FC atmospheric processes and cycles Flashcards
Define source
point from which a gas or aerosol is released into the atmosphere
Define sink
point where a gas or aerosol is removed from the atmosphere physically or chemically e.g precipitation, radical reaction and photosynthesis
Define atmosphere residence time
average period of time a molecule or particle resides within atmosphere aka lifetime
What is atmospheric residence time determined by
determined by relative rates of emissions from source and removal by sink
What is vertical mixing
refers to the movement of air or water masses in the verticle direction
What is horizontal mixing
refers to the process of mixing substances along a horizontal plane
What is vertical mixing due to
due to heating/cooling of air particles and turbulence from winds
What is horizontal mixing due to
driven by pressure difference due to uneven solar heating
Describe biogeochemical cycles
over geological timescales, small amounts of matter can be brought into or escape the atmosphere.
To a first approximation lithosphere-hydrosphere-atmosphere can be considered a closed system
Describe the breakdown of the earths oxygen
Most of the earths oxygen is in the lithosphere (99.5%), 0.5% in the atmosphere, 0.01% in the marine biosphere
What is the greatest fluxes of oxygen due to
the greatest fluxes are to/from the biosphere. Short term fluxes driven by photosynthesis
How often does oxygen cycle through the biosphere
2400 years
Outline the carbon cycle
Plants absorb CO2 through photosynthesis and organisms release it via respiration. Oceans also absorb CO2 while fossil fuels store carbon long term. Human activities like burning fossil fuels release stored carbon
Which major carbon species are present in the troposphere and how much is there
CO2 - 385ppm
CH4 - 1.7-1.8pp,
CO - 0.04 - 0.2 ppm
Describe how the concentration of CH4 changes of the hemisphere
Concentration of CH4 is about 6% higher in N hemisphere to S beacause the sources are on land
What is the most important CH4 sink
Oxidation by OH radicals
CH4 + OH-> CH3 + H2O
Which leads to further radicals and CO
Where does 50% of CO come from
Up to 50% of CO comes from oxidation of terpenes (VOCs)
Describe the sinks for CO and the relavent reactions
Major CO sink (90%) is oxidation by OH radicals
CO + OH -> CO2 + H
Remaining 10% sinks via microbiological processes at the soil surface
Describe how atmospheric nitrogen is fixed
Most atmospheric nitrogen is fixed biochemically within the soil by microorganisms
Describe the nitrogen cycle
Bacteria converts atmospheric nitrogen into ammonia. The bacteria converts the ammonia into nitrites (NO2^-) and nitrates (NO3^-) which plants absorb. Through the process of denitrification nitrates are then converted back into nitrogen gas and release it back into the atmosphere
Describe how N2O is produced in the nitrogen cycle
N2O is liberated from solid as a result of incomplete microbiological denitrification
Describe how NOx are produced using equations
O* + N2O -> NO + NO -> NO2
What is the problem with NOx
NOx contribute to the problem of air pollution, playing roles in the formation of both smog and acid rain
What colour is NO
Colourless
What colour is NO2
Deep red-orange
How does NO2 lead to the production of O3
NO2 + hv -> NO + O
O + O2 -> O3
Describe the sulphur cycle
Reduced species oxidised to SO2 and ultimately SO3 which then Hydrolyses and is incorporated in clouds as H2SO4 (acid rain). CS2 oxidised to COS which is fhe only s-gas reaching the stratosphere which has a potential impact on O3 depletion
