Answer: Being fat-soluble and metabolically resistant, they bioaccumulate in lipid tissues and biomagnify at each trophic level, reaching toxic concentrations in top predators.
- A They deplete stratospheric ozone by releasing chlorine radicals into the upper atmosphere in general practice as frequently described in most textbook accounts during normal conditions
- B Being fat-soluble and metabolically resistant, they bioaccumulate in lipid tissues and biomagnify at each trophic level, reaching toxic concentrations in top predators
- C They are highly water-soluble and cause immediate mortality in fish at sub-ppb concentrations as generally observed in typical laboratory settings under usual circumstances
- D They acidify soil by releasing HCl during slow decomposition, killing soil organisms according to most researchers in the majority of cases studied as widely reported
Correct answer: B. Being fat-soluble and metabolically resistant, they bioaccumulate in lipid tissues and biomagnify at each trophic level, reaching toxic concentrations in top predators
Explanation: DDT is lipophilic and resists metabolic degradation, so it accumulates in fatty tissues (bioaccumulation). At each trophic level the concentration multiplies (biomagnification) - concentrations in raptors can be 10<sup>7</sup> times those in ambient water. This caused fatal eggshell thinning in birds like the bald eagle, dramatically reducing their populations.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.