Ozone depletion describes two related events observed since the late 1970s: a steady decline of about four percent in the total amount of ozone in the Earth's atmosphere (ozone layer), and a much greater spring decline in stratospheric ozone around the Earth's polar regions. The latter phenomenon is referred to as ozone hole . There is also a tropospheric ozone depletion event spring in the spring in addition to these stratospheric events.
The main causes of ozone depletion and ozone holes are man-made chemicals, especially human-made halocarbon coolers, solvents, propellants, and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), which are referred to as ozone-zippering substances ( ODS ). These compounds are transported to the stratosphere by wind after being emitted on the surface. Once in the stratosphere, they release a halogen atom through photodissociation, which catalyzes the breakdown of ozone (O 3 ) into oxygen (O 2 ). Both types of ozone depletion were observed to increase as halocarbons emissions increased.
The depletion of ozone and ozone holes has raised concerns worldwide over an increased risk of cancer and other negative effects. The ozone layer prevents the most dangerous UVB waves from ultraviolet rays (UV light) from passing through Earth's atmosphere. This wavelength causes skin cancer, burning skin, and cataracts, which are projected to increase dramatically as a result of ozone depletion, as well as damage to plants and animals. This concern led to the adoption of the Montreal Protocol in 1987, which prohibited the production of CFCs, halogens and other ozone depleting chemicals.
The ban came into force in 1989. The ozone level stabilized in the mid-1990s and began to recover in the 2000s. The recovery is projected to continue over the coming century, and the ozone hole is expected to reach pre-1980 levels around 2075. The Montreal Protocol is considered the most successful international environmental treaty to date.
Video Ozone depletion
Summary ozone cycle
Three forms (or allotropes) of oxygen are involved in ozone-oxygen cycle: oxygen atom (O or atomic oxygen), oxygen gas ( O
2 or diatomic oxygen), and ozone gas ( O
3 or triatomic oxygen). Ozone is formed in the stratosphere when the oxygen molecule photodissociate after the photon ultraviolet intact. This changes one O
2 into two radicals of atomic oxygen. The atomic oxygen radicals then join O
2 molecule to create two O
3 molecule. This ozone molecule absorbs ultraviolet (UV) light, after which ozone is divided into molecules O
2 and oxygen atoms. The oxygen atom then joins the oxygen molecule to regenerate ozone. This is an ongoing process that ends when an oxygen atom rejoins the ozone molecule to create two O
2 .
O O
3 -> 2 O
2
The total amount of ozone in the stratosphere is determined by the balance between photochemical production and recombination.
Ozone can be destroyed by a number of free radical catalysts; the most important are hydroxyl radicals (OH Â ·), radical nitric oxide (NOÃ,), chlorine radicals (Cl Ã, Â ·) and bromine radicals (BrÃ, Â ·). The point is a notation to indicate that each species has unpaired electrons and is thus highly reactive. All of these have natural and man-made resources; at the moment, most of the OHA and NO in the stratosphere are naturally occurring, but human activity has drastically increased chlorine and bromine levels. These elements are found in stable organic compounds, especially chlorofluorocarbons, which can travel into the stratosphere without being destroyed in the troposphere because of its low reactivity. Once in the stratosphere, Cl and Br atoms are released from the parent compound by the action of ultraviolet light, for example
CFCl
3 Electromagnetic radiation - > CLÃ, Â · Ã, Â · CFCl
2
Ozone is a highly reactive molecule that is easily reduced to a more stable form of oxygen with the help of a catalyst. Cl and Br atoms destroy ozone molecules through various catalytic cycles. In the simplest example of the cycle, the chlorine atom reacts with the ozone molecule ( O
3 ), taking the oxygen atoms to form chlorine monoxide (ClO) and leaving the oxygen molecule ( O
2 ). ClO can react with a second ozone molecule, releasing chlorine atoms and producing two oxygen molecules. The chemical term for this gas-phase reaction is:
- ClÃ, Â · O
3 -> ClO O
2
Chlorine atoms transfer oxygen atoms from ozone molecules to form ClO molecules - ClO O
3 -> ClÃ, Â · 2 O
2
This ClO can also excrete oxygen atoms from other ozone molecules; chlorine free to repeat this two-step cycle
The overall effect is the decrease in the amount of ozone, although the rate of this process can be reduced by the effect of the zero cycle. More complicated mechanisms have also been found that cause ozone damage in the lower stratosphere.
A single chlorine atom will continue to destroy ozone (causing catalysts) up to two years (time scale for transport back to the troposphere) if not for a reaction that removes them from this cycle by forming reservoir species such as hydrogen chloride (HCl) and chlorine nitrate ( ClONO
2 ). Bromine is even more efficient than chlorine in destroying ozone on a per atom basis, but there is less bromine in the atmosphere today. Both chlorine and bromine contribute significantly to overall ozone depletion. Laboratory studies have also shown that the fluorine and iodine atoms participate in the analog catalytic cycle. However, fluorine atoms react quickly with water and methane to form HFs that are strongly bound in the Earth's stratosphere, whereas iodine-containing organic molecules react so quickly in the lower atmosphere that they do not reach the stratosphere in significant amounts.
Single chlorine atoms are able to react with an average of 100,000 ozone molecules before being excluded from the catalytic cycle. This fact plus the amount of chlorine released to the atmosphere each year by chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFCs) indicates the hazards of CFC and HCFC to the environment.
Maps Ozone depletion
Observation on ozone layer depletion
The ozone hole is usually measured by a total reduction of the ozone column above the point on the Earth's surface. This is usually expressed in the Dobson unit; abbreviated as "DU". The most prominent reduction of ozone occurs in the lower stratosphere. Marked down in the ozone column in the Antarctic spring and early summer compared to the early 1970s and had previously been observed using instruments such as Total Ozon Mapping Spectrometer (TOMS).
