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

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

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

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)

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

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

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

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.

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]

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]

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) 0.09 0.6 0.3 CH2 Br2 OH 91 days Br BrO BrNO3 CHBr3 hv, OH 14 days including HBr+HOBr on aerosols HBr HOBr Sea salt 1.4 0.9 debromination industry deposition plankton Parrella et al. [2012]

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

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

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

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]

“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]

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]

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]

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

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 http://mercurypolicy.org/wp-content/uploads/2010/06/skincreamhgfactsheet_may31_final.pdf

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 http://mercurypolicy.org/wp-content/uploads/2010/06/skincreamhgfactsheet_may31_final.pdf

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]

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 http://www.earthyreport.com/site/wp-content/uploads/2011/10/smokestack.jpg; http://www.airfields-freeman.com/TX/GreaterSW_TX_field_02.jpg; http://www.thenanfang.com/blog/wp-content/uploads/2012/07/sewage.jpg; http://www.colbond-usa.com/images/colbond-products/Geosynthetics/civil.landfills.jpeg.jpg; http://dddigitalcolour.com/wp-content/uploads/2012/10/green-recycling-symbol.jpg

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

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]

Atmospheric mercury in the Arctic is high and not decreasing; why? Atmospheric mercury concentration 2000-2009 trend BLUE: decrease RED: increase Fisher et al. [2013], Chen et al. {2015]

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

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.