What are the effects? Reductions in stratospheric ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Ozone layer depletion increases the amount of UVB and the risk of health effects. Laboratory and epidemiological studies demonstrate that UVB causes non melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to glaucoma and cataracts -- a clouding of the eye’s lens. Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Despite mechanisms to reduce or repair these effects and a limited ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation. Effects on Marine Ecosystems Phytoplanktons form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB. One study has indicated a 6-12% reduction in the marginal ice zone. Solar UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians and other animals. The most severe effects are decreased reproductive capacity and impaired larval development. Even at current levels, solar UVB radiation is a limiting factor, and small increases in UVB exposure could result in significant reduction in the size of the population of animals that eat these smaller creatures. Effects on Biogeochemical Cycles Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important trace gases e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulphide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere-atmosphere feedbacks that attenuate or reinforce the atmospheric build up of these gases. Effects on Materials Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation. What are the steps taken to remedy it? We should stop the use of products like aerosols, refrigerators that emit CFC and HCFC in the atmosphere. Also we should use alternatives like card board and mount board instead of thermacol, the breaking and burning of which releases CFC in the atmosphere. In 1978, the use of CFC propellants in spray cans was banned in the U.S. In the 1980s, the Antarctic "ozone hole" appeared and an international science assessment more strongly linked the release of CFCs and ozone depletion. It became evident that a stronger worldwide response was needed. In 1987, the Montreal Protocol was signed and the signatory nations committed themselves to a reduction in the use of CFCs and other ozone-depleting substances.
What is ozone depletion? Ozone is a naturally-occurring gas. The ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. The stratosphere, the next higher layer, extends about 10-50 kilometres above the Earth's surface. Stratospheric ozone is a naturally-occurring gas that filters the sun's radiation, to protect us from the harmful ultra violet rays. When chemicals like CFCs and HCFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules. How it is caused? It is caused by the release of chlorofluorocarbons (CFCs), hydro fluorocarbons (HCFCs), and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents, deodorants and aerosols. Other chemicals that damage the ozone layer include methyl bromide (used as a pesticide), halons (used in fire extinguishers), and methyl chloroform (used as a solvent in industrial processes for essential applications). As methyl bromide and halons are broken apart, they release bromine atoms, which are 60 times more destructive to ozone molecules than chlorine atoms. Aircrafts and satellites also emit CFC and HCFC. Will the ozone layer recover? Can we make more ozone to fill in the hole? Provided that we stop producing ozone-depleting substances, ozone will be created through natural processes that should return the ozone layer to normal levels by about 2050. It is very important that the world comply with the Montreal Protocol; delays in ending production could result in additional damage and prolong the ozone layer's recovery.
OZONE: The ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. Stratospheric ozone is a naturally-occurring gas that filters the sun's ultraviolet (UV) radiation. A diminished ozone layer allows more radiation to reach the Earth's surface. For people, overexposure to UV rays can lead to skin cancer, cataracts, and weakened immune systems. Increased UV can also lead to reduced crop yield and disruptions in the marine food chain. UV also has other harmful effects. Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere, 6.2 to 31 miles (10 to 50 kilometers) above Earth, in the region called the stratosphere. Today, there is widespread concern that the ozone layer is deteriorating due to the release of pollution containing the chemicals chlorine and bromine. Such deterioration allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer and cataracts in humans and harm animals as well.
Ozone depletion : It is caused by the release of chlorofluorocarbons (CFCs), hydrofluorocarbons (HCFCs), and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. The discussion below focuses on CFCs, but is relevant to all ODS. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years. Measurements of CFCs in the stratosphere are made from balloons, aircraft, and satellites. When CFCs and HCFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules. While it is true that volcanoes and oceans release large amounts of chlorine, the chlorine from these sources is easily dissolved in water and washes out of the atmosphere in rain. In contrast, CFCs are not broken down in the lower atmosphere and do not dissolve in water. The chlorine in these human-made molecules does reach the stratosphere. Measurements show that the increase in stratospheric chlorine since 1985 matches the amount released from CFCs and other ozone-depleting substances produced and released by human activities
Why did the ozone hole develop over Antarctica, and not over Detroit or some other manufacturing center where chlorofluorocarbons, or CFCs, are released prodigiously? https://www.nsf.gov/about/history/nsf0050/arctic/migration.htm
In winter, the stratosphere above the Antarctic continent gets colder than it does anywhere else on Earth. Temperatures frequently drop below -112ºF. Antarctica is also one of the windiest places on Earth. In May and June, strong winds in the stratosphere begin to blow clockwise around the continent. These howling stratospheric winds gradually form an enormous ring of moving air, called the Antarctic polar vortex, that swirls around and around, far above the frozen land…. During the winter, temperatures inside the Antarctic polar vortex fall so low that water vapor and several other types of molecules in the stratosphere condense into extremely small icy particles. These icy particles, in turn, make up polar stratospheric clouds (PSCs). When the sun sets in the Antarctic around the end of March each year, its disappearance marks the beginning of a long, dark winter. Once the last rays of sunlight have faded away, temperatures on land and in the air fall very quickly. In the stratosphere, high-altitude winds that create the polar vortex begin to blow around the continent. Isolated from warmer air outside the vortex, the air inside gets colder and colder. Eventually, it is cold enough for PSCs to form. And that is when the trouble really begins. Drifting around inside the polar vortex are reservoir molecules that have bonded with chlorine atoms and in so doing prevented them—so far—from attacking ozone. When PSCs form above Antarctica, chlorine reservoir molecules bind to the icy particles that make up the clouds. Once this happens, complex chemical reactions begin to take place that result in molecules of chlorine gas (Cl ) being released from the reservoirs. In this form, however, chlorine doesn't attack ozone. It just collects inside the vortex. All through the long, dark winter, especially during July and August, the chemical reactions taking place on the surfaces of the PSC particles continue, and more and more Cl builds up inside the vortex. At this point, the stage is set for ozone destruction. All that is needed is a trigger to get the process going.
