what increases the proportion of chlorofluorocarbon (CFC) in the atmosphere?
Answers
Answer:
Explanation:
One must consider two issues: the mechanisms for mixing between the troposphere (the bottom layer of the atmosphere) and the overlying stratosphere, and the average time that CFCs remain in the troposphere before chemical processes scrub them from the air. In very general terms, mixing within the atmosphere is caused by differences in temperature and by pressure gradients. These irregularities make some parcels of air buoyant, which results in the transport of pollutants throughout the atmosphere. Given sufficiently large variations in temperature and pressure, air parcels containing contaminants can be transported through the troposphere and into the stratosphere, in much the way that a hot air balloon can be used to loft people high above the ground and transport them from one place to another. Pollutants can reach the stratosphere, however, only if there are no major mechanisms that pull them out of the air while they are still in the troposphere.
"In general, there are two main mechanisms that remove compounds in the atmosphere: deposition and reaction. A common example of deposition is 'rain out': compounds that are soluble in water can be removed from the atmosphere by precipitation. This phenomenon is responsible for acid rain. The most abundant CFCs emitted into the troposphere are CFC 11 and CFC 12. These CFCs are not soluble in water, so deposition does not removed them from the air.
"The only other mechanism that removes compounds from the troposphere is reaction with an abundant oxidizing agent--such as hydroxyl radicals, ozone, or nitrate radicals. Atmospheric researchers have determined the rates at which several CFCs react with hydroxyl radicals; the lifetimes for these CFCs with respect to hydroxyl radicals is approximately 80 years. In other words, if hydroxyl radicals were the only thing reacting with the CFCs, it would take 80 years to completely remove them from the atmosphere. That is a long time! In comparison, methanol, a component of some alternative fuels, has a lifetime with respect to hydroxyl radical reaction of just 17 days. Ozone and nitrate radicals are even less effective at breaking down CFCs.
Answer:
machines increase the CFC in the atmosphere