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Analysis of the ultraviolet index in the region of Puno, Peru
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This research aims to validate ultraviolet index data obtained from the Ozone Monitoring Instrument (OMI) for the city of Puno. Data analysis was conducted on data from the DAVIS Vantage Pro 2 Plus meteorological station located in the city of Puno and data obtained from the OMI for the quadrant -70.540214, -15.982311, -69.540214, -14.982311. The comparison of the UV index data showed a linear correlation of 0.937 and an overestimation of values by the OMI; thus, a data correction equation was formulated for later analysis based on the linear regression of the maximum ultraviolet index values of both datasets at solar noon for the years 2016, 2017 and 2018. The evolution of the UV index shows clear seasonal behavior, both in the ground-based and satellite data, with maximum values obtained in summer and minimum values obtained in winter. The validation results show good correlation between the satellite data and ground-based measurements.
The study shows an analysis of a 7-year data set measuring Ultraviolet-B (UVB) irradiance values and ultraviolet index TABLEUVI) values derived from ground-based broadband irradiance measurements, satellite-derived total ozone, and UVB solar irradiance recorded in Valladolid (Central Spain). Ultraviolet-B (UVB) solar irradiance measurements in the range (280–315 nm) carried out during the period 2013–2019 at a continental Mediterranean solar station, located in Valladolid (Spain), were analyzed. UVB data recorded using a YES UVB-1 pyranometer were used to estimate erythemal irradiance, ultraviolet erythemal irradiance (UVER), UVI, cumulative dose, and sun protection. Hourly UVER data in January (minimum values) and June (maximum values) were analyzed as an average year for the measurement station. Differences between UVI values at solar noon and the maximum daily value were minimal. It was found that on certain summer days, maximum daily UVI and SED (cumulative daily dose) could be over 12 and 60, respectively. The cumulative dose on the horizontal surface was calculated at the station for different skin types. It was observed that over 45% of the annual dose is received in summer, about 30% in spring, over 15% in autumn, and less than 10% in winter. In addition, the relationship between the maximum daily UVI and the annual accumulated dose in SEDs was studied to provide information on sun protection under low UVI conditions.
Data of the Total Ozone Column have been analyzed in this paper,which were derived from the measurements performed by the Earth Probe TotalOzone Mapping Spectrometer (EPTOMS) of the National Aeronautics andSpace Administration (NASA), by assessing its suitability for the predictionof the Ultraviolet (UV) Index for the city of Puno (15.83◦south latitude and70.03◦west longitude). After a one-year analysis was performed by means ofadjustments of sinusoidal functions, it is observed that the gap changes, fromone year to the next. Additionally, during the period studied (2005-2017), threedates were found in which ozone holes were presented: On February 5, 2010 andApril 29, 2016, values of 218 Dobson Units (DU) were presented, and on May17, 2005, a value of 219 DU was presented. The behavior of the ozone column,per year, displays a sinusoidal cyclical shape, as it is established in the seasonalcycle.
La excesiva exposición a la radiación solar, específicamente la ultravioleta (RUV), ha sido causa de diferentes enfermedades, en especial de cáncer de piel. En 1995 el Círculo Dermatológico del Perú realizó la primera “Campaña de Educación, Prevención y Detección Temprana de Cáncer de Piel y Melanoma” denominada el “Día del Lunar”. Fue oficializada por el Ministerio de Salud, y cuenta con la participación del Seguro Social de Salud (EsSalud). Es una campaña gratuita que se realiza cada año a nivel nacional, en ella, desde 1995 al 2011 se atendieron a 118 092 personas, en 76 sedes distribuidas en 18 ciudades de todo el país, en el 2,8% de estas se pudo identificar alguna lesión cutánea sospechosa de malignidad, de las cuales el 64,9% correspondió a carcinoma basocelular, 26,7% a melanoma cutáneo y 8,4% a carcinoma espinocelular. Estas campañas destacan en importancia no solo por la práctica asistencial en ellas realizada, sino por las actividades educativas orientadas a fomentar una cultura de prevención en favor de las poblaciones más vulnerables. Finalmente, consideramos que es fundamental seguir educando a la población en la prevención del cáncer de piel, crear conciencia en las autoridades para que participen activamente en la realización de estas actividades, además de solicitar a todos los médicos que se sumen coordinadamente a este esfuerzo para seguir avanzando y mejorar lo logrado en beneficio de nuestro país.
