Flavonoid concentrations in three grass species and a sedge grown in the field and under controlled environment conditions in response to enhanced UV-B radiation

An investigation was carried out to find whether enhanced levels of UV-B radiation induce increased concentrations of flavonoids in the leaves of the grass species Deschampsia antarctica, Deschampsia borealis and Calamagrostis epigeios and the sedge Carex arenaria. Whether the enhanced levels of UV-B influenced the proportions of the various flavonoids in the leaves was also studied. Increased flavonoid concentrations would improve the UV-B shielding of UV-B susceptible tissues. Using HPLC analysis the flavonoids orientin and luteolin were identified in D. antarctica, orientin in D. borealis and tricin in C. arenaria. Neither flavonoid concentrations nor the proportion of the various flavonoids in climate room grown D. antarctica and D. borealis plants differed between individuals grown under 0, ambient or elevated UV-B levels. After 12 weeks of growth biomass production and shoot-to-root ratios of D. antarctica were not affected by elevated UV-B radiation. Greenhouse grown C. epigeios plants contained higher concentrations and different proportions of flavonoids grown under elevated levels of UV-B than when grown under ambient or 0 UV-B. In C. epigeios plants grown in their natural habitat in the field under ambient or elevated levels of UV-B, flavonoid concentrations and proportions were the same in plants from both treatments. In the leaves of the sedge C. arenaria grown in a greenhouse flavonoid concentrations and proportions were not affected by UV-B radiation. Leaves were harvested four times during the growing season from C. arenaria plants grown in their natural habitat in the field under ambient or elevated levels of UV-B. Leaves harvested in January contained higher concentrations of flavonoids when grown under elevated UV-B than when grown under ambient UV-B radiation. In leaves harvested in May, September and December flavonoid concentrations were the same in plants grown under ambient or elevated UV-B. The proportion of the different flavonoids was the same for both treatments in all months. These results indicate that constitutive levels of flavonoids in these grass and sedge species are adequately high to protect them against ambient and elevated levels of solar UV-B radiation.     

Vertical migration and motility responses in three marine phytoplankton species exposed to solar radiation

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280-400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280-700 nm), PA (320-700 nm) and P (400-700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2-3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem.     

Comparative measurements of solar UV radiation with spore dosimetry at three European and two Japanese sites

Spore dosimetry of solar UV radiation has been employed in several field intercomparison campaigns carried out in summer months in Japan and Europe. The dose-rate profiles, total daily doses and personal daily exposures have been determined and compared at five sites based on the spore inactivation dose (SID). The maximum dose rate (0.83 SID/min) and the maximum daily dose (197 SID) observed at subtropical Naha (26.2 degrees N) are about three times those observed at subarctic Abisko (68.4 degrees N). The amounts of personal exposure during three European campaigns are moderate and show a tendency of inverse relationships with the daily doses.     

Zinc oxide mediated heterogeneous photocatalytic degradation of organic species under solar radiation

The photocatalytic decomposition of eco-persistent toluene, salicylic acid and 4-chlorophenol with sun light in an oxygenated aqueous suspension has been studied under nanocrystalline hexagonal ZnO photocatalyst. The effect of substrate temperature onto the structural, morphological and photoactive properties has been investigated. The degradation of toluene, salicylic acid and 4-chlorophenol were achieved using a photoelectrochemical reactor module equipped with synthesized ZnO electrodes. Kinetic parameters have been investigated in terms of a first order rate equation. The rate constant (-k) for this heterogeneous photocatalysis was evaluated as a function of the initial concentration of original species. Substantial reduction in concentrations of toluene, salicylic acid and 4-chlorophenol was achieved as analyzed from COD and TOC studies. The mechanism for the degradation of toluene, salicylic acid and 4-chlorophenol could be explained on the basis of Langmuir-Hinshelwood mechanism.     

