt Ice Shelf – large amounts. Atmospheric IO of up to 7 pptv was measured from the ship, and the average sum of HOI and ICl was 1.9 pptv. These measurements confirm the Weddell Sea as an iodine hotspot. Average atmospheric concentrations of CH₃I, C₂H₅I, CH₂ICl, 2-C₃H₇I, CH₂IBr and 1-C₃H₇I were each 0.2 pptv or less. On the Brunt Ice Shelf, enhanced concentrations of CH₃I and C₂H₅I (up to 0.5 and 1 pptv respectively) were observed in firn air, with a diurnal profile that suggests the snow may be a source. In the sea ice brine, iodocarbons concentrations were over 10 times those of the sea water below. The sum of iodide + iodate was depleted in sea ice samples, suggesting some missing iodine chemistry. Flux calculations suggest I₂ dominates the iodine atom flux to the atmosphere, but models cannot reconcile the observations and suggest either a missing iodine source or other deficiencies in our understanding of iodine chemistry. The observation of new particle formation, consistent with the model predictions, strongly suggests an iodine source. This combined study of iodine compounds is the first of its kind in this unique region of sea ice rich in biology and rich in iodine chemistry

[1] Frost flowers play a role in air-ice exchange in polar regions, contribute to tropospheric halogen chemistry, and affect ice core interpretation. Frost flowers were observed and collected on the Hudson Bay in March 2008. Their specific surface area (SSA) was measured using CH 4 adsorption at 77 K. The Brunauer-Emmett-Teller analysis produced SSA values between 63 and 299 cm 2 g À1 (mean 162 cm 2 g À1 , accuracy and reproducibility 5%). This range is very similar to that of Dominé et al. (2005) but our correlation of results with growth time and chemistry reveals the factors responsible for the wide range of SSA values. Longer growth time leads to higher SSA at low temperatures, so frost flowers are more likely to affect total surface area during colder periods. Chemical analysis was performed on frost flower melt and on local seawater and brine. We examined salinity and sulfate and bromide enrichment. The relationship between growth time and salinity varied spatially because of a freshwater plume from a nearby river and of tidal effects at the coast. Enrichment of certain ions in frost flowers, which affects their contribution to atmospheric chemistry, depends heavily on location, growth time, and temperature. No significant enrichment or depletion of bromide was detected. The low surface area index of frost flowers plus their lack of destruction in wind suggest their direct effect on sea salt mobilization and halogen chemistry may be less than previously thought, but their ability to salinate wind-blown snow may increase their indirect importance.

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SummaryObjective Optimal thyroxine replacement following total thyroidectomy is critical to avoid symptoms of hypothyroidism. The aim of this study was to determine the best formula to determine the initiated replacement dose of levothyroxine immediately following total thyroidectomy. Design Prospective study. All patients were initiated on 100 lg levothyroxine and titrated to within the reference range for TSH and free T4. Correlations to height, weight, age, lean body mass (LBM), body surface area (BSA) and body mass index (BMI) were calculated. Patients One hundred consecutive adult patients underwent total thyroidectomy for non-malignant disease. Measurements Comparison between three methods of levothyroxine dose prediction, aiming for a levothyroxine dose correct to within 25 lg of actual dose required. Results Correlations were seen between levothyroxine dose and patient age (r = )0AE346, P < 0AE01), bodyweight (r = 0AE296, P < 0AE01), LBM (r = 0AE312, P < 0AE01), BSA (r = 0AE319, P < 0AE01) and BMI (r = 0AE172, P < 0AE05). A regression equation was calculated (predicted levothyroxine dose = [0AE943 · bodyweight] + [)1AE165 · age] + 125AE8), simplified to (levothyroxine dose = bodyweight ) age + 125) pragmatically. Initiating patients empirically on 100 lg post-operatively showed that 40% of patients achieved target within 25 lg of their required dose; this increased to 59% when using a weight-only dose calculation (1AE6 lg/kg) and to 72% using the simplified regression equation. Conclusions A simple calculated regression equation gives a more accurate prediction of initiated levothyroxine dose following total thyroidectomy, reducing the need for outpatient attendance for dose titration.