Bassins À Résidus

Question 1

What was the method used for tailings disposal from 1900 to 1940?

Answer 1

Direct disposal into watercourses

This period marked the beginning of environmental concerns regarding mining waste.

Question 2

What significant legal action occurred in 1910?

Answer 2

First legal actions against mining tailings disposal

This was a response to the environmental impact of mining activities.

Question 3

What method was introduced in 1915 for tailings management?

Answer 3

Confinement structures, upstream method

This method aimed to contain mining waste more effectively.

Question 4

What advancement in tailings management occurred in 1930?

Answer 4

Cyclones, centerline method

This method improved the separation of solids from liquids in tailings.

Question 5

What major equipment was used for tailings management in the 1950s?

Answer 5

Heavy earthmoving equipment, dams

This equipment facilitated the construction of more robust containment structures.

Question 6

What environmental issues arose between 1960 and 1975?

Answer 6

Seepage problems and Acid Mine Drainage (AMD)

These issues prompted a shift to downstream methods for tailings disposal.

Question 7

What are the physical characteristics of soft rock tailings?

Answer 7

Potassium (K2CO3), fine coal tailings, trona [Na3(CO3)(HCO3).2H2O]

These materials are significant in assessing the environmental impact of mining.

Question 8

What are the predominant characteristics of hard rock tailings?

Answer 8

Lead (Pb), Zinc (Zn), Copper (Cu), Gold (Au), Molybdenum (Mo), Nickel (Ni)

These metals are often present in mining waste and can contaminate the environment.

Question 9

What is a major environmental problem associated with tailings disposal?

Answer 9

Water contamination by solids, heavy metals, and chemical reagents

This contamination has serious implications for local ecosystems and water quality.

Question 10

What is the objective of tailings management?

Answer 10

Tailings must be disposed of in an acceptable manner

This involves compliance with legislation and potential long-term site rehabilitation.

Question 11

What is a challenge in tailings management?

Answer 11

The nature of tailings varies significantly

This variability complicates their transportation and disposal.

Question 12

What is backfilling in mining?

Answer 12

Returning tailings underground to fill mined-out spaces

This method reduces surface footprint and can support remaining ore extraction.

Question 13

What is a common method for treating mining tailings?

Answer 13

Treatment with lime (CaO) to neutralize acids

This process helps precipitate heavy metals as insoluble hydroxides.

Question 14

What are conventional tailings characterized by?

Answer 14

30-40% solids

This is typical for tailings that are not thickened before disposal.

Question 15

What are thickened tailings?

Answer 15

Tailings with 60-70% solids, often in a paste form

These tailings have a higher density and lower water content.

Question 16

What is a key feature of thickened tailings in cake form?

Answer 16

80-90% solids

This form allows for easier handling and transportation.

Question 17

What is the role of thickeners in tailings management?

Answer 17

Concentrate solids and reduce water content

Thickeners enhance the efficiency of tailings disposal.

Question 18

What type of filtration operates continuously?

Answer 18

Vacuum filtration

This type allows for simultaneous discharge of solids and filtrate.

Question 19

What are the main types of filters used in tailings management?

Answer 19

Drum filters, disc filters, horizontal belt filters

Each type has specific applications in mineral processing.

Question 20

What is the purpose of drying in tailings processing?

Answer 20

Reduce moisture content to about 5 wt.%

This step is crucial for preparing tailings for safe disposal or reuse.

Question 21

What is a significant advantage of recycling water in mining?

Answer 21

Reduces financial risks associated with dam failures

Water recycling also improves environmental performance.

Question 22

What is the definition of toxicity in terms of heavy metals?

Answer 22

The capacity of a substance to produce harmful effects on health

This is critical for assessing the impact of mining on human and ecological health.

Question 23

What is the definition of toxicity?

Answer 23

The capacity of a substance to produce harmful effects on health.

The degree of damage caused by exposure of an organism to a toxic substance.

Question 24

What does the phrase ‘the dose makes the poison’ imply?

Answer 24

There are no non-toxic substances, only appropriate ways to use substances.

This highlights that toxicity is related to dose, duration, concentration, route of exposure, and frequency.

Question 25

What does LD50 stand for?

Answer 25

Lethal Dose 50: the amount of a substance that will cause death in 50% of a test population. ## Footnote It measures short-term poisoning potential (acute toxicity).

Question 26

What does LC refer to in toxicology?

Answer 26

Lethal Concentration, typically referring to a chemical substance in the air. ## Footnote It is used to assess the risk posed by airborne toxins.

Question 27

What is the Maximum Concentration Limit (MCL)?

Answer 27

The maximum allowable concentration of a substance in drinking water. ## Footnote It is set to protect public health.

Question 28

What are heavy metals?

Answer 28

Metals with a density greater than 5 g/cm³. ## Footnote Important heavy metals include arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), tin (Sn), vanadium (V), and zinc (Zn).

Question 29

Fill in the blank: The human body requires certain metals such as _______ and _______.

Answer 29

calcium, iron ## Footnote Other essential metals include sodium, potassium, magnesium, and zinc.

Question 30

What can occur if there is either too little or too much of a metal in the body?

Answer 30

Too little can be dangerous, and too much can also be dangerous. ## Footnote This emphasizes the importance of balance in nutrient intake.

Question 31

What is the significance of the Recommended Dietary Allowance (RDA)?

Answer 31

Establishes nutritional intake levels for most metals and minerals. ## Footnote It helps prevent deficiencies and toxicities.

Question 32

What is the relationship between metals and health effects?

Answer 32

Metal speciation determines the risks associated with their exposure. ## Footnote This includes considerations of size and form of particles.

Question 33

True or False: All substances can have a lethal concentration.

Answer 33

True ## Footnote This highlights the universal potential for toxicity.

Question 34

What is meant by 'speciation' in the context of metals?

Answer 34

Refers to the different forms in which metals exist, impacting their toxicity. ## Footnote For example, lead oxide is very soluble while lead sulfide is not.

Question 35

What are the effects of methylmercury?

Answer 35

Highly toxic with teratogenic, carcinogenic, and mutagenic effects. ## Footnote Methylmercury forms naturally in the environment.

Question 36

What is Natural Attenuation as defined by the EPA?

Answer 36

Processes that reduce the mass, toxicity, mobility, volume, or concentration of pollutants without human intervention. ## Footnote Processes include biodegradation, dispersion, and chemical stabilization.

Question 37

What is the role of Permeable Reactive Barriers (PRB) in remediation?

Answer 37

Used for passive remediation of contaminated sites. ## Footnote They function by allowing water to flow through while treating contaminants.

Question 38

What is the importance of continuous monitoring in Natural Attenuation?

Answer 38

To certify the effectiveness of processes in reducing contamination. ## Footnote Monitoring is crucial for regulatory acceptance of this method.

Question 39

Fill in the blank: The relationship between Cr6+ and Cr3+ is that Cr6+ is _______ while Cr3+ is _______.

Answer 39

toxic, non-toxic ## Footnote This distinction is important for understanding the health risks associated with chromium exposure.

Question 40

What are some examples of physical mechanisms in natural attenuation?

Answer 40

* Filtration * Dispersion * Dilution * Volatilization ## Footnote These processes help in reducing contaminant concentrations in the environment.

Question 41

What is the impact of complexation in metal toxicity?

Answer 41

Certain metal ions can form complexes that can be more or less toxic than their individual components. ## Footnote For example, Zn(CN)₂ is more toxic than Zn²⁺ and CN⁻ alone.