Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 65
Filtrar
1.
Nature ; 596(7872): 384-388, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34408332

RESUMO

The control of the production of ozone-depleting substances through the Montreal Protocol means that the stratospheric ozone layer is recovering1 and that consequent increases in harmful surface ultraviolet radiation are being avoided2,3. The Montreal Protocol has co-benefits for climate change mitigation, because ozone-depleting substances are potent greenhouse gases4-7. The avoided ultraviolet radiation and climate change also have co-benefits for plants and their capacity to store carbon through photosynthesis8, but this has not previously been investigated. Here, using a modelling framework that couples ozone depletion, climate change, damage to plants by ultraviolet radiation and the carbon cycle, we explore the benefits of avoided increases in ultraviolet radiation and changes in climate on the terrestrial biosphere and its capacity as a carbon sink. Considering a range of strengths for the effect of ultraviolet radiation on plant growth8-12, we estimate that there could have been 325-690 billion tonnes less carbon held in plants and soils by the end of this century (2080-2099) without the Montreal Protocol (as compared to climate projections with controls on ozone-depleting substances). This change could have resulted in an additional 115-235 parts per million of atmospheric carbon dioxide, which might have led to additional warming of global-mean surface temperature by 0.50-1.0 degrees. Our findings suggest that the Montreal Protocol may also be helping to mitigate climate change through avoided decreases in the land carbon sink.


Assuntos
Sequestro de Carbono , Perda de Ozônio/prevenção & controle , Ozônio Estratosférico/análise , Dióxido de Carbono/análise , Sequestro de Carbono/efeitos da radiação , Aquecimento Global/prevenção & controle , Aquecimento Global/estatística & dados numéricos , História do Século XXI , Fotossíntese/efeitos da radiação , Plantas/metabolismo , Plantas/efeitos da radiação , Temperatura , Raios Ultravioleta
2.
Glob Chang Biol ; 27(22): 5681-5683, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34392574

RESUMO

The Montreal Protocol and its Amendments have been highly effective in protecting the stratospheric ozone layer, preventing global increases in solar ultraviolet-B radiation (UV-B; 280-315 nm) at Earth's surface, and reducing global warming. While ongoing and projected changes in UV-B radiation and climate still pose a threat to human health, food security, air and water quality, terrestrial and aquatic ecosystems, and construction materials and fabrics, the Montreal Protocol continues to play a critical role in protecting Earth's inhabitants and ecosystems by addressing many of the United Nations Sustainable Development Goals.


Assuntos
Perda de Ozônio , Ozônio , Mudança Climática , Ecossistema , Humanos , Ozônio Estratosférico , Raios Ultravioleta/efeitos adversos
6.
Ambio ; 50(1): 40-43, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33219940

RESUMO

We here reflect on two important articles on stratospheric ozone depletion written by P. J. Crutzen (1974) and P. J. Crutzen and D. H. Ehhalt (1977) in the early 1970s. These articles provide a clear description of the stratosphere and the most important chemical reactions involved in stratospheric ozone depletion. They present modeling results and provide recommendations for future research on stratospheric ozone depletion caused by chloro-fluoro-carbons, supersonic transport, nitrous oxide, and nuclear explosions. These two articles represent the beginning of a scientific era, which led to discovery of the Antarctic ozone hole and political action in the form of the Montreal Protocol and its amendments.


Assuntos
Ozônio , Ozônio Estratosférico , Aniversários e Eventos Especiais , Atmosfera , Efeito Estufa
7.
Ambio ; 50(1): 44-48, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33219941

RESUMO

Crutzen (1974) and Crutzen and Ehhalt (1977) presented two key papers in Ambio that in Ambioexemplify how science first revealed to humankind the potential for damage to our ozone shield in the Anthropocene. Crutzen's (1974) review is a sweeping summary of the risks to the ozone layer from supersonic aircraft, chlorofluorocarbons, as well as nuclear weapons testing and nuclear war. Crutzen and Ehhalt (1977) described how the nitrous oxide produced from fertilizers could pose another threat to the stability of the stratospheric ozone layer. The two papers are part of a body of influential scientific work that led to the pioneering Montreal Protocol to Protect the Earth's Ozone Layer to phase out production of chlorofluorocarbons (in 1987), as well as national decisions that slowed or stopped production of supersonic planes (in the 1970s). They remain guideposts today for ongoing international negotiations regarding reducing emissions from fertilizer and limiting nuclear testing.


