LCM a) b

Hg concentration in precipitation, ng L-1

Supplementary Information

120

a)

GTC 100 80 60 40 20 0

9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 01 01 01 01 01 01 01 01 01 01 01 2/2/10/29/7/2/30/2/23/2/25/22/9/2/19/2/10/2/28/25/5/26/2/2/22/2/29/2/16/20/5/2/26/2/14/22/9/2 2 / 7 8 9 10 11 1 12 3 3 6 7 9 1 10 11 1

Hg concentration in precipitation, ng L-1

120

b)

LCM 100 80 60 40 20 0

09 09 09 09 09 10 10 10 10 10 10 10 10 10 10 10 /20 9/20 5/20 8/20 /9/20 4/20 5/20 1/20 /6/20 1/20 2/20 1/20 7/20 /6/20 /4/20 0/20 2 1 9/ 9/2 10/1 11/1 12 1/2 3/2 5/1 6 7/1 7/2 8/1 9/2 10 11 11/3

Figure S1. Hg concentrations in rainfall collected at the GTC site in Cleveland, OH (a) and the LCM site in Medina, OH (b) from July 2009 – December 2010. 1

41.8 41.7

TOLEDO

LATITUDE

41.6 CLEVELAND

41.5 41.4 41.3 41.2

YOUNGSTOWN 41.1 41.0 -84.0

AKRON -83.5

-83.0

-82.5

-82.0

-81.5

-81.0

-80.5

LONGITUDE

N to S

2009

Akron Youngstown Cleveland Toledo

2010

0

200

400

600

800

1000

1200

precipitation in mm

1200

W to E

Toledo Cleveland Akron Youngstown

precipitation in mm

1000 800 600 400 200 0 2009

2010

Figure S2. Top panel, GPS coordinates for cities in Ohio, middle panel, north to south annual 2009 and 2010 precipitation gradients for these cities, bottom panel, west to east gradient annual 2009 and 2010 precipitation gradients for these cities. 2

OHIO STATEWIDE CLEVELAND AKRON YOUNGSTOWN 1980-2014 BASELINE

1400

Annual Precipitation (mm)

1300 1200 1100 1000 900 800 700 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Calendar Year Figure S3. Annual precipitation depth (mm) in Ohio for the 2000-2010 decade (source National Oceanic and Atmospheric Administration).

3

0.8

Hg wet deposition, g m

-2

a) 0.6

0.4

0.2

0.0 9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 01 01 01 01 01 01 01 01 01 01 01 /2 0/2 7/2 0/2 3/2 5/2 9/2 9/2 0/2 8/2 5/2 2/2 2/2 9/2 6/2 5/2 6/2 4/2 9/2 2 2 1 9/ /3 /2 /2 2/ /1 /1 /2 5/ 6/ /2 /2 /1 0/ /2 /1 2/ 7/ 8/ 9 10 11 1 12 3 3 6 7 9 1 10 11 1

0.6

Hg wet deposition, g m-2

b) 0.5 0.4 0.3 0.2 0.1 0.0 9 9 0 0 9 9 9 0 0 0 0 0 0 0 0 0 00 00 00 00 00 01 01 01 01 01 01 01 01 01 01 01 /2 9/2 5/2 8/2 9/2 4/2 5/2 1/2 6/2 1/2 2/2 1/2 7/2 6/2 4/2 0/2 2 / 1 1 1 2 2 2 1 6/ 7/1 7/2 8/1 9/2 10/ 11/ 1/3 9/ 9/ 10/ 11/ 12 1/ 3/ 5/ 1

Figure S4. Hg wet deposition collected at GTC site in Cleveland, OH (a) and the LCM site in Medina, OH (b) from July 2009 – December 2010. 4

Figure S5. US surface weather map for 2200 hours local time (0300Z, 10/28/2009) (top panel) and surface analysis/radar composite (lower panel) on October 27, 2009. 5

Figure S6. U.S. surface weather map for 1600 hours local time (2100Z, top panel) and surface analysis/radar composite (lower panel) on September 16, 2010.

6

Table S1 Source data used in Figure 1 ID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Type Electricity Generation Unit Steel Mill Plastics Mfg Hospital Medical Center Rail Yard Foundries, non-ferrous Steel Mill Medical Center Electricity Generation Unit Steam/Heating Facility Steel Mill Wastewater Treatment Facility Steam/Heating Facility School Bakeries Chemical Mfg Steel Mill Electricity Generation Unit Biochemical Research Rail Yard Oil Fired Power Plant

Latitude Longitude Kg of Hg 41.53560 -81.6419 9.07 41.46349 -81.6678 7.59 41.46139 -81.6250 3.72 41.51330 -81.6139 0.51 41.50306 -81.6242 0.11 41.43856 -81.6516 0.11 41.44584 -81.6917 0.10 41.44266 -81.6642 0.05 41.46139 -81.6972 0.04 41.47380 -81.7142 0.03 41.49611 -81.6214 0.03 41.52195 -81.6517 0.03 41.42611 -81.6514 0.02 41.50928 -81.6827 0.01 41.48639 -81.6672 0.01 41.48361 -81.6336 0.01 41.43417 -81.6356