These statements are related to carbon cycle. Which of them is/are true?(Image: flickr.com, CC BY-NC-SA 2.0)

Question

BlackTom AI · Accepted Answer

Diving into the Carbon Cycle statements, we need to assess each option's accuracy based on how CO2 moves between atmosphere, oceans, biosphere, and lithosphere.
Option a: 'Rain forests capture about 70% of all the CO2 emissions.' This overstates the role of rain forests. While forests sequester a substantial amount of CO2 through photosynthesis and storage in biomass and soils, the figure of 70% globally is not supported by current measurements; regional uptake varies and is much smaller when looking at global totals. Hence this is not correct.
Option b: 'The oceans have a large role in capturing the CO2 from atmosphere.' This is true. The oceans act as a major carbon sink through physical dissolution of CO2, chemical buffering as carbonic acid and bicarbonate, and biological pump processes (phytoplankton photosynthesis, sinking organic matter). The scale of ocean uptake is large and well-established in carbon cycle science.
Option c: 'Volcanoes emit annually more CO2 than what is caused by human activities.' This is incorrect. While volcanoes emit CO2, the total annual volcanic emissions are dwarfed by human CO2 emissions from fossil fuel combustion, cement production, and other activities. Therefore this statement misrepresents the relative magnitudes.
Option d: 'CO2 is no longer stored to soil crust and rocks.' This is false. Carbon is continuously stored and stored long-term in soils, sedimentary rocks, and carbonate minerals through weathering and geological processes; soil and rock reservoirs remain important components of the carbon cycle, not obsolete.
In summary, option b accurately reflects the key role of the oceans in CO2 capture, while options a, c, and d contain common misconceptions or exaggerated/incorrect claims about carbon storage and fluxes. The distinctions hinge on understanding the relative scales and mechanisms of carbon transfer among the Earth’s reservoirs.

These statements are related to carbon cycle. Which of them is/are true?(Image: flickr.com, CC BY-NC-SA 2.0)多项选择题

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