Question 1

Multiple choiceMedium1 mark

A methane source inventory records total emissions of 1.0×105 kg day−11.0\times10^5\ \text{kg day}^{-1} Wetlands are the only natural source in the inventory and emit methane at 1.5×103 kg h−11.5\times10^3\ \text{kg h}^{-1} all other emissions are human-made. What is the mass emitted by human-made sources per day?

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Answer: B. The human-made emissions are the total emissions minus the natural emissions. Wetlands emit 1.5×103×24=3.6×104 kg day−11.5\times10^3\times24=3.6\times10^4\ \text{kg day}^{-1} so the human-made emissions are 1.0×105−3.6×104=6.4×104 kg day−11.0\times10^5-3.6\times10^4=6.4\times10^4\ \text{kg day}^{-1}

A: converts the wetland rate to a daily mass but gives the natural emissions alone.
C: uses the total daily emissions without subtracting the natural contribution.
D: adds the natural contribution to the total instead of subtracting it.

Remember: convert rates to matching time units before combining emissions.

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