Kinetics and photochemistry Flashcards
What is the earth’s atmosphere a mixture of
Transparent, odourless gases and aerosols held to earth by gravity
What are the 3 main types of constituents in the earths atmosphere and give examples
Permanent gases – e.g. nitrogen, oxygen, argon
Variable gases (greenhouse gases and reactive species) – e.g. CO2, CH4, radicals
Aerosols (non-gaseous components) – e.g. sea salt, soot particles, volcanic ash
What is the percentage by volume of the earths atmosphere is made up of nitrogen
78.08%
What is the percentage by volume of the earths atmosphere is made up of oxygen
20.95
What is the percentage by volume of the earths atmosphere is made up of Argon
0.93
What is the importance of nitrogen
Biologically inert – remains
stable. Needed to make
proteins and DNA
What is the importance of oxygen
Needed for aerobic respiration
What is the importance of carbon dioxide
Major contribution to the greenhouse effect but essential for photosynthesis
What is the importance of methane
Major contribution to the greenhouse effect and acid rain
What is the importance of nitrous oxide
Major contribution to the greenhouse effect
What is the importance of ozone
Stratospheric: filters UV radiation
Tropospheric: health hazard
How do permanent gases occur
Mostly passive in weather related processes
How do variable gases occur and what do they affect
Occur as a result of both natural
processes (e.g. carbon cycle) and human activities (e.g. burning coal)
Affect transmission of radiation through atmosphere
Importance of water vapour
Clouds + Precipitation
Major Greenhouse Gas
Importance of sulphur dioxide
Volcanic origin
Contributes to acid rain
Importance of nitrous dioxide
Produced by combustion
Contributes to acid rain and smog
What are the main layers of the earths atmosphere
– Troposphere
– Stratosphere
– Mesosphere
– Thermosphere
What varies with altitude
Complex variation of temperature with altitude
Describe the troposphere
- Surface to roughly 10 km
- ¾ of atmosphere’s mass
- Heated from below
- Temperature generally decreases with height, by ~6.5 oC per
km, from 17 to -52 - That’s where most weather occurs
Describe the stratosphere
- 10-50 km above the surface
- Stable (not a lot of vertical mixing) and dry
- Temperature increasing to -3 oC with height: heated by Ozone
absorbing UV light - Jet aircraft frequently enter this layer
Describe the mesosphere
- 50-80 km above the surface
- Mass of atmosphere 0.1%
- Density is too low for ozone chemistry to heat
- Temperature falls to -93 oC
with increasing altitude - place of Noctilucent Clouds (ice coated meteor dust)
Describe the thermosphere
- 80-700 km above the surface
- Heated by UV ionization and the solar wind
- place of Aurora (polar light)
Describe the exosphere
- 700-10,000 km above the surface
- Density so low space shuttles orbit here, with little drag
- Hydrogen and helium are the primary elements
What is the ionosphere
50-1,000 km above the surface (meso + thermo + exo)
Describe the ionosphere
- Ionised part of the atmosphere, by solar radiation
- Reflect many types of radio waves
- Forms the inner edge of the magnetosphere
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
Define atmospheric residence time
average period of time a molecule or particle resides within atmosphere (aka lifetime)
What is atmospheric residence time determined by
Relative rates of emission from source and removal via sink
Where is the most of earths oxygen and where are the greatest fluxes and what is the short term fluxes driven by
most Earth’s Oxygen is in the Lithosphere but the greatest fluxes are to/from the Biosphere. Short term fluxes driven by photosynthesis
What major carbon species are in the troposphere
major Carbon species in the troposphere: CO2 (~385 ppm), CH4 (1.7-1.8 ppm) and CO (0.04-0.20 ppm)
What percentage is CH4 higher in the northern hemisphere than the southern hemisphere and why
6% higher in N hemisphere because sources are on land
What is the most important sink in terms CH4
most important sink is oxidation by ·OH which leads to further radicals and CO
Where does 50% of CO come from
Comes from oxidation of terpenes (VOCs)
What is the sink for CO
major CO sink (90%) is oxidation by ·OH
remaining 10% sinks via microbiological processes at the soil surface
Describe what is responsible for the intake and release for CO2
Photosynthesis responsible for CO2 intake while respiration and decay is responsible for release
Outline the nitrogen cycle
Most atmospheric N2 is fixed biochemically within the soil by micro-organisms, a small part turned into NOx by lightning, then to acids and rained out. Released back into the atmosphere through a series of bacterial oxidation steps followed by reduction to N2. N2O liberated from soils as a result of incomplete denitrification
What is the problem with NOx
NOx contributes to the problem of air pollution, Plainfield roles in the formation of both smog and acid rain
What colour is NO
Colourless
What colour is NO2
Deep red-orange
