Week 3 Flashcards
What are air pollutants ?
Substances which adversely impact environment by harming physiology of plants, animals, and ecosystems
What are greenhouse gases?
Gases which absorb radiation and interfere with radiation balance - climate impacted
What are natural pollutants?
Ones which come from nature
What are anthropogenic pollutants?
Ones which are manmade
What are emissions units? What is the emissions rate units? What needs to happen to emissions for them to be concentrations? How are they normalised?
Units : kg
Rate : kg/s
Need to disperse in atmosphere
By distance (kg/km) or by energy (kg/kWh)
What are concentration units? How does concentration occur? How are air quality regulations set? What is the mixing ratio units?
ug/m3
Result of emissions and atmosphere pollutants mixing
Regulations set by average concentrations
Mixing ratio in ppm
What is the mass concentration?
Mass of pollutant per m3 of air
What is the mixing ratio?
Moles of pollutant per moles of air (can be volume instead)
Common units are ppm or %
What are primary pollutants?
Pollutants emitted from source (NOx or particulates)
What are secondary pollutants?
Formed when primary pollutants react in atmosphere
- NO2 from NO and O
- Ozone from hydrocarbons and NOx combining
What are transport sources of particulates ? What are climate and health impacts?
Transport source - incomplete combustion making soot (made of black carbon (<100nm diam), organic carbon from lubrication oils/unburned carbon from fuel, and sulphuric acid as SO2 oxidised to SO4- and taken up by water)
Brake wear releasing metal compounds
Tyre/road wear
Climate impacts : less visibility
Health impacts: increased risk of heart disease or lung cancer
What are the sizes of particulates in micrometers ? What’s notable about PM 2.5?
<=10um (coarse), <=2.5 (fine) greatest impact on airways, <=0.1 (ultra fine) - greatest damage on alveolar region of lungs, deeply embedded
PM 2.5 exposure correlated to mortality and morbidity
What are nitrogen oxides made of?
Nitric oxide (NO)
Nitrogen dioxide (NO2) - has strongest impacts
How is NOx reported on mass scale?
All NO mass assumed to be in terms of NO2
Mass NOx - mass NO2 + mass NO*(molecular weight(NO2)/molecular weight(NO))
MW NO2- 46g/mol
MW NO- 30g/mol
How are NO and NO2 made?
Thermal mechanism
Oxygen dissociates (O2-> O+O)
At high temperatures N2 and O react (N2+O -> NO+N)
N+O2-> NO+O
2NO + O2-> 2NO2
What is the NOx CO2 trade off?
At higher temperature NOx increases but engine efficiency improves and reduces CO2
What are the environmental impacts and health impacts of NOx?
Env - photochemical smog, acid rain, nitrate particulate matter
Health - bronchitis in asthmatic children, reduced lung function, reduced life expectancy
What is the source, environmental impact and health impact of carbon monoxide?
Source - incomplete combustion
Environment impact - ozone and photochemical smog formation
Health - less oxygen to body (binds to haemoglobin (COHb) blocking oxygen uptake and increases oxygen-Hb affinity so oxygen not released to tissues)
What is photochemical smog? What is it’s colour?
Set of chemical reactions involving sunlight, NOx, and volatile organic compounds (HC and CO) to form ground level ozone and organic particles.
Brown in colour due to NO2 and aerosol scatter
Why is ozone good in atmosphere and bad in troposphere?
Atmosphere(10-15km) - forms ozone layer and absorbs UV
Troposphere (<10km)- secondary pollutant, makes up smog and hurts health
What is the photo stationary state for ozone production?
NO2 creates ozone while NO destroys it. The rate of creation = rate of destruction
Why does ozone increase in cities?
CO and volatile organic compounds react with oxygen and eventually form ozone in addition to reactions which occur in photo stationary state involving NOx
How does ozone Isopleth work?
/_ shaped curves show increasing ozone concentration with NOx on y axis and VOC on x
Above diagonal line which cuts contours is VOC limited zone.
Below is NOx limited zone
What is the emissions factor for roads?
Emissions of pollutants (g)/ distance (km)
What affects emissions factor?
Vehicle character and type (fuel, vehicle type, engine size)
Age and emission standards
Vehicle speed
Fleet mix
Cold start and degradation factorsb
What is the relation between NOx and vehicle acceleration?
NOx proportional to acceleration
How can emissions factor be found ?
By a plot which compares average speed of vehicle to emissions factor for pollutant and vehicle type (average speed emissions model)
What are the flight stages?
Planning, pre departure, taxi out, takeoff, climb, cruise, descent, landing, taxi in, post landing
What is the landing and takeoff (LTO) cycle?
Approach, taxi, takeoff, and climb (<1000ft)
How can the LTO emissions be assessed?
Emissions = sum(emissions index (g/kg fuel)mdotf(kg fuel/s)no of engines*time in mode )
For modes of flight in LTO
How can cruise emissions be found?
EEA inventory handbook
Which particles can cause health damage?
PM2.5 as evidenced by epidemiological studies
There is a correlation between exposure to it and mortality/morbidity
No threshold of unsafe effects - unsafe at any dose
Research ongoing into health effects of properties: size, composition, surface area
Why do NOx emissions rise when a plane engine thrusts?
Because the temperature is raised
What must wavelength of photon from sun which makes NO2 in atmosphere be less than?
420 nm
Represent in equation as hv