In the highland region of Puno-Peru, the Ultraviolet Radiation Index (IUV) on the international scale are higher than normal at certain seasons of the year and reflect high risk of erythema in people, alterations in the terrestrial and aquatic ecosystem. For that reason an automatic radiometric station was installed and certified in the National University of the Altiplano, being the main objective the search of a spectral model of the IUV. We chose arbitrarily 6 days of clear sky without clouds, one day for each month from August of 2015. A good performance was demonstrated between the model and the measurements, being the correlation in average 0.99. Also the model allows to estimate the rate of ultraviolet radiation type B that is approximately 76.4% and 23.6% corresponds to type A, that is when the sun is at the zenith. On the other hand the measurements show a sinusoidal behavior noting some stability in the summer, the values Index daily maximum was on average of 14 from October until February. The dissemination of IUV data will inform, alert and sensitize the population of the harmful effects on health
Ozone Monitoring Instrument (OMI), launched in July 2004, is dedicated to the monitoring of the Earth's ozone, air quality and climate. OMI provides among other things the total column of ozone (TOC), the surface ultraviolet (UV) irradiance at several wavelengths, the erythemal dose rate and the erythemal daily dose. The main objective of this work is to validate OMI data with ground-based instruments in order to use OMI products (collection 2) for scientific studies. The Laboratoire d'Optique Atmosphérique (LOA) located in Villeneuve d'Ascq in the north of France performs solar UV measurements using a spectroradiometer and a broadband radiometer. The site of Briançon in the French Southern Alps is also equipped with a spectroradiometer operated by Interaction Rayonnement Solaire Atmosphère (IRSA). The instrument belongs to the Centre Européen Médical et Bioclimatologique de Recherche et d'Enseignement Supérieur. The comparison between the TOC retrieved with ground-based measurements and OMI TOC shows good agreement at both sites for all sky conditions. Comparisons of spectral UV on clear sky conditions are also satisfying whereas results of comparisons of the erythemal daily doses and erythemal dose rates for all sky conditions and for clear sky show that OMI overestimates significantly surface UV doses at both sites.
The increase in reports of novel diseases in a wide range of ecosystems, both terrestrial and marine, has been linked to many factors including exposure to novel pathogens and changes in the global climate. Prevalence of skin cancer in particular has been found to be increasing in humans, but has not been reported in wild fish before. Here we report extensive melanosis and melanoma (skin cancer) in wild populations of an iconic, commercially-important marine fish, the coral trout Plectropomus leopardus. The syndrome reported here has strong similarities to previous studies associated with UV induced melanomas in the well-established laboratory fish model Xiphophorus. Relatively high prevalence rates of this syndrome (15%) were recorded at two offshore sites in the Great Barrier Reef Marine Park (GBRMP). In the absence of microbial pathogens and given the strong similarities to the UV-induced melanomas, we conclude that the likely cause was environmental exposure to UV radiation. Further studies are needed to establish the large scale distribution of the syndrome and confirm that the lesions reported here are the same as the melanoma in Xiphophorus, by assessing mutation of the EGFR gene, Xmrk. Furthermore, research on the potential links of this syndrome to increases in UV radiation from stratospheric ozone depletion needs to be completed.