A reduction of up to 70 percent in the ozone column was observed in austral (southern hemispheres) above Antarctica and first reported in 1985 (Farman et al.). The total ozone column of Antarctica in September and October continues to be 40-50 percent lower than the pre-ozone-hole value since the 1990s. The gradual trend toward "healing" is reported in 2016. By 2017, NASA announced that the ozone hole is the weakest since 1988 due to the warm stratospheric conditions. Expected to recover around 2070.
The amount of lost varies more from year to year in the Arctic than in Antarctica. The largest Arctic decline occurs in winter and spring, reaching up to 30 percent when the stratosphere is the coldest.
Reactions that occur in stratospheric polar clouds (PSCs) play an important role in increasing ozone depletion. The PSC's shape is easier in the extreme cold of the Arctic and Antarctic stratosphere. This is why the ozone hole was first formed, and deeper, above Antarctica. The initial model failed to take into account the PSC and predicted the global depletion gradually, which is why the Antarctic ozone hole suddenly shocked many scientists.
It's more accurate to talk about ozone depletion in the middle latitudes than holes. The number of ozone columns decreased below pre-1980 values ​​between 1980 and 1996 for mid-latitudes. In the northern central latitudes, it increased from a minimum value of about two percent from 1996 to 2009 when the regulation came into force and the amount of chlorine in the stratosphere decreased. In the South Central latitudes, total ozone remains constant over that time period. There is no significant trend in the tropics, especially since halogen-containing compounds do not have the time to break down and release chlorine and bromine atoms in tropical latitudes.
Large volcanic eruptions have been shown to have an uneven effect of ozone depletion, as observed in the 1991 volcano eruption. Pinotubo in the Philippines.
Ozone depletion also explains the many observed decreases in the stratosphere and upper troposphere temperatures. The stratospheric heat source is the absorption of UV radiation by ozone, thereby reducing the ozone causing cooling. Some stratospheric cooling is also predicted from increases in greenhouse gases such as CO
2 and the CFC itself; however, ozone induced cooling appears dominant.
Predicted ozone levels remain difficult, but the precision of model predictions of observed values ​​and agreement among different modeling techniques has been increasing steadily. World Meteorological Organization Global Ozone Research and Supervision Project - Report no. 44 strongly supports the Montreal Protocol, but notes that the 1994 UNEP Assessment exaggerates the loss of ozone for the period 1994-1997.
Chemicals in the atmosphere
Chlorofluorocarbons (CFCs) and other halogenated ozone-depleting substances (ODS) are primarily responsible for the man-made chemical ozone depletion. The total amount of effective halogens (chlorine and bromine) in the stratosphere can be calculated and known as the effective equivalent of stratospheric chlorine (EESC).
CFC was created by Thomas Midgley, Jr. in the 1930s. They are used in air conditioners and refrigeration units, as spray aerosol propellants prior to the 1970s, and in the process of cleaning of delicate electronic appliances. They also occur as a by-product of several chemical processes. No significant natural source has ever been identified for these compounds - their presence in the atmosphere is almost entirely due to human production. As mentioned above, when ozone-depleting chemicals reach the stratosphere, they are separated by ultraviolet light to release chlorine atoms. The chlorine atoms act as catalysts, and each can break down tens of thousands of ozone molecules before being excreted from the stratosphere. Given the length of the CFC molecule, recovery times are measured in decades. It is estimated that the CFC molecule takes an average of about five to seven years to go from the ground to the upper atmosphere, and it can survive there for about a century, destroying up to a hundred thousand ozone molecules during that time.
1,1,1-Trichloro-2,2,2-trifluoroethane, also known as CFC-113a, is one of four man-made chemicals newly discovered in the atmosphere by a team at the University of East Anglia. CFC-113a is the only known CFC whose abundance in the atmosphere is still growing. The source remains a mystery, but illegal manufacturing is suspected by some. CFC-113a seems to have accumulated since 1960. Between 2010 and 2012, gas emissions jumped by 45 percent.
Computer modeling
Scientists have linked the depletion of ozone with the increase of anthropogenic (human anthropogenic) halogen compounds from CFCs by combining observational data with computer models. This complex chemical transport model (eg SLIMCAT, CLAMS - Chemical Model Lagrangian from Stratosphere) works by combining chemical measurements and meteorological fields with chemical rate reaction rates. They identify major chemical reactions and transport processes that carry CFC photolysis products into contact with ozone.
The ozone hole and its cause
The Antarctic ozone hole is an Antarctic stratosphere area where ozone levels have recently dropped to 33 percent from their pre-1975 values. The ozone hole occurs during the Antarctic spring, from September to early December, when strong west winds begin to circulate throughout the continent and create atmospheric containers. In this polar vortex, more than 50 percent of the lower stratospheric ozone is destroyed during the Antarctic spring.
As described above, the main cause of ozone depletion is the presence of chlorine-containing gases (especially CFCs and associated halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then proceed to catalyze ozone damage. The ozone depletion catalyzed by Cl may occur in the gas phase, but it dramatically increases with the presence of stratospheric polar clouds (PSCs).
This stratospheric polar cloud (PSC) forms during winter, in very cold weather. The dark polar winter, consisting of 3 months without solar radiation (sunlight). The lack of sunlight contributes to the decrease in temperature and the vortex of the polar vortex and the cold air. Temperatures range from or below -80 ° C. These low temperatures form cloud particles. There are three types of PSC clouds - trihydric nitric acid clouds, slowly cooling ice-water clouds, and nacerous ice-water clouds - provide a surface for chemical reactions whose products will, in spring cause ozone damage.