Facial solar UV exposure of Austrian farmers during occupation

Optoelectronic personal UV-meters were used to monitor the occupational facial solar erythemally effective exposure of 12 Austrian full-time farmers with high temporal resolution. To ensure high quality measurements several quality assurance procedures were applied, like calibration with respect to solar elevation and total ozone column. From April to October the test persons carried the UV-meters on the forehead during working hours. A digital diary (activity, location, weather, photoprotective measures) was completed on an hourly basis. Our field test produced 1427 complete daily records (measurement and diary). The total exposures showed high variability (77 –757 standard erythema dose [SED]) which correlates with the number of working days and even stronger with the little numbers of days with high exposure (>10 SED). Risk factors for high exposures were: mixed-culture farms with aggravated working conditions, low degree of automation of working processes, inadequate operating logistics (summarized as manual work outdoor), driving machines without cabins, and female gender. UV exposure of female farmers was approximately twice as high as that of men: Women received 15% of ambient radiation while men got 8%. Avoiding daily exposure >10 SED could reduce exposure down to 40% and the risk in developing skin cancer by a factor of 40.     

Phlorotannin and antioxidant responses upon short-term exposure to UV radiation and elevated temperature in three south Pacific kelps

Rapid adjustments of the photosynthetic machinery and efficient antioxidant mechanisms to scavenge harmful ROS are physiologic adaptions exhibited by intertidal seaweeds to persist in temperate regions. This study examines short-term (3 h) responses of three large kelps from the cold-temperate coast of Chile, normally adapted to water temperatures <16°C, but exposed abruptly to simultaneous high temperatures and UV radiation during low tide in summer. The kelps were exposed in the laboratory to three temperatures (10, 20 and 28°C) with and without UV radiation, and photochemical reactions, concentration of phlorotannins and antioxidant activity were examined. The exposure to elevated temperature (slightly exacerbated by the presence of UV radiation) decreased photochemical processes (measured as fluorescence kinetics) in the three studied species and increased lipid peroxidation in two of them. The concentration of total soluble phlorotannins was variable and correlated with the antioxidant activity in the presence of UV radiation. Insoluble phlorotannins did not change during the exposure. In all, the downregulation of the photochemical machinery, which was expressed as dynamic photoinhibition, and the rapid induction of soluble phlorotannins triggered by UV radiation minimized the effects of oxidative stress and maintained the operation of photochemical processes during short-term thermal stress.     

Evaluation of a high exposure solar UV dosimeter for underwater use

Solar ultraviolet radiation (UV) is known to have a significant effect upon the marine ecosystem. This has been documented by many previous studies using a variety of measurement methods in aquatic environments such as oceans, streams and lakes. Evidence gathered from these investigations has shown that UVB radiation (280-320 nm) can negatively affect numerous aquatic life forms, while UVA radiation (320-400 nm) can both damage and possibly even repair certain types of underwater life. Chemical dosimeters such as polysulphone have been tested to record underwater UV exposures and in turn quantify the relationship between water column depth and dissolved organic carbon levels to the distribution of biologically damaging UV underwater. However, these studies have only been able to intercept UV exposures over relatively short time intervals. This paper reports on the evaluation of a high exposure UV dosimeter for underwater use. The UV dosimeter was fabricated from poly 2,6-dimethyl-1,4-phenylene oxide (PPO) film. This paper presents the dose response, cosine response, exposure additivity and watermarking effect relating to the PPO dosimeter as measured in a controlled underwater environment and will also detail the overnight dark reaction and UVA and visible radiation response of the PPO dosimeter, which can be used for error correction to improve the reliability of the UV data measured by the PPO dosimeters. These results show that this dosimeter has the potential for long-term underwater UV exposure measurements.     

Mean exposure fractions of human body solar UV exposure patterns for application in different ambient climates

In this research, the erythemally effective UV measured using miniaturized polysulphone dosimeters to over 1250 individual body sites and collected over a 4-year period is presented relative to the total exposed skin surface area (SSA) of a life-size manikin model. A new term is also introduced, the mean exposure fraction (MEF). The MEF is used to weight modeled or measured horizontal plane UV exposures to the total unprotected SSA of an individual and is defined as the ratio of exposure per unit area received by the unprotected skin surfaces of the body relative to the exposure received on a horizontal plane. The MEF has been calculated for a range of solar zenith angles (SZA) to provide a sunburning energy data set weighted to the actual SSA of a typically clothed individual. For this research, the MEF was determined as 0.15, 0.26 and 0.41 in the SZA ranges 0°-30°, 30°-50° and 50°-80° providing information that can be used in a variety of different ambient, latitudinal and seasonal climates where total human body UV exposure information is not available.     