Assuntos
Ozônio , Ozônio Estratosférico , Aniversários e Eventos Especiais , Clorofluorcarbonetos , Óxido Nitroso
8.
Astrobiology ; 20(12): 1465-1475, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33320780

RESUMO

The discovery of potentially habitable planets around the ultracool dwarf star Trappist-1 naturally poses the question: could Trappist-1 planets be home to life? These planets orbit very close to the host star and are most susceptible to the UV radiation emitted by the intense and frequent flares of Trappist-1. Here, we calculate the UV spectra (100-450 nm) of a superflare observed on Trappist-1 with the K2 mission. We couple radiative transfer models to this spectra to estimate the UV surface flux on planets in the habitable zone of Trappist-1 (planets e, f, and g), assuming atmospheric scenarios based on a prebiotic and an oxygenic atmosphere. We quantify the impact of the UV radiation on living organisms on the surface and on a hypothetical planet ocean. Finally, we find that for non-oxygenic planets, UV-resistant life-forms would survive on the surface of planets f and g. Nevertheless, more fragile organisms (i.e., Escherichia coli) could be protected from the hazardous UV effects at ocean depths greater than 8 m. If the planets have an ozone layer, any life-forms studied here would survive in the habitable zone planets.


Assuntos
Atmosfera , Meio Ambiente Extraterreno , Oceanos e Mares , Planetas , Exobiologia , Ozônio Estratosférico , Raios Ultravioleta
9.
Int J Mol Sci ; 21(19)2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33019598

RESUMO

The protective ozone layer is continually depleting due to the release of deteriorating environmental pollutants. The diminished ozone layer contributes to excessive exposure of cells to ultraviolet (UV) radiation. This leads to various cellular responses utilized to restore the homeostasis of exposed cells. DNA is the primary chromophore of the cells that absorbs sunlight energy. Exposure of genomic DNA to UV light leads to the formation of multitude of types of damage (depending on wavelength and exposure time) that are removed by effectively working repair pathways. The aim of this review is to summarize current knowledge considering cellular response to UV radiation with special focus on DNA damage and repair and to give a comprehensive insight for new researchers in this field. We also highlight most important future prospects considering application of the progressing knowledge of UV response for the clinical control of diverse pathologies.


Assuntos
Ciclo Celular/efeitos da radiação , Reparo do DNA/efeitos da radiação , DNA/efeitos da radiação , Regulação da Expressão Gênica/efeitos da radiação , Raios Ultravioleta/efeitos adversos , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Ciclo Celular/genética , Quinase 1 do Ponto de Checagem/genética , Quinase 1 do Ponto de Checagem/metabolismo , DNA/química , DNA/genética , DNA/metabolismo , Dano ao DNA , Escherichia coli/genética , Escherichia coli/metabolismo , Escherichia coli/efeitos da radiação , Humanos , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Dímeros de Pirimidina/química , Dímeros de Pirimidina/metabolismo , Transdução de Sinais , Ozônio Estratosférico/análise , Luz Solar/efeitos adversos
11.
Photochem Photobiol Sci ; 19(5): 542-584, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32364555

RESUMO

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.


Assuntos
Mudança Climática , Ozônio Estratosférico , Raios Ultravioleta , Saúde Ambiental , Humanos , Microplásticos , Nações Unidas
14.
Science ; 365(6453): 587-590, 2019 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395782

RESUMO

In 2017, western Canadian wildfires injected smoke into the stratosphere that was detectable by satellites for more than 8 months. The smoke plume rose from 12 to 23 kilometers within 2 months owing to solar heating of black carbon, extending the lifetime and latitudinal spread. Comparisons of model simulations to the rate of observed lofting indicate that 2% of the smoke mass was black carbon. The observed smoke lifetime in the stratosphere was 40% shorter than calculated with a standard model that does not consider photochemical loss of organic carbon. Photochemistry is represented by using an empirical ozone-organics reaction probability that matches the observed smoke decay. The observed rapid plume rise, latitudinal spread, and photochemical reactions provide new insights into potential global climate impacts from nuclear war.