The involved photochemical processes are complex but well understood. The main observation is that, usually, most of the chlorine in the stratosphere is in a compound "reservoir", especially chlorine nitrate ( ClONO
2 ) as well as a stable end product such as HCl. The formation of the final product essentially removes the Cl of the ozone depletion process. The former Cl sequester, which can then be available through light absorption at wavelengths shorter than 400 nm. During the Antarctic winter and spring, however, reactions on the surface of polar stratospheric cloud particles transform these "reservoir" compounds into reactive free radicals (Cl and ClO). Process where the cloud deletes NO
2 of the stratosphere by converting it to nitric acid in the PSC particles, which are then lost by sedimentation called denitrification. This prevents the newly formed ClO from converting to ClONO
2 .
The role of sunlight in ozone depletion is the reason why ozone depletion is greatest in the Antarctic during spring. During the winter, although the PSC is at most, there is no light above the poles to induce a chemical reaction. During the spring, the sun rises, providing energy to induce photochemical reactions and liquefy polar stratosphere clouds, releasing considerable ClO, which pushes the hole mechanism. Further warming temperatures near the end of spring break the vortex around mid-December. Like warm, ozone and NO
2 airflow-rich in from low latitudes, PSC is destroyed, the process of increased ozone depletion will die, and the ozone hole closes.
Most of the destroyed ozone is in the lower stratosphere, in contrast to the much smaller ozone depletion through a homogenous gas phase reaction, which occurs mainly in the upper stratosphere.
Interest in ozone layer depletion
Public misunderstandings and misconceptions of complex issues such as ozone depletion are common. Limited scientific knowledge of the community causes confusion with global warming or perceptions of global warming as part of the "ozone hole". Initially, classic green NGOs refrained from using CFC depletion to campaign, as they found the topic too complicated. They became active much later, for example in Greenpeace support for the CFC free refrigerators produced by former East German companies VEB et al. Scharfenstein.
The metaphors used in CFC discussions (ozone shields, ozone holes) are not "exact" in the scientific sense. The "ozone hole" is more like depression , less "hole in the windshield". Ozone is not lost through the coating, nor is there a "thinning" of a uniform ozone layer. However they resonate better with non-scientists and their concerns. The ozone hole is seen as a "hot problem" and an imminent risk when the layman is afraid of serious personal consequences such as skin cancer, cataracts, crop damage, and plankton population reduction in oceanic photon zones. Not only at the policy level, the ozone regulation compared to climate change fared much better in public opinion. Americans voluntarily switched from aerosol sprays before the law came into effect, while climate change failed to achieve comparable attention and public action. The sudden recognition in 1985 that substantial "holes" were widely reported in the media. The rapid ozone depletion in Antarctica has previously been considered a measurement error. The scientific consensus was established after the rule.
While the Antarctic ozone hole has a relatively small effect on global ozone, the hole has generated much public attention because:
- Many are concerned that ozone holes may start appearing over other regions of the world, although to date the only other large-scale depletion is the smaller "oceans" of ozone observed during the Arctic spring around the Poles North. Ozone in the middle latitudes has decreased, but is much smaller (about 4-5 percent decreases).
- If stratospheric conditions become more severe (colder temperatures, more clouds, more active chlorine), global ozone may decrease at a greater rate. The standard global warming theory predicts that the stratosphere will cool.
- When Antarctic ozone holes break down every year, ozone-depleted air drifts out into nearby areas. Decreased levels of ozone up to 10 percent have been reported in New Zealand in the months after the outbreak of the Antarctic ozone hole, with the intensity of B-ultraviolet radiation rising by more than 15 percent since the 1970s.
Consequences of ozone layer depletion
Because the ozone layer absorbs UVB ultraviolet light from the sun, the depletion of the ozone layer increases the surface UVB level (all others equal), which can cause damage, including increased skin cancer. This is the reason of the Montreal Protocol. Although the decrease in stratospheric ozone is closely related to CFC and increased UVB surface, there is no direct observational evidence linking ozone depletion with the incidence of skin cancer and higher eye damage in humans. This is partly because UVA, which is also involved in some forms of skin cancer, is not absorbed by ozone, and because it is virtually impossible to control statistics for lifestyle changes over time.
UV Improvement
Ozone, while a minority of constituents in the Earth's atmosphere, is responsible for most UVB radiation absorption. The amount of UVB radiation that permeates the ozone layer decreases exponentially with the thickness of the oblique path and the density of the layer. When the stratospheric ozone level decreases, a higher UVB level reaches the Earth's surface. UV-driven phenolic formations in tree circles have set the date for the start of ozone depletion in the northern latitudes until the late 1700s.
In October 2008, the Ecuadorian Space Agency published a report called HIPERION. This study uses soil instruments in Ecuador and the latest 28 years data from 12 satellites from several countries, and found that UV radiation reaching the equatorial latitude is much greater than expected, with the UV Index climbing as high as 24 in Quito; WHO considers 11 as an extreme index and a major health risk. The report concludes that the reduced ozone levels around the planet's centerline are already endangering large populations in the region. Then, CONIDA, the Peruvian Space Agency, published its own research, which yielded almost the same findings as Ecuadorian research.
Biological effects
The main public concern about the ozone hole is the effect of increased surface UV radiation on human health. So far, ozone depletion in most locations is usually only a few percent and, as noted above, there is no direct evidence of damage to health available in most latitudes. If high levels of depletion seen in the ozone hole are common throughout the world, the effect can be much more dramatic. When the ozone hole over Antarctica in some cases grows so large that it affects parts of Australia, New Zealand, Chile, Argentina, and South Africa, environmentalists have been concerned that increased UV surfaces could be significant.
