Geology Final

Chile’s copper production share

Chile produces about one-third of the world’s copper supply with companies including BHP Billiton, Anglo American, and Japan’s Sumitomo Corp

Average copper concentration in the rock mined at Las Pelambres

1%

Average winter snow depth at Las Pelambres

5 meters

Hospital items made of copper

Sink, bedrails, and stethoscope

Examples of jobs at the U.S. Borax Mine

Chemist, geologist, engineer, environmental scientist, millwright, electrician, equipment operator, shipping team, commercial team, strategic planning, quality specialist

China’s position in rare earth production

China controls the world’s largest reserves of rare earth elements and is now tightening its grip

Where does 90% of the world’s rare earth refining happen?

China

What is one of the most widely applicable products that rare earths are necessary for?

Magnets

Separating rare earths from the rock they are in requires a huge amount of ___

Energy

Conflict minerals

Tin, tantalum, tungsten, gold

Definition of conflict minerals

Minerals mined in conditions of conflict where profits may fund armed groups

Value of untapped mineral resources in the DRC

Estimated at about $24 trillion

Definition of coltan

A mineral called columbite-tantalite, the main source of niobium and tantalum which are used to create capacitors for modern electronics like smartphones and laptops

Function of tin (Sn) in phones

Used to solder circuit boards

Function of tantalum (Ta) in phones

Stores electrical energy for batteries

Function of tungsten (W) in phones

Creates the vibration function

Function of gold (Au) in phones

Coats wires

What coltan is refined into

tantalum metal

Conflict situation in eastern DRC

Over 25 years of violence involving around 120 armed groups and Congolese security forces, M23 has grown large and powerful

How do some armed groups fund their conflicts?

Trade of “conflict minerals”

Oxidation of pyrite

Fe changes valence from +2 in pyrite (FeS₂) to +3 in ferric hydroxide (Fe(OH)₃)

Fe oxidation

Fe is oxidized because its valence number increases

Main oxidizing agent

Oxygen (O₂) is the most common oxidizing agent in environments in contact with the atmosphere

Pyrite oxidation reaction

4 moles of pyrite react with O₂ and H₂O to release 16H⁺, causing acidification

Where pyrite occurs

Often found in shales interbedded with coal seams, especially those formed in marine coastal swamps

Effect of strip mining coal seams

Causes acidification of local surface waters because of the oxidation of pyrite by exposure to O2 and H2O, supply of O2 and H2O is usually unlimited

Ferric hydroxide

Insoluble yellow-orange precipitate formed (Fe(OH)₃), also called yellow iron oxide

Thiobacillus ferrooxidans

Bacterium that catalyzes FeS₂ oxidation to ferric ions and H ions, increasing rate by 1,000,000× compared to O₂ alone

Characteristics of Thiobacillus ferrooxidans

Colourless, rod-shaped, aerobic, airborne, and acid-loving (pH 1.5–2.0), obtains energy through the oxidation of iron, convert insoluble metals to their soluble state

pH scale is ____ meaning a small change in pH represents a __ change in H+ concentration

logarithmic, large

Buffers

Solutions that resist pH changes by absorbing excess H⁺

Strong natural buffers

Fluids in living organisms and seawater

Weak natural buffer

Rainwater; easily acidified

Where are acid soils commonly found?

Rainforests and jungles

Where are alkaline soils commonly found?

Deserts

Effect of rainfall on soil pH

Rain combines with CO₂ to form weak carbonic acid (H₂CO₃), lowering pH to 5.6–5.7

Natural pH range for most plants

Acidic, between 5.5 and 7

True or false: sulfide minerals like pyrite that are underwater will not weather significantly. Explain.