Assuntos
Fumaça , Ozônio Estratosférico/análise , Incêndios Florestais , Canadá
15.
Nature ; 570(7760): 224-227, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31190014

RESUMO

Tropospheric ozone (O3) is a key component of air pollution and an important anthropogenic greenhouse gas1. During the twentieth century, the proliferation of the internal combustion engine, rapid industrialization and land-use change led to a global-scale increase in O3 concentrations2,3; however, the magnitude of this increase is uncertain. Atmospheric chemistry models typically predict4-7 an increase in the tropospheric O3 burden of between 25 and 50 per cent since 1900, whereas direct measurements made in the late nineteenth century indicate that surface O3 mixing ratios increased by up to 300 per cent8-10 over that time period. However, the accuracy and diagnostic power of these measurements remains controversial2. Here we use a record of the clumped-isotope composition of molecular oxygen (18O18O in O2) trapped in polar firn and ice from 1590 to 2016 AD, as well as atmospheric chemistry model simulations, to constrain changes in tropospheric O3 concentrations. We find that during the second half of the twentieth century, the proportion of 18O18O in O2 decreased by 0.03 ± 0.02 parts per thousand (95 per cent confidence interval) below its 1590-1958 AD mean, which implies that tropospheric O3 increased by less than 40 per cent during that time. These results corroborate model predictions of global-scale increases in surface pollution and vegetative stress caused by increasing anthropogenic emissions of O3 precursors4,5,11. We also estimate that the radiative forcing of tropospheric O3 since 1850 AD is probably less than +0.4 watts per square metre, consistent with results from recent climate modelling studies12.


Assuntos
Atmosfera/química , Ozônio/análise , Ozônio/química , Arquivos , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Atividades Humanas/história , Isótopos de Oxigênio/análise , Isótopos de Oxigênio/química , Ozônio/história , Reprodutibilidade dos Testes , Ozônio Estratosférico/análise , Ozônio Estratosférico/química
16.
J Environ Sci (China) ; 83: 152-160, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31221378

RESUMO

The structure of the boundary layer affects the evolution of ozone (O3), and research into this structure will provide important insights for understanding photochemical pollution. In this study, we conducted a one-month observation (from June 15 to July 14, 2016) of the boundary layer meteorological factors as well as O3 and its precursors in Luancheng County, Shijiazhuang (37°53'N, 114°38'E). Our research showed that photochemical pollution in Shijiazhuang is serious, and the mean hourly maximum and mean 8-hr maximum O3 concentrations are 97.9 ±â€¯26.1 and 84.4 ±â€¯22.4 ppbV, respectively. Meteorological factors play a significant role in the formation of O3. High temperatures and southeasterly winds lead to elevated O3 values, and at moderate relative humidity (40%-50%) and medium boundary layer heights (1200-1500 m), O3 production sensitivity occurred in the transitional region between volatile organic compounds (VOC) and nitrogen oxides (NOx) limitations, and the O3 concentration was the highest. The vertical profiles of O3 were also measured by a tethered balloon. The results showed that a large amount of O3 was stored in the residual layer, and the concentration was positively correlated with the O3 concentration measured the previous day. During the daytime of the following day, the contribution of O3 stored in the residual layer to the boundary layer reached 27% ±â€¯7% on average.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Ozônio Estratosférico , China , Óxidos de Nitrogênio/análise , Compostos Orgânicos Voláteis/análise
17.
Photochem Photobiol Sci ; 18(3): 641-680, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30810559

RESUMO

The Montreal Protocol has limited increases in the UV-B (280-315 nm) radiation reaching the Earth's surface as a result of depletion of stratospheric ozone. Nevertheless, the incidence of skin cancers continues to increase in most light-skinned populations, probably due mainly to risky sun exposure behaviour. In locations with strong sun protection programs of long duration, incidence is now reducing in younger age groups. Changes in the epidemiology of UV-induced eye diseases are less clear, due to a lack of data. Exposure to UV radiation plays a role in the development of cataracts, pterygium and possibly age-related macular degeneration; these are major causes of visual impairment world-wide. Photodermatoses and phototoxic reactions to drugs are not uncommon; management of the latter includes recognition of the risks by the prescribing physician. Exposure to UV radiation has benefits for health through the production of vitamin D in the skin and modulation of immune function. The latter has benefits for skin diseases such as psoriasis and possibly for systemic autoimmune diseases such as multiple sclerosis. The health risks of sun exposure can be mitigated through appropriate sun protection, such as clothing with both good UV-blocking characteristics and adequate skin coverage, sunglasses, shade, and sunscreen. New sunscreen preparations provide protection against a broader spectrum of solar radiation, but it is not clear that this has benefits for health. Gaps in knowledge make it difficult to derive evidence-based sun protection advice that balances the risks and benefits of sun exposure.