Ozone depletion will magnify all UV effects in human health, both positive (including Vitamin D production) and negative (including sunburn, skin cancer, and cataracts). In addition, increased UV surface leads to an increase in tropospheric ozone, which is a health risk for humans.
Basal and squamous cell carcinoma
The most common form of skin cancer in humans, basal cell carcinoma and squamous, is strongly associated with UVB exposure. The mechanism by which UVB induces this cancer is well understood - the absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcriptional errors when the DNA replicates. This cancer is relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery. By combining epidemiological data with animal studies, scientists estimate that any one percent reduction in long-term stratospheric ozone would increase the incidence of this cancer by up to two percent.
Malignant melanoma
Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, killing about 15-20 percent of cases diagnosed. The association between malignant melanoma and ultraviolet exposure is not fully understood, but it appears that both UVB and UVA are involved. Because of this uncertainty, it is difficult to estimate the effect of ozone depletion on the incidence of melanoma. One study showed that a 10% increase in UVB radiation was associated with a 19% increase in melanoma for men and 16% for women. A study of people in Punta Arenas, on the southern tip of Chile, showed a 56 percent increase in melanoma and a 46 percent increase in nonmelanoma skin cancer over a seven-year period, along with a decrease in ozone and elevated UVB levels.
Cortical cataracts
Epidemiological studies show an association between ocular cortical cataracts and UVB exposure, using rough estimates of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UVB was performed in a study at Chesapeake Bay Watermen, where increased mean annual ocular exposure was associated with an increased risk of cortical opacity. In this highly exposed group of white men, evidence linking cortical turbidity with sun exposure is the strongest to date. Based on these results, ozone depletion is thought to cause hundreds of thousands of additional cataracts by 2050.
Increased tropospheric ozone
Increased surface UV leads to an increase in tropospheric ozone. Basic level ozone is generally recognized as a health risk, since ozone is toxic because of its strong oxidizing properties. The risk is very high for children, the elderly, and those who suffer from asthma or other breathing difficulties. At the moment, ground-based ozone is generated primarily by the action of UV radiation on combustion gases from vehicle exhaust.
Increased vitamin D production
Vitamin D is produced in the skin by ultraviolet light. Thus, higher UVB exposure increases vitamin D in human deficiencies in it. Recent studies (especially since the Montreal Protocol) show that many humans have less than optimal levels of vitamin D. Specifically, in the US population, a quarter of the lowest vitamin D (<17.8 ng/ml) was found using information from the National Health and Nutrition Examination Survey to be associated with an increase in all-cause mortality in the general population.. While vitamin D levels in the blood of over 100 ng/ml seem to increase blood calcium in excess and are associated with higher mortality, the body has a mechanism that prevents sunlight from producing vitamin D beyond the body's needs.
Effects on non-human animals
The November 2010 report by scientists at the Institute of Zoology in London found that whales off the coast of California have shown a sharp increase in sun damage, and scientists are "afraid that a thin layer of ozone should be blamed." The study photographed and took skin biopsies from more than 150 whales in the Gulf of California and found "widespread evidence of epidermal damage commonly associated with acute and severe sunburn", has cells that form when DNA is damaged by UV radiation. The findings suggest "elevated UV levels as a result of ozone depletion is a cause of observed skin damage, in the same way that human skin cancer rates have increased in recent decades."
Effects on plants
Increased UV radiation is expected to affect plants. A number of economically important plant species, such as rice, depend on cyanobacteria located at their roots to maintain nitrogen. Cyanobacteria are sensitive to UV radiation and will be affected by the increase. "Although the mechanisms for reducing or improving the effects of ultraviolet radiation are increasing, plants have limited ability to adapt to elevated UVB levels, therefore plant growth can be directly affected by UVB radiation."
Public policy
The extent to which damage caused by CFCs in the ozone layer is unknown and will not be known for several decades; However, a marked decrease in the ozone column has been observed. The Montreal and Vienna Conventions were installed long before scientific consensus was established or significant uncertainties in the field of science were being finalized. The ozone case well understood by ordinary people such as Ozone shield or ozone hole is an "easy to understand" bridging metaphor. Americans voluntarily switched from aerosol sprays, generating a 50 percent loss sale even before the law came into effect.
After a 1976 report by the US National Academy of Sciences concluded that credible scientific evidence supports the ozone depletion hypothesis of several countries, including the United States, Canada, Sweden, Denmark and Norway, moved to eliminate the use of CFCs in aerosol sprays. cans. At present it is widely considered the first step towards a more comprehensive regulatory policy, but progress in this direction slows down in subsequent years, due to a combination of political factors (continued resistance from the halocarbon industry and general changes in attitudes to the regulatory environment during the first two years Reagan administration) and scientific developments (the next National Academy appraisal that indicates that the first estimate of the magnitude of the ozone depletion has been too great). The critical DuPont manufacturing patent for Freon is set to expire in 1979. The United States banned the use of CFCs in aerosol cans in 1978. The European Society rejected proposals to ban CFCs in aerosol sprays, and in the US CFCs continued to be used as cooling and for cleaning boards circuit. Worldwide CFC production fell sharply after the US aerosol ban, but by 1986 it had returned to its 1976 level. In 1993, DuPont Canada closed its CFC facility.
