ARSENIC
Very common in most geological environments, igneous,
metamorphic and sedimentary, causing a high
background in many parts of north America
Chalcophile, oxyanionic or metalloid element often
associated with sulphide ores
Crustal abundance: 1.8 ppm, ranging from 0.1 to several
hundred ppm.
Major source of anthropogenic arsenic mobilization is
weathering of mine waste rock and tailings as gold is
often associated with arsenopyrite especially in Canada
Also common in reduced environment of coal deposits
Arsenopyrite
Orpiment
Realgar
Arsenic contamination
WHO recommended maximum in drinking water 10μg/l
EU and US EPA recommended level is 50 μg/l, which is the
level detectable by ICP OES.
Up to 5000 μg/l in contaminated water
Groundwater contamination
Argentina, Bangladesh, Chile, China, Hungary, Nepal, India,
Mexico, Romania, Taiwan, Vietnam, SW USA, Myanmar
Contamination from Geothermal Water
Argentina, Dominica, Chile, France, Japan, Iceland, New Zealand,
Alaska USA
In Mining Effluents
Canada, Ghana, Greece, Italy, Russia, Thailand, USA
Periodic Table of
the Elements
As is a Group V element (like N and P)
Replaces S in minerals and metabolic system
replaces P in minerals and ATP energy cycle
Arsenic Chemistry
Several oxidation states:
As-1 in sulphide minerals,
As0, metal, only stable in very reduced conditions but can be reduced
to As-3 in the most toxic form of arsine gas (AsH3)
As3+ As5+ are common in oxidizing conditions and soluble at all values
of Eh and pH
Oxidation of As3+ to less toxic As5+ is slow so usually both are
present in oxidized environments like mine tailings.
Arsenic can be removed from mine water by the addition of a
solution containing FeSO4.
Fe2+ is oxidized to Fe3+ and precipitates as FEOOH
Arsenate is strongly absorbed by FeOOH and precipitated
Toxicity of Arsenic
Historically arsenic trioxide was known as “inheritance dust”
In 55 AD Nero poisoned Britannicus with arsenic to secure the Roman throne
15th/16th centuries, the Italian Borgias used arsenic for political assassinations.
Napoleon may have been poisoned by arsenic-tainted wine or by the wallpaper
AsO4-3 replaces PO4-3 and cells die
AsO4-3 inhibits oxidative phosphorylation in the ATP energy cycle
AsO3-3 replaces S in thiol groups and inhibits protein functions
Absorbed by inhalation or digestion and transferred via the bloodstream to all
organs producing systemic damage.
Long term low level exposure causes hyper pigmentation (black spots on skin),
followed by skin malignancy, peripheral arteriosclerosis (black foot disease)
Lung, liver and kidney cancer develop over time.
Acute arsenic exposure results in vomiting, abdominal pain and bloody diarrhea and
death.
Killer Wallpaper
As was used in 1800s as paint, wallpaper and fabric pigments including:
Scheele’s green (copper arsenite), Emerald green (copper
acetoarsenite) arsenical Naples ’s yellow, white arsenic trioxide.
William Morris
paper a red
Mass poisoning of Victorian’s, initially attributed to green dust detached rose (Hg) on a
green branch
from the wallpaper being inhaled.
(As-Cu).
Around 1900, fungi living on wallpaper paste were found to convert
inorganic arsenic into a toxic gas trimethylarsine. This gas had killed
many children in their green decorated bedrooms.
By 1863, 700 ton of arsenic green had been manufactured in Britain.
William Morris (1834 –1996) produced beautiful papers from hand
printed, hand carved blocks from 1864 onwards.
1871. The British Medical Journal: “In the majority of dwelling houses,
from palace down to the navy’s hut, it is rare to meet with a house
where arsenic is not visible on the walls”. Often there were multiple
layers of green wallpaper.
William Morris (1834–1896) and Mining
William Morris was a utopian idealist, member of the green
movement and spoke against the environmental and
human degradation caused by industrial activity.
His mining company Devon Great Consols (DGC) was the
largest producer of arsenic in the world.
He used his income from DCG to finance his wallpaper
design company.
From 1867, DGC was the major supplier of arsenic for the
production of Scheele's green for wallpaper
Arsenic pigments were also used extensively in paints and
to dye clothes, paper, cardboard, food, soap, and
artificial and dried flowers.
Mine workers suffered widely from skin lesions known as
arsenic 'pock', and many died from arsenic-related lung
disease.
The vast environmental pollution caused by DGC persists
Domestic use of arsenic
Clothes were coloured with arsenic dyes.
1848 fashion plate: The dress is dyed with
arsenic green and the ink used on the print
green is a copper-arsenic salt.
Eating arsenic produced a rosy complexion
and enhanced “beauty”
Arsenic eaters became immune to the toxic
effects
The “arsenic eaters” of Austria found that
arsenic has a tonic effect and have built up
a tolerance for it, so that they can ingest
each day an amount that would normally be
a fatal dose.
Pressure treated lumber used arsenic to kill
insects and bacteria until high arsenic was
found beneath children’s play structures just
a few years ago. Now chromate is used.