The Dutch-Finnish Ozone Monitoring Instrument (OMI) on board the NASA EOS Aura spacecraft is a nadir viewing spectrometer that measures solar reflected and backscattered light in a selected range of the ultraviolet and visible spectrum. The instrument has a 2600 km wide viewing swath and it is capable of daily, global contiguous mapping. The Finnish Meteorological Institute and NASA Goddard Space Flight Center have developed a surface ultraviolet irradiance algorithm for OMI that produces noontime surface spectral UV irradiance estimates at four wavelengths, noontime erythemal dose rate (UV index), and the erythemal daily dose. The overpass erythemal daily doses derived from OMI data were compared with the daily doses calculated from the ground-based spectral UV measurements from 18 reference instruments. Two alternative methods for the OMI UV algorithm cloud correction were compared: the plane-parallel cloud model method and the method based on Lambertian equivalent reflectivity. The validation results for the two methods showed some differences, but the results do not imply that one method is categorically superior to the other. For flat, snow-free regions with modest loadings of absorbing aerosols or trace gases, the OMI-derived daily erythemal doses have a median overestimation of 0-10%, and some 60 to 80% of the doses are within +/-20% from the ground reference. For sites significantly affected by absorbing aerosols or trace gases one expects, and observes, bigger positive bias up to 50%. For high-latitude sites the satellite-derived doses are occasionally up to 50% too small because of unrealistically small climatological surface albedo.
Numerous studies have examined plant responses to elevated ultraviolet-B radiation at the species level. More than 140 studies conducted within the past three decades were collected for meta-analysis to generalize and examine overall responses of two main life-forms, woody plants and herbaceous plants under two supplemental UV-B levels. The analysis suggested that both life-forms would suffer an overall negative effect in total biomass under the two UV-B levels, and the reduction was 7.0–14.6% of the value at ambient UV-B radiation. Comparing the overall responses under the high supplemental UV-B level with those under the low supplemental UV-B level, woody plants showed no significant changes in any variables. As opposed to this, decreases in herbaceous plant height and specific leaf area as well as increase in herbaceous UV-B-absorbing compounds under the higher UV-B level were significantly greater than those under the lower UV-B level. With continued increases in UV-B levels, the two life-forms would show different response strategies for their different intrinsic capabilities to resist UV-B damage. Woody plants would not invest in large additional amounts of UV-B-absorbing compounds, while herbaceous plants would need to induce stronger defense mechanisms to protect themselves from the associated detrimental effects of UV-B radiation. A higher number of response variables were significantly affected by UV-B radiation for herbaceous plants than for woody plants. Most of the studied variables were not affected significantly under elevated UV-B for woody plants and exhibited very large confidence intervals. Further studies should investigate if the response to elevated UV-B radiation varies between different functional groups of woody species. To sum up, we suggest that as UV-B radiation continues to increase, grassland ecosystems should receive more attention for future vegetation management.
The main objective of this study is to compare the erythemal UV irradiance (UVER) and spectral UV irradiances (at 305, 310 and 324 nm) from the Ozone Monitoring Instrument (OMI) onboard NASA EOS/Aura polar sun-synchronous satellite (launched in July 2004, local equator crossing time 01:45 p.m.) with ground-based measurements from the Brewer spectrophotometer #150 located at El Arenosillo (South of Spain). The analyzed period comprises more than four years, from October 2004 to December 2008. The effects of several factors (clouds, aerosols and the solar elevation) on OMI-Brewer comparisons were analyzed. The proxies used for each factor were: OMI Lambertian Equivalent Reflectivity (LER) at 360 nm (clouds), the aerosol optical depth (AOD) at 440 nm measured from the ground-based Cimel sun-photometer ( http://aeronet.gsfc.nasa.gov ), and solar zenith angle (SZA) at OMI overpass time. The comparison for all sky conditions reveals positive biases (OMI higher than Brewer) 12.3% for UVER, 14.2% for UV irradiance at 305 nm, 10.6% for 310 nm and 8.7% for 324 nm. The OMI-Brewer root mean square error (RMSE) is reduced when cloudy cases are removed from the analysis, (e.g., RMSE~20% for all sky conditions and RMSE smaller than 10% for cloud-free conditions). However, the biases remain and even become more significant for the cloud-free cases with respect to all sky conditions. The mentioned overestimation is partially due to aerosol extinction influence. In addition, the differences OMI-Brewer typically decrease with SZA except days with high aerosol loading, when the bias is near constant. The seasonal dependence of the OMI-Brewer difference for cloud-free conditions is driven by aerosol climatology.