The attitude of the US Government began to change again in 1983, when William Ruckelshaus replaced Anne M. Burford as US Environmental Protection Agency Administrator. Under Ruckelshaus and his successor, Lee Thomas, the EPA encourages an international approach to halocarbon regulation. In 1985, 20 countries, including most of the major CFC producers, signed the Vienna Convention for the Protection of the Ozone Layer, which established a framework for negotiating international regulations on ozone depleting substances. In the same year, the discovery of the Antarctic ozone hole was announced, causing a revival of public attention to this issue. In 1987, representatives from 43 countries signed the Montreal Protocol. Meanwhile, the halocarbon industry shifted its position and began supporting the protocol to limit the production of CFCs. However, this shift is uneven with DuPont acting faster than their European counterparts. DuPont may be worried about court action linked to an increase in skin cancer mainly because the EPA has published a study in 1986 claiming that an additional 40 million cases and 800,000 cancer deaths are estimated to occur in the US in the next 88 years. The European Union shifted its position also after Germany handed its defense to the CFC industry and began to support the step toward regulation. Governments and industries in France and Britain are trying to maintain their CFC production industry even after the Montreal Protocol is signed.
In Montreal, the participants agreed to freeze CFC production at the 1986 level and to reduce production by 50 percent in 1999. After a series of scientific expeditions to Antarctica yield convincing evidence that the ozone hole was caused by chlorine and bromine from manmade organohalogens. , The Montreal Protocol was strengthened at the 1990 meeting in London. Participants agreed to abolish CFCs and halons altogether (other than very small amounts marked for certain "essential" uses, such as asthma inhalers) in 2000 in non-Article 5 countries and in 2010 in Article 5 (less developing) signer. At a 1992 meeting in Copenhagen, the transfer date was moved until 1996. At the same meeting, methyl bromide (MeBr), a fumigant used primarily in agricultural production, was added to the list of controlled substances. For all substances controlled under the protocol, delayed phase-out schedules for less developed countries ('Article 5 (1)'), and termination in these countries are supported by the transfer of expertise, technology and money from non-Article 5 ( 1) Parties to the Protocol. In addition, exceptions from the approved schedule may be applied for under the Essential Use Exclusion (EUE) process for substances other than methyl bromide and under the Critical Use Exemption process for methyl bromide.
Civil society, including especially NGOs, play an important role at all stages of policy development leading to the Vienna Conference, the Montreal Protocol, and in assessing subsequent compliance. Big companies claim that there is no alternative to HFC. Safe ozone hydrocarbon refrigerants were developed at a Hamburg institute of technology in Germany, and in 1992 became the concern of Greenpeace non-governmental organizations (NGOs). Greenpeace was granted a patent, calling it "Greenfreeze," and leaving the patent as open source. NGOs then worked successfully first with small companies and struggled to market tools that began in Europe, then Asia and then Latin America, received the UNEP 1997 award. In 1995, Germany had made the refrigerators of CFCs illegal. Since 2004, companies like Coca-Cola, Carlsberg, and IKEA have formed a coalition to promote Greenfreeze units that are safe for ozone. Production spread to companies such as Electrolux, Bosch, and LG, with sales reaching about 300 million refrigerators in 2008. In Latin America, an Argentinian domestic company started production of Greenfreeze in 2003, while Bosch giant in Brazil started a year later. In 2013, it is used by about 700 million refrigerators, which is about 40 percent of the market. But in the US, change is much slower. To some extent, CFCs are being replaced by less damaging hydrochlorofluorocarbons (HCFCs), though concerns remain about HCFC as well. In some applications, hydrofluorocarbons (HFCs) are used to replace CFCs. HFC, which contains no chlorine or bromine, does not contribute at all to ozone depletion even though they are a powerful greenhouse gas. The most famous of these compounds is probably the HFC-134a (R-134a), which in the United States has replaced the CFC-12 (R-12) in the car air conditioner. In laboratory analysis (former "essential" use) ozone-depleting substances can be replaced with other solvents. Chemical companies like Du Pont, whose representatives even underestimated Greenfreeze as "German technology," maneuvered the EPA to block technology in the US until 2011. Ben & amp; Jerry's of Unilever and General Electric, sparked by Greenpeace, have expressed an official interest in 2008 specified in the final approval of the EPA.
Recently, policy experts have advocated efforts to link ozone protection efforts with climate protection efforts. Many BPOs are also a greenhouse gas, several thousand times stronger radiation-coating agents than carbon dioxide over the short and medium term. So policies that protect the ozone layer have benefits in climate change mitigation. In fact, the reduction of radiation imposition due to ODS may mask the level of actual climate change effects of other GHGs, and is responsible for the global warming "slowdown" of the mid-90s. Policy decisions in one arena affect the cost and effectiveness of environmental improvements in others.
ODS requirements in marine industry
IMO has amended MARPOL Annex VI of Regulation 12 on ozone depleting substances. Since July 1, 2010, all vessels in which MARPOL Annex VI applies must have a list of equipment using ozone depleting substances. The list must include the name of the ODS, the type and location of the equipment, the quantity in kg and date. All changes since that date should be recorded in the ODS Notes book on the board noting all intended or intentional releases to the atmosphere. Furthermore, a new supply of ODS or landing to a beach facility should be recorded as well.
Ozone depletion prospect
Since the adoption and strengthening of the Montreal Protocol has led to CFC emission reductions, atmospheric concentrations of the most significant compounds have declined. These substances are gradually removed from the atmosphere; since its peak in 1994, the effective Chlorine Equivalence (EECl) level in the atmosphere has dropped by about 10 percent in 2008. The decline in ozone-depleting chemicals has also been significantly affected by the decline of bromine-containing chemicals. The data show that large natural resources exist for atmospheric methyl bromide ( CH
3 Br ). The phase out of the CFC means nitrous oxide ( N
2 O ), which is not covered by the Montreal Protocol, has become the highest emission ozone powder and is expected to remain so throughout the 21st century.
The 2005 IPCC review of ozone observation and model calculations concluded that the global ozone amount has now been almost stable. Although considerable variability is expected from year to year, including in the polar regions where the depletion is greatest, the ozone layer is expected to begin to recover in the next few decades due to the reduced concentration of ozone-depleting substances, assuming full compliance with the Montreal Protocol.
