Quantitative assessment of upstream source influences on total gaseous mercury observations in Ontario, Canada

Abstract

Abstract. Hourly total gaseous mercury (TGM) concentrations at three monitoring sites (receptors) in Ontario were predicted for four selected periods at different seasons in 2002 using the Stochastic Time-Inverted Lagrangian Transport (STILT) model, which transports Lagrangian air parcels backward in time from the receptors to provide linkages to the source region in the upwind area. The STILT model was modified to deal with Hg deposition and high stack Hg emissions. The model-predicted Hg concentrations were compared with observations at three monitoring sites. Estimates of transport errors (uncertainties in simulated concentrations due to errors in wind fields) are also provided that suggest such errors can reach approximately 10% of simulated concentrations. Results from a CMAQ chemical transport model (CTM) simulation in which the same emission and meteorology inputs were used are also reported. The comparisons show that STILT-predicted Hg concentrations usually agree better with observations than CMAQ except for a subset of cases that are subject to biases in the coarsely resolved boundary conditions. In these comparisons STILT captures high frequency concentration variations better than the Eulerian CTM, likely due to its ability to account for the subgrid scale position of the receptor site and to minimize numerical diffusion. Thus it is particularly valuable for the interpretation of plumes (short-term concentration variations) that require the use of finer mesh sizes or controls on numerical diffusion in Eulerian models. We report quantitative assessments of the relative importance of different upstream sources for the selected episodes, based on emission fluxes and STILT footprints. The STILT simulations indicate that natural sources (which include re-emission from historical anthropogenic activities) contribute much more than currentday anthropogenic emissions to the Hg concentrations observed at the three sites.

How relevant is the deposition of mercury onto snowpacks? – Part 2: A modeling study

“…2005; Durnford et al, 2010). Point Petre is a rural site that is affected by regional pollution episodically (Blanchard et al, 2002;Kellerhals et al, 2003;Temme et al, 2007;Wen et al, 2011). Thus, although the latitudinal difference is not the only difference between these three stations, it is likely the most important difference.…”

An assessment of atmospheric mercury in the Community Multiscale Air Quality (CMAQ) model at an urban site and a rural site in the Great Lakes Region of North America

“…A number of studies have used these data to evaluate CMAQ-Hg (Bash, 2010;Bullock and Brehme, 2002;Bullock et al, 2008Bullock et al, , 2009Gbor et al, 2006Gbor et al, , 2007Lin et al, 2007;Lin and Tao, 2003;Pongprueksa et al, 2008;Sunderland et al, 2008;Vijayaraghavan et al, 2007), and other atmospheric chemistry models that include mercury (Cohen et al, 2004;Holmes et al, 2010;Sanei et al, 2010;Seigneur et al, 2003;Selin and Jacob, 2008;Vijayaraghavan et al, 2008). Until recently, most studies that evaluate model estimates of ambient mercury compare with Total Gaseous Mercury (TGM) and/or Hg 0 (Gbor et al, 2006(Gbor et al, , 2007Holmes et al, 2010;Lin and Tao, 2003;Lohman et al, 2008;Selin et al, 2007;Soerensen et al, 2010;Wen et al, 2011).…”

Estimation of mercury emissions from forest fires, lakes, regional and local sources using measurements in Milwaukee and an inverse method

“…Other studies have identified alternative sources such as Taconite mining (Han et al, 2005) as well as melting snow and local mobile sources . In addition to anthropogenic sources, several studies identified the importance of natural sources, including vegetation sources (Wen et al, 2011) and the Atlantic Ocean .…”