Supporting Materials

Analysis of trace elements in samples

Once received from the field, samples were conveyed to a class 100 clean room. Small aliquots (15 mls) were subsampled for use in analysis of major ions by ion chromatography. The remaining larger aliquot was acidified with concentrated HNO3 to a 1% solution (v/v) and kept in a cold room for no less than two weeks to guarantee sufficient time for optimum leaching before analysis by magnetic sector inductively coupledplasma mass spectrometry, ICP-MS. Analysis for a suite of trace elements was carried out using a Finnigan MAT Element magnetic sector high-resolution ICP-MS and a method previously described was used(Keeler et al, 2006). The method detection limit, MDL, was calculated as three times the standard deviation of seven replicate sample analyses. Information regarding MDL, % samples above MDL and uncertainty (% RSD) for the reported trace elements is given in Table SI 1. The volume of each trace element precipitation sample was determined gravimetrically and precipitation depth was determined by dividing the volume of precipitation by the area of the funnel.

Fig. SI 1. Mercury concentration versus precipitation depth for rainfall samples (n = 20) collected at AMS 6 in Fort McMurray, AB, November 2010-September 2012.

Fig. SI 2. Moderate Resolution Imaging Spectroradiometer (MODIS) image of northeastern Alberta taken by NASA in June 2011. Smoke especially to the east of the oil sands mining facilities and the city of Fort McMurray is evident in this image.

Fig. SI 3. Hysplit 24 hour back trajectories for June 15, 2011, at Fort McMurray, AB. Note this region is in the mountain time zone and is UTC-7 hours. Back trajectories are calculated at 6am, noon, 6 pm and midnight local time.

(a)Jun 16, 2011

(b)Jun 17, 2011

(c)June 18, 2011

Fig. SI 4. Wind rose plots at AMS 6 in Fort McMurray, AB, June 16-18, 2011..

Table SI1 Annual estimate of mercury emissions in kg for facilities in Alberta as reported in the National Pollutant Release Inventory.

Facility / 2010 / 2011 / 2012
Genesee Generating Station / 185 / 56 / 50
Sheerness Generating Station / 95 / 33 / 38
Suncor Energy / 43 / 37 / 35
Syncrude / 23 / 15 / 17

Table SI 2 Method Detection Limit, (MDL) and relative standard deviation,RSD (%) for analytes in wet deposition samples collected at AMS 6 in Fort McMurray, Alberta.

Analyte / Symbol / MDL
(µg L-1) / RSD(%) / Rain samples above MDL (%) / Mix Samples above MDL (%) / Snow samples above MDL (%)
Mercury / Hg / 0.3a / 2.6 / 100 / 100 / 100
Aluminum / Al / 0.5532 / 0.7 / 100 / 100 / 100
Sulfur / S / 17.024 / 1.0 / 100 / 100 / 100
Zinc / Zn / 0.0457 / 1.3 / 100 / 83 / 87
Arsenic / As / 0.0113 / 17.9 / 95 / 100 / 100

ain ng L-1

Table SI3 VWM concentrations (ng L-1) and wet deposition flux (µg m-2 yr-1) of mercury at selected world locations.

Location / Site Type / Date / Sample Type / VWM (ngL-1) / Flux (µg m-2 yr-1) / Reference
Fort McMurray, AB / urban / 2010-2012 / event / 11.2 / 1.1 / This Study
Poland / urban / 2013-2014 / event / 5.9 / 3.94a / Siudek et al. 2016
Chongquing, China / urban / 2010-2014 / event / 34.25 / 37.83b / Qin et al. 2016
Hidalgo,Mexico
Oaxaca, Mexico / urban
coastal / 2003-2005
2003-2005 / weekly
weekly / 8.2
7.9 / 9.42
7.06 / Hansen et al. 2013
Bermuda / coastal / 2008-2009 / weekly / 4.7 / 7.18c / Gichuki et al. 2014
Poland, Baltic Sea / coastal / 2008-2009 / event / 4.0 / 8.3 / Siudek et al. 2015
Cape Point, S. Africa
Pretoria, S. Africa / coastal
urban / 2007-2009
2007-2009 / weekly
weekly / 10.6
15.8 / 8.84c
20.28c / Gichuki et al. 2013
Southeast Tibet / forest / 2010-2012 / event / 4.0 / 3.9 / Huang et al. 2015
Southwest China / rural / 2012-2013 / event / 11.9 / 15.9 / Ma et al. 2015

a18 month total, b4 year average, cannual flux calculated from weekly deposition amount in µg m-2 wk-1 times 52.

References

Gichuki SW, Mason RP (2013) Mercury and metals in South African precipitation. Atmos Env 79: 286-298

Gichuki SW, Mason RP (2014) Wet and dry deposition of mercury in Bermuda, Atmos Env 87: 249-257

Hansen AM, Gay DA (2013) Observations of mercury wet deposition in Mexico. Environ Sci Pollut Res 20: 8316-8325

Huang J, Kang S, Zhang Q, Guo J, Sillan M, Wang Y, Sun S, Sun X, Tripathee L (2015) Characterizations of wet mercury deposition on a remote high-elevation site in the southeastern Tibetan Plateau. Environmental Pollution 206: 518-526

Ma M, Wang D, Du H, Sun T, Zhao Z, Wei S (2015) Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China. Environ Sci Pollut Res 22: 20007-20018

Qin C, Wang T, Peng Y, Wang D, (2016) Four-year record of mercury wet deposition in one typical industrial city in southwest China. Atmos Environ 142: 442-451

Siudek P, Falkowska, Brodecka A, Kowalski A, Frankowski M, Siepak J (2015) Mercury in precipitation over the coastal zone of the Baltic Sea, Poland. Environ Sci Pollut Res 22: 2546-2557

Siudek P, Kurzyca I, Siepak J, (2016) Atmospheric deposition of mercury in central Poland: Sources and seasonal trends. Atmospheric Research 170: 14-22

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