Atmosphere- 2 Air pollution Flashcards
What must happen with the reactants when a chemical reaction occurs?
Come together
In correct orientation
Enough energy (activation energy)
What does activation energy lead to?
temperature dependence
What happens to most reactions as they get hotter?
Get faster
Where does the energy come from for photochemical reactions?
Sunlight
What are thermal reactions driven by?
energy possessed by reactants
How do you calculate the rate of change of concentration?
Rate Law x stoichiometry
What does stoichiometry tell us?
relative numbers of reactant and product species destroyed / created per reactive
encounter
What does the rate of a chemical reaction tell us?
the rate of change of concentration of reactants or products
What does Rate Law tell us?
how/what the rate depends on
What is the rate of reaction like for an elementary reaction?
proportional to concentration of all reactants
What is the equation for temperature/ temperature dependence?
k= A exp (-Ea / RT)
What do the letters in the temperature dependence equation mean?
A= pre-exponential factor
Ea= activation energy (Joules per mole)
R= Gas constant
T= temp in Kelvin
What will the equation be like if there is positive temperature dependence?
Ea is positive
Rate constant increases with higher temp
What will the equation be like if there is negative temperature dependence?
Ea negative
Rate constant decreases with higher temp
What has happened to air quality in the UK since 1950’s?
substantially improved
How does the UK’s current air quality affect the life of the human population?
34,000 deaths/yr
4-6 month life expectancy reduction
What is the economic cost per year of the air quality?
£20bn
How many global deaths are there resulting from air quality per year?
8 million
How much of people living in urban areas live with air quality worse than WHO guidelines?
80%
What does ground level cause significant damage to?
plants
How does ozone damage plants?
enters the leaf through stomata, and attacks cell membranes, reducing plant health & growth / yield
What losses does ozone have on global crop yield?
5-12%
What are 2 key air pollutants?
NOx
Fine particles (PM2.5)
What are the sources of NOx?
Local road traffic (60%)
Road traffic background (18%)
Homes, industry and commerce (9%)
Regional background (8%)
Non-road transport and mobile machinery (5%)
What is the make up of the local road traffic source of NOx?
Biggest is diesel cars with other diesel vehicles being the biggest contributors
When a NOx concentration map is put of the west midlands what image do you get?
highest concentration map out road systems
How does concentration of NO2 change throughout the day?
Peaks when there is both rush hours
(UoB peak later as people work till later at uni)
What are some of the sources of PM2.5?
Road traffic
Power generation
Aircraft
Agriculture
Shipping
Home (cooking)
Industry
What does the longer lifespan of PM2.5 mean?
areas will all have similar concentrations thus concerted local, regional and national action needed
What type of pollutant is ozone?
secondary pollutant formed in atmosphere
What is the formula for the formation of ozone?
VOC + NOx + sunlight = Ozone (O3)
Why can ozone be a transboundary pollutant?
VOC and NOx emissions might be quite far upwind
What is the formation timescale of ozone?
days-weeks
What is ozone formation exacerbated by?
fine weather
Sunshine
Airmass from Europe (UK formation)
What are the UKs air quality objectives for NOx and PM2,5?
NOx= 40 ug/m3 - Annual Average
PM2.5= 10 ug/m3 Annual Average, by 2040
What are the WHO guidelines for NOx and PM2.5?
NO2= 10 ug/m3 Annual average
PM2.5= 5 ug/m3 Annual average
What has Birmingham done to reduce NO2?
Created the bham clean air zone
Offending cars- £8 per day
HGV- £50 per day