Estimation of pedestrian level UV exposure under trees

Trees influence the amount of solar UV radiation that reaches pedestrians. A three-dimensional model was developed to predict the ultraviolet-B (UV-B) irradiance fields in open-tree canopies where the spacing between trees is equal to or greater than the width of individual tree crowns. The model predicted the relative irradiance (fraction of above-canopy irradiance) under both sunlit and shaded conditions under clear skies with a mean bias error of less than 0.01 and a root mean square error of 0.07. Both model and measurements showed that the locations people typically perceive as shady, low-irradiance locations in the environment can actually have significant UV-B exposure (40-60% of that under direct sunlight). The relationship of tree cover in residential neighborhoods to erythemal UV-B exposure for children and adults was modeled for the 4 h around noon in June and July. Results showed that human exposures (on the horizontal) in cities located at 15 and 30 degrees latitudes are nearly identical. For latitudes between 15 and 60 degrees, ultraviolet protection factors (UPF) were less than 2 for less than 50% tree cover. A UPF of 10 was possible at all latitudes for tree cover of 90%.     

The role of solar UV radiation in the ecology of alpine lakes.

Solar ultraviolet radiation (UVR, 290-400 nm) is a crucial environmental factor in alpine lakes because of the natural increase of the UVR flux with elevation and the high water transparency of these ecosystems. The ecological importance of UVR, however, has only recently been recognized. This review, examines the general features of alpine lakes regarding UVR, summarizes what is known about the role of solar UVR in the ecology of alpine lakes, and identifies future research directions. Unlike the pattern observed in most lowland lakes, variability of UV attenuation in alpine lakes is poorly explained by differences in dissolved organic carbon (DOC) concentrations, and depends mainly on optical characteristics (absorption) of the chromophoric dissolved organic matter (CDOM). Within the water column of lakes with low DOC concentrations (0.2-0.4 mg l(-1)), UV attenuation is influenced by phytoplankton whose development at depth (i.e. the deep chlorophyll maximum) causes important changes in UV attenuation. Alpine aquatic organisms have developed a number of strategies to minimize UV damage. The widespread synthesis or bioaccumulation of different compounds that directly or indirectly absorb UV energy is one such strategy. Although most benthic and planktonic primary producers and crustacean zooplankton are well adapted to high intensities of solar radiation, heterotrophic protists, bacteria, and viruses seem to be particularly sensitive to UVR. Understanding the overall impact of UVR on alpine lakes would need to consider synergistic and antagonistic processes resulting from the pronounced climatic warming, which have the potential to modify the UV underwater climate and consequently the stress on aquatic organisms.     

Oxidation of guanine in cellular DNA by solar UV radiation: biological role.

The formation of cyclobutane pyrimidine dimers (CPD) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) was investigated in Chinese hamster ovary cells upon exposure to either UVC, UVB, UVA or simulated sunlight (SSL). Two cell lines were used, namely AT3-2 and UVL9, the latter being deficient in nucleotide excision repair and consequently UV sensitive. For all types of radiation, including UVA, CPD were found to be the predominant lesions quantitatively. At the biologically relevant doses used, UVC, UVB and SSL irradiation yielded 8-oxodGuo at a rather low level, whereas UVA radiation produced relatively higher amounts. The formation of CPD was 10(2) and 10(5) more effective upon UVC than UVB and UVA exposure. These yields of formation followed DNA absorption, even in the UVA range. The calculated relative spectral effectiveness in the production of the two lesions showed that efficient induction of 8-oxodGuo upon UVA irradiation was shifted toward longer wavelengths, in comparison with those for CPD formation, in agreement with a photosensitization mechanism. In addition, after exposure to SSL, about 19% and 20% of 8-oxodGuo were produced between 290-320 nm and 320-340 nm, respectively, whereas CPD were essentially (90%) induced in the UVB region. However, the ratio of CPD to 8-oxodGuo greatly differed from one source of light to the other: it was over 100 for UVB but only a few units for UVA source. The extent of 8-oxodGuo and CPD was also compared to the lethality for the different types of radiation. The involvement of 8-oxodGuo in cell killing by solar UV radiation was clearly ruled out. In addition, our previously reported mutation spectra demonstrated that the contribution of 8-oxodGuo in the overall solar UV mutagenic process is very minor.     

Degradation of complexons derived from succinic acid under UV radiation

The destruction of complexons derived from succinic acid under the action of UV radiation was studied. IR spectroscopy, thin-layer paper chromatography, and complexometric titration were used to determine the destruction products of these complexons. It was found that the complexons decompose under UV irradiation substantially more easily than ethylenediaminetetraacetic acid does, and the products of their decomposition can undergo a biological utilization under natural conditions. The data obtained in the study make it possible to choose, instead of ethylenediaminetetraacetic acid, ligands that will be nearly fully destructible in the light without deteriorating the ecology.     

丙烯酸在牙釉质表面的紫外光共辐射接枝

龋坏的过程是牙釉质脱矿和再矿化长期交替进行的过程,当脱矿大于再矿化时,就导致了釉质脱矿从而引起龋病的发生[1]。本文设想在牙釉质表面接枝一些羧基活性官能团,为进一步在牙釉质表面引入牙釉蛋白分子提供活性基团和接位空穴,并为深入探讨牙釉蛋白诱导牙釉质的再矿化提供基础     

Formulation selection of aliphatic aromatic biodegradable polyester film exposed to UV/solar radiation

Aliphatic aromatic copolyester films, poly(butylene adipate-co-terephthalate) or PBAT, are susceptible to photodegradation, leading to main chain scission and crosslinking. The presence of crosslinked structures not only decreased the mechanical properties of the film due to embrittlement, but also hindered the biodegradation process by limiting access of water and microorganisms to the polymer chains. This has limited the use of PBAT for outdoor applications, such as mulch films. In this study, response surface methodology (RSM) was used to determine the optimal concentrations of carbon black (CB) and the chain breaking antioxidant butylated hydroxytoluene (BHT) for the design of mulch films that can prevent the formation of crosslinked structures from recombination of free radicals. An overlaid contour plot of suitable concentrations of CB and BHT for the formulation of mulch film for crop production in Michigan or regions with similar solar radiation was established using selection criteria of light transmission of less than 20%, final tensile strength of at least 6.35 MPa, maximum gel fraction of 0.30, and positive number average molecular weight reduction sensitivity in the early stage of degradation.     

Degradability of biodegradable plastic under controlled composting conditions

Biodegradability of poly(ß-propiolactone) (PPL), one of biodegradable plastics, was tested in a bench-scale composting reactor under controlled conditions, with uniform temperature, moisture content, and aerobiosis maintained. The composting raw mixture was prepared by mixing commercial dog food instead of real organic waste, saw dust as a bulking agent, commercial inoculum sold for acceleration of composting, and PPL in the ratio of 10:9:1:10 on dry weight basis. The degree and rate of PPL degradation were determined by comparing the difference in the CO₂ evolution for composting with and without addition of PPL. The influence of temperature on the degradability of PPL was investigated at 40, 50, and 60 °C and the optimum temperature was found to be around 40-50°C where ca. 40 wt.-% of PPL was decomposed in 8 days. The effect of inoculum on the degradability of PPL during 50 °C composting was then examined, a considerable difference (100%) being observed in the biodegradability using two different inocula.     

Stabilizer additives in ionizing radiation environments under oxidizing conditions

Very little work has been done with energy-scavenger additives in radiation environments under oxidizing conditions. In this study, the stabilizing effect of an energy scavenger (pyrene) and a radical scavenger (hindered phenol), which were incorporated in a polychloroprene rubber, has been evaluated in a γ-radiation environment in air under conditions which gave rise to oxidation throughout the sample. Both compounds were found to significantly inhibit changes in macroscopic tensile properties of the materials. The pyrene enhanced the material's radiation resistance when used alone and also when used in conjunction with the hindered phenol. The rate of radiation-induced chemical destruction of the two additives was monitored by gas chromatography after solvent-extraction from degraded samples. Following a dose of 3 × 10⁵ Gy, only a few per cent of the hindered phenol remained, whereas more than 90% of the pyrene was still present. The rate of disappearance of the hindered phenol was slower in samples which also contained the pyrene.     

Sublethal exposure to UV radiation affects respiration rates of the freshwater cladoceran Daphnia catawba

We examined the effects of UV radiation (UVR) on metabolic rates of the freshwater cladoceran Daphnia catawba. We exposed D. catawba to UVB for 12 h in a lamp phototron at levels of 2.08 and 4.16 kJ m(-2) both with and without concomitant exposure to UVA and visible photorepair radiation (PRR). We also included a group that received PRR only and a dark control group. Respiration rates were measured for 6 h following exposure. Respiration rates increased by 31.8% relative to the dark control at the lowest level of UVB stress (2.08 kJ m(-2) UVB with PRR), whereas respiration was inhibited by 70.3% at the highest stress level (4.16 kJ m(-2) UVB without PRR). Survival rates in the group that received PRR only and the group exposed to 2.08 kJ m(-2) and PRR were not significantly different from that in the control group; however, the survival rate was reduced for all other UVR exposures. We hypothesize that enhanced respiration rates reflect energetic costs related to repair of cellular components damaged by sublethal levels of UVR. Increases in respiration rate of the magnitude we found in our experiment could significantly reduce energetic reserves available for growth and reproduction, especially in cases where these costs are incurred repeatedly during a series of days with high levels of UVR.     

Global forecast model to predict the daily dose of the solar erythemally effective UV radiation

A worldwide forecast of the erythemally effective ultraviolet (UV) radiation is presented. The forecast was established to inform the public about the expected amount of erythemally effective UV radiation for the next day. Besides the irradiance, the daily dose is forecasted to enable people to choose the appropriate sun protection tools. Following the UV Index as the measure of global erythemally effective irradiance, the daily dose is expressed in units of UV Index hours. In this study, we have validated the model and the forecast against measurements from broadband UV radiometers of the Robertson-Berger type. The measurements were made at four continents ranging from the northern polar circle (67.4 degrees N) to the Antarctic coast (61.1 degrees S). As additional quality criteria the frequency of underestimation was taken into account because the forecast is a tool of radiation protection and made to avoid overexposure. A value closer than one minimal erythemal dose for the most sensitive skin type 1 to the observed value was counted as hit and greater deviations as underestimation or overestimation. The Austrian forecast model underestimates the daily dose in 3.7% of all cases, whereas 1.7% results from the model and 2.0% from the assumed total ozone content. The hit rate could be found in the order of 40%.     

Rat lens glycolysis after in vivo exposure to narrow band UV or blue light radiation

UV radiation and short wavelength visible light are known to damage various tissues in the eye. This paper investigates the effect on rat lens glycolysis after in vivo exposure with 90 kJ m⁻² narrow band UV radiation (UVB, 300 nm) and 90 kJ m⁻² blue light (435 nm) radiation. After exposure, all lenses were incubated in Medium 199. Samples of culture medium were withdrawn after 2, 4, 6 h and 5, 10, 20 h in two UVB studies and after 5, 10 and 20 h in a blue light study. Lactate is the major end product of lens glycolysis. Lactate was determined with a modified enzymatic-photometric method. Intralenticular lactate was determined in one UVB experiment. In the UVB experiments we found a lower lactate production in the exposed lenses 2–6 h after exposure. There was an accumulation of lactate inside UVB-exposed lenses after 6 h incubation compared with their contralateral lenses. No significant effect on lactate production was observed in the blue light experiment. Conclusions. UVB induced a reversible inhibition of glycolysis. UVB also induced an accumulation of lactate inside the lens. Blue light tended to increase glycolysis.     

Modeling of complex-forming chromatographic systems under ionizing radiation conditions

Simulation of displacement complex-forming chromatography systems under irradiation conditions was performed for eluents based on diethylenetriaminepentaacetate. Acetates, iminodiacetates, formates, glycinates, and succinates were considered as radