6.2 Stratospheric ozone

explain the dynamic equilibrium in the stratospheric ozone

some UV radiation from the sun is absorbed by stratospheric ozone, causing the ozone molecule to break apart, under normal conditions, the ozone will reform, the rate of destruction and reformation is practically the same

what is an example of an ozone depleting substance

chlorofluorocarbons

what are ozone depleting substances used in

aerosols, gas-blown plastics, pesticides, flame retardants, refrigerants

what is the result of UV light reaching the earth (on humans)

damages human living tissues, increasing the incidence of cataracts, mutation during cell division, skin cancer and other subsequent effects on health

what are the effects of increased UV radiation on biological productivity

damage to photosynthetic organisms, especially phytoplankton which forms the basis of aquatic food webs

how can pollution management be achieved

by reducing the manufacture and release of ozone depleting substances.

what are some methods for this reduction include

recycling refrigerants, developing alternatives to gas-blown plastics, halogenated pesticides, propellants and aerosols, developing non propellant alternatives

what does the United Nations Environment Programme play a role in in terms of the stratospheric ozone

it provides information and creates and evaluated international agreements for the protection of stratospheric ozone

what is the montreal protocol

an international agreement on the reduction of use of ozone depleting substances signed under the direction of UNEP, national governments complying with the agreement made national laws and regulations to decrease consumption and production of halogenated organic gases such as chlorofluorocarbons

where is ozone said to be good

the stratosphere

where is ozone said to be bad

the troposphere

what is ozone made up of

three oxygen atoms

is ozone a greenhouse gas

no

where are the highest ozone concentrations seen

between 20 and 40 km

what happens to UV radiation in the formation and destruction of ozone

UV radiation is absorbed

explain the basics of ozone formation

under the influence of UV radiation, oxygen molecules are split into oxygen atoms, oxygen atoms are extremely reactive so they combine with an oxygen molecule to form ozone

why is the adsorption of UV radiation by the ozone layer crucial

without it, life on land would be impossible

what are the three main types of UV radiation

UV-A, UV-C, UV-B

which type of UV radiation has the highest energy

UV-C

how much UV-C radiation is absorbed by the ozone layer

99%

how much UV-B radiation is absorbed by the ozone layer

about half

what are the damaging effects of UV exposure

genetic mutation and subsequent effects on health, damage to living tissues, cataract formation in eyes, skin cancers, suppression of the immune system, damage to photosynthetic organisms, especially phytoplankton, damage to consumers of photosynthetic organisms, especially zooplankton

how does UV radiation cause cataracts

it denatures the protein of the lens, turning it cloudy instead of clear

what is a positive impact of UV radiation on animals

it stimulates the production of vitamin D in our bodies

what does vitamin D deficiency cause

rickets (in children)

what can UV radiation be used to treat

psoriasis and vitiligo

what are five ozone depleting substances

chlorofluorocarbons, hydrochlorofluorocarbons, halons, methyl bromide, nitrogen oxides

what is a use of chlorofluorocarbons

propellants in spray cans, plastic foam expanders, refrigerants

what is a use of hydrochlorofluorocarbons

as replacements for CFCs

why are HCFCs slightly better than CFCs

they have a shorter lifetime in the atmosphere

what is a use of halons

fire extinguishers

what is a use of methyl bromide

pesticide

what are two sources of nitrogen oxides

bacterial breakdown of nitrites and nitrates in the soil, high flying supersonic aircraft

what were CFCs originally used as

propellants in aerosols, expanders of gas blown plastics, pesticides, flame retardants, refrigerants

why do CFCs become a problem in the stratosphere

exposure to UV radiation releases chlorine atoms from the CFCs, these chlorine atoms can react with ozone, which results in ozone destruction, they can also react with oxygen atoms, preventing ozone formation

why is chlorines destruction of ozone an example of positive feedback

the chlorine atoms are reformed after reacting with oxygen or ozone so one chlorine atom can destroy many molecules of ozone in a chain reaction with positive feedback

how long can CFCs stay in the atomosphere

up to 100 years

why will measures taken to prevent release of CFCs into the atmosphere take a long time to result in a thicker ozone layer

CFCs can persist in the atmosphere for up to 100 years after their release

what are three strategies for reducing ozone harming pollutants

altering the human activity producing pollution, regulating and reducing the pollutants at the point of emission, clean up and restoration

what are some examples of altering human activities producing pollution

replace gas-blown plastics, replace CFCs with carbon dioxide, propane or air, replace aerosols with pump action sprays, replace methyl bromide pesticides

what are some examples of regulating and reducing the pollutants at the point of emission

recover and recycle CFCs from refrigerators and AC units, legislate to have fridges returned to the manufacturer and coolands removed and stored, capture CFCs from scrap car air conditioner units

what are some examples of clean up and restoration in terms of ozone depleting substances

add ozone to or remove chlorine from stratosphere, not practical but is was once suggested that ozone filled balloons should be releases

what does UNEP do

forge international agreements, study the effectiveness of these agreements and the difficulties in implementing and enforcing them, give information to states, organizations and the public

how many countries ratified the montreal protocol

197

what was the first universally ratified UN agreement

the montreal protocol

why did China and India continue to produce CFCs despite agreeing to the Montreal protocol

these countries need for refrigerators and air conditioners is quickly growing because of the fast economic growth they are experiencing

what are some significant facts about the montreal protocol

the best example of international cooperation on an environmental issue, an example of the precautionary principle in science-based decision making, an example of many experts in their different fields coming together to research the problem and find solutions, the first to recognize that different countries could phase-out ODS chemicals at different times depending on their economic status, the first with regulations that were carefully monitored

when did chlorine levels in the atmosphere reach their peak

2005

when will the chlorine levels in the atmosphere reach pre-ODS levels

around 2050

what ODS are LEDCs allowed to make and use until 2030

some HCFCs