To account for the aerosol effect, a first evaluation in order to compare with previous TOMS results (Antón et al., 2007) was performed. This comparison shows that the OMI bias is between +14% and +19% for UVER and spectral UV irradiances for moderately-high aerosol load (AOD>0.25). The OMI bias is decreased by a factor of 2 (the typical bias varies from +8% to +12%) under cloud-free and low aerosol load conditions (AOD<0.1). More detailed analysis of absorbing aerosols influence on OMI bias at our station is presented in a companion paper (Cachorro et al., 2010).
Increased incident ultraviolet (UV) radiation due to ozone depletion has heightened interest in plant responses to UV because solar UV wavelengths can reduce plant genome stability, growth, and productivity. These detrimental effects result from damage to cell components including nucleic acids, proteins, and membrane lipids. As obligate phototrophs, plants must counter the onslaught of cellular damage due to prolonged exposure to sunlight. They do so by attenuating the UV dose received through accumulation of UV-absorbing secondary metabolites, neutralizing reactive oxygen species produced by UV, monomerizing UV-induced pyrimidine dimers by photoreactivation, extracting UV photoproducts from DNA via nucleotide excision repair, and perhaps transiently tolerating the presence of DNA lesions via replicative bypass of the damage. The signaling mechanisms controlling these responses suggest that UV exposure also may be beneficial to plants by increasing cellular immunity to pathogens. Indeed, pathogen resistance can be enhanced by UV treatment, and recent experiments suggest DNA damage and its processing may have a role.
En el presente trabajo se exponen las mediciones de la radiación ultravioleta tipo A; la de tipo B y el INDICE en la ciudad de Upina – Puno. La dependencia entre el INDICE y la radiación ultravioleta fue investigada y se encontró un excelente grado de asociación. Sé observo que el INDICE es 1.6 veces la radiación ultravioleta tipo B, mientras que el INDICE es 3.207 veces el tipo A. Posteriormente en la Universidad Nacional del Altiplano, se ha medido la radiación ultravioleta tipo B para cielos despejados sin nubes. A partir de estos datos se ha estimado el INDICE, notándose un incremento de 5,92 hasta 9,376, desde el 28 de setiembre el 20 de noviembre del 2014. Si se considera la radiación tipo A y el efecto espejo del lago Titicaca, los valores del ÍNDICE son mayores a 12 para el mes de noviembre, que es el valor máximo permitido por la Organización Mundial de la Salud. Para obtener los valores estimados de la radiación ultravioleta tipo A y tipo B en cielos claros, se ha utilizado el modelo parametrico, programado en MATLAB. El modelo explica el comportamiento de la radiación para cielos parciamente nublados, notándose que las características de las nubes pueden aumentar o disminuir dicha radiación
Soybean [Glycine max (L.) Merr.] cultivars Williams-82 and Maverick were grown in a polycarbonate greenhouse (P-GH), a glass greenhouse (G-GH), and outdoors during daytime (control) to investigate the effect of (i) exclusion of both ultraviolet B (UV-B, 280–320 nm) and ultraviolet A (UV-A, 320–400 nm), (ii) exclusion of UV-B only, and (iii) exposure to daytime solar UV radiation (09:00–17:00 h local time daily). Both the P-GH and the G-GH were maintained at day/night air temperatures of 30/22 °C. The purpose was to quantify the growth differences due to partial and total UV exclusion compared with the control. Exclusion of both UV-B and UV-A radiation caused elongated internodes on the plants, which resulted in greater plant height. Mean mainstem length of Williams-82 was 50.2 cm for the control, but they were 45% and 237% greater for excluded UV-B radiation only and both excluded