Lance Connell
Addias Mervin
Monique M. Nurse
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There are two methods of extracting gold from
ore
 Vat leaching involves mixing extracted ore with
a CN solution in large vats.
 Heap leaching involves piling ore into large
heaps and then spraying a CN solution on the
heap and allowing the CN solution to trickle
through, stripping the gold from the ore.
Gold is readily dissolved by cyanide.
 Most the world’s gold supply is found in low
concentrations in nature and must be dissolved
from ore to be acquired. Less than 10 grams/ton
of ore excavated.
 NaCN is typically used as a solvent and diluted to
a concentration of 0.015 – 0.035% NaCN.
 Gold extraction in the Aurul plant was
approximately 700 mg/liter of slurry.

Most gold mines are often found near water
sources since water is used to dilute the NaCN to
acceptable levels for mining.
 Having a readily available supply of water cuts
down on transportation and other costs
associated with water needs.
 In the case of Baia Mare, the tailings from the
old Meda ponds, used for gold extraction are
combined with water to form a slurry that was
pumped to a processing plant where more CN is
added if needed. Then the slurry is pumped the
rest of the 6.5 km to the new Aurul gold mining
site.
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The processing plant was in charge of receiving the slurry
from the chronically leaking Meda ponds, assessing the
level of cyanide in the slurry and adding more if needed.
Cyanide levels were monitored and if needed brought to an
acceptable range of 0.015 – 0.035% NaCN within the slurry
and then pumped into the new tailing dams.
Extraction of gold as well as other precious metals were
done at this site and remaining tailings were then pumped
to the dams.
To maximize gold extraction, tailings from the new dam
were pumped back to the plant for further extraction of
extremely low levels of gold and were then pumped back
to the tailing dam.
Tailing dams hold CN treated ore wastes from
which gold has been removed.
 The Aurul tailings contained concentrations of
400 mg/liter of CN and concentrations of free CN
of 120 mg/liter.
 Tailings typically contain 0.60 g/ton of
recoverable gold.
 The Aurul tailings also contained high
concentrations of heavy metals such as: iron,
cooper, arsenic, cadmium, lead, nickel, and
manganese.
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The new Aurul tailing dams were built to replace the
chronically leaking Meda ponds located near Baia
Mare.
The dam covered 93 hectares and was 20 meters
high.
The dam was built to take advantage of the sloping
hills in the area.
Lining the dam was a plastic liner that afforded 0%
discharge into the surrounding area.
The dam wall was constructed on top of a starter
dam, with the new dam wall added as more slurry
was pumped in. The idea was to have the tailings
form the wall as more and more slurry was deposited
into the dam. Hydrocyclones were added to assist in
lining the dam wall with the tailings.
The dam wall was constructed so that the dam
could deal with storm run-off up to 118 mm.
 A decanting well was fitted in the center of the
dam so that the slurry could be re-circulated
back to the processing plant.
 Drains were also created as additional protection
against seepage into the environment.

Large businesses often find it beneficial to found
operations in areas where governmental
regulations may not be up to par.
 Many environmental organizations have pointed
this out as a major contribution to the cyanide
spill in Baia Mare.
 The Serbian Minister of Environment announced
that he will be suing the company responsible
and asks for an international trial to be held.

