MERCURY IN THE GLOBAL ENVIRONMENT Where does it

MERCURY IN THE GLOBAL ENVIRONMENT: Where does it come from, where does it go? Hg Hg Hg Daniel J. Jacob, Harvard University

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

Mercury from fish consumption: a global environmental issue EPA reference dose (Rf. D): 0. 1 μg kg-1 d-1 (about 2 fish meals per week) Children IQ deficits (fetal exposure) Well-established Adult cardiovascular effects Suspected Cod Croaker Squid Whitefish Pollock Crab Salmon Bluefish Grouper, Rockfish Scorpionfish Halibut Sea trout Sablefish Lobster Snapper Lobster Mackerel Skate Canned Tuna (lt) Orange Roughy Marlin Canned Tuna (alb) Tilefish Shark Swordfish Hg (mg/kg) Mercury biomagnification factor

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

Mercury is present in the atmosphere as an elemental gas …a property that it shares only with the noble gases! Rn Hg He Ne Kr Ar Xe But unlike noble gases, mercury has a biogeochemical cycle driven by: oxidation Hg(II) Hg(0) elemental mercury 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) uplift reduction Hg(II) 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 Deep soils Surface soils oce e c a f r u s /sub an Surface an e oc Coastal sediments ep De 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 1970 s 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.