Environmental risks practice questions.

Each machine wash of a synthetic fleece jacket releases thousands of plastic microfibres. Which pathway best explains how those fibres reach marine food webs far from the country in which the jacket was washed?

• They evaporate during the wash cycle and return to the ocean surface in rainfall
• They are burnt in municipal incinerators and settle on the sea as ash particles
• They travel with second-hand clothing exports and are released at coastal landfill sites
• They pass through waste water treatment into rivers, and ocean currents disperse them

Answer: They pass through waste water treatment into rivers, and ocean currents disperse them

Treatment works are built to remove solids and nutrients, not fibres a few micrometres across, so a share passes on into rivers and then into the sea, where currents and filter-feeding organisms move them further. The risk is generated by ordinary consumption in one place and realised in fisheries somewhere else entirely.

Ballast water discharged by ships has introduced species to ports far from their native range, some of which have displaced native species. Which category of environmental risk is this?

• Biological invasion transmitted by global transport networks
• Transboundary air pollution transported by prevailing winds
• Localised habitat loss caused by port construction
• Overexploitation of a shared marine resource

Answer: Biological invasion transmitted by global transport networks

Global shipping moves organisms between ocean basins that geography had kept separate, and a species without local predators or disease can expand rapidly. It is an environmental cost created directly by the connectivity that trade depends on, which is why the convention on ballast water treatment targets the vector rather than the species.

Emissions produced in one country to manufacture goods consumed in another are counted in the producing country's national inventory. What does this accounting choice conceal?

• That some countries have reduced territorial emissions partly by importing goods
• That total global emissions are lower than reported
• That manufacturing produces no emissions in any country
• That consumption has no relationship to emissions at all

Answer: That some countries have reduced territorial emissions partly by importing goods

Territorial accounting assigns the emissions to the smokestack, so relocating production abroad reduces a country's reported total without reducing global emissions or its own consumption. Consumption-based accounting typically raises the figure for high-income importers considerably.

Persistent organic pollutants applied to farmland in warm mid-latitudes are found at high concentrations in the fat of Arctic seals and in the diet of Arctic communities that never used them. Which process best explains this pattern?

• Repeated evaporation in warm regions and condensation at cold high latitudes.
• Direct discharge of the compounds into rivers that drain into the Arctic Ocean.
• Transport of the compounds in the ballast water of ships trading in the Arctic.
• Deposition of the compounds in dust blown northwards from low-latitude deserts.

Answer: Repeated evaporation in warm regions and condensation at cold high latitudes.

These compounds are semi-volatile, so they evaporate in the heat, travel in the air and condense where it is cold, arriving in stages; once there they are stored in fat and concentrated up long marine food chains, which is why the burden is highest where nothing was ever sprayed.

A city states that it recycles 62 % of its plastic packaging, and supports the figure with the share of packaging that households place in the recycling bin, much of which is then exported for processing. Which error does the claim contain?

• It reports the collection rate as if it were the share actually reprocessed.
• It counts the reuse of containers as if it were recycling of the material.
• It compares a rate for one year with an absolute tonnage for another year.
• It applies a national figure to a single city without adjusting for population.

Answer: It reports the collection rate as if it were the share actually reprocessed.

Collection is only the first step of the chain: contaminated or mixed loads that are exported may be landfilled or burned at the destination, so the claim measures an input to the system and reports it as an outcome.

A country imports 250 000 tonnes of wheat in one year. Producing one tonne of that wheat required 1 800 m3 of water in the exporting country (hypothetical data). Calculate the virtual water imported, to the nearest whole number, in million m3. Answer: ___

Answer: 450

Virtual water = 250 000 t x 1 800 m3 per t = 450 000 000 m3, which is 450 million m3. The trade transfers the water use, and any resulting depletion, to the exporting basin rather than to the consumer.