cyanide spill at baya mare by lance connell, addias mervin, monique m. nurse

8/10/2019 CYANIDE SPILL at BAYA MARE by Lance Connell, Addias Mervin, Monique M. Nurse

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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.


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Gold is readily dissolved by cyanide.

Most the worlds 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.


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Most gold mines are often found near watersources since water is used to dilute the NaCN toacceptable levels for mining.

Having a readily available supply of water cuts

down on transportation and other costsassociated with water needs.

In the case of Baia Mare, the tailings from theold Meda ponds, used for gold extraction arecombined with water to form a slurry that waspumped to a processing plant where more CN isadded if needed. Then the slurry is pumped therest of the 6.5 km to the new Aurul gold miningsite.


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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 slurryand 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 damwere pumped back to the plant for further extraction of

extremely low levels of gold and were then pumped back

to the tailing dam.


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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 thechronically leaking Meda ponds located near BaiaMare.

The dam covered 93 hectares and was 20 metershigh.

The dam was built to take advantage of the slopinghills 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 slurrywas pumped in. The idea was to have the tailingsform the wall as more and more slurry was depositedinto the dam. Hydrocyclones were added to assist inlining the dam wall with the tailings.


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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.


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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.


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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 accommodatestorm 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 wallwas washed away.


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Marine Life

Plant Life

Water compositional change


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Estimated 80% of all fish inthe Tisza River died.Thousands of tons of fishdied.Some fish were found tocontain 2.6 mg of cyanideper kilogram of weight.

Extensive damage done tothe rivers ecosystems andits fauna, affecting birds,and carnivores.The Cyanide plume thattraveled through the rivers

was 100 times moreconcentrated than the limitvalue for drinking water inthe region.30%-60% plankton killed


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The initial affect of thehigh Cyanide concentrations

on the ecosystem was

devastating, however due

to Cyanides short lived

presence in the water theenvironment was able to

begin recovery.


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Heavy metals persist inthe environment andbioaccumulate in livingorganisms.

Since the incident the

heavy metals haveaccumulated in thesediments are collecting6-10km downstream ofBaia Mare. They willcontinue to be washed

downstream and spreadthroughout the riversystem.


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The rivers that fed or werefed 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.


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Cyanide comes in many formsThe 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])


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Cyanide in nature Time in the environment

Reactions in the water, and wildlife Forms of cyanide.

The behavior of heavy metals in nature What is difficult about removing these contaminants?

Where does it collect?


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The Cyanide plume was measured for 2000km fromthe 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.


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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 intocyanate 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


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The heavy metals that wereincluded 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 arenot 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.


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If the wastewater had anytreatment beforehand, thedamage would have beenlessened. Normally heavymetals can be removed fromwastewater throughflocculation, but this is in acontrolled setting.

The heavy metals willcontinue to be pushed andaccumulated throughout theentire region by the physicalforces of the water current.

New exfilitration and tailingsdams were built to collectthese moving heavy metals.


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The heavy metal contaminants are pumped into an exfiltration

pond where the heavy metals settle and water is drained back intothe main pond.


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Cyanide breakdown quickly in sunlight

Into less toxic but longer-lasting forms, such as

cyanate and cyanogen

Free cyanide breakdown slowly when wateris covered by ice

Protected from direct sun


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Sodium hypochlorite was poured into the spill in anattempt 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

A limited outflow of 40-50 liters per second continued

and was treated with sodium hypochlorite untilFebruary 2.

The cyanide was biologically degraded and diluted asit moved along the length of the river.


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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

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 samplesfrom 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 of0.058 mg/L


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?

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).


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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 : 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 inorder to ensure that tailings ponds and lagoons are designed tocope with extreme weather events

Assessments will be made of the structural capacity of thetailings dams and impoundments to withstand extremeprecipitation and snowmelt events

Immediate steps to improve safety will be carried out wherethese are deemed necessary

Operational and accident/emergency procedures will bereviewed and improved where necessary at both a facility andlocal administration level

All sites, will immediately be placed under regular surveillance

Abandoned sites

Daily inspection and tests in times of adverse weatherconditions


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1. Kovac, C ,Cyanide spill threatens health in Hungary. 2000 BMJ320,7234

2. UNITED NATIONS OFFICE FOR THE COORDINATION OF HUMANITARIAN AFFAIRS - OCHA-Online

http://www.reliefweb.int/ocha_ol/programs/response/unep/rombaiamare.html

3. Argeseanu, Solveig. "Incident, Accident, Catastrophe: The Baia Mare Cyanide Spill"Paperpresented at the annual meeting of the American Sociological Association, Hilton SanFrancisco & Renaissance Parc 55 Hotel, San Francisco, CA,, Aug 14, 2004 . 2009-05-26

4. www.wise-cranium.org/mdafbm.html

5. http://www.allacademic.com//meta/p_mla_apa_research_citation/1/0/9/1/8/pages109181/p109181-1.php

6. Cyanide Spill at Baia Mare Assessment misson report UNEP OCHA

7. www.lenntech.com/environmental-disasters.htm

8. www.reliefweb.iint.ocha_ol/programs/respons/unep/rombaiamare.html

9. Kanthak, J,The Baia Mare Gold Mine Cyanide Spill: Causes, Impacts, and Liability, GreenpeaceInternational, 2000

10. http://www.lenntech.com/environmental-disasters.htm

11. Garvey, Tom et. al., Report of the International Task Force for assessing the Baia MareAccident. December 2000

12. Shefchek, J et al., Subsurface fate and transport of Cyanide at MGP sites, Land Contaminationand Reclamation, 3 n4 1995

13. Levei, E.A. et al, Surface water pollution with heavy metals in Baia Mare mining basin,Research institute for Analytical Instrumentation, 2000

14. www.enviroliteracy.org/article.php/1120.html
http://www.reliefweb.int/ocha_ol/programs/response/unep/rombaiamare.htmlhttp://www.wise-cranium.org/mdafbm.htmlhttp://www.lenntech.com/environmental-disasters.htmhttp://www.reliefweb.iint.ocha_ol/programs/respons/unep/rombaiamare.htmlhttp://www.lenntech.com/environmental-disasters.htmhttp://www.enviroliteracy.org/article.php/1120.htmlhttp://www.enviroliteracy.org/article.php/1120.htmlhttp://www.lenntech.com/environmental-disasters.htmhttp://www.lenntech.com/environmental-disasters.htmhttp://www.lenntech.com/environmental-disasters.htmhttp://www.reliefweb.iint.ocha_ol/programs/respons/unep/rombaiamare.htmlhttp://www.lenntech.com/environmental-disasters.htmhttp://www.lenntech.com/environmental-disasters.htmhttp://www.lenntech.com/environmental-disasters.htmhttp://www.wise-cranium.org/mdafbm.htmlhttp://www.wise-cranium.org/mdafbm.htmlhttp://www.wise-cranium.org/mdafbm.htmlhttp://www.reliefweb.int/ocha_ol/programs/response/unep/rombaiamare.html

cyanide spill at baya mare by lance connell, addias mervin, monique m. nurse

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