UV-B and UV-A radiation, respectively. Similarly, mean mainstem length of Maverick was 55.2 cm for the control, but they were 52% and 198% greater for excluded UV-B only and both excluded UV-B and UV-A, respectively. There also was a slight increase in the number of nodes with increasing extent of UV radiation exclusion. The mean final V-stage of Williams-82 was 14.2 for the control, but they were 11% and 18% greater for excluded UV-B only and both excluded UV-B and UV-A, respectively. Likewise, the mean final V-stage of Maverick was 14.5 for the control, but they were 12% and 22% greater for excluded UV-B only and both excluded UV-B and UV-A, respectively. With exclusion of both UV-B and UV-A, pod yield for the Maverick cultivar was greater but this effect was not as clear for the Williams-82 cultivar. In summary, most of the total UV-exclusion effects were due to the exclusion of the UV-A radiation component. Finally, UV spectral transmission of greenhouse or controlled environment covering material should be considered before conducting research on plants, or producing plants commercially, that are sensitive to UV exclusion, such as certain grain legumes or horticultural crops.
Laboratory methods to simulate the short- and long-term ageing occuring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a “protection” of the elastomers by the studied bitumen towards UV radiation.
Effects of ultraviolet-B (UV-B) radiation on amphibian embryonic and larval development have been investigated in a number of studies, but the effects on later life-stages (metamorphosis) have received less attention. Hence, the effects of UV-B radiation treatments (control (no UV-B), normal and 26% enhanced levels of UV-B) on the development of the common frog Rana temporaria embryos from fertilization until metamorphosis were investigated. Survival until metamorphosis was significantly higher among individuals exposed to normal, as compared to individuals sheltered from, UV-B or those exposed to enhanced levels of UV-B radiation. There were no effects of normal or enhanced levels of UV-B radiation on the frequency of developmental anomalies. However, UV-B radiation delayed the timing of metamorphosis in a dose-dependent fashion, and the individuals from the normal and enhanced UV-B treatments metamorphosed at smaller size than those raised in the absence of UV-B radiation. These results suggest that UV-B radiation experienced through embryonic and larval stages can have negative effects on the growth and development of R. temporaria. Delayed metamorphosis at reduced size is also likely to lower the fitness during later life-stages.
Evapotranspiration is one of the most important elements for quantifying available water since it generally constitutes the
largest component of the terrestrial water cycle. This study evaluated four models (Makkink, Turc, Priestley–Taylor and Hargreaves)
commonly used to estimate monthly reference crop evapotranspiration (ETo) values. The main aim of this study was to determine the model used to estimate ETo with small data requirements and high accuracy for twelve synoptic stations in four climates of Iran. The results showed
that the Turc model was the best suited model in estimating ETo for cold humid and arid climates. The Hargreaves model turned out to be the most precise model under warm humid and semi-arid
climatic conditions. In contrast, the Makkink model presented the poorest estimates in all of the climates exception for cold
humid environment. In cold humid climate, the Hargreaves model was the least accurate model in estimating ETo. In general, the results obtained from this study revealed very clearly that the Makkink and Priestley–Taylor models estimated
ETo values less accurately than Turc and Hargreaves models for the all climates.
