EVS1101 Midterm 1

earths core is rich in

Fe and Ni

The bulk of Canadas U mines are found in

northern SK

Canadian limit of ppl for safe drinking water

10ppb

_________ is used to extract gold

cyanide

T or F: adding lime to mine tailings can help attenuate acid mine drainage by raising pOH

F, increase the pH

Acid mine drainage

liquid solution originating from the oxidation of metal sulphides present in mining residues that is acid and contains high concentration of sulphate and heavy metals

Canada is the ___ largest producer of oil in the world

6th

What does the following equation represent?

FeS2 (s) + 7/2O2 + H2O = Fe2+ + 2SO42‐ + 2H+

Chemical oxidation of iron di‐sulfide

What does the following equation represent"

14 Fe3+ + FeS2 (s) + 8H2O = 15 Fe2+ + 2SO42‐ + 16H+

Chemical oxidation of pyrite by oxidized iron

What are mine tailings?

crushed rocks and water originating from the ore extraction and placed in natural or artificial impoundments --> waste form mining

what is potash made of?

NaCl, KCl. Canada is a leading producer

T or F: in situ carbonation does not work in acidic rocks

T because carbonate minerals dont form under acidic conditions, they dissolve

What does the following equation represent? 2NaAlSi3O8 + 2 H+ + H2O = Al2Si2O5(OH)4 + 4SiO2 + 2Na+

Partial transformation of a sodium feldspar into mica and silica

Total Dissolved Solids (TDS)

in river: 118mg/L

in lake: 7?

in ocean:35 mg/L

water res: 7mg/L

Explain how diatoms can be used to reconstruct pH conditions of lake bodies in the past

- Different species of diatoms are known to prefer particular windows, or niches, in pH (some prefer slightly acidic waters, some prefer non-acidic settings). By following the change in the distribution of such species we can work out how the pH of the water changed

- Made of silica, they do not break down easily so are preserved in the lake sediments

What does the following chemical equation represent? H+ (aq) + HCO3- (aq) = H2CO3 (aq)

Neutralization of acidity by bi-carbonate ions

why does thermal stratification develop in some lakes?

because the density of water varies with temperature. cold water sinks to the bottom of lakes in the summer because they are desire than warm water

two natural sinks of CO2

oceans and forests

Dobson unit

Used to measure the concentration of the ozone.

pyrometallurgy (smelting)

use of high temp to process metals or their ores.

step 1: roasting

step 2: reduction

earth stats (mass, age, diameter)

mass: 5.98x10^24 kg

circumference: 40 041 km

diameter: 12 742km

age: 4.6 billion

oldest rock ~4.55 billion

earths structure

inner core, outer core, mantle, crust

core

Fe, Ni and some Si

outer: liquid Fe

inner: Fe, Mg, Si, and O

Mantle

the layer of the earth between the crust and the core, variable comp, Fe, Mg and Si an O; 2800km thick

crust

rocky outer skin; mostly O and Si

continental (~45km; mostly granite) and oceanic (~8km)

asthenosphere

the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

rock cycle

1. igneous: cooling of molten rock

2. sedimentary: precipitation (chemically) or cementation of particles

(erosion of other rocks) compressed to form new rock

3. metamorphic: heat and pressure transforming sed rock

carbon cycling

CO2 -->CH2O via photosynthesis

-Inorganic carbon dioxide (CO2) undergoes photosynthesis (redox reaction) by plants to become organic carbohydrates (CH2O). Organic carbohydrates then are OXIDIZED for energy which releases carbon dioxide.

sulfur cycling

Fe2+--> Fe3+ via oxidation

iron cycling

S2- to SO4 via oxidation

hydrosphere

All the water at and near the surface of the earth, 97% of which is in oceans; 70% of surface covered with water

lithosphere

solid reservoir

Ecosphere

living reservoir

point source pollution

Pollutants discharged from a single identifiable location (e.g., pipes, ditches, channels, sewers, tunnels, containers of various types). readily measurable

nonpoint source pollution

pollution that originates from a large, diffuse area. more Dif to measure

sinks

a process that removes substance form ac certain reservoir

major sources of acidity in water

1. carbonic acid (H2CO3): dissolution of CO2 and carbonate minerals

2. organic acids: breakdown of vegetation

3. sulfuric acid: oxidation of sulphide minerals and AMD

acid crater lakes

formed by gases such as HCL, H2S and SO2 bubbling up from the earths deep underlying magmas and issuing into water to form sulfurous, sulfuric and hydrochloric acids

1 ppm

1000ppb

1ppb

10^-6g/L

1ppm

1mg/L or 10^-3g/L

1m^3

1000L

µ

micro (10^-6)

m

milli (10^-3)

n

nano (10^-9)

Mining Activities

U: worlds leading producer --> northern SK

potash: largest in world (for fertilizer) --> southern SK and western MB

diamond: canada is the 5th largest producer --> NW territories

Mining process

1. exploration

2. mining/milling --> tailings

3. smelting/processing

- SO2 air pollution --> can be turned into acid rain

4. post-operational

smelting

pyrometallurgy (use of high temp to process metals or their ores (step 1=roasting, step 2=reduction)

hydrometallurgy (leaching): extraction of metals from dissolution of ore in acid conditions

