Calculate the residence time of chemical species in the atmosphere having a mixing ratio of 1 part per billion (ppb) by mass.
Given: Total flux of species (natural and anthropogenic sources) is 200×1012 g/year, and the mass of the atmosphere is 4×1021 g.

Correct option is B

The residence time of a species is calculated using the formula:

Step-by-Step Solution: 1. Mass of the Species in the Atmosphere: The species' mixing ratio is 1 ppb=1×10−9, and the total mass of the atmosphere is 4×1021 g:
Mass of species=1×10−9×4×1021=4×1012 g
2. Residence Time Calculation: Using the formula and substituting values:

3. Convert to Weeks: Since 1 year ≈ 52 weeks:
T=0.02×52=1.04weeks.
Additional Information: 1. Residence Time: Indicates how long a pollutant remains in the atmosphere before being removed.
2. Short Residence Time: Pollutants are rapidly removed, showing localized impacts (e.g., particulate matter).
3. Long Residence Time: Persistent pollutants like CO₂ cause global impacts.
4. Flux Sources: Include natural processes (volcanic emissions, forest fires) and anthropogenic emissions (fossil fuel combustion).
5. Mixing Ratio: Expresses the proportion of a gas relative to the total atmospheric mass.