Wet Deposition of Mercury in the U.S. and Canada, 1996-2004

Wet Deposition of Mercury in the U.S.
and Canada, 1996-2004
Results from the NADP Mercury Deposition Network (MDN)
David Gay
(coauthors Eric Prestbo, Bob Brunette, Clyde Sweet)
Illinois State Water Survey
University of Illinois
Champaign, IL
dgay@uiuc.edu, (217) 244.0462
http://nadp.sws.uiuc.edu
Goal of this Presentation….
 A short introduction to the
Mercury Deposition Network.
 A description what we know about the
deposition of mercury and trends
What is the Mercury Deposition Network?
 A Cooperative Research Program
 Part of National Atmospheric Deposition Network
 93 sites (one more next few weeks)
 Federal, State, Local and Tribal Governments
members, private organizations
 Mea4suring wet deposition of mercury
 Our Charge:
 to determine if trends exist in wet deposition of
mercury over time
Federal Agency
Members
University
Members
Tribal
Organizations
Other Organizations
and States
Prime Members of MDN
 States






Wisconsin
Minnesota
Indiana
Pennsylvania
Florida
Louisiana
 USGS

EPA

Tribal Nations


Cherokee, particularly
Several Tribes in Maine
Why Monitor Mercury in
Precipitation?
The mercury problem?
Bioaccumulation
Dry Deposition
Geologic Sources
(soil, rock, base flow etc.)
Wet Deposition
Water Body
Hg
Hg
Hg
Methylation
Bacterial action
(water and sediment)
Smaller fish
Zooplankton
predatory fish
Why monitor for Mercury in Precipitation?
 Atmospheric transport and deposition is the
dominant pathway to most aquatic ecosystems.
 Between 40 and 75% of the mercury input to lakes
and streams is by wet deposition
 probably less in the West.
(Sorensen et al., 1997; Scherbatskoy et al., 1997; Lamborg et al., 1995; Mason et al., 1997; Landis and Keeler, 2002)
 “New” mercury is more likely converted to
organic form than “old” mercury
How Mercury is Wet Deposited
RGM
Hgp
RGM
Hgp
Hgo
Hgo
rainout
Hgp
RGM
washout
How Mercury is Wet Deposited
RGM
Hgo
oxidation
RGM
Atmospheric Mercury Species Abundance
Hg0 – Elemental Mercury
RGM – Reactive Gaseous Mercury
Hgp – Particulate Bound Mercury
1.4-1.8
ng/m3
Typical Atm. Mercury
Species Abundance
Sources of Mercury


Coal combustion
Incineration






Industrial emissions (chlor-alkali)
Cement production (Hg in lime)
Mining





Hg use in gold and silver mining (amalgam formation)
Mining for Hg
taconite
Automobile Recycling
Mercury in Landfills






Medical
Trash
Cremation
Fluorescent lamps
dental amalgams (also in sewers)
Thermometers
Batteries
Discarded electrical switches
Others will surface

Other carbon fossil fuels (gas/oil/diesel)?


Volcanoes (St. Helens)
Naturally enriched ores/soils




Soils and rocks (0.08 to 0.5 ppm in crust)
Evaporation



Plate tectonic boundaries
Cinnabar (HgS), taconite, others
Soils
Fresh water and OCEANS
Natural forest fires

Tree bark (wood fire places)

Volatilization from rocks?

Wind Blown reintroduction



Mine tailings
Industrial contaminated soils
Evolving Gases



Mines, industrial areas
Waste facilities (municipal in particular)
Out of soil
Interesting Source Note
 U. S. Military huge stockpiles of elemental
mercury (from WWII)
 Light-up children’s shoes
MDN Sites
(January 2006)
Calculation of Deposition
Annual Wet Deposition ConcPW * PPT
obsT
(Ci * Pvoli )
ConcPW
i 1
PPT
obsT
PPTi
i 1
obst
PPTi
i 1
What the Data Show….
Hg Conc. (ng/L)
Weekly Total Mercury vs. Precipitation
(1996 to 2004, n=24,139)
400
350
300
250
200
150
100
50
0
0
50
100
150
200
250
Precipitation (mm)
300
350
400
Mercury Concentrations in Precipitation
2003
Mercury Concentrations in Precipitation
2004
Average Mercury Concentrations in Precipitation
2001-2004
Mercury Wet Deposition
2003
Mercury Concentrations in Precipitation
Mercury Wet Deposition
2004
Average Mercury Wet Deposition
2001 to 2004
Hg Conc.
(ng/L)
Yearly Average Mercury Concentrations
(All Sites)
15
10
5
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
19
96
0
Year
15
10
5
Year
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
0
19
96
Hg Dep.
(ug/m2 yr)
Yearly Average Mercury Deposition
(All Sites)
Seasonal Nature of Mercury
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
Win
Spr
Sum
Fall
Deposition (ug/m2 yr) and Concentration (ng/L)
Conc
Depo
Yearly Average Mercury Concentrations
Hg Conc. (ng/L)
15.0
10.0
5.0
0.0
MW
NE
OR
SE
Region
1996
1997
1998
1999
2000
2001
2002
2003
2004
IL11
500
MI48
0
96
nJu
97
nJu
98
nJu
99
nJu
00
nJu
01
nJu
02
nJu
03
nJu
04
nJu
05
nJu
IN34
95
nJu
2000
1500
1000
ng/m2 week
2000
1500
1000
ng/m2 week
Midwest Deposition Over Time
3000
2500
Midwest Deposition Over Time
3000
2500
500
0
95
nJu
96
nJu
97
nJu
98
nJu
99
nJu
00
nJu
01
nJu
02
nJu
03
nJu
04
nJu
05
nJu
MN16
WI08
Percent Occurance of Deposition > 1500 ug/m2
(%, by Region)
Midwest, 11.8
Northeast, 2.5
West, 2.0
Ohio R., 6.9
Southeast,
76.9
Trends In
Wet Deposition
Trend Methods
 Seasonal Kendall Test for Trends
 Seasonal Kendall Slope Estimator