Antarctic ozone holes are expected to continue for decades. The concentration of ozone in the upper Antarctic upper stratosphere will increase 5-10 percent by 2020 and return to pre-1980 levels around 2060-2075. This is 10-25 years slower than expected in the previous assessment, due to a revised estimate of atmospheric concentrations of ozone-depleting substances, including larger estimates of future usage in developing countries. Another factor that can prolong the depletion of ozone is the withdrawal of nitrogen oxides from the top of the stratosphere due to changes in wind patterns. The gradual trend toward "healing" is reported in 2016.
Research history
The basic physical and chemical processes leading to the formation of the ozone layer in the Earth's stratosphere were discovered by Sydney Chapman in 1930. Short-term UV radiation separates oxygen ( O
O
3 -> 2 O
2 . In the 1950s, David Bates and Marcel Nicolet presented evidence that a variety of free radicals, especially hydroxyl (OH) and nitric oxide (NO), can catalyze this recombination reaction, reducing the overall ozone amount. These free radicals are known to be present in the stratosphere, and are considered part of the natural equilibrium - it is thought that in their absence the ozone layer will be twice as thick as it is today.
In 1970, Paul Crutzen showed that emissions from nitrous oxide ( N
2 O ), a stable and long-lived gas produced by soil bacteria, from the Earth's surface can affect the amount of nitric oxide (NO) in the stratosphere. Crutzen shows that nitrous oxide lives long enough to reach the stratosphere, where it is converted to NO. Crutzen later noted that increased use of fertilizers may have led to an increase in nitrous oxide emissions above the natural background, which in turn would result in an increase in the amount of NO in the stratosphere. Thus human activity can affect the stratospheric ozone layer. The following year, Crutzen and (independent) Harold Johnston suggested that NO emissions from a supersonic passenger plane, which would fly in the lower stratosphere, could also drain the ozone layer. However, a recent analysis in 1995 by David W. Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration, found that the decrease in ozone would be 1-2 percent if a fleet of 500 supersonic passenger aircraft were operated. This, Fahey stated, would not be a showstopper for the development of sophisticated supersonic passenger aircraft.
Rowland-Molina Hypothesis
In 1974 Frank Sherwood Rowland, Professor of Chemistry at the University of California at Irvine, and his postdoctoral colleague Mario J. Molina suggested that long-lived organic halogen compounds, such as CFCs, might behave in the same way that Crutzen proposed for nitrous oxide.. James Lovelock recently discovered, during a voyage in the South Atlantic in 1971, that almost all CFC compounds produced since their discovery in 1930 still exist in the atmosphere. Molina and Rowland conclude that, like N
2 O , CFCs will reach the stratosphere where they will be separated by UV light, releasing chlorine atoms. A year earlier, Richard Stolarski and Ralph Cicerone at the University of Michigan have shown that Cl is even more efficient than NOT in catalyzing the destruction of ozone. A similar conclusion was achieved by Michael McElroy and Steven Wofsy at Harvard University. However, both groups were unaware that CFCs were a potentially large source of stratospheric chlorine - on the contrary, they have investigated the possibility of the HCl emission effects of the much smaller Space Shuttle.
The Rowland-Molina hypothesis is highly debated by representatives of the aerosol and halocarbon industries. The Chairman of the DuPont Board was quoted as saying that the theory of ozone depletion is "a science fiction story... a load of rubbish... nonsense". Robert Abplanalp, President of Precision Valve Corporation (and inventor of the first practical aerosol spray valve), wrote a letter to Chancellor UC Irvine to complain about Rowland's public statements. Nevertheless, in three years, most of the basic assumptions made by Rowland and Molina are confirmed by laboratory measurements and by direct observation in the stratosphere. Source gas concentration (CFC and related compounds) and chlorine reservoir species (HCl and ClONO
2 ) is measured throughout the stratosphere, and shows that CFCs are indeed the main source of stratospheric chlorine, and that almost all CFCs emitted will eventually reach the stratosphere. More convincingly is the measurement, by James G. Anderson and his collaborator, chlorine monoxide (ClO) in the stratosphere. ClO is produced by Cl's reaction with ozone - his observations show that Cl radicals are not only present in the stratosphere but also actually involved in destroying ozone. McElroy and Wofsy expanded the work of Rowland and Molina by showing that bromine atoms and even catalysts are more effective for ozone loss than chlorine atoms and argue that brominated organic compounds known as halons, widely used in fire extinguishers, are potentially huge stratospheric sources. bromine. In 1976, the United States Academy of Sciences issued a report concluding that the ozone depletion hypothesis is strongly supported by scientific evidence. In response to the United States, Canada and Norway banned the use of CFCs in aerosol spray cans in 1978. The initial estimate is that, if CFC production continues at 1977 levels, the total atmospheric ozone will be after a century or more reaching a steady state, 15 to 18 percent in below the normal level. In 1984, when better evidence of critical reaction velocity was available, these estimates were converted to 5 to 9 percent steady-state depletion.
Crutzen, Molina, and Rowland were awarded the 1995 Nobel Prize in Chemistry for their work in stratospheric ozone.
Antarctic ozone hole
The discovery of the "Antarctic ozone hole" by British scientists Antarctic Survey Farman, Gardiner and Shanklin (first reported in a paper in Nature in May 1985) came as a surprise to the scientific community, as observations of polar ozone decrease were much greater than anticipated. Satellite measurements indicate the large ozone depletion around the south pole becomes available at the same time. However, this was initially rejected as unreasonable by data quality control algorithms (they were filtered as errors due to their unexpectedly low values); the ozone hole is only detected in the satellite data when the raw data is reprocessed following ozone depletion evidence in observation of in situ . When the software was relaunched without a flag, the ozone hole was visible as far back as 1976.
