1. Mercury in the environment:
where does it come from? Hg Hg

2. A brief human history of mercury poisoning
Qin Shi Huang,
1st emperor of China
Mad hatters
Minimata disaster
Iraq grain disaster
200 BC
Karen Wetterhahn,
Dartmouth professor
19th-20th century
1950s
1971
1997

3. The perils of eating too much fish
Jeremy Piven, actor
Richard Gelfond IMAX CEO
Both hospitalized for extended time due to mercury poisoning
from daily fish consumption over many years

4. Mercury from fish consumption: a global environmental issue
EPA reference dose (RfD): 0.1 μg kg-1 d-1 (about 2 fish meals per week)
Children IQ deficits (fetal exposure)
Well-established
$8 billion per year cost in US
Adult cardiovascular effects
Suspected
Hg (mg/kg)
Tilefish
Shark
Swordfish
Orange Roughy
Marlin
Canned Tuna (alb)
Bluefish
Grouper, Rockfish
Scorpionfish
Halibut
Sea trout
Sablefish
Lobster
Snapper
Mackerel
Skate
Canned Tuna (lt)
Cod
Croaker
Squid
Whitefish
Pollock
Crab
Mercury biomagnification factor
Salmon

5. Electronic structure of mercury
Mass number = 80: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2
6s2
Filling of subshells makes elemental Hg(0) liquid, volatile
Mercury can also shed its two outer electrons (6s2)
and be present as Hg(II)

6. Mercury is present in the atmosphere as an elemental gas
…a property that it shares only with the noble gases! Xe Kr Ne Ar He Hg Rn
But unlike noble gases, mercury has a biogeochemical cycle driven by:
oxidation
Hg(0)
Hg(II)
elemental
mercury
reduction
mercuric
compounds

7. Biogeochemical cycle of mercury
ANTHROPOGENIC
PERTURBATION:
fuel combustion
Mining
~10x natural
VOLATILE
WATER-SOLUBLE
oxidation
Hg(0)
Hg(II)
volcanoes
erosion
ATMOSPHERE
OCEAN/SOIL
Hg(0)
Hg(II)
particulate Hg
reduction
biological
uptake
burial
uplift
SEDIMENTS

8. Rising mercury in the environment
Mercury in Wyoming ice core
Mercury in Arctic wildlife
Dietz et al. [2009]
Present-day mercury levels in global environment are about ten-fold higher than natural

9. Global transport of mercury through the atmosphere
Implies gPresent-day cale transport of anthropogenic emissions
Present-day emission of mercury to atmosphere from coal and mining
Atmospheric concentrations
Observed variability of atmospheric Hg implies an atmospheric lifetime against deposition of ~0.5 years
UNEP [2013]; Horowitz, in prep.

10. Mercury wet deposition is controlled by global transport
EPA deposition data (circles), model (background)
Florida T-storm
Global Hg(II) pool
scavenging
Highest mercury deposition in US is along the Gulf Coast,
where thunderstorms scavenge globally transported mercury from high altitudes
Selin and Jacob [2008]

11. Atmospheric redox chemistry of mercury: driver of mercury deposition
Oxidation of Hg(0) by OH is endothermic: too slow to be of relevance
Oxidation by Br atoms involves two steps:
Hg(II)-organic complexes in aqueous solutions are known to photolyze
Global rates in GEOS-Chem
Horowitz et al. [2017]

12. Mean tropospheric concentrations (ppt)
TROPOSPHERIC BROMINE CHEMISTRY simulated in GEOS-Chem global chemical transport model
GEOS-Chem
Observed
CHBr3
440 Gg a-1
CH2Br2
62 Gg a-1
Vertical profiles of short-lived bromocarbons at northern mid-latitudes
CH3Br OH
1.1 years
Mean tropospheric concentrations (ppt)
CH2 Br2 OH
91 days Br
BrO
BrNO3
CHBr3
hv, OH
14 days
including
HBr+HOBr
on aerosols
HBr
HOBr
Sea salt
debromination
industry
deposition
plankton
Parrella et al. [2012]

13. Current view of atmospheric Hg budget
Horowitz et al., 2017

14. UNEP Minimata Convention on Mercury First major global environmental treaty in over a decade
Opened for signatures in October 2013; signed by 128 countries
Requires best available technology
for coal-fired power plants
Mercury mining to be banned in 15 years
Regulation of mercury use in artisanal gold mining
Convention requires ratification by 50 countries to go into effect;
35 (including China and the US) have ratified so far

15. Mercury pollution is in large part a legacy problem
Global emissions from coal combustion, mining, and industry
The dominance of Asian emissions is a recent development
Streets et al. , 2011