cont...........why did ozone hole develop over Antarctica?
That trigger comes in late August, when the sun begins to rise. As the first rays of spring sunlight strike the stratosphere high over the frozen continent, conditions change very rapidly. The UV rays coming from the sun strike the Cl molecules inside the vortex. The molecules break apart, releasing billions of chlorine atoms that begin an attack on ozone molecules. The result is massive ozone destruction. Before long, so much ozone is destroyed inside the vortex that an ozone hole is formed. Ozone destruction continues—and the hole remains—until conditions in the stratosphere above Antarctica change. This change usually begins in early October, when the continent and the air above it finally begin to warm up. Warmer temperatures in the stratosphere melt the icy particles that make up PSCs. The PSCs disappear, and the reservoir molecules that were bound to the icy particles are released. Free at last, the reservoir molecules bind Cl atoms once again, and ozone destruction stops. By early November, the strong stratospheric winds circling Antarctica die down, and the polar vortex breaks up. As it does, ozone-rich air from outside the vortex flows in, and much of the ozone that was destroyed is replaced. In a sense, the hole in the ozone layer fills in. Usually by the end of November, the amount of ozone in the stratosphere over Antarctica has almost returned to normal. The next winter, however, the cycle will begin again.
What are the effects?
ReplyDeleteReductions in stratospheric ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Ozone layer depletion increases the amount of UVB and the risk of health effects.
Laboratory and epidemiological studies demonstrate that UVB causes non melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to glaucoma and cataracts -- a clouding of the eye’s lens.
Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Despite mechanisms to reduce or repair these effects and a limited ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation.
Effects on Marine Ecosystems
Phytoplanktons form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB. One study has indicated a 6-12% reduction in the marginal ice zone.
Solar UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians and other animals. The most severe effects are decreased reproductive capacity and impaired larval development. Even at current levels, solar UVB radiation is a limiting factor, and small increases in UVB exposure could result in significant reduction in the size of the population of animals that eat these smaller creatures.
Effects on Biogeochemical Cycles
Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important trace gases e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulphide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere-atmosphere feedbacks that attenuate or reinforce the atmospheric build up of these gases.
Effects on Materials
Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation.
What are the steps taken to remedy it?
We should stop the use of products like aerosols, refrigerators that emit CFC and HCFC in the atmosphere. Also we should use alternatives like card board and mount board instead of thermacol, the breaking and burning of which releases CFC in the atmosphere.
In 1978, the use of CFC propellants in spray cans was banned in the U.S. In the 1980s, the Antarctic "ozone hole" appeared and an international science assessment more strongly linked the release of CFCs and ozone depletion. It became evident that a stronger worldwide response was needed. In 1987, the Montreal Protocol was signed and the signatory nations committed themselves to a reduction in the use of CFCs and other ozone-depleting substances.
What is ozone depletion?
ReplyDeleteOzone is a naturally-occurring gas. The ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. The stratosphere, the next higher layer, extends about 10-50 kilometres above the Earth's surface. Stratospheric ozone is a naturally-occurring gas that filters the sun's radiation, to protect us from the harmful ultra violet rays.
When chemicals like CFCs and HCFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules.
How it is caused?
It is caused by the release of chlorofluorocarbons (CFCs), hydro fluorocarbons (HCFCs), and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents, deodorants and aerosols. Other chemicals that damage the ozone layer include methyl bromide (used as a pesticide), halons (used in fire extinguishers), and methyl chloroform (used as a solvent in industrial processes for essential applications). As methyl bromide and halons are broken apart, they release bromine atoms, which are 60 times more destructive to ozone molecules than chlorine atoms. Aircrafts and satellites also emit CFC and HCFC.
Will the ozone layer recover? Can we make more ozone to fill in the hole?