Canadas energy portfolio

-Oil - proven resources, oil sands Primarily in the form of oil sands

-Natural gas - World s 4th largest producer & 6th largest consumer -Uranium - Largest producer of uranium in the world -Hydroelectricity - 3rd lrgst producer of hydro electricity -Significant undeveloped potential -Renewables - large land area & coastline suit exploitation of solar, wind (and perhaps wave) energies

environmental impacts: air

SOx and NOx directly into atmosphere

- ie Queenstown, Tasmania, AU

environmental impacts: water

treated and stored on site, spills can occur though. from mine dewatering, liquid effluents in mining and surface water drainage

- example: Omai gold mine in Guyana 1995 3.2 million m3 of cyanide tailings into adjacent river

Acid mine drainage

- Exposure of metal sulfides (e.g. pyrite FeS2) in mine tailings and waste rock may generate acid mine drainage

- Acidic waters rich in dissolved metals

pyrite

iron disulfide (FeS2).Pyrite is crushed waste rock of mines, it is mixed with water and released into open air pits where it slowly reacts with oxygen, oxidizes and dissolves. Acidity from H+ generated.

- oxidized to from Fe2+ and 2SO4

steps of AMD

1. oxidation of sulphide

2. oxidation of iron

why is AMD a problem?

1 mole of Pyrite oxidized produces 16 moles of acidity. It is also a positive feedback reaction as Fe3+ can become an oxidant of pyrite (FeS2). This means that once acid mine drainage starts it will continue as long as there is pyrite because iron is recycled.

AMD mitigation

1. constructed wetlands

2.anoxic limestone drainage

3. phytomediation

constructed wetlands

Artificially constructed wetlands with no oxygen allowing for the residence of sulphate-reducing bacteria. This bacteria turns sulfate into sulfide which precipitates as a metal sulfide. Requires plants that tolerate acidity.

anoxic limestone drainage

A bed of limestone for the acidic water to run through and react with it's calcium carbonate, increasing pH of water. This does not remove sulfate but allows metals to precipitate.

Phytoremediation

A method of cleaning hazardous waste by using plants to take up toxic material such as heavy metals from the soil. If plant dies on site, however it will decompose and oxidize and waste will return to where it originally was

organic compounds association with AMD

Base metal milling uses a flotation process where chemicals are mixed with ore in water solutions to separate the mineral from the ore. Flotation reagents used may include kerosene, organic flotation agents, and sulfuric acid. Residual reagents can be found in liquid waste from mill or in tailings

cyanide association with AMD

Used to concentrate gold in milling process & can be found in milling water and tailings. Toxic but can be removed from effluent by natural degradation or through treatment before discharge.

natural gas mining

Through drilling and pumping towards surface. Canada is world's 4th producer and it mostly comes from offshore Atlantic & Alberta

thermogenic natural gas and biogenic natural gas

- A natural gas that results from compression and heat deep underground, often found with oil

- Created at shallow depths such as landfills and swamps by bacterial anaerobic decomposition of organic matter

fracking

A hole is drilled and a high pressure of water, sand, and chemicals displaces methane from pores causing it to rise to surface for use. This method is controversial & banned in many European countries (minus UK)

3 options for CO2 sequestration

1. Geological storage

2. Ocean storage

3. Mineral storage

geological

CO2 placed in sedimentary rock, depleted oil reservoirs, or coal beds to prevent it from escaping into atmosphere. There must be an impermeable rock above to prevent escape. Exists in Norway & Canada but only small facilities.

ocean storage

CO2 placed deep into Ocean to be isolated from atmosphere. Not effective because CO2 would dissolve into ocean to form carbonic acid & acidify the ocean, ruining shell life. Also still contributes to global carbon budget.

mineral storage

Creating stable minerals like calcite and magnesite, by reacting CO2 with silicate minerals containing Ca and Mg. This would be a large operation where silicates would have to be mined and crushed. CO2 could also be injected in basaltic rocks to form new carbonates in situ.

soil profile

O-thin layer of OM

A- topsoil, inorganic minerals and partly decayed OM

E- leached zone, minerals remaining from dissolution

B- accumulation zone

C- course rock, large particles only slightly weathered

R- bedrock

Lakes

- Residence time (how long water stays in lake)

- TDS depends on that of the rivers flowing into in

Rivers

- derived from rainwater that has either run off or run thru its surrounding rocks

- TDS=118mg/L

- Q= AV (m^3/sec)

- A= cross sectional area

- V= average velocity

oceans

- TDS= 35g/L

pollutants

- PAH (polycyclic aromatic hydrocarbons)

- PCB (polychlorinated biphenyl) & persistent organic pollutants (POP)

- heavy metal (natural and anthropogenic sources)

change in storage of mass

mass transported in - mass transported out = mass eliminated by sinks or produced

transport and dispersion

J=CV

- J=fluid density --> rate at which a chemical is transported by unit area

- C=chemical concentration

-V= fluid/air velocity