Assuntos
Oftalmopatias/etiologia , Imunidade/efeitos da radiação , Neoplasias Cutâneas/etiologia , Ozônio Estratosférico/análise , Raios Ultravioleta , Deficiência de Vitamina D/etiologia , Mudança Climática , Dano ao DNA/efeitos da radiação , Oftalmopatias/prevenção & controle , Saúde , Humanos , Dermatopatias/etiologia , Dermatopatias/prevenção & controle , Neoplasias Cutâneas/prevenção & controle , Luz Solar , Raios Ultravioleta/efeitos adversos , Vitamina D/análise , Deficiência de Vitamina D/prevenção & controle
18.
Photochem Photobiol Sci ; 18(3): 681-716, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30810560

RESUMO

Exposure of plants and animals to ultraviolet-B radiation (UV-B; 280-315 nm) is modified by stratospheric ozone dynamics and climate change. Even though stabilisation and projected recovery of stratospheric ozone is expected to curtail future increases in UV-B radiation at the Earth's surface, on-going changes in climate are increasingly exposing plants and animals to novel combinations of UV-B radiation and other climate change factors (e.g., ultraviolet-A and visible radiation, water availability, temperature and elevated carbon dioxide). Climate change is also shifting vegetation cover, geographic ranges of species, and seasonal timing of development, which further modifies exposure to UV-B radiation. Since our last assessment, there has been increased understanding of the underlying mechanisms by which plants perceive UV-B radiation, eliciting changes in growth, development and tolerances of abiotic and biotic factors. However, major questions remain on how UV-B radiation is interacting with other climate change factors to modify the production and quality of crops, as well as important ecosystem processes such as plant and animal competition, pest-pathogen interactions, and the decomposition of dead plant matter (litter). In addition, stratospheric ozone depletion is directly contributing to climate change in the southern hemisphere, such that terrestrial ecosystems in this region are being exposed to altered patterns of precipitation, temperature and fire regimes as well as UV-B radiation. These ozone-driven changes in climate have been implicated in both increases and reductions in the growth, survival and reproduction of plants and animals in Antarctica, South America and New Zealand. In this assessment, we summarise advances in our knowledge of these and other linkages and effects, and identify uncertainties and knowledge gaps that limit our ability to fully evaluate the ecological consequences of these environmental changes on terrestrial ecosystems.


Assuntos
Mudança Climática , Ozônio Estratosférico/análise , Raios Ultravioleta , Animais , Dióxido de Carbono/análise , Ecossistema , Poluentes Ambientais/análise , Água Doce/análise , Aquecimento Global , Proliferação Nociva de Algas/efeitos da radiação , Luz , Modelos Químicos , Recursos Naturais , Fotólise/efeitos da radiação , Água do Mar/análise
19.
Photochem Photobiol Sci ; 18(3): 717-746, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30810561