 The
Baia Mare area received approximately
120 mm of snowfall and 40 mm of rain from
mid-December until the end of January.
 The dam was only able to accommodate
storm run-off up to 118 mm.
 On January 30, 2000, due to the
precipitation in the area the dam crest was
flooded and over 25 meters of the dam wall
was washed away.
•Marine
Life
•Plant Life
•Water compositional change
Estimated 80% of all fish in
the Tisza River died.
Thousands of tons of fish
died.
Some fish were found to
contain 2.6 mg of cyanide
per kilogram of weight.
Extensive damage done to
the river’s ecosystems and
its fauna, affecting birds,
and carnivores.
The Cyanide plume that
traveled through the rivers
was 100 times more
concentrated than the limit
value for drinking water in
the region.
30%-60% plankton killed
The initial affect of the
high Cyanide concentrations
on the ecosystem was
devastating, however due
to Cyanide’s short lived
presence in the water the
environment was able to
begin recovery.
Heavy metals persist in
the environment and
bioaccumulate in living
organisms.
Since the incident the
heavy metals have
accumulated in the
sediments are collecting
6-10km downstream of
Baia Mare. They will
continue to be washed
downstream and spread
throughout the river
system.
The rivers that fed or were
fed into the Tisza river, have
very high heavy metal
concentrations, and the
concentration is increasing
over time.
The plume traveled down the
length of the river, into the
Danube river and then into
the Black Sea by which time
it had significantly diluted .
The waters pH would have
changed from the chemical
reactions taking place within
it.
Cyanide comes in many forms
The most lethal being that of Hydrogen
cyanide , HCN, which is lethal to
humans at 1.1 mg/kg in the blood.
In the plume that sweeped through the
river, Cyanide most likely formed
complexes with heavy metals
associated with it.
Even though free floating Cyanide is
readily degradable when it forms into a
complex ,dilution and degradation
become complicated.
Complexes: Ferrous ferrocyanide
(Fe[FeCN6]) and ferric ferrocyanide
(Fe4[FeCN6]3). And Copper ferrocyanide
(Cu2[Fe(CN)6])
 Cyanide
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Time in the environment
Reactions in the water, and wildlife
Forms of cyanide.
 The
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in nature
behavior of heavy metals in nature
What is difficult about removing these contaminants?
Where does it collect?
The Cyanide plume was measured for 2000km from
the point of origin to the Danube delta.
Free Cyanide is biodegradable, and as it continued
downstream it was easily diluted, this made the
ongoing effects of the plume short lived.
The oxidation of cyanide, can
produce cyanate which is less toxic,
and readily hydrolyzes to ammonia
and carbon dioxide.
Cyanide also reacts to Sulfur which is
found in the ore and also in the
wastewater from the tailings dam.
Cyanide and sulfur react to produce
thiocyanate, which degrades into
cyanate and sulfuric acid.
The sulfuric acid would create
Hydronium ions which would allow
for the further degradation of the
cyanate.
Hydrogen cyanide gas which has the
ability to form during these reactions
does not occur, because hydrogen
cyanide ionizes in water. Forming
CN- anions which contribute to the
reaction
The heavy metals that were
included in the plume consisted
of copper, iron, zinc, and lead.
The high levels of these heavy
metals discharged into the rivers,
would cause long term affects in
the ecosystem, because they are
not readily degradable.
This discharge creates a chronic
pollution whose damage is harder
to estimate.
These heavy metals mix with the
sediments at the water bed, are
bioaccumulated from plant and
animal life and enter into the
ecosystems food chain.
If the wastewater had any
treatment beforehand, the
damage would have been
lessened. Normally heavy
metals can be removed from
wastewater through
flocculation, but this is in a
controlled setting.
The heavy metals will
continue to be pushed and
accumulated throughout the
entire region by the physical
forces of the water current.
New exfilitration and tailings
dams were built to collect
these moving heavy metals.
The heavy metal contaminants are pumped into an exfiltration
pond where the heavy metals settle and water is drained back into
the main pond.
 Cyanide

breakdown quickly in sunlight
Into less toxic but longer-lasting forms, such as
cyanate and cyanogen
 Free
cyanide breakdown slowly when water
is covered by ice

Protected from direct sun
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Sodium hypochlorite was poured into the spill in an
attempt to neutralize the cyanide.
 Turns cyanide into a less toxic compound
The remaining water in the containment pool was
diverted into a nearby tailing dam.
Sediments from other tailing deposits
Were used to seal the breach
 Reinforce other parts of the dam
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A limited outflow of 40-50 liters per second continued
and was treated with sodium hypochlorite until
February 2.
The cyanide was biologically degraded and diluted as
it moved along the length of the river.
Water samples from surface water were taken by
three teams from the 21 sampling stations.
 Typically, the water sampling locations were
identical with those for the sediment sampling.
 The UN sampling took place about three weeks
after the plume had passed
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Could not validate any of the results obtained by the
Romanian, Hungarian or Yugoslavian experts.
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The UNEP Balkans Task Force took water samples
from the river Danube in FRY on 15-17 February
 Between Pancevo and the Iron Gate
o Cyanide concentrations were from
0.008 mg/L to 0.117 mg/L
UN team sampled surface water at the Tisza river
 Free cyanide concentrations of 0.014 mg/L
 Within an acceptable range
The UN Team recorded the plume of cyanide
contamination in the Danube Delta
 Measurements were taken between 26 and 28 of
February gave a maximum concentration of
0.058 mg/L
?

Very high concentrations of heavy metals were
detected
 Copper (total concentration 412.3 mg/L)
 Iron (total concentration 31.3 mg/L)
 Manganese (total concentration 18.0 mg/L)
 Zinc (total concentration 14.5 mg/L).
UNEP prepared new guidelines for mining
 UNEP joined with ICOLD to produce two
Technical Bulletins for laying down design
requirements and providing lessons from past
incidents as a guide to designers.
 International Council for Metals and the
Environment, a multi-stakeholder process was
launched to develop a management code for
cyanide
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Short term regulations :
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Each site will be inspected by suitably qualified personnel and
a safety/risk assessment made
Hydro-meteorological data for each site will be re-evaluated in
order to ensure that tailings ponds and lagoons are designed to
cope with extreme weather events
Assessments will be made of the structural capacity of the
tailings dams and impoundments to withstand extreme
precipitation and snowmelt events
Immediate steps to improve safety will be carried out where
these are deemed necessary
Operational and accident/emergency procedures will be
reviewed and improved where necessary at both a facility and
local administration level
All sites, will immediately be placed under regular surveillance
 Abandoned sites
 Daily inspection and tests in times of adverse weather
conditions
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