The Biogeochemistry of Mercury

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The Biogeochemistry of Mercury
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Principal forms and transformations of mercury in
the environment
(redrawn from Jitaru and Adams 2004)
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Terrestrial Hg cycle
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Terrestrial Hg cycle
(redrawn from Hall 2007)
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Terrestrial Hg balance
(redrawn from Drigal 2002)
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The importance of wetlands
(redrawn from Drigal 2002)
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Separating the new from the old
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Aquatic Hg cycle
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(redrawn from Huckabee et al 1994)
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Bioacumulation and biomagnification
Methyl mercury concentration in a typical
freshwater foodweb
(Redrawn from Jones and Slotton 1996)
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Mercury dynamics in the atmosphere
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Natural sources of mercury
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Anthropogenic sources of mercury
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Historical deposition
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The geography of Hg contamination
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Who is responsible ?
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What are the main anthropogenic sources?
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Where does it all go?
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Does pollution control work?
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Mercury in Reservoirs
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Fludex Experiments short term effects
(redrawn from Hall et al 2005)
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Long term effects
(redrawn from Bodaly et al 1994)
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Effects on aquatic biota
(redrawn from Bodaly et al 1994)
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Effects on human populations
Peacock bass
Human hair
(Weisser and Forsberg, unpublished)
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Mercury in the Amazon goldminers and peacock
bass
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Finding mercury where it isnt supposed to be
Redrawn from Silva-Forsberg et al. 1999
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Where did it come from?
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When did it get there?
Global Anthropogenic sources
Amazon gold mining
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Where does it really come from?

• Mercury is derived predominantly from the soils
  and is natural in origin

(redrqwn from Zeidemann 1998)
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How does it get in the river?
MERCURY MASS BALANCE
Campina Basin (hydromorphic podsol)
Barro Branco Basin (latossol)
NET EXPORT 10µg/m2
NET EXPORT 20µg/m2
(redrqwn from Pacheco 2007)
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What happens further downstream?
(redrqwn from Scheideman 2005)
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What controls bioaccumulation?

• Water chemistry
• pH
• DOC
• Availability of methylation sites
• Wetlands
• Hydromorphic soils?

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Flooded forest
Dry foreest
Open water/wet savana
Distribution of wetlands in the Negro River Basin
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Distribution of hydromorphic soils in the Negro
basin
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BIO-INDICATORS
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COLLECTION SITES
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Estimation of wetland area with JERS-1 L-band SAR
imagery
Image supplied by NASDA, Japan
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Estimation of hydromorphic soil area from digital
soil maps, Hydromorphic soils indicated in
yellow.
Image supplied by NASDA, japan Soil map from
IBGE (1997)
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• Hgtotal B0 B1(SL) B2(pH) B3(DOC)
  B4(HMS) B4(W)
• Hgtotal total mercury in fish, ppm
• SL standard length of fish, cm
• pH pH in surface water
• DOC dissolved organic carbon, mg/l
• HMS of hydromorphic soils in upstream
  drainage basin and
• W of wetlands in upstream drainage basin

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Cichla spp.
Hoplias sp.
(redrawn from Belger and Forsberg 2006
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(redrawn from Belger and Forsberg 2006
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Hoplias sp.
(redrawn from Belger and Forsberg 2006
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(redrawn from Belger and Forsberg 2006
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Negro
Flooded forest
Dry forest
Open water/ savana
Maderia
Tapajós
Why do fish and people from the Negro have higher
mercury levels?
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Consequences for human health?
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