Carbon Cycle I

A pool contains 15 Pg of C. The three fluxes out of it are 3 Pg/yr, 2.5 Pg/yr, and 0.5 Pg/yr. What is the residence time of the pool?

• 6 years

• 2.5 years

• 3 years

What taxonomic group contains the most carbon in its biomass?

• Plants

• Bacteria

• Fish

Which of the following is the largest land-to-atmosphere CO₂ flux?

• Microbial respiration

• Plant respiration

• Fossil fuel emissions

When CO₂ is consumed by carbonate and silicate weathering reactions, into what form of carbon is it transformed?

• Calcium carbonate (CaCO₃)

• Organic carbon (CH₂O)

• Bicarbonate (HCO₃^-)

Approximately what percent of anthropogenic CO₂ emissions have been taken up by the land and ocean sinks over the last decade?

• 55%

• 70%

• 45%