KeywordsReference crop evapotranspiration-Penman–Monteith FAO 56-Climatic conditions-Iran
Polymers are known for their susceptibility to degradation as a result of ultra-violet (UV) radiation. In this study, the UV stability of bloodmeal-based thermoplastics (BMT) was evaluated over a period of 12 weeks. Formulations with and without plasticiser were tested and moisture was excluded during accelerated weathering to isolate the effect of UV because of the material’s known sensitivity to moisture. It was found that embrittlement due to loss of water overshadowed the effect of UV degradation. Embrittlement caused the material’s toughness to be reduced by an order of magnitude after only two weeks of exposure, for either plasticised or unplasticised samples. An initial increase in tensile strength was observed after two weeks followed by a steady decline in strength. The elastic modulus reached a plateau after about two weeks of exposure. FTIR did not confirm any chemical changes after 12 weeks exposure and TGA suggested that low molecular mass species were quickly lost during the course of the test. The absence of chemical changes does not suggest resistance to environmental degradation, although the dark pigmentation of bloodmeal may have contributed to the lack of UV degradation. Embrittlement remains a greater concern and requires further attention.
In a previous paper [Alexandris, S., Kerkides, P., 2003. New empirical formula for hourly estimations of reference evapotranspiration. Agric. Water Manage. 60, 181–198.] the Copais empirical function for estimating hourly reference evapotranspiration ETo using data of three attributes (solar radiation, temperature and relative humidity) was presented. In this work, a similar empirical equation for estimating daily ETo is proposed. Bilinear surface regression analysis is used to determine the equation coefficients. Results are compared with corresponding estimates obtained by the widely used physically sound methods of ASCE Penman–Monteith, CIMIS–Penman, FAO-56 Penman–Monteith and the empirical hourly Copais and daily Hargreaves–Samani models. Comparison shows that the new empirical function operates quite consistently and satisfactorily, providing reliable daily ETo estimates, slightly (on average by 3.5%) underestimating the summed hourly estimates by the combination equations, applied under three climatic regimes. Behaviour of the other empirical model (Hargreaves–Samani) is climate depending. The proposed empirical model may become a useful tool for routine daily reference evapotranspiration estimations.
The purpose of this paper is to review procedures which are used for the evaluation of the durability of polymer coatings. In particular, methods of environmental acceleration and techniques of assessment of coating degradation have been examined, with an emphasis upon those which may produce reliable fast answer durability predictions. The advantages and disadvantages of the various exposure regimes currently used (such as Florida exposure, EMMAQUA or artificial light sources) have been discussed in terms of correlation with actual durability data and of degree of acceleration. A general rule of thumb is that the correlation of accelerated methods with natural exposure is inversely proportional to the degree of acceleration used. The common physical methods used to assess the extent of coating durability have been presented, with the general drawbacks to these techniques being highlighted. Finally, the benefits and drawbacks of a number of chemical techniques (in particular electron spin resonance (ESR), Fourier transform infrared spectroscopy (FTIR), hydroperoxide determination and chemiluminescence), which in principal could provide durability information in a fraction of the time of the physical techniques mentioned earlier, have been discussed. Of these, both ESR and FTIR spectroscopy show particular potential because of the short exposure times necessary to obtain significant results under UVA exposure.
Erythemally weighted solar ultraviolet (UV) radiation is often used to characterize the production of vitamin D in a human body. However, the vitamin D production action spectrum is different than that for erythemal UV. The vitamin D action spectrum weighted UV is more sensitive to UV-B, while the erythemal UV action spectrum has higher weighting coefficients than the vitamin D action spectrum in the UV-A part of the spectrum. Therefore, by using the erythemal UV as an estimate for the vitamin D action spectrum weighted UV can give results that differ by up to a factor of 5. This study examines the relationship between erythemal and vitamin D action spectrum weighted UV radiation using measurements of spectral UV at the surface by Brewer spectrophotometers that are part of the US and Canadian observational networks. It is shown that the ratio of vitamin D action spectrum weighted UV to erythemal UV is nearly constant for high levels of UV (UV Index greater than 5.5) and therefore vitamin D action spectrum weighted UV can be described in terms of erythemal UV. For lower levels of UV though this relationship should not be used. A simple formula that calculates vitamin D action spectrum weighted UV from UV Index is developed. An empirical formula that expresses the ratio of vitamin D action spectrum weighted UV to erythemal UV as a function of the solar zenith angle and column ozone is also suggested. The geographical distributions of vitamin D action spectrum weighted UV in the US and Canada are discussed.
