Measurement of gaseous mercury emissions from natural sources

To better estimate natural source emissions of gaseous mercury, air-surface emission rates (fluxes) were measured from contrasting geological settings (natural sources) across Canada and the United States using micrometeorological (micromet) and chamber techniques. Micrometeorological measurements were made using a flux gradient approach. Chamber measurements were made using Teflon ®-lined plexiglass, quartz glass and poly-carbonate chambers. Fluxes were measured from substrates (soils) containing high concentrations (>100 μg g−1) of mercury in the substrate (Pinchi Lake, Clyde Forks), moderately high (1 to 10 μg g−1) substrate mercury concentrations (Klages, Steamboat Springs), as well as from background (<200 μg g−1) sites (Kakabeka Falls, Wilson Farm site).; Fluxes of gaseous mercury were found to correlate strongly with total substrate mercury concentration, on a log-log basis, for both the chamber and micromet methods. Relationships between total substrate mercury concentration (μg g−1) and gaseous mercury flux (ng m−2 h−1) were found to be: logFluxm icromet=0.60^*logH gsubstrate+1.7 logFluxc hamber=0.35^*logHg substrate+1.5 for the micromet and chamber methods, respectively. Fluxes measured using the flux gradient technique were approximately twice the magnitude as those measured using chamber techniques. Differences between the two relationships were attributed to the limitations of the methods.; Factors influencing mercury emissions including environmental conditions and chamber operating parameters were examined. Increases in temperature, both soil and air, net radiation and wind speed, and decreases in absolute humidity, were found to correlate with increased mercury emissions. When all environmental parameters were examined simultaneously, chamber air temperature was found to have the greatest effect on mercury flux. Varying chamber hydraulic retention time appeared to affect flux measurements but the effects were not statistically significant. It was suggested that blank corrections for chamber measurements were unnecessary under steady-state conditions. Spectral properties of chamber materials were also examined.; Relationships developed through this research may be useful to regulators and modelers of mercury emissions and may be combined with geochemical data to scale up natural source mercury emissions for Canada. They may also be used to put anthropogenic emissions estimates into perspective.