The Causes and Effects of Mercury Contamination in the Amazon River

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The Causes and Effects of Mercury Contamination
in the Amazon River

• Presented by
• Steven Wilson

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Objective
What We'll Be Discussing During This Presentation

• Some demographic facts about the Amazon River
  system
• A look at the amount of biodiversity of life that
  the river sustains
• An idea of how vital fish are from an economic
  perspective as well as that of a survival
  necessity for local Amazonian citizens
• The current gold mining rush and why gold mining
  is an important factor in mercury addition to the
  Amazon River
• A brief look at the impact that pollution of the
  river from mercury has on both humans as well as
  top aquatic carnivores

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Introduction
The Amazon River
the worlds second longest river which is
estimated to be about 6,280 km long feeds
nearly 175,000 m³/sec. of water into the Atlantic
Ocean drains nearly 6,915,000 square kilometers
of land within the Amazon River Basin has an
average depth of about 50 m contains 20 of the
Earths fresh water is one of the most
mineralized river systems in the world
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Introduction
A River of Life
2,000 fish species
1,000 bird species
60 reptile species
300 mammal species
10 million humans
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Introduction

• Fishing is by far the leading source of protein
  and income for people living along the Amazon
  River
• Its estimated that about 54,672 subsistence
  fishers support about 76,000 families with Amazon
  River fish
• The Amazon River is also a key ecosystem for
  global fish production
• The annual gross catch usually averages about
  83,800 tons of fish which are compromised of
  about 200 marketable species
• About 168,315 people are employed through the
  fishing industry and around 389 million is
  generated annually
• In 2001, about 5 million tourists visited the
  Brazilian Amazon River
• About 10.8 of the gross domestic product in
  Brazil derives from ecotourism