–There is highly significant evidence that non-melanoma skin cancers are primarily due to chronic repeated exposure to solar ultraviolet radiation, and that there is a significant, although somewhat different relationship between solar radiation and the development of cutaneous malignant melanoma.
Recent experimental and epidemiologic studies show that the biologically most effective UVR wavelengths are in the segment of the solar UVR spectrum that would be significantly augmented by decreases in stratospheric ozone content.
A recent report on measurements of column ozone changes in the stratosphere has shown that in the past 18 yr, there has been an ozone decrease between 2 and 3%, greater in the winter months, and somewhat differing with latitude in the Northern Hemisphere.
Calculations of the relationship of ozone decrease to increase in biologically effective UVR show great dependence on the biologic action spectrum assumed.
Based on extensive epidemiologic studies of skin cancer incidence, it appears that the estimated increase in biologically effective UVR due to the measured ozone decreases in the past (almost) two decades are not likely to be the cause of the sharp increase in skin cancer incidence which have been observed. Most likely these increases in incidence are the result of increasing personal exposure, due to striking changes in personal behavior that have taken place for social reasons.
However, there is every reason to believe that increases in biologically effective UVR due to stratospheric ozone decreases will have significant impact on human skin cancer incidence in the future.
We analysed and compared the functioning of UV-B screening pigments in plants from marine, fresh water and terrestrial ecosystems, along the evolutionary line of cyanobacteria, unicellular algae, primitive multicellular algae, charophycean algae, lichens, mosses and higher plants, including amphibious macrophytes. Lichens were also included in the study. We were interested in the following key aspects: (a) does the water column function effectively as an 'external UV-B filter'?; (b) do aquatic plants need less 'internal UV-B screening' than terrestrial plants?; (c) what role does UV screening play in protecting the various plant groups from UV-B damage, such as the formation of thymine dimers?; and (d) since early land 'plants' (such as the predecessors of present-day cyanobacteria, lichens and mosses) experienced higher UV-B fluxes than higher plants, which evolved later, are primitive aquatic and land organisms (cyanobacteria, algae, lichens, mosses) better adapted to present-day levels of UV-B than higher plants? Furthermore, polychromatic action spectra for the induction of UV screening pigments of aquatic organisms have been determined. This is relevant for translating 'physical' radiation measurements of solar UV-B into 'biological' and 'ecological' effects. From the action spectra, radiation amplification factors (RAFs) have been calculated. These action spectra allow us to determine any mitigating or antagonistic effects in the ecosystems and therefore qualify the damage prediction for the ecosystems under study. We summarize and discuss the main results based on three years of research of four European research groups. The central theme of the work was the investigation of the effectiveness of the various screening compounds from the different species studied in order to gain some perspective of the evolutionary adaptations from lower to higher plant forms. The induction of mycosporine-like amino acids (MAAs) was studied in the marine dinoflagellate Gyrodinium dorsum, the green algal species Prasiola stipitata and in the cyanobacterium Anabaena sp. While visible (400-700 nm) and long wavelength UV-A (315-400 nm) showed only a slight effect, MAAs were effectively induced by UV-B (280-315 nm). The growth of the lower land organisms studied, i.e. the lichens Cladina portentosa, Cladina foliacaea and Cladonia arbuscula, and the club moss Lycopodiumannotinum, was not significantly reduced when grown under elevated UV-B radiation (simulating 15% ozone depletion). The growth in length of the moss Tortula ruralis was reduced under elevated UV-B. Of the aquatic plants investigated the charophytes Chara aspera showed decreased longitudinal growth under elevated UV-B. In the 'aquatic higher plants' studied, Ceratophyllum demersum, Batrachium trichophyllum and Potamogeton alpinus, there was no such depressed growth with enhanced UV-B. In Chara aspera, neither MAAs nor flavonoids could be detected. Of the terrestrial higher plants