Gas-phase mercury in the atmosphere of the United Kingdom

Measurements of total gaseous mercury have been made over a period of 1 yr using a cold vapour atomic fluorescence absorption technique at Harwell, a rural site in central southern England. The mean concentration was 1.68 ng m−3, with a maximum hourly mean concentration of 20.5 ng m−3 and a minimum hourly mean concentration of 0.26 ng m−3. Gaseous mercury concentrations are not greatly different from those measured at a remote rural site in Ireland, nor other measurements in Europe. The data from Harwell show greater variability than those from more remote sites but indicate a “background” of approximately 1.5 ng m−3, which is consistent with these other data. The diurnal variability of gaseous mercury at this site suggests a surface source, estimated to be of the order of 15 ng m−2 day. Two fossil-fuel combustion plants were located in the same 30° wind sector but no clear effect of these sources on gaseous mercury concentrations could be established, using sulphur dioxide as a tracer in combination with meteorological data.