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In the last 20-30 years, carnivorous apex
predators have undergone large declines and
native fishermen have an increasing series of
health risks facing them.
Management Problems
the Amazon River Dolphin was listed as a
vulnerable species in 1994 the Giant Otter has
been listed as an endangered species since 1973
testing of human hair samples, in several
different experiments, along main tributaries
of the Amazon River, epidemiological and
toxicological data have shown fish-eating
riverside populations with mercury levels of
more than 10 µg/g which is the limit of
tolerance determined by the World Health
Organization high mercury levels will
eventually affect the human nervous system and
levels over 10 µg/g have been linked as being a
cause of chronic Minamata disease
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Management Problems
This could be attributed to the effects of severe
deforestation
Slash and burn methods of land clearance do, in
fact, release large amounts of mercury out of
plant tissue and out in to the atmosphere Its
thought that Brazil has lost 150,000 sq. km. of
forest in only the last 5 years from methods
such as these
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Some declines may be linked to agricultural
expansion which has contributed significantly to
slash and burn deforestation. Livestock
production has increased dramatically in the
Amazon region and cattle are very large producers
of methane gas (CH4), which well come back to.
Between 1991 and 2001, the Amazon cattle
population grew from 21.6 million to 56.2 million
and very little research has been done to
determine effects caused by overgrazing.
Management Problems
Or maybe even some type of over-hunting/harvesting
is changing the ecosystem.
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It has been pretty well established though,
that these problems do derive from some type of
pollution. In the last two decades it has been
concluded by most scientists that the cause of
these extirpations and poor human health is most
likely a result of some type of severe mercury
contamination of the Amazon River, most likely
methylmercury (MeHg). MeHg is an abreviation for
CH3Hg which is a highly toxic form of organic
mercury. Its levels in the Amazon River has
increased rapidly in the last few decades. My
selected publication was written in 1999 by
Helena do Amaral Kehrig and Olaf Malm. It
documents the capture of 164 fish from study
areas along smaller river systems which adjoin
the Brazilian Amazon River. Each fish captured is
tested for the amount of Me and MeHg that is
present in its tissue. The capture site as well
as the species and feeding tendency of each fish
is also recorded.
Management Problems
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Starting in 1520, Spanish conquistadors conquered
the Aztec city of Tenochtitlan with the hope of
taking over the Aztec gold and gold deposits.
This one element and first additional gold rush
was the main priority in this dramatic and brutal
inquisition of Central and South America.
Management Problems
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Even today, priorities seem to have changed very
little as large scale gold mining operations
along the Amazon River and its many tributaries
has increased dramatically since 1980.
Management Problems
With S. America now in this second gold rush,
Brazil is the 2nd largest gold producing
country in the world and the 1st in S. America
Between about 200,000 and 400,000 miners are
thought to make a living from mining along the
Amazon River system currently
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The problem is that the cheapest, most efficient
method of panning gold out of the river sediments
is to amalgamate the Gold particles using Mercury.
Management Problems
Its though that about 170 tons of Hg enter the
Amazon system every year because of improper
use of these methods Its estimated that
between 1550 and 1880, 200 thousand metric tonnes
of mercury was released into the Amazon
ecosystem Since only 1980 though, about an
additional 2,000 tons of Mercury has been
dumped into the river system as a result of this
Gold extraction method
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A total of 164 fish were captured in several
different areas along the Brazilian Amazon in the
Medeira River and the Tapajos River for testing
of specific mercury concentrations. These capture
sites can be seen here.
Materials and Methods
Source from Kehrig and Malm, 1999
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Special emphasis during the capture was placed on
obtaining Amazonian fish that match the criteria
of the four different feeding habits
carnivores (Piranha, Bagre, Pescada, Tucunare,
Aruana, Mapara, and Bagre) omnivores (Pacu,
Piau, Sardinha, and Acara) detrivores
(Branquinha and Cara,) herbivores (Aracu)
Materials and Methods
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Total numbers of each type of fish captured.
Materials and Methods
Source from Kehrig and Malm, 1999
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Fish were tested in the Laboratorio de
Radioisotopos (UFRJ) in Rio De Janeiro, Brazil)
For total mercury (Hg) -muscle tissue of fish
samples was acid-digested and was subject to
atomic absorption and spectrometryFor
methylmercury (CH4Hg) -muscle tissue was
digested with an alcoholic potassium hydroxide
solution before the digested sample was slightly
acidified with hydrochloric acid -the sample
was then washed with n-hexyl and the
methylmercury was re-extracted with
dithizonebenzene - the organic layer was then
washed twice with sodium hydoxide to remove
excess dithizone and subsequently with distilled
water before being acidified with hydrochloric
acid -this procedure was then followed by ECD-GC
measurement where the quality of the analytical
methylmercury and total mercury was certified
through inter-comparison exercises between UFRJ
and the National Institute for Minamata
Disease
Materials and Methods
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Results
Source from Kehrig and Malm, 1999
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Results
Source from Kehrig and Malm, 1999
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because carnivorous fish species are at the top
end of the food chain, they are a very good
indicator of mercury in fish of these 45
carnivorous fish species collected, 37 had a
Mercury concentration above the maximum limit of
0.5 mg kg-1 wet. Wt. established for food by
Brazilian legislation the mean percentage of
MeHg relative to total mercury were more than
80, indicating that organic mercury was the
predominant form of mercury in the fish muscle
tissue which has been indicated in table 2 in
table 2, methylmercury concentrations also showed
a decreasing value along the food chain from
carnivorous to omnivorous, detrititivores and
herbivore species which indicates that
bio-magnification is probably occurring in these
food chains in general, concentrations of MeHg
in carnivorous fish was higher in places close to
gold mining activity such as the Madeira River
Basin ( one of the most mineralized river systems
in South America) and the Tapajos River basin
near Itaituba City though the Negro River has
little gold mining activity, unique
biogeochemical characteristics give it a
naturally high Hg concentration fish taken from
other non-gold mining areas, like the Balbina
Reservoir, presented a much lower mean MeHg
concentration
Results
What The Results Tell Us
About Mercury Levels In The Amazon River
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Results
Bio-magnification
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the Amazon River harbors an extreme abundance
of diversity many parts of the economy, as well
as that of local consumers, rely heavily on fish
production which can be as high as 83.8 thousand
tons each year eco-tourism around the river
system accounts for 10 of the GDP though gold
extraction has been a priority for nearly 500
years all over South America, since only 1980,
2,000 tons of Mercury has been dumped into the
Amazon River system as a result of the poor
extraction methods being used there since then,
local extinctions and large scale declines of
many apex predators has followed as well as a
significantly increased level of Hg levels in
human consumers there is now scientific data
proving a direct link between the gold mining
sites and the areas where fish mercury levels are
highest
Conclusions
A Brief Review
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Conclusions
Future Recommendations
One problem is that this isnt just happening
on the Amazon River system, this is a problem all
over S. America. Brazil has always attempted
to be a pro-environmental country, so for the
issue to be resolved in the near future Brazil
will have to lead the way in the formation of
some type of treaty pact with all of the rest of
the S. American gold producing countries like
Peru, Columbia, Venezuela, and Bolivia. Things
a successful pact would have to include - a
clear restriction on the use of mercury for gold
mining - education of alternative methods of
gold panning - an enforcement method to control
the trade and sales of mercury another option
Brazil might consider is to work harder at
expanding its still small eco-tourism industry
which has been so successful in countries like
Costa Rica this could harbor a lot jobs for many
would-be gold miners that might find
eco-tourism safer and more fulfilling.
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References
Almeida, O., Lorenzen, K., and McGrath D., 2001.
The Commercial Fishing Sector of the Regional
Economy of the Brazilian Amazon. Blackwell
Synergy, 8 p 253. Filho, Rodrigues and Maddock,
J.E.L., 1997. Mercury pollution in two gold
mining areas of the Brazilian Amazon. Journal of
Geochemical Exploration, 58 231-240. Kehrig,
Helena do Amaral and Malm, Olaf, 1999.
Methylmercury in fish as a tool for understanding
the Amazon mercury contamination. Applied
Organometallic Chemistry. 10 689-696. Malm,
Olaf, 1998. Gold Mining as a Source of Mercury
Exposure in the Brazilian Amazon. Environmental
Research, 77 73-78. Palheta, Dulcideia and
Taylor, Andrew, 1995. Mercury in environmental
and biological samples from a gold mining area in
the Amazon region of Brazil. The Science of the
Total Environment, 168 63-69. Uryum, Yumiko
Malm, Olaf Thornton, Iain and Cleary, David,
2001. Mercury Contamination of Fish and Its
Implication for other Wildlife of the Tapajos
Basin, Brazilian Amazon. The Journal of the
Society for Conservation Biology, 15 p
438-446. Webb, Jena, 2004. Mercury in Fish-eating
Communities of the Andean Amazon, Napo River
Valley, Eduador. EcoHealth, 1 SU59-SU71.