studied, Fagopyrum esculentum, Deschampsia antarctica, Vicia faba, Calamagrostis epigejos and Carex arenaria, the growth of the first species was depressed with enhanced UV-B, in the second species length growth was decreased, but the shoot number was increased, and in the latter two species of a dune grassland there was no reduced growth with enhanced UV-B. In the dune grassland species studied outdoors, at least five different flavonoids appeared in shoot tissue. Some of the flavonoids in the monocot species, which were identified and quantified with HPLC, included orientin, luteolin, tricin and apigenin. A greenhouse study with Vicia faba showed that two flavonoids (aglycones) respond particularly to enhanced UV-B. Of these, quercetin is UV-B inducible and mainly located in epidermal cells, while kaempferol occurs constitutively. In addition to its UV-screening function, quercetin may also act as an antioxidant. Polychromatic action spectra were determined for induction of the UV-absorbing pigments in three photosynthetic organisms, representing very different taxonomic groups and different habitats. In ultraviolet photobiology, action spectra mainly serve two purposes: (1) identification of the molecular species involved in light absorption; and (2) calculation of radiation amplification factors for assessing the effect of ozone depletion. Radiation amplification factors (RAFs) were calculated from the action spectra. In a somewhat simplified way, RAF can be defined as the percent increase of radiation damage for a 1% depletion of the ozone layer. Central European summer conditions were used in the calculations, but it has been shown that RAF values are not critically dependent on latitude or season. If only the ultraviolet spectral region is considered, the RAF values obtained are 0.7 for the green alga Prasiola stipitata, 0.4 for the dinoflagellate Gyrodinium dorsum, and 1.0 for the cyanobacterium Anabaena sp. In the case of P. stipitata, however, the effect of visible light (PAR, photosynthetically active radiation, 400-700 nm) is sufficient to lower the RAF to about 0.4, while the PAR effect for G. dorsum is negligible. RAFs for some damage processes, such as for DNA damage (RAF=2.1 if protective effects or photorepair are not considered [1]), are higher than those above. Our interpretation of this is that if the ozone layer is depleted, increased damaging radiation could overrule increased synthesis of protective pigments. In addition to investigating the functional effectiveness of the different screening compounds, direct UV effects on a number of key processes were also studied in order to gain further insight into the ability of the organisms to withstand enhanced UV-B radiation. To this end, the temperature-dependent repair of cyclobutane dimers (CPD) and (6-4) photoproducts induced by enhanced UV-B was studied in Nicotiana tabacum, and the UV-B induction of CPD was studied in the lichen Cladonia arbuscula. Also, photosynthesis and motility were monitored and the response related to the potential function of the screening compounds of the specific organism.
Increases in ultraviolet radiation at the Earth's surface due to the depletion of the stratospheric ozone layer have recently fuelled interest in the mechanisms of various effects it might have on organisms. DNA is certainly one of the key targets for UV-induced damage in a variety of organisms ranging from bacteria to humans. UV radiation induces two of the most abundant mutagenic and cytotoxic DNA lesions such as cyclobutane–pyrimidine dimers (CPDs) and 6–4 photoproducts (6–4PPs) and their Dewar valence isomers. However, cells have developed a number of repair or tolerance mechanisms to counteract the DNA damage caused by UV or any other stressors. Photoreactivation with the help of the enzyme photolyase is one of the most important and frequently occurring repair mechanisms in a variety of organisms. Excision repair, which can be distinguished into base excision repair (BER) and nucleotide excision repair (NER), also plays an important role in DNA repair
in several organisms with the help of a number of glycosylases and polymerases, respectively. In addition, mechanisms such as mutagenic repair or dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis and certain alternative repair pathways are also operative in various organisms. This review deals with UV-induced DNA damage and the associated repair mechanisms as well as methods of detecting DNA damage and its future perspectives.
- R P Gallagher
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