True, if you are underwater there is not much free O2 around to make the reaction happen (O2 is required for the forward reaction)

Rusty exposure of rock

Gossan

Treatments for acid mine drainage (AMD)

Add a buffer material like limestone, limit exposed rock, compact acid-generating rock, or cover rock with sealing layers

Goal of AMD treatments

Delay or prevent oxidation of sulfides, but all have limitations

Effectiveness of wet/dry covers

Slowed sulfide oxidation, short term effectiveness, wet cover is suitable at specific sites where complete inundation is established, but it requires high maintenance costs. Dry cover plastic liners are expensive and rarely used to large volumes of waste

Bactericides for AMD

Can suppress oxidation, short-lived (not permanent solution), effective only on fresh tailings, may be toxic to aquatic life

Chemical barriers for AMD

On sulfide surfaces (applying organic and/or inorganic coatings) are effective in preventing AMD. Among inorganic coatings, silica is the most promising/stable/acid resistant and long lasting

AMD duration

Acid will leach from the rock as long as the source rock is exposed to air and water and until the sulphides are reached out - can last hundreds to thousands of years

Transport of acid from AMD

Carried off mine sites by rain or surface water into nearby streams, rivers, lakes and groundwater

Environmental impact of AMD

Causes physical, chemical, and biological degradation of stream habitats. Jeopardizes not only fish but the animals who feed on them

Physical properties of gold

Soft, malleable, pounded thin, drawn out to make a thin wire, made into shapes, doesn’t rust or tarnish

Gold bonding

Usually bonded to other metals like silver

Role of cyanide in gold processing

Helps extract gold from the other metals and leach it into the surrounding water

Gold Smelter temperature

1600°C

Name of impurities in gold smelting

Slag

Gold cyanidation

Used in 90% of gold production; most common compound is NaCN

Process of gold cyanidation

Gold is dissoluted and then recovered from solution

Problem with cyanidation

Cyanide is highly toxic and can devastate rivers and ecosystems downstream

Baia Mare cyanide spill (2000)

Massive cyanide leak in Romania from Aurul mining company into the Somes River by Aurul gold mining company. Contaminated Tisza and Danube Rivers, killing fish in Hungary and Romania. Been called the worst environmental disaster in Europe since the Chernobyl disaster

How is cyanide toxicity typically expressed?

Concentration that is lethal to 50% of the population (LC50)

Cyanide inhalation toxicity

LC50 for gaseous HCN: 100–300 ppm; causes death within 10–60 minutes

Cyanide ingestion toxicity

LC50: 1–3 mg per kg of body weight

Cyanide skin/eye absorption toxicity

LC50: 100 mg per kg of body weight

Mechanism of cyanide toxicity

Interferes with the cell’s ability to use oxygen → cellular suffocation → CNS depression and respiratory arrest

Cyanide pros and cons

Cheap, effective, biodegradable, but extremely toxic

Cyanide bans

Banned for mining in Montana, Wisconsin, Czech Republic, and Hungary. currently protests in Romania calling for a ban on the use of cyanide in mining

EU cyanide regulations (after 2000)

Mines after May 1, 2008 can’t discharge waste containing >10 ppm cyanide; companies must place financial guarantees to ensure clean up after the mine has finished. EU requires that the concentration of cyanide is reduced to the lowest possible level using best available techniques

Cyanide Code

Voluntary mining industry program for safer cyanide management with third-party audits of a company’s cyanide management

How does mercury get into the environment?

Mercury occurs naturally in small concentrations in rocks and is the main component of cinnabar (HgS); Natural background levels exist in soil, air, and water globally.

Mercury in gas

Mercury is present in gases emitted by volcanoes, mining and industrial applications for the metal have increased significantly since the industrial revolution

Base metal smelting and gold mining mercury levels

These industries emit mercury vapor, posing environmental and health hazards.

Mercury mines environmental concern

They present an environmental concern

1990 US mercury emissions

Three sectors produced two-thirds of total emissions: medical waste incinerators, municipal waste combustors, and coal-fired power plants. The first two of these sectors have been subject to emissions standards for years and as a result have reduced their mercury emissions

Coal and oil-fired power plants mercury emission

Emit mercury, metallic toxins, and acid gases; they account for 50% of US mercury air pollution.

US EPA 2011 legislation

Aimed to prevent 90% of mercury emissions, reduce 88% of acid gases, and cut 41% of sulfur dioxide from power plants.

Elemental mercury

Liquid metal form of mercury.

