ARSENIC

1
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
2
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

3
Periodic Table of the Elements
As is a Group V element (like N and P) Replaces
S in minerals and metabolic systems replaces P
in minerals and ATP energy cycle
4
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

5
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.

6
Killer Wallpaper

• As was used in 1800s as paint, wallpaper and
  fabric pigments including Scheeles green
  (copper arsenite), Emerald green (copper
  acetoarsenite) arsenical Naples s yellow, white
  arsenic trioxide.
• By 1863, 700 ton of arsenic green had been
  manufactured in Britain.
• Mass poisoning of Victorians, initially
  attributed to green dust detached from the
  wallpaper being inhaled.
• 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.
• 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 navys 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 paper a red rose (Hg) on a green
branch (As-Cu).
7
William Morris (18341896) 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

8
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 childrens play structures just a few
  years ago. Now chromate is used.
• Still used as a pesticide

9
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.

10
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.

11
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 Fe3oxyhydroxides 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

12
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

13
Giant Mine Yellowknife

• Produced gt7 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

14
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
15
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

16
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

17
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

18
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