Susan Solomon, an atmospheric chemist at the National Oceanic and Atmospheric Administration (NOAA), proposed that chemical reactions in stratospheric polar clouds (PSC) in the cold Antarctic stratosphere led to large increases, although local and seasonal, the amount of chlorine present in the active, ozone. Arctic stratospheric clouds in Antarctica only form when there is a very low temperature, as low as -80 ° C, and early spring conditions. Under such conditions, ice crystals from the cloud provide a suitable surface for conversion of inactive chlorine compounds into reactive chlorine compounds, which can drain ozone easily.
Moreover, the polar vortices that form on Antarctica are very tight and the reactions occurring on the surface of the cloud crystals are very different from when they occur in the atmosphere. This condition has led to the formation of an ozone hole in Antarctica. This hypothesis was confirmed conclusively, first by laboratory measurements and then by direct measurement, from soil and from high altitude aircraft, to very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere.
An alternative hypothesis, which links the ozone hole with variations in solar UV radiation or changes in atmospheric circulation patterns, is also tested and proven untenable.
Meanwhile, ozone measurement analysis of Dobson-based spectrophotometer networks worldwide leads an international panel to conclude that the ozone layer has actually been depleted, at all latitudes outside the tropics. This trend is confirmed by satellite measurements. As a result, major halokarbon-producing countries agreed to stop production of CFCs, halons, and related compounds, a process completed in 1996.
Since 1981, the United Nations Environment Program, under the auspices of the World Meteorological Organization, has sponsored a series of technical reports on the Scientific Assessment of Ozone Depletion, based on satellite measurements. The 2007 report shows that holes in the ozone layer are recovering and the smallest is about a decade. The 2010 report finds, "Over the past decade, global ozone and ozone in the Arctic and Antarctic region have ceased to fall but the ozone layer outside the Polar region is projected to recover to levels before 1980 sometime before the middle of the century, ozone spring above Antarctica is expected to recover considerably thereafter. "In 2012, NOAA and NASA reported" The warmer air temperatures above Antarctica caused the second smallest ozone hole in 20 years averaging 17.9 million square kilometers. reached its maximum size for the season on September 22, extending to 21.2 million square kilometers.'The gradual trend toward "healing" is reported in 2016.
Holes in the Earth's ozone layer above the South Pole have affected the atmospheric circulation in the Southern Hemisphere to the equator. The ozone hole has affected the atmospheric circulation to the tropics and increased rainfall in low latitudes, subtropics in the Southern Hemisphere.
Arctic ozone hole
On March 3, 2005, the journal Nature published an article linking the huge Arctic ozone hole of 2004 for solar wind activity.
As of March 15, 2011, records of the loss of the ozone layer were observed, with about half of the ozone present in the Arctic being destroyed. This change is associated with an increasingly cold winter in the Arctic stratosphere at a height of about 20 km (12 miles), changes related to global warming in relationships still under investigation. As of March 25, ozone loss has been the largest compared to that observed in all previous winters with the possibility that it will become an ozone hole. This would necessitate the amount of ozone to fall below 200 Dobson units, of the 250 listed above central Siberia. It is estimated that thinning layers will affect parts of Scandinavia and Eastern Europe on March 30-31.
On October 2, 2011, a study was published in the journal Nature, which says that between December 2010 and March 2011 up to 80 percent of the ozone in the atmosphere is about 20 kilometers (12 miles) above. the surface was destroyed. The rate of ozone depletion is severe enough that scientists say it can be compared to the ozone hole that forms over Antarctica every winter. According to the study, "for the first time, quite a lot of losses occur to be reasonably described as Arctic ozone holes." This study analyzed data from Aura and CALIPSO satellites, and determined that ozone loss greater than normal was caused by an unusually long period of cold weather in the Arctic, about 30 days more than usual, allowing for more ozone destruction. chlorine compound to be made. According to Lamont Poole, co-author of the study, clouds and aerosol particles in which chlorine compounds were found "abundantly in the Arctic until mid-March 2011 - much slower than usual - with average numbers at some altitudes similar to those observed in Antarctica, and dramatically larger than the almost zero value seen in March in much of the Arctic winter ".
Tibetan ozone hole
Because winter is cooler is more affected, sometimes there is an ozone hole on top of Tibet. In 2006, a 2.5 million square kilometer ozone hole was detected over Tibet. Also again in 2011 an ozone hole appeared in Tibet, Xinjiang, Qinghai and Hindu Kush mountains, along with an unprecedented hole in the Arctic, although Tibet is one much less intense than those above the Arctic or Antarctic.
Depreciation potential by storm cloud
Research in 2012 shows that the same process that produced an ozone hole over Antarctica occurred during a summer cloud storm in the United States, and thus could damage the ozone there as well.
Ozone depletion and global warming
Among other things, Robert Watson has a role in the assessment of science and in efforts to regulate ozone depletion and global warming. Prior to the 1980s, the EU, NASA, NAS, UNEP, WMO and the British government had rejected the scientific report and Watson played a role in the integrated assessment process. Based on ozone experience, IPCC began working on integrated reporting and science assessment to reach consensus to provide IPCC Summary for Policy Makers.
