Sub-topic 1
2025 · National One-Eighth
Free
Algal blooms and environmental factors
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Sub-topic 2
2026 · National Semifinal
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Main ecological effect of eutrophication: reduced dissolved oxygen
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Sub-topic 3
2023 · National Preliminary
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Main ecological effect of eutrophication: reduced dissolved oxygen
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Sub-topic 4
2026 · National Semifinal
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Biomagnification of non-biodegradable substances up the food chain
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Sub-topic 5
2025 · National Semifinal
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Distinguishing primary from secondary air pollutants
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Sub-topic 6
2016 · National Preliminary
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Sewage and intensive agriculture as major sources of excess nitrate/phosphate in waterways
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Sub-topic 7
2022 · National Preliminary
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True or false: ddt accumulation causes thinning of bird eggshells
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Sub-topic 8
2022 · National Preliminary
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True or false: ddt accumulation causes premature breaking of bird eggs
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Sub-topic 9
2022 · National Preliminary
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True or false: ddt accumulation disturbs calcium metabolism in birds
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Sub-topic 10
2023 · National Preliminary
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Riddle: water vapor, the most abundant greenhouse gas
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Sub-topic 11
2023 · National One-Eighth
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True or false: toxic wastewater substances decrease at successive trophic levels
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Sub-topic 12
2023 · National One-Eighth
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True or false: sewage-decomposing microorganisms deplete oxygen and can kill aquatic organisms
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Sub-topic 13
2023 · National One-Eighth
Premium
True or false: algae blooms impart distinct colors to water bodies
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