Still used as a pesticide
Arsenic as Medicine
Inorganic arsenic has been used in medicine for over 2500 years.
Fowler solution, 1% potassium arsenite, was widely used for treating
psoriasis since 1786.
Donovan's solution, AsI3, and de Valagin's solution, AsCl3, treated
rheumatism, arthritis, malaria, trypanosome infections, tuberculosis,
and diabetes.
Salvarsan, arsphenamine, was the main treatment for syphilis from 1909
until it was replaced by penicillin in the 1940s.
Arsenic is still used in the treatment of severe parasitic diseases.
2004, Switzerland: arsenic trioxide is licensed for patients who have
relapsed after initial therapy for acute promyeloctytic leukaemia.
Oriental medicines can contain arsenic
January 24, 2008 Health Canada has issued a safety alert warning
consumers that Yeniujyn, a natural health product sold as a treatment for
"involuntary passage of urine diseases," contains high levels of lead and
arsenic.
Arsenic in India and Bangladesh
Water from tube wells is contaminated with
arsenic.
Surface water is contaminated with
pathogenic bacteria causing cholera etc.
The tube wells were put in to provide “safer”
water with no pathogens and irrigation
water for more intensive agriculture during
the “Green Revolution”
People become sick with skin lesions, black
skin, and eventually cancer. They are
shunned by others who think that the
disease is contagious.
Men and children are more affected than
women.
Bangladesh about 20% of wells are
contaminated and an estimated 80 million
people are dependent on those wells for
domestic purposes and affected by
arsenic poisoning.
Source of Arsenic (Kirk Nordstrom)
• As-rich sulphide deposits in the Himalayas erode and
As-rich sediment is continuously deposited in the
Ganges Delta.
• Mobilization in the well water.
• Oxidation of As rich pyrite with lowering of water table
and oxygenation of ground water. Fe2+ oxidizes to Fe3+
and precipitates as Fe oxyhydroxides scavenging As.
• Dissolution of Fe3+oxyhydroxides with the release of As
from the surface in reduced conditions in the aquifer.
• Phosphate, from seawater flooding area, can replace As
in absorption sites on Fe oxyhydroxides and in
sulphides. As released in aquifer
Solutions to arsenic poisening in Bangladesh
A period of drinking clean water improves the condition of least affected
people as As does not bioaccumulate unlike heavy metals.
Educate people about cause of illness. This has been done in most areas
Switch to less contaminated wells. This has been shown to be successful
despite prognosis that people would not switch if it involved a longer
walk
Dig deeper wells into uncontaminated aquifer. This is proving to be
successful in Bangladesh and the deep wells are not becoming
contaminated
Treat well water with Fe or Al to precipitate As. This is not very successful as
people stop treating after a time
Use surface or rainwater for drinking but chlorinate to prevent disease. This
is not successful and may lead to further outbreaks of cholera etc.
Increase nutrition particularly folic acid. There is a relationship between folic
acid and the effect of As
Increase Se. There is a relationship between Se deficiency and the effect of
the As.
More doctors to evaluate and monitor health. This is happening
Giant Mine
Yellowknife
Produced >7 million oz
Au from1948 to 1999
from refractory
arsenopyrite ore. Au is
submicroscopic and
not extractable by
cyanidation
Extraction process was
crushing, grinding
flotation and roasting
ore
Tailings
1948-1951 deposited directly into Yellowknife
Bay close to Townsite community.
After 1951 deposited into Bow Lake on Giant
Minesite.
Streams carried tailings, and calcined ore
from ponds to Yellowknife Bay
In 1971 clay cored dams were constructed to
prevent runoff from tailings
Intake for Yellowknife water in Bay moved up
stream of discharge from mine.
Beach at Town site is contaminated
with As.Houses (and playground)
are being demolished
Legacy of Roasting Ore
1949 to 1951 the As2O3 and SO2 went
up the stack and was deposited
down wind of the mine
After 1951 As2O3 was collected using
in an electrostatic precipitator,
(ESP) collected and blown directly
underground and stored behind
bulkheads in mine out chambers
1958 dust from ESP treated with
cyanide to remove Au prior to
deposition in tailings ponds
Environmental
Issues
Tailings in ponds
Contaminated beach area
Contaminated Streams on
Mine Site
Roaster Ore deposited on
Mine Site
Soluble As2O3 stored
underground in
chambers that are the
equivalent size of
seven 11 story office
blocks and are leaking
Solutions to Environmental Issues
Tailings pond water being treated with FeSO4 to
remove As
Monitoring of ground and surface water
Mineralogical and geochemical studies of tailings,
calcined ore, soil, beach deposits and lake
sediments by INAC
Solution to 237,000 tonnes
As2O3 dust releasing As from
underground chambers
Not possible to remove and bury
elsewhere because of expense and
danger to community and workers
during removal and after reburial.
Solution accepted by community and
INAC is to reintroduce permafrost
around the chambers using active
and passive refrigeration units.
Now there is a new public review called
for to determine if this is the correct
solution