Inorganic mercury

Includes mercuric chloride and mercuric sulfide (cinnabar).

Organic mercury

Contains methyl groups, such as methylmercury.

Mercury conversion in water

Bacteria in sediments convert mercury to methylmercury.

Methylmercury biomagnification

Concentrations increase up to a million-fold in top aquatic predators.

Absorption of methylmercury

100% absorbed through the GI tract and distributed throughout the body.

Methylmercury formula

[H3CHg]+, major source of organic mercury exposure for humans.

Mercury cycle in power plants and fish

Coal fired power plants emit mercury —> mercury returns to the earth through precipitation. Bacteria in water convert mercury to more toxic methyl mercury —> fish accumulate methyl mercury through plants and organisms that have taken in the mercury —> people accumulate mercury through fish consumption

Health effects of mercury

Mercury is a reproductive toxin and potent neurotoxin affecting the brain and CNS.

Vulnerable populations to mercury

Pregnant women, women of childbearing age and children are most at risk; mercury crosses the placenta causing neurological damage.

CDC 2001 Mercury Women study

Found 1 in 10 US women had mercury levels high enough to cause neurological damage in their children (about 400k babies a year)

Symptoms of mercury

Deterioration of nervous system, impaired hearing, speech, vision, and gait; involuntary muscle movements, corrodes skin and mucous membranes, causes chewing and swallowing to become difficult

1971 Iraq Poison Grain Disaster

• Mass methylmercury poisoning incident that began in late 1971

• Grain treated with a methylmercury fungicide and never intended for human consumption was imported into Iraq as seed grain from Mexico and the US

• Due to a number of factors, including foreign language labelling and late distribution within the growing cycle, this toxic grain was consumed as food by Iraqi residents in rural areas

• People suffered from paresthesia (numbness of skin), ataxia (lack of coordination of muscle movements) and vision loss

• Recorded death toll was 459 people

Minamata disease

Neurological syndrome caused by severe mercury poisoning in Japan.

Minamata symptoms

Ataxia (poor muscle control causing clumsy movements), numbness, muscle weakness, vision loss, hearing and speech damage.

Minamata cause

Release of methylmercury from Chisso Corporation wastewater (1932–1968).

Minamata outcome

Methylmercury accumulated in shellfish and fish in the Minamata Bay which led to poisoning; by 2001 2,265 victims recognized (1,784 deaths).

Ontario Minamata disease

Neurological mercury poisoning affecting First Nations in Ontario. Severely affected Grassy Narrows and Whitedog and one FN in Southern Ontario due to illegal disposal of industrial chemical waste

Mercury dumping in Ontario

Over 9,000 kg of mercury released into Wabigoon-English River in the 1960s–70s by Dryden Chemical Company

Methylmercury formation in rivers

Bacteria transformed dumped mercury into toxic methylmercury.

Health impacts on First Nations

Over 90% showed poisoning signs; 28% of adults in Grassy Narrows attempted suicide (more than double the rate of other FNs)

Dental amalgam

A dental filling material of liquid elemental mercury mixed with silver, tin, and copper alloy used to fill cavities caused by tooth decays

Amalgam elemental mercury by weight/chemcials

50%, chemical properties of EM allow it to react with and bind together the silver/copper/tin alloy particles to form an amalgam

“Silver fillings”

Term refers to amalgam fillings; they do not contain pure silver but include mercury

Amalgam placement process

Tooth decay is removed, tooth cavity shaped, amalgam mixes powdered alloy and liquid mercury to form an amalgam putty. The softened amalgam putty is placed and shaped in the prepared cavity, where it rapidly hardens into a solid filling

Mercury in amalgam vs fish

Not the same as in some types of fish. Dental amalgam releases elemental mercury vapor; fish contain methylmercury (organic).

Mercury absorption routes

Mercury vapor absorbed by lungs; methylmercury absorbed through digestion. Body processes these forms of mercury differently and has different levels of tolerance for mercury vapor and methylmercury

Benefits of amalgam fillings

Durable, long-lasting, and least expensive type of filling material