Provided that we stop producing ozone-depleting substances, ozone will be created through natural processes that should return the ozone layer to normal levels by about 2050. It is very important that the world comply with the Montreal Protocol; delays in ending production could result in additional damage and prolong the ozone layer's recovery.
OZONE:
ReplyDeleteThe ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. Stratospheric ozone is a naturally-occurring gas that filters the sun's ultraviolet (UV) radiation. A diminished ozone layer allows more radiation to reach the Earth's surface. For people, overexposure to UV rays can lead to skin cancer, cataracts, and weakened immune systems. Increased UV can also lead to reduced crop yield and disruptions in the marine food chain. UV also has other harmful effects.
Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere, 6.2 to 31 miles (10 to 50 kilometers) above Earth, in the region called the stratosphere.
Today, there is widespread concern that the ozone layer is deteriorating due to the release of pollution containing the chemicals chlorine and bromine. Such deterioration allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer and cataracts in humans and harm animals as well.
Ozone depletion :
It is caused by the release of chlorofluorocarbons (CFCs), hydrofluorocarbons (HCFCs), and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. The discussion below focuses on CFCs, but is relevant to all ODS. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years. Measurements of CFCs in the stratosphere are made from balloons, aircraft, and satellites.
When CFCs and HCFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules.
While it is true that volcanoes and oceans release large amounts of chlorine, the chlorine from these sources is easily dissolved in water and washes out of the atmosphere in rain. In contrast, CFCs are not broken down in the lower atmosphere and do not dissolve in water. The chlorine in these human-made molecules does reach the stratosphere. Measurements show that the increase in stratospheric chlorine since 1985 matches the amount released from CFCs and other ozone-depleting substances produced and released by human activities
Why did the ozone hole develop over Antarctica, and not over Detroit or some other manufacturing center where chlorofluorocarbons, or CFCs, are released prodigiously?
ReplyDeletehttps://www.nsf.gov/about/history/nsf0050/arctic/migration.htm
In winter, the stratosphere above the Antarctic continent gets colder than it does anywhere else on Earth. Temperatures frequently drop below -112ºF. Antarctica is also one of the windiest places on Earth. In May and June, strong winds in the stratosphere begin to blow clockwise around the continent. These howling stratospheric winds gradually form an enormous ring of moving air, called the Antarctic polar vortex, that swirls around and around, far above the frozen land….
During the winter, temperatures inside the Antarctic polar vortex fall so low that water vapor and several other types of molecules in the stratosphere condense into extremely small icy particles. These icy particles, in turn, make up polar stratospheric clouds (PSCs). When the sun sets in the Antarctic around the end of March each year, its disappearance marks the beginning of a long, dark winter. Once the last rays of sunlight have faded away, temperatures on land and in the air fall very quickly.
In the stratosphere, high-altitude winds that create the polar vortex begin to blow around the continent. Isolated from warmer air outside the vortex, the air inside gets colder and colder. Eventually, it is cold enough for PSCs to form. And that is when the trouble really begins.
Drifting around inside the polar vortex are reservoir molecules that have bonded with chlorine atoms and in so doing prevented them—so far—from attacking ozone. When PSCs form above Antarctica, chlorine reservoir molecules bind to the icy particles that make up the clouds. Once this happens, complex chemical reactions begin to take place that result in molecules of chlorine gas (Cl ) being released from the reservoirs. In this form, however, chlorine doesn't attack ozone. It just collects inside the vortex. All through the long, dark winter, especially during July and August, the chemical reactions taking place on the surfaces of the PSC particles continue, and more and more Cl builds up inside the vortex. At this point, the stage is set for ozone destruction. All that is needed is a trigger to get the process going.
cont...........why did ozone hole develop over Antarctica?
ReplyDeleteThat trigger comes in late August, when the sun begins to rise. As the first rays of spring sunlight strike the stratosphere high over the frozen continent, conditions change very rapidly. The UV rays coming from the sun strike the Cl molecules inside the vortex. The molecules break apart, releasing billions of chlorine atoms that begin an attack on ozone molecules. The result is massive ozone destruction. Before long, so much ozone is destroyed inside the vortex that an ozone hole is formed.
Ozone destruction continues—and the hole remains—until conditions in the stratosphere above Antarctica change. This change usually begins in early October, when the continent and the air above it finally begin to warm up. Warmer temperatures in the stratosphere melt the icy particles that make up PSCs. The PSCs disappear, and the reservoir molecules that were bound to the icy particles are released. Free at last, the reservoir molecules bind Cl atoms once again, and ozone destruction stops.
By early November, the strong stratospheric winds circling Antarctica die down, and the polar vortex breaks up. As it does, ozone-rich air from outside the vortex flows in, and much of the ozone that was destroyed is replaced. In a sense, the hole in the ozone layer fills in. Usually by the end of November, the amount of ozone in the stratosphere over Antarctica has almost returned to normal. The next winter, however, the cycle will begin again.