A comparison of methyl iodide emissions from seawater and wet depositional fluxes of iodine over the southern North Sea

The results of measurements of sea-to-air fluxes of methyl iodide and air-to-sea wet depositional fluxes of iodide and iodate over the southern North Sea are reported. The estimated average annual flux of methyl iodide out of the southern North Sea is 8×10⁵ moles yr^-1 while the iodine deposition flux, based on average rainwater concentrations, is 6×105 moles yr^-1. Both emission fluxes of methyl iodide and deposition fluxes of total iodine show a modest seasonality with minimum fluxes in winter. The average concentration of iodine in the rainwater samples (n = 40) over a one year period was 6.8 + 7.5 nM for total iodine, 3.1 + 2.7 nM for iodate and 3.7 + 6.6 nM for iodide. There is no evidence of seasonality in the iodide/iodate ratio in rainwater over the year.