Answer: Using plants to absorb and accumulate toxic heavy metals from contaminated soils (hyperaccumulators like Thlaspi, Alyssum, sunflower) to clean up pollution.
- A Using living plants as a biological raw material source for manufacturing commercial chemical fertilizers on a large scale according to most researchers
- B Using plants to absorb and accumulate toxic heavy metals from contaminated soils (hyperaccumulators like Thlaspi, Alyssum, sunflower) to clean up pollution
- C Using plants mainly to fix atmospheric nitrogen gas directly into the surrounding contaminated soil over time in the majority of cases studied as widely reported
- D Growing plants in contaminated soil mainly to physically prevent surface erosion, with little decontamination effect noted in standard practice under most conditions encountered
Correct answer: B. Using plants to absorb and accumulate toxic heavy metals from contaminated soils (hyperaccumulators like Thlaspi, Alyssum, sunflower) to clean up pollution
Explanation: Phytoremediation uses plants that hyperaccumulate heavy metals (Zn, Cd, Ni, Pb) in their shoots. Thlaspi caerulescens hyperaccumulates Zn and Cd; Alyssum species accumulate Ni. After harvest, the metal-rich biomass is disposed of safely. It is a low-cost, ecological approach to soil decontamination.
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.