16. Global biogeochemical model for mercury
7-box model with 7 coupled ODEs dm/dt = s(t) – km where s is primary emission
Transfer rate constants k are specified from best knowledge
thermocline
Primary
emissions
Model is initialized at natural steady state, and then forced with anthropogenic emissions for 2000 BC – present; % present-day enrichments are indicated
Amos et al. [2013]

17. “Grasshopper effect” keeps mercury in environment for decades
deep ocean
rivers
SEDIMENTS
Land
Ocean
Reservoir fraction
Fate of an atmospheric pulse emitted at time zero:
Atmosphere
Surface soils
Deep soils
Surface/subsurface ocean
Coastal sediments
Deep sediments
Deep ocean
Amos et al. [2014]

18. Who is responsible for mercury in the present-day ocean?
by time of initial emission:
by source continent:
Europe
Asia
N America
S America
former
USSR
Rest of world
pre-1850
natural
Half of human-derived mercury presently in the ocean
was emitted before 1950
Amos et al. [2013]

19. Atmospheric mercury has been decreasing from 1990 to 2010; why?
Circles = observations Background = model
Long-term stations for atmospheric mercury Long-term wet deposition flux data
Decreasing trend is inconsistent with standard emission inventories
Zhang et al. [2016]

20. Disposal of mercury in commercial products: a previously missing component of the biogeochemical cycle
Global production of commercial mercury peaked in 1970
Global inadvertent Hg emission
[Streets et al., 2011]
Global Hg production
Commercial Hg enters environment upon use or disposal;
much larger source than inadvertent emission
Use of commercial mercury has decreased since the 1970s due to environmental concern; could this explain the observed atmospheric decrease?
Horowitz et al., 2014

21. Many commercial products contain mercury
Medical Devices
Wiring Devices &
Industrial Measuring Devices
Pharmaceuticals & Personal Care Products
Just pictures of paint
Lamps
Batteries
Split into two if necessary
Cosmetics - Products contain up to 60,000 PPM – generally >1 ppm is restricted

22. Many commercial products contain mercury Pesticides and Fertilizer
Dyes/Vermilion
Pesticides and Fertilizer
Explosives/Weapons
Just pictures of paint
Lamps
Batteries
Split into two if necessary
Cosmetics - Products contain up to 60,000 PPM – generally >1 ppm is restricted

23. Global historical use of mercury in commercial products
Artisanal gold mining
Consumption, Mg per year
I HAVE PRESENTED METHODS BEFORE
INCLUDE METHODS OF HOW TO DO THIS IN THE SUPPLEMENTAL SLIDES
-fine tuning, MAIN DIFFERENCE BETWEEN THIS TIME & LAST TIME IS CHLOR ALKALI!!!!!! More consistent with global importance of chlor alkali!!
---- can touch base w/ David Kocman
--- explain what other is !!!
Year AD
Horowitz et al. [2014]

24. Tracking the environmental fate of commercial mercury
Global mercury mined per decade
Commercial use by country
Disposal
Air
Land
Water
Recycled goes back into Hg supply. Have an arrow of that. It would be better to add the Hg supply back in to the mined amount. The recycled has to go somewhere – feeds back into Hg supply.
Now we have Hg consumption in each product: next step is where does it go. Quantifying five ultimate fates:
Landfill
Horowitz et al., 2014

25. Historical release of commercial mercury to the environment
Additional releases from commercial Hg in the context of atmospheric emissions
Historical release of commercial mercury to the environment
Decreasing disposal of commercial mercury can explain atmospheric mercury trend
Landfills
Water
Commercial mercury
Soil
Make streets orangey red two tone!!!!!!!! From Mined Hg and non-Hg mined related sources!
Air
“Inadvertent” mercury (coal combustion, silver/gold mining)
Horowitz et al., 2014; Yanxu Zhang, in prep.
Estimate:
“Distribution factors”: fraction of Hg entering each pathway
“Release factors”: fraction of Hg released into air, water, land

26. What can we hope from the Minimata Convention?
Effect of zeroing
all human emissions
by 2015
Zeroing human emissions right now would decrease ocean mercury by 50% by 2100, while keeping emissions constant would increase it by 40%
Amos et al. [2013, 2014]

27. Atmospheric mercury in the Arctic is high and not decreasing; why?
Atmospheric mercury concentration
trend
BLUE: decrease
RED: increase
Fisher et al. [2013],
Chen et al. {2015]

28. What is going on in the Arctic?
Large river inputs to shallow Arctic Ocean; melting sea ice allows mercury to escape
Northern Dvina in Arkhangelsk
mercury
mercury
Ocean mercury, pM

29. The wild card of climate change: potential mobilization of the large soil mercury pool
Atmosphere: 5,000 tons
Increasing soil respiration
due to warmer temperature
Global soils: 270,000 tons mercury
Oceans: 330,000 tons
Climate change may be as important as emission controls
for the future of environmental mercury in the century ahead.