Air Pollution and Climate Håkan Pleijel Biological and Environmental Sciences

What is air? Nitrogen gas N 2 – 78% Oxygen gas O % Argon Ar – 1% In additions grace gases – many, but far from all, occur naturally Some of the naturally occurring are strongly elevated as a result of anthropogenic emissions Quantitatively most important: carbon dioxide (~390 ppm) and water vapour (very variable)

Examples of trace gases Low concentrations of 1.Carbon monoxide (CO) – < ca 0,2 ppm 2.Methane (CH 4 ) – 1,9 ppm 3.Nitrous oxide (N 2 O) – 0,3 ppm Very low concentrations of e.g. 1.Sulphur dioxide (SO 2 ) ~1-100 ppb 2.Nitrogen oxides (NO x = NO + NO 2 ) ~ ppb 3.Ozone (O 3 ) ~ ppb Despite low levels large effects may occur

Geographical scales on enviromental problems For air pollutants the typical lifetime in the atmosphere is critical

More on scales Global air pollution – Mostly caused by compunds with long of very long lifetimes in the atmsophere – The concentration of many of these cojmpunds vary rather little geographically Regional air pollution – Moslty by compunds with lifetimes in the range days- weeks – The load at a certaibn mlocation is the sum of a very large number of small contriobutions from many sources Local air pollution – The linkt beteen source an load is clear – Your tasks will moslty be on local pollution

The life history of an air pollutant Emission Sources Conversion Chemical & Physical Dispersal Transport + Deposition Wet/Dry Gas/Particle Effects Plants, Humans, Materials Decomposition

Important sources to air pollution Traffic – dominating source to local pollution in many cities of e.g. NO x, VOC (volatile organic compounds), particles, CO Small scale combustion – locally very important for e.g. particles and VOC Shipping and harbour activity – increasingly important Industry – locally very important for a wide range of compounds – increasing in developing countries decreasing in rich countries Energy production – similar to industry Agriculture – mostly ammonia (NH 3 )

Dispersal and transport Two (partly interrelated) key factors for dispersal – Wind speed – Temperature stratification High local air pollution levels: low wind speed, clear sky, night-time or low elevation of the sun Winter, anticyclonic conditions, winds from east- north result in promote high local air pollution levels in Northern Europe

Two emissions from one point source!?

Chimney plumes

One more Why do the plumes look different on in different situations? Why do they rise to different extents? Are there other types of emissions that do not rise to the same extent? What does this mean for risks with air pollution?

Inversion Temperaturen increases with height Reduces air mixing (strongly) Ground inversion is most common Height inversion – may (more rarely) be important for air pollution levels Let us do in on the black/whiteboard … Unstable Neutral Stable Extremely stable

The gaussian plume model What is the implication of emission height? Emission temperature? Day/night Summer/winter?

Inversion and traffic sources In the winter inversions somtimes last over sevelr days? Role of topography?

Now a number of examples of the air pollution situation in Göteborg January 2005

Nitrogen oxides (NO x = NO + NO 2 )

NO 2 – considered the more toxic Air quality standards

Wind speed – very dynamic

Particles – PM 10 mass of particles < 10 micrometer per cubic metre air

Relation PM 10 with wind speed

Carbon monoxide, CO

Chemical and physical conversion Oxidation – e.g. of NO 2 to HNO 3 and of SO 2 to H 2 SO 4 Decomposition (oxidation) of VOC to CO 2 and H 2 O Formation of ozone from NO 2 and VOC Particle formation and growth

Processes in particle formation and conversion

Ozone formation in the troposphere VOC chemistry sunlightNO 2 -NO-O 3 cycle

Step by step

Leyton´s formlula The photostationary state J is the constant of photolysis of NO 2 : k is the rate constant for the reaction

1 Rodes and Holland

2 Rodes och Holland

3 Rodes och Holland

4 Rodes och Holland

Less ozone injury close to the road

Variation in ozone concentrations

Influence of NO titration on [O 3 ] Östad – rural, inland Råö – rural, coastal Femman – urban, coastal Femman - urban

Primary NO 2 fraction - increasing

Deposition Wet deposition – with precipitation Dry deposition – as gas or with particles For gases – reactivity with surfaces important Uptake in organisms – e.g. plant and humans – represent deposition

Effects Reduced growth, yield, quality etc of plants Health effect – morbidity, mortality Effects on materials Climate effects Effects on the ozone layer in the stratosphere

The urban landscape

NO 2 summer 2007 Five periods, one week each

Urban background vs. traffic route

Example of an urban model

Group work 1 Group 1 - O 3, NO and NO 2 at Femman (rooftop monitoring station) Group 2 – NO and NO 2 at Gårda (traffic route monitoring station), including also a comparison of NO and NO 2 at Gårda and Femman. For the general tasks use only Gårda data. Group 3 – CO, PM 10, NO, NO 2, NO x at Femman and Gårda. For the general tasks use only CO and PM 10 data.

General tasks Plot the average diurnal variation of the pollutants for the whole year! What time of the day do the pollutants typically peak and when is the minimum? What might be the reasons the pollutants peaking at this particular time of the day. Note that the answer may not be one single factor. Which season of the year (Spring = March-May, Summer = June-August, Autumn = September- November, Winter = December-February) has the highest and lowest average levels of the different pollutants, respectively. Try this for average values and for the 98-percentile of the different pollutants in the different seasons. Please explain the observed pattern.

Specific tasks Group 1 Calculate the relationship (photostationary state, explained in lecture) [NO][O 3 ]/[NO 2 ]. How is it related to global radiation (Rad)? You can for example calculate the average of the relationship for the following global radiation intervals: 5-100, , , , W m -2. Try to explain the observed pattern. Study the limited number of situations (hours) with high ozone concentrations (> 100 µg m -3 ). What are the characteristics of these situations with respect to season, time of the day and meteorology? Explain your observations.

Specific tasks Group 2 Compare the ratio [NO]:[NO 2 ] at Femman and Gårda. In which of the sites is the ratio higher? Why? Also study the [NO]:[NO 2 ] ratio with respect to its relationship with meteorological variables. How large is the difference (absolute and relative) in [NO x ], [NO] and [NO 2 ] concentration between Femman and Gårda (average and 98- percentile). How are these differences related to weather conditions, especially wind speed and temperature inversion?

Specific tasks Group 3 Plot the relationship between the four pollutants and wind speed. Do this for all hourly values and for daily average values. What is the relationship between the concentrations of the different pollutants and wind speed? How much does it differ between different pollutants and why does it differ? Calculate [NO 2 ]/[NO x ] and plot it vs. [NO x ] (molar units, hourly values). What does the plot tell us about the primary NO 2 fraction of the vehicle exhausts?

Why percentiles? The 98-precentile is the concentration which is exceeded 2% of the time The 50-percentile is also called the median To represent the high end of the exposure without being very sensitive to single values Very common in setting air quality standards – AQS What is the 10-percentile of: 5, 8, 10, 11, 2, 22, 30, 14, 7, 18, 3, 10, 9, 9, 4, 5, 13, 17, 11, 1?

Converion between mass and molar units

Why use molar units? AQS often use mass units – simple to understand and explain to policy makers etc If you wish to compare different gases, sum or subtract them you need to use molar units (e.g. ppb or ppm) – e.g. if you wish to sum NO and NO 2 to NO x Such as for Leyton´s formula ppb and ppm is like percent, but where % is pars of hundred, ppb is part per billion and ppm is parts per million

Data base

Questions: Supervision of all groups: 18 December 13:00 – 15:00