There are various areas of linkage between ozone depletion and the science of global warming:
- CO
2 imposed radiation that produces global warming is expected to cool the stratosphere. This cooling, in turn, is expected to produce a relatively increase in ozone ( O
3 ) depletion in the polar area and ozone hole frequency. - Conversely, ozone depletion is the coercion of radiation from the climate system. There are two opposite effects: Reducing ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the cooler stratosphere generated emits less long wavelength radiation, thereby cooling the troposphere. Overall, cooling dominates; IPCC concludes " observes the stratosphere O
3 Loss over the last two decades has caused negative pressure from the troposphere-surface system " around -0.15 Â ± 0.10 watts per square meter (W/m 2 ). - One of the strongest predictions of the greenhouse effect is the stratosphere will cool. Although this cooling has been observed, it is not trivial to separate the effects of changes in greenhouse gas concentrations and ozone depletion as both will cause cooling. However, this can be done by numerical stratospheric modeling. The results of the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory show that above 20 km (12 mi), greenhouse gases dominate cooling.
- As stated in "Public Policy", ozone-depleting chemicals are also often greenhouse gases. Increased concentrations of these chemicals have resulted in 0.34 Â ± 0.03 W/m 2 of forced radiation, corresponding to about 14 percent of total radiation forcing from increased concentrations of mixed greenhouses. gas.
- Modeling long-term processes, their measurements, studies, theoretical design and testing take decades to document, gain widespread acceptance, and eventually become the dominant paradigm. Several theories about the destruction of ozone were hypothesized in the 1980s, published in the late 1990s, and are currently under investigation. Dr. Drew Schindell, and Dr. Paul Newman, NASA Goddard, proposed the theory in the late 1990s, using a computational modeling method to model the destruction of ozone, which accounts for 78 percent of the ozone being destroyed. Further refinement of the model accounted for 89 percent of the destroyed ozone, but pushed back estimates of ozone hole recovery from 75 years to 150 years. (An important part of the model is the lack of stratospheric flight due to the depletion of fossil fuels.)
Misconceptions
Weight CFC
Because CFC molecules are heavier than air (nitrogen or oxygen), it is generally believed that CFC molecules can not reach the stratosphere in significant amounts. However, atmospheric gases are not sorted by weight; the power of the wind can completely mix gas in the atmosphere. Lighter CFCs are spread evenly throughout the turbosphere and reach the upper atmosphere, although some heavier CFCs are not evenly distributed.
Percentage of man-made chlorine
Another misconception is that "it is generally accepted that the natural source of tropospheric chlorine is four to five times greater than that made by humans." Although very true, troposphere chlorine is irrelevant; it is a stratospheric chlorine that affects ozone depletion. The chlorine from the sea spray dissolves and is thus washed by rainfall before reaching the stratosphere. CFCs, on the other hand, are insoluble and live long, allowing them to reach the stratosphere. In lower atmospheres, there is far more chlorine than CFCs and related haloalkanes than exist in HCl from salt sprays, and in halocarbons dominant stratosphere. Only methyl chloride, which is one of these halocarbons, has a primarily natural source, and is responsible for about 20 percent of chlorine in the stratosphere; The remaining 80 percent comes from manmade sources.
Very loud volcanic eruptions can inject HCl into the stratosphere, but researchers have shown that its contribution is insignificant compared to CFCs. A similarly false claim is that the soluble halogen compound from the volcanic clumps of Mount Erebus on Ross Island, Antarctica is a major contributor to the Antarctic ozone hole.
Nevertheless, a study of 2015 suggests that the role of Mount Erebus volcanoes in Antarctic ozone depletion may be underestimated. Based on NCEP/NCAR re-analysis data for the past 35 years and using the NOAA HYSPLIT trajectory model, the researchers demonstrated that Erebus volcanic gas emissions (including hydrogen chloride (HCl)) can reach the Antarctic stratosphere through high-latitude cyclones and then polar vortices. Depending on the activity of the Erebus volcano, additional annual HCl mass entering the stratosphere of Erebus varies from 1.0 to 14.3 kt.
First observation
G.M.B. Dobson (explains the Atmosphere, 2nd Edition, Oxford, 1968) mentions that when the ozone spring level in Antarctica in Halley Bay was first measured in 1956, he was surprised to find that they were ~ 320 DU, or about 150 DU under the Arctic spring level ~ 450 DU. It is at that moment the only available Antarctic ozone value. What Dobson describes is basically the baseline of where the ozone hole is measured: the actual ozone hole value is in the range 150-100 DU.
The difference between the Arctic and Antarctic noted by Dobson is mainly a matter of time: during the Arctic ozone spring rate rises smoothly, peaking in April, while in Antarctica they remain about constant during early spring, rising unexpectedly in November when the polar vortex destroyed.
The behavior seen in the Antarctic ozone hole is completely different. Instead of staying constant, ozone levels in early spring suddenly drop from their already very low winter rates, by as much as 50 percent, and normal values ​​are not reached again until December.
The hole location
Some people think that the ozone hole must be above the CFC source. However, CFCs are mixed globally in the troposphere and stratosphere. The reason for ozone holes over Antarctica is not because there are more CFCs concentrated but because low temperatures help form polar stratospheric clouds. In fact, there are significant findings of "ozone holes" that are localized on other parts of the earth.
World Ozone Day
In 1994, the UN General Assembly voted to establish Sept. 16 as the International Day for the Preservation of the Ozone Layer, or "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987.
References
Further reading
- Andersen, S.O. and K. M. Sarma. (2002). Protecting the Ozone Layer: The History of the United Nations , Earthscan Press. London.
- Benedick, Richard Elliot; World Wildlife Fund (USA); Institute for Diplomacy Studies. Georgetown University. (1998). Ozone Diplomacy: New Directions in Safeguarding the Planet (2nd ed.). Harvard University Press. ISBN 978-0-674-65003-9 . Retrieved May 28 2016 . (Ambassador Big Benedick is the Head of US Negotiators at the meeting that produced the Montreal Protocol.)
- Chasek, Pamela S., David L. Downie, and Janet Wels
Source of the article : Wikipedia
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