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
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
Children IQ deficits (fetal exposure)
Well-established
CodCod
Croaker
Croaker
Squid
Squid
Whitefish
Whitefish
Pollock
Pollock
Crab
Crab
Salmon
1.4
Tuna-canned alb
Bluefish
Bluefish
Grouper, Rockfish
Grouper, Rockfish
Scorpionfish
Scorpionfish
Halibut
Halibut
Sea trout
Sea trout
Sablefish
Sablefish
Lobster
Snapper
Snapper
Lobster
Lobster
Mackerel
Mackerel
Skate
Skate
Tuna-canned
lght
(lt)
Canned Tuna
Orange Roughy
Orange Roughy
Marlin
Marlin
Tuna-fresh
Canned Tuna (alb)
Tilefish
Tilefish
Shark
Shark
Swordfish
Swordfish
Hg (mg/kg)
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)
Adult cardiovascular effects
Suspected
1.6
Mercury biomagnification factor
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Most US states have freshwater fish advisories…
but our exposure is mainly rom ocean fish caught worldwide
Why are atmospheric chemists
interested in mercury?
Mass number = 80: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2
• Filling of subshells makes elemental Hg(0) liquid, volatile
• Mercury can also shed its two outer electrons (6s2)
and be present as Hg2+ , also called Hg(II)
6s2
Mercury is present in the atmosphere as an elemental gas
…a property that it shares only with the noble gases!
Rn
Hg
Ar
He
Xe
Ne
Kr
But unlike noble gases, mercury has a biogeochemical cycle driven by:
oxidation
Hg(0)
elemental
mercury
Hg(II)
reduction
mercuric
compounds
Natural biogeochemical cycle of mercury
HUMAN
PERTURBATION:
fuel combustion
mining
VOLATILE
Hg(0)
volcanoes
erosion
oxidation
WATER-SOLUBLE
Hg(II)
deposition
ATMOSPHERE
re-emission
OCEAN/SOIL
Hg(0)
Hg(II)
reduction
uplift
particulate
biological
uptake
Hg
burial
SEDIMENTS
Rising mercury in the environment
Mercury in Wyoming ice core
Mercury in Arctic wildlife
Dietz et al. [2009]
Human perturbation started in Antiquity;
present-day mercury levels in global environment
are about ten-fold higher than natural
Global transport of mercury through the atmosphere
Implies global-scale transport
of anthropogenic
emissions
Human emission
of mercury to
atmosphere
Mercury emitted anywhere
deposits to oceans worldwide
Atmospheric concentrations
Circle around mid-latitudes:
1 month
Transport to southern hemisphere:
1 year
UNEP [2013]; Soerensen et al. [2010]
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]
UNEP Minimata Convention on Mercury
First major global environmental treaty in over a decade
Opened for signatures in October 2013; already signed by 128 countries
• Requires best available control technology
for coal-fired power plants
• Mercury mining to be banned in 15 years
• Many mercury-containing commercial
products to be banned
Convention requires ratification by 50 countries to go into effect;
nine (including the US) have ratified so far
But 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
Grasshopper effect keeps mercury in environment for decades
Hg
Land
Ocean
rivers
deep ocean
SEDIMENTS
Reservoir fraction
Fate of an atmospheric pulse in the Harvard global biogeochemical model for mercury:
Atmosphere
Surface soils
Deep soils
Coastal sediments
Deep sediments
0
Amos et al. [2013, 2014] – ex UW!
Global source contributions to Hg in present-day surface ocean
by time of initial emission:
by source continent:
natural
pre-1850
Rest of world
Half of human-derived mercury
presently in the ocean
was emitted before 1950
former
USSR
N America
S America
Europe
Asia
Amos et al. [2013]
Atmospheric mercury has been decreasing from 1990 to 2010;
why?
Circles = observations
Long-term stations for atmospheric mercury
Background = model
Long-term wet deposition flux data
Decreasing trend is inconsistent with standard emission inventories
Yanxu Zhang (ex UW!)
Disposal of mercury in commercial products:
a previously missing component of the biogeochemical cycle
Global production of commercial mercury peaked in 1970
Global Hg production
Global inadvertent Hg emission
[Streets et al., 2011]
• 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
Many commercial products contain mercury
Medical Devices
Wiring Devices &
Industrial Measuring Devices
Pharmaceuticals & Personal Care Products
Many commercial products contain mercury
Dyes/Vermilion
Pesticides and Fertilizer
Explosives/Weapons
Global historical use of mercury in commercial products
Consumption, Mg per year
Artisanal gold mining
Year AD
Horowitz et al. [2014]
Tracking the environmental fate of commercial mercury
Global mercury mined
per decade
Commercial use by country
Disposal
Land
Air
Water
Landfill
Horowitz et al., 2014
Additional releases from commercial Hg in the context of atmospheric
Historical release of commercial mercury to the environment
emissions
Water
Landfills
Soil
Air
Commercial mercury
Decreasing disposal of
commercial mercury can
explain atmospheric mercury
trend
“Inadvertent” mercury (coal combustion, silver/gold mining)
Horowitz et al., 2014; Yanxu Zhang, in prep.
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]
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.