RESUMO

This assessment summarises the current state of knowledge on the interactive effects of ozone depletion and climate change on aquatic ecosystems, focusing on how these affect exposures to UV radiation in both inland and oceanic waters. The ways in which stratospheric ozone depletion is directly altering climate in the southern hemisphere and the consequent extensive effects on aquatic ecosystems are also addressed. The primary objective is to synthesise novel findings over the past four years in the context of the existing understanding of ecosystem response to UV radiation and the interactive effects of climate change. If it were not for the Montreal Protocol, stratospheric ozone depletion would have led to high levels of exposure to solar UV radiation with much stronger negative effects on all trophic levels in aquatic ecosystems than currently experienced in both inland and oceanic waters. This "world avoided" scenario that has curtailed ozone depletion, means that climate change and other environmental variables will play the primary role in regulating the exposure of aquatic organisms to solar UV radiation. Reductions in the thickness and duration of snow and ice cover are increasing the levels of exposure of aquatic organisms to UV radiation. Climate change was also expected to increase exposure by causing shallow mixed layers, but new data show deepening in some regions and shoaling in others. In contrast, climate-change related increases in heavy precipitation and melting of glaciers and permafrost are increasing the concentration and colour of UV-absorbing dissolved organic matter (DOM) and particulates. This is leading to the "browning" of many inland and coastal waters, with consequent loss of the valuable ecosystem service in which solar UV radiation disinfects surface waters of parasites and pathogens. Many organisms can reduce damage due to exposure to UV radiation through behavioural avoidance, photoprotection, and photoenzymatic repair, but meta-analyses continue to confirm negative effects of UV radiation across all trophic levels. Modeling studies estimating photoinhibition of primary production in parts of the Pacific Ocean have demonstrated that the UV radiation component of sunlight leads to a 20% decrease in estimates of primary productivity. Exposure to UV radiation can also lead to positive effects on some organisms by damaging less UV-tolerant predators, competitors, and pathogens. UV radiation also contributes to the formation of microplastic pollutants and interacts with artificial sunscreens and other pollutants with adverse effects on aquatic ecosystems. Exposure to UV-B radiation can decrease the toxicity of some pollutants such as methyl mercury (due to its role in demethylation) but increase the toxicity of other pollutants such as some pesticides and polycyclic aromatic hydrocarbons. Feeding on microplastics by zooplankton can lead to bioaccumulation in fish. Microplastics are found in up to 20% of fish marketed for human consumption, potentially threatening food security. Depletion of stratospheric ozone has altered climate in the southern hemisphere in ways that have increased oceanic productivity and consequently the growth, survival and reproduction of many sea birds and mammals. In contrast, warmer sea surface temperatures related to these climate shifts are also correlated with declines in both kelp beds in Tasmania and corals in Brazil. This assessment demonstrates that knowledge of the interactive effects of ozone depletion, UV radiation, and climate change factors on aquatic ecosystems has advanced considerably over the past four years and confirms the importance of considering synergies between environmental factors.


Assuntos
Adaptação Biológica , Organismos Aquáticos/fisiologia , Mudança Climática , Perda de Ozônio , Raios Ultravioleta , Animais , Aquicultura , Organismos Aquáticos/efeitos da radiação , Ecossistema , Poluição Ambiental/efeitos adversos , Poluição Ambiental/análise , Peixes/fisiologia , Água Doce/análise , Camada de Gelo/química , Oceanos e Mares , Fotossíntese , Ozônio Estratosférico/análise , Raios Ultravioleta/efeitos adversos , Zooplâncton/fisiologia
20.
Photochem Photobiol Sci ; 18(3): 775-803, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30810564

RESUMO

The composition of the air we breathe is determined by emissions, weather, and photochemical transformations induced by solar UV radiation. Photochemical reactions of many emitted chemical compounds can generate important (secondary) pollutants including ground-level ozone (O3) and some particulate matter, known to be detrimental to human health and ecosystems. Poor air quality is the major environmental cause of premature deaths globally, and even a small decrease in air quality can translate into a large increase in the number of deaths. In many regions of the globe, changes in emissions of pollutants have caused significant changes in air quality. Short-term variability in the weather as well as long-term climatic trends can affect ground-level pollution through several mechanisms. These include large-scale changes in the transport of O3 from the stratosphere to the troposphere, winds, clouds, and patterns of precipitation. Long-term trends in UV radiation, particularly related to the depletion and recovery of stratospheric ozone, are also expected to result in changes in air quality as well as the self-cleaning capacity of the global atmosphere. The increased use of substitutes for ozone-depleting substances, in response to the Montreal Protocol, does not currently pose a significant risk to the environment. This includes both the direct emissions of substitutes during use and their atmospheric degradation products (e.g. trifluoroacetic acid, TFA).


Assuntos
Poluição do Ar/análise , Mudança Climática , Ozônio Estratosférico/análise , Poluentes Atmosféricos/efeitos adversos , Poluentes Atmosféricos/análise , Poluição do Ar/efeitos adversos , Animais , Doenças Cardiovasculares/etiologia , Monitorização de Parâmetros Ecológicos , Ecossistema , Saúde , Humanos , Ozônio/efeitos adversos , Ozônio/análise , Perda de Ozônio , Reprodução , Doenças Respiratórias/etiologia , Raios Ultravioleta/efeitos adversos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...