mercury in the environment
DESCRIPTION
Mercury in the Environment. What is Mercury (Hg). Hg is a silvery, liquid metal at room temperature "heavy metals." Like water, Hg can evaporate and become airborne. Because it is an element, mercury does not break down into less toxic substances. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/1.jpg)
Mercury in the Environment
![Page 2: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/2.jpg)
What is Mercury (Hg)• Hg is a silvery, liquid metal at room temperature
• "heavy metals." • Like water, Hg can evaporate and become airborne.
• Because it is an element, mercury does not break down into less toxic substances.
• Once mercury escapes to the environment, it circulates in and out of the atmosphere until it ends up in the bottoms of lakes and oceans.
![Page 3: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/3.jpg)
Where Does Mercury Come From?
• Mercury is a naturally occurring element.
• Mercury ore - cinnabar - is mined
• History of SJ
![Page 4: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/4.jpg)
Mercury enters the environment from:
• Natural sources such as volcanoes and the weathering of rocks;
• Our intentional uses of mercury;
• Our unintentional releases of mercury from burning fossil fuels and smelting metals.
• CFL• E-waste
![Page 5: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/5.jpg)
Bioaccumulation= an increase in the
concentration of a chemical in an organism over time, compared to the chemical's concentration in the environment.
• Occurs naturally– And necessary for certain minerals and macromolecules
• Problematic when bioaccumulate toxins
![Page 6: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/6.jpg)
Bioaccumulation of Hg
• Hg enteres food chain via anaerobic bacteria (SRBs)
• Why does Tuna have such high [Hg]?
![Page 7: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/7.jpg)
![Page 8: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/8.jpg)
Hg(II) Hgo (aq)
Hgo (g)Hg(II) (s)
volatilization
deposition
oxidation
reduction
Water
Air
Natural concentrations: 5 to 100 pM (1 – 20 ng /L)
Hgo (l)dissolution
ng/L = ppt; µg/L = ppb; mg/L = ppm
Basic Chemistry of Hg
![Page 9: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/9.jpg)
Morel et al., 2002
![Page 10: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/10.jpg)
Hg(II) Hgo (aq)
oxidation
reduction
- Done by bacteria
Hg(II)Hgo (aq)
- Limited in freshwater (since not many molecules to bond with)
Oxidation-Reduction Reactions
![Page 11: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/11.jpg)
Hg(II)
Water
Air
Natural concentrations: 5 to 100 pM (1 – 20 ng /L)
Hgo (aq)
oxidation
reduction
Hgo (g)Hg(II) (s)
Hg2+, HgCl2o,
Hg(OH)2o, Hg(SH)2
o,
HgS(SH)-,
CH3Hg(SH)o
Versions of Hg (II):
![Page 12: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/12.jpg)
MeHgMeHg
HgS(HS)-
Hg(HS)2
Hg(Sn)HS-
Hgo (aq)oxidation
reduction
Hg(II)
SO42-
H2S, HS-
SRB
Sulfide and Methyl Mercury
SRB = Sulfide reducing Bacteria
(these by-products perpetuate methylation, since they cycle back into the rxn)
![Page 13: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/13.jpg)
Guadalupe River WatershedRiver system low [methylated] Hg since low [SRB]
Bay has highest [methylated Hg] since high [SRB]
![Page 14: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/14.jpg)
San Francisco Bay, ‘Stinky Mud’
Salt H2O has 1000x more sulfate than fresh H2O
![Page 15: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/15.jpg)
Hg(SH)2o
HgS(SH)-
Hg(Sn)SH-
Hg2+ + HS-
Sulfide Complexes of Hg
![Page 16: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/16.jpg)
Hg(HS)2
HgS(HS)-SRB MeHg
MeHg = CH3HgS-
CH3HgCl
CH3HgOH
Methyl Mercury (MeHg)
Less toxicMore toxic
![Page 17: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/17.jpg)
Hg(II) Hgo (aq)
Hgo (g)Hg(II) (s)
volatilization
deposition
oxidation
reduction
Water
Air
Hgo (l)
Dissolution/precipitation
Sediment(solid)
Interaction with Solids
HgS
(mined mercury)
![Page 18: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/18.jpg)
Interaction with Solids
![Page 19: Mercury in the Environment](https://reader036.vdocuments.us/reader036/viewer/2022081515/56816057550346895dcf8005/html5/thumbnails/19.jpg)
Cylcing of Mercury