Answer: Being a Group 2 element chemically similar to calcium, ⁹⁰Sr is taken up by plants and deposited in animal bones in place of Ca²⁺, where its beta emissions irradiate bone marrow and raise the risk of leukaemia.
- A ⁹⁰Sr decays quickly to stable ⁸⁸Sr within months, but its intense initial beta radiation causes acute radiation sickness in field workers under normal conditions as generally observed in typical laboratory settings
- B It releases intense gamma radiation in soil, sterilising all microbial life and blocking plant growth for decades under usual circumstances according to most studies in the majority of documented cases as widely reported
- C ⁹⁰Sr bonds permanently with soil clay minerals, preventing root uptake but contaminating surface water as clay erodes into rivers in standard reference material under most conditions studied in most observed cases
- D Being a Group 2 element chemically similar to calcium, ⁹⁰Sr is taken up by plants and deposited in animal bones in place of Ca²⁺, where its beta emissions irradiate bone marrow and raise the risk of leukaemia
Correct answer: D. Being a Group 2 element chemically similar to calcium, ⁹⁰Sr is taken up by plants and deposited in animal bones in place of Ca²⁺, where its beta emissions irradiate bone marrow and raise the risk of leukaemia
Explanation: Strontium is in Group 2, directly below calcium in the periodic table, and mimics calcium in biological systems. After entering the food chain via plant uptake, ⁹⁰Sr is deposited in bones and teeth in place of calcium. Its half-life of ~29 years means contamination persists for centuries, and the continuous beta radiation emitted inside bone irradiates haematopoietic (blood-forming) tissue in the marrow, raising the risk of leukaemia.
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.