From the “Mann Kendall” as extended by van Belle and Hughes, 1984
non-parametric, normality not assumed
allows for seasonality and multiple stations
allows for missing data
from “Statistical Methods for Environmental Pollution Monitoring”, R. O. Gilbert, 1987
 Examines differences over time


Difference (obs1 – obs2) > 0, then =+1
< 0, then =-1

= 0, then = 0
Observation
Seasonal Kendall Example
3 Up
= +3
1 down
= -1
1 no change = 0
SUM
= +2
3 Up
= +4
1 down
= -0
1 no change = 0
SUM
= +4
TIME
TOTAL = +6
Positive Trend
How is Slope Determined?
 Determine all observation differences
 Normalized to change per year
difference
obsT 1 obsT 2
yearT 1 yearT 2
(by season)
 Median of all differences is the slope estimate
(ng/L yr, or ug/m2 yr)
Conditions For Trend Observations
 39 of 52 valid observations for 5 years at
least
 Urban sites removed from regions
 Run seasonally (seasonal signal)
 “Trace” rain events removed
 subppt < 0.128 mm
 highly variable concentration
Sites Meeting Test Conditions for Trends
All Seasons Mercury Concentration Trends
Decreases
Increases
One tail, =0.05
All Seasons Precipitation Trends
Decreases
Increases
One tail, =0.05
All Seasons Mercury Deposition Trends
Decreases
Increases
One tail, =0.05
All Seasons Mercury Concentration, Deposition,
and Precipitation Trends
Depo.
Conc./Prec.
Decreases
Increases
One tail, =0.05
Mercury Concentration Trend Slopes
(percent/yr)
-3.1
-3.0
-1.8
-2.1
-2.5
-1.1
-3.2
-4.0
-5.2
-4.8
-3.1
-4.3
-2.2
-3.5
-1.4
-2.0
-4.0
Decreases
Increases
One tail, =0.05
Regions and Sites Tested for Trends
Northeast
Upper Midwest
not enough data
Ohio River
Southeast
Regions
Upper
Midwest Region
• MW is a homogeneous group in Dep, ppt
• Concentration, stations independent
• seasonal differences present
• NO regional trend in Deposition
• NO regional trend in precipitation
• NO regional trend in Concentration
Seasonal
Conc
Fall
-
Win
+
Spr
-
Sum
0
Depo.
Conc./Prec.
Depo.
Conc./Prec.
Decreases
Decreases
Increases
Increases
Regions
Upper
Midwest Region, Summer Only
Depo.
Conc./Prec.
Depo.
Conc./Prec.
Decreases
Decreases
Increases
Increases
Regions
Upper
Midwest Region, Winter Only
Depo.
Conc./Prec.
Depo.
Conc./Prec.
Decreases
Decreases
Increases
Increases
Dry Deposition
?
•Very few measurements (Risch)
•Modeled dry deposition (Bullock)
Summary
 Mercury concentration and deposition show
reasonably consistent patterns over eastern US
and Canada
 Trends, particularly in concentration, are negative
for the majority of the country (1996 to 2004)
 No regional trends for the upper Midwest
 Mixed concentration changes, particularly in Winter
Wet Deposition of Mercury in the U.S.
and Canada, 1996-2004
Results from the NADP Mercury Deposition Network (MDN)
David Gay
(coauthors Eric Prestbo, Bob Brunette, Clyde Sweet)
Illinois State Water Survey
University of Illinois
Champaign, IL
dgay@uiuc.edu, (217) 244.0462
http://nadp.sws.uiuc.edu
Regions
Northeast Region
• NE is a homogeneous group in Conc, Dep, ppt
• Significant regional trend is down for C,D
8/9 sites decreasing in all seasons
NB
02
Depo.
Conc./Prec.
Decreases
Increases
Ohio River Region
• OR (Penn) is a homogeneous group for Conc, Dep, ppt
• But no significant regional trends
• Seasons are showing different changes:
Conc
Dep
ppt
Fall
-
0
+
Win
-
-
+
Spr
0
+
-
Sum
-
-
+
Depo.
Conc./Prec.
Decreases
Increases
Southeast Region
• SE is a homogeneous group only in Conc
• Significant regional Conc trend is down
8/11 sites decreasing in all seasons
Depo.
Conc./Prec.
Decreases
Increases