Mercury in the environment where does it come

Mercury in the environment: where does it come from? 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 months 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 $8 billion per year cost in US Adult cardiovascular, fertility effects Suspected Hg (mg/kg) Mercury biomagnification factor 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 Hong Kong legal limit

Mercury exposure of Hong Kong residents Hong Kong (mean population) 4 fish meals per week or more less than 4 fish meals per week no fish US (mean population) 0 1 2 3 Mercury concentration in hair, mg/kg 4 5 Dickman and Leung [1999]

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 commercial products Hg(0) oxidation WATER-SOLUBLE Hg(II) deposition volcanoes erosion re-emission ~10 x natural uplift VOLATILE Hg(0) reduction ATMOSPHERE OCEAN/SOIL biological/ Hg(II) particulate biological Hg uptake burial 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 Present-day emission mercury to fromemissions coal and mining Implies g. Present-day caleoftransport ofatmosphere anthropogenic Atmospheric concentrations, 2007 -2013: observations (symbols), model (background) Circle around mid-latitudes: 1 month Transport to southern hemisphere: 1 year Mercury emitted anywhere can deposit to oceans worldwide UNEP [2013]; Horowitz et al. , submitted

Mercury deposition is controlled by this global transport EPA deposition data (circles), model (background) Florida thunderstorm 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]

Mercury wet deposition in China is comparable to US 2007 -2013 monitoring data (symbols), model (background) …evidence again that mercury deposition is controlled globally Horowitz et al. , submitted

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

But mercury pollution is in 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 mercury Land Ocean rivers deep ocean SEDIMENTS Reservoir fraction Fate of an atmospheric pulse emitted at time zero: Atmosphere Deep soils Surface soils oce e c a f r u s /sub Surface an an e oc Coastal sediments ep De Deep sediments 0 Amos et al. [2014]

Who is responsible for mercury in the present-day 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]

Observations show decrease in atmospheric mercury since 1990, despite increasing emissions from coal combustion Symbols = observations Background = model This appears due to decreased environmental discharge of commercial mercury products 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 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 Horowitz et al. [2014]

Many commercial products contain(ed) 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 Landfill Water

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 Total release peaked in 1970, has been decreasing since “Inadvertent” mercury (coal combustion, silver/gold mining) Horowitz et al. [2014]

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.