Ten years of mercury measurement at urban and industrial air quality monitoring stations in the UK

•Concentrations from 10 years of gaseous mercury measurements across the UK.•Emissions and ambient concentrations of mercury have fallen over this period.•Small urban increments of about 0.4 ng/m3 above background concentrations.•Total gaseous mercury to particulate phase mercury ratio was large across the UK.•Higher particulate phase mercury concentrations close to emissions point sources.

Concentrations and trends from a decade of measurements of total gaseous mercury and particulate phase mercury at a number of monitoring stations across the UK are presented. Both emissions and ambient concentrations of mercury in the UK have continued to fall slightly during the measurement period despite already being at historically low levels. The median UK concentration of total gaseous mercury recorded in recent years was around 2.0 ng/m3. Small urban increments of about 0.4 ng/m3 above background concentrations were noted, with larger increments above the background only observed close to industrial point sources. The total gaseous mercury to particulate phase mercury ratio was large across the UK - indicating the dominance of the gaseous mercury in the atmosphere - and was observed to be larger at background and urban locations than at industrial sites, as a result of higher relative particulate phase mercury concentrations close to primary emissions point sources.

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