* not completed

. Which of the following statements about mine/metal waste is/are correct? (Please select all that apply)

Tailings are a byproduct of the smelting of mineral ores correct incorrect

Essentially silicate-based tailings are chemically benign correct incorrect

Because tailings particles tend to be in the clay-sized fraction, permeability is usually a problem correct incorrect

In order to stabilize inert tailings by growing plants, organic amendments may be required correct incorrect

Dark-coloured tailings have a high albedo correct incorrect

* not completed

. Which of the following statements about sulfur-containing tailings is/are correct? (Please select all that apply)

The physical problems associated with sulfide tailings are less severe than those with silicate-based tailings correct incorrect

Some iron(II) can be oxidized within the tailings correct incorrect

The oxidation of pyrite in tailings results in the production of sulfuric acid correct incorrect

Submerging sulfide tailings in a pond minimizes their oxidation correct incorrect

Coal spoils are often the source of acid mine drainage correct incorrect

* not completed

. Which of the following statements about sulfur-containing tailings is/are correct? (Please select all that apply)

Generation of acidity in sulfide tailings is an oxidative process correct incorrect

Low water permeability is a problem in many tailings correct incorrect

The nitrogen content of most such tailings is too low to support good plant growth correct incorrect

Solid sulfur is sometimes formed as an intermediate in the acid generating process correct incorrect

Metals other than iron are sometimes present in the drainage of sulfide tailings correct incorrect

* not completed

. Which of the following statements correctly describes aspects of plant growth on tailings?

Sulfur compounds produced in plants aid in the uptake of Type A metals from tailings correct incorrect

Phytostabilization requires the planting of species that are able to take up metals present in tailings correct incorrect

A large translocation factor is essential in choosing plants that are to be used for phytostabilization correct incorrect

The term phytoremediation includes both phytoextraction and phytostabilization correct incorrect

A limited root system minimizes uptake of metals and is beneficial for plants used for phytostabilization correct incorrect

* not completed

. Which of the following statements correctly apply to red muds from bauxite mining?  (Please select all that apply)

Al(OH)₄^- and AlO₂^- are equivalent ways of expressing the soluble species of aluminium that is formed in the Bayer process correct incorrect

The solid component of red muds typically contain percentage amounts of aluminium, iron and titanium correct incorrect

Many other (sometimes toxic) metals are also solubilized in the red mud slurry correct incorrect

Calcium carbonate can be used as an amendment in order to prepare the red mud for establishing vegetation correct incorrect

The large sodium content in the red mud slurry inhibits formation of aggregates correct incorrect

* not completed

. Which of the following statements about animal manures used in agriculture is/are true? (Please select all that apply)

Phosphorus in manure is less susceptible to leaching than is nitrogen correct incorrect

Poultry manure usually contains greater concentrations of the major nutrients, NPK, than manure from other animals correct incorrect

Animal manure can contribute to increase salinity in soils correct incorrect

Under anaerobic conditions, nitrous oxide can be produced during decomposition of manures correct incorrect

Phosphorus and potassium from manure can be lost by erosion correct incorrect

* not completed

. Which of the following statements about compost is/are true? (Please select all that apply)

Composting reactions are essentially anaerobic correct incorrect

Undecomposed compost, when added to the soil can inhibit uptake of nitrogen by plants correct incorrect

A large C:N ratio (40 or more) is characteristic of appropriate feedstock to produce good compost correct incorrect

Trace metal content of most composts is smaller than that of most soils correct incorrect

The addition of compost to soils increases the soils cation exchange capacity correct incorrect

* not completed

. Which of the following statements about sewage sludge is/are true? (Please select all that apply)

The macronutrient content of sewage sludge is typically greater than that of compost correct incorrect

The activated sludge process produces an anaerobic sludge correct incorrect

Sludge application rates are usually limited by their nitrogen content correct incorrect

Metals present in sludge are mostly retained in the top layer of the soil to which it is added correct incorrect

Sludge-amended tailings are an appropriate resource for growing agricultural crops correct incorrect

* not completed

. Which of the following statements regarding biogas production from organic wastes is/are true? (Please select all that apply)

For biogas production, the C:N ratio of the feedstock should be similar to that appropriate for composting correct incorrect

Biogas production is an aerobic process correct incorrect

Nitrogen is necessary in the waste material in order to generate methane correct incorrect

In addition to methane and carbon dioxide, some hydrogen may also be produced in biogas from organic waste correct incorrect

Protein materials are biorefractory and are not degraded during biogas production correct incorrect

* not completed

. Which of the following statements regarding municipal waste is/are true? (Please select all that apply)

Degradation processes in a sanitary landfill over its lifetime are largely anaerobic correct incorrect

As degradation proceeds over a period of years, the leachate from a landfill contains increasingly high levels of dissolved organic material correct incorrect

The fuel value of methane obtained from a landfill is greater than that obtained by burning the waste directly correct incorrect

Metals found in fly ash are usually present in forms that are unavailable to plants correct incorrect

During limited-oxygen combustion, sulfides of metals may be released in fly ash correct incorrect

* not completed

. Which of the following statements regarding combustion of chlorine-containing organic matter is/are true? (Please select all that apply)

For PCBs, increasing chlorine content is accompanied by increasing toxicity correct incorrect

For PCBs, the vapour pressure increases with the number of chlorines correct incorrect

For PCBs, the half-life in air increases with the number of chlorines correct incorrect

Dioxins deposited on soil are readily leached into the groundwater correct incorrect

PAH compounds typically have small (10² to 10³) K_ow values correct incorrect