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

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

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

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: 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 4f 14 5s 2 5p 6 5d 10 6s 2 Filling of subshells makes elemental Hg(0) liquid, volatile Mercury can also shed its two outer electrons (6s 2 ) and be present as Hg 2+, also called Hg(II) 6s 2

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

Natural biogeochemical cycle of mercury Hg(0) Hg(II) particulate Hg burial SEDIMENTS uplift volcanoes erosion oxidation Hg(0)Hg(II) reduction biological uptake HUMAN PERTURBATION: fuel combustion mining ATMOSPHERE OCEAN/SOIL VOLATILE WATER-SOLUBLE deposition re-emission

Rising mercury in the environment Dietz et al. [2009] Mercury in Wyoming ice coreMercury in Arctic wildlife 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 Circle around mid-latitudes: 1 month Transport to southern hemisphere: 1 year Implies global-scale transport of anthropogenic emissions Mercury emitted anywhere deposits to oceans worldwide Human emission of mercury to atmosphere Atmospheric concentrations UNEP [2013]; Soerensen et al. [2010]

Mercury wet deposition is controlled by global transport EPA deposition data (circles), model (background) Global Hg(II) pool scavenging Florida T-storm 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 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 Opened for signatures in October 2013; already signed by 128 countries 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 The dominance of Asian emissions is a recent development Streets et al., 2011 Global emissions from coal combustion, mining, and industry

Grasshopper effect keeps mercury in environment for decades Amos et al. [2013, 2014] – ex UW! Reservoir fraction Fate of an atmospheric pulse in the Harvard global biogeochemical model for mercury: Atmosphere Surface soils Deep soils Surface/subsurface ocean Coastal sediments Deep sediments Deep ocean Hg deep ocean rivers SEDIMENTS Land Ocean 0

Global source contributions to Hg in present-day surface ocean Amos et al. [2013] Europe Asia N America S America former USSR Rest of world pre-1850 natural by time of initial emission: by source continent: Half of human-derived mercury presently in the ocean was emitted before 1950

Atmospheric mercury has been decreasing from 1990 to 2010; why? Circles = observations Background = model Decreasing trend is inconsistent with standard emission inventories Yanxu Zhang (ex UW!) Long-term stations for atmospheric mercury Long-term wet deposition flux data

Disposal of mercury in commercial products: a previously missing component of the biogeochemical cycle Global production of commercial mercury peaked in 1970 Horowitz et al., 2014 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? Global Hg production Global inadvertent Hg emission [Streets et al., 2011]

Many commercial products contain mercury Wiring Devices & Industrial Measuring Devices Medical Devices Pharmaceuticals & Personal Care Products

Pesticides and Fertilizer Explosives/Weapons Dyes/Vermilion Many commercial products contain mercury

Global historical use of mercury in commercial products Horowitz et al. [2014] Consumption, Mg per year Year AD Artisanal gold mining

Tracking the environmental fate of commercial mercury content/uploads/2012/07/sewage.jpg; symbol.jpg Global mercury mined per decade Commercial use by country Disposal Air Land Water Landfill Horowitz et al., 2014

Additional releases from commercial Hg in the context of atmospheric emissions Estimate: –“Distribution factors”: fraction of Hg entering each pathway –“Release factors”: fraction of Hg released into air, water, land Historical release of commercial mercury to the environment Horowitz et al., 2014; Yanxu Zhang, in prep. Decreasing disposal of commercial mercury can explain atmospheric mercury trend “Inadvertent” mercury (coal combustion, silver/gold mining) Air Soil Water Landfills Commercial mercury

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 Global soils: 270,000 tons mercuryOceans: 330,000 tons Atmosphere: 5,000 tons Increasing soil respiration due to warmer temperature Climate change may be as important as emission controls for the future of environmental mercury in the century ahead.