Long Range Transboundary Air Pollution

Question 1

What is tropospheric ozone ?

Answer 1

This is a very reactive molecule ( this reactivity stems from the three oxygen atoms bonded together with one of these bonds being relatively unstable and prone to breaking to react with other compounds )

Question 2

What else can you say about Ozone ?

Answer 2

It occupies a small part of the atmosphere but it is still extremely potent.

Question 3

Formation of Ozone .

Answer 3

Ozone is a secondary pollutant formed from ozone precursors (NO2 and VOC) in sunlight .

Question 4

Does location matter with Ozone formation ?

Answer 4

Yes in the cities where there are high levels of VOC’s ozone formation is primarily limited by availability of NO2. In rural areas where NO2 are in high amounts ozone formation is limited by availability of VOC’s.

Question 5

At various times what does ozone concentration in the atmosphere depend on?

Answer 5

1. The formation of ozone from precursors by photochemical reactions driven by sunlight.
   2.chemical destruction of ozone by NO2(double sword )
2. The vertical transport of ozone from high altitudes towards the earth , dependent on turbulence .
   4.the deposition of ozone from the atmosphere onto vegetation,soil and water

Question 6

What is the AOT40 Index?

Answer 6

Accumulated exposure Over a threshold of 40ppb. This the measure of the total amount of ozone that a plant is exposed to over a given period usually growing seasons.(only daytime hours are considered in this calculation. This metric is used in the Eu air quality directive.

Question 7

How does Ozone affect the plants

Answer 7

Also ozone can only affect the plant if it is in the interior .

Question 8

What is ozone flux ?

Answer 8

It is a criteria used to understand how ozone moves from the atmosphere into the interior of a leaf

Question 9

What are some of the factors that affect ozone flux ?

Answer 9

1. The concentration of Ozone in the atmosphere ( the higher the greater the ozone flux)
2. Stomata conductance ( the wider the stomata opens the higher the ozone flux)
3. The resistance of ozone diffusion : these are factors that impede ozone’s movement into the leaf ( could be external or internal )

Question 10

What is POD?

Answer 10

Phytotoxic Ozone dose is build up on ozone flux which measures ozone risk to vegetation.( considered much better than AOT40)

Question 11

Ozone impacts

Answer 11

Causes physical injuries to leaves (physical necrosis).
IN wheat it causes leaves to senesce (age) prematurely and die earlier than normal(because chlorophyll is reduced) which leads to reduced grain filling and ultimately reduced yield .
It affects biomass of forest trees as well

Question 12

True or false : ozone is expected to impact global yield levels drastically specifically in Europe , Asia and USA

Answer 12

True