Sources Of Total Gaseous Mercury In Alberta, Canada: Local Emissions and Long Range Transport

摘要

Continuous measurements of total gaseous mercury (TGM) concentration were taken atrnEsther, a remote grassland site on the Canadian Prairies, starting July 1998. The site isrnpart of the Canadian Atmospheric Mercury Measurement Network (CAMNet), and isrnintended to represent background prairie concentrations of TGM. TGM measurementsrnwere made using a Tekran 2537A vapour mercury analyzer. TGM concentrationsrnaveraged 1.69 ng/m~3 with a standard deviation of 0.19 ng/m~3 during the first eighteenrnmonths of monitoring. Median TGM concentrations were highest in late winter andrnlowest in fall. The TGM data were analyzed with the goal of determining the relativerncontributions of local emissions and long range transport to observed concentrations.rnTGM concentrations were only weakly dependent on local wind direction, reflecting thernabsence of nearby point sources of mercury emissions. Preliminary results from a backrntrajectory analysis of the mercury data suggest that TGM is higher in air masses arrivingrnfrom the east and south than in air masses arriving from the west and north. Forest firesrnin northern Alberta and Saskatchewan appear to be responsible for episodes of high TGMrnconcentrations at Esther. The measurements also suggest that local emissions of TGMrnfrom the soil may sometimes have been a significant contributor to observed TGMrnconcentrations.