A comparison of speciated atmospheric mercury at an urban center and an upwind rural location

Abstract

Gaseous elemental mercury (GEM), particulate mercury (PHg) and reactive gaseous mercury (RGM) were measured every other hour at a rural location in south central Wisconsin (Devil's Lake State Park, WI, USA) between April 2003 and March 2004, and at a predominantly downwind urban site in southeastern Wisconsin (Milwaukee, WI, USA) between June 2004 and May 2005. Annual averages of GEM, PHg, and RGM at the urban site were statistically higher than those measured at the rural site. Pollution roses of GEM and reactive mercury (RM; sum of PHg and RGM) at the rural and urban sites revealed the influences of point source emissions in surrounding counties that were consistent with the US EPA 1999 National Emission Inventory and the 2003-2005 US EPA Toxics Release Inventory. Source-receptor relationships at both sites were studied by quantifying the impacts of point sources on mercury concentrations. Time series of GEM, PHg, and RGM concentrations were sorted into two categories; time periods dominated by impacts from point sources, and time periods dominated by mercury from non-point sources. The analysis revealed average point source contributions to GEM, PHg, and RGM concentration measurements to be significant over the year long studies. At the rural site, contributions to annual average concentrations were: GEM (2%; 0.04 ng m(-3)); and, RM (48%; 5.7 pg m(-3)). At the urban site, contributions to annual average concentrations were: GEM (33%; 0.81 ng m(-3)); and, RM (64%; 13.8 pg m(-3)).

Concentration-weighted trajectory approach to identifying potential sources of speciated atmospheric mercury at an urban coastal site in Nova Scotia, Canada

“…The higher GOM concentrations in spring at Dartmouth were consistent with some urban sites, including Rochester, New York; Beltsville, Maryland; New Brunswick, New Jersey; The Bronx, New York; and Birmingham, Alabama. However, many of the urban sites also experienced higher GOM concentrations in summer or fall (Rutter et al, 2007;Lyman and Gustin, 2009;Song et al, 2009;Liu et al, 2010). Potential explanations for the seasonal GOM trend include, the influence of point sources (Rutter et al, 2007), increase oxidation of GEM due to the seasonal variation of atmospheric oxidants (Selin and Jacob, 2008;Liu et al, 2010), and free troposphere transport ).…”

“…The higher PBM concentrations can be explained by increased absorption of gaseous mercury on particles at lower temperatures in winter and regional source emissions (e.g. increased fossil fuel combustion for heating) (Rutter et al, 2007;Lyman and Gustin, 2009;Huang et al, 2010;Liu et al, 2010). However, some sites saw higher average PBM concentrations in spring (Toronto, ON; Beltsville, MD; Birmingham, AL) or fall (Birmingham, AL; Salt Lake City, UT).…”

“…Speciated atmospheric mercury concentrations have been measured at many urban locations across the United States, including Detroit (Liu et al, 2007(Liu et al, , 2010, Houston (Brooks et al, 2010), Tuscaloosa (Gabriel et al, 2005), Reno Peterson et al, 2009), Birmingham (Nair et al, 2012), Milwaukee (Rutter et al, 2007), and Rochester . In Canada, these measurements have taken place at two urban locations: Toronto and Windsor (Xu and Akhtar, 2010).…”

Overview of receptor-based source apportionment studies for speciated atmospheric mercury

“…Back trajectories are often included in source apportionment studies to supplement the multivariate models previously described because the simulated airflows incorporate meteorological data (Hopke and Cohen, 2011). The HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model (Draxler and Rolph, 2014; has often been used in atmospheric mercury source-receptor studies (Han et al, 2004(Han et al, , 2005Lynam and Keeler, 2005;Liu et al, 2007;Rutter et al, 2007;Abbott et al, 2008;Choi et al, 2008;Li et al, 2008;Lyman and Gustin, 2008;Sprovieri and Pirrone, 2008;Cheng et al, 2009;Peterson et al, 2009;Sigler et al, 2009;Kolker et al, 2010). The HYSPLIT model simulates the transport of an air parcel by wind and estimates the position of the parcel using velocity vectors that have been spatially and temporally interpolated onto a grid (Han et al, 2005).…”

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

“…These results suggest that that erroneous processing of boundary inflow combines with additional errors -especially regional emissions and/or deposition -such that the signature of nearby plumes is evident in the observations but not in the model. (Rutter et al, 2008a); (b) CMAQ-Hg (10-m wind-speed generated by the WRF model and processed with MCIP v. 3.4). Wind direction was aggregated such that all directions between 0°and 179°were considered from the east and all wind directions greater than or equal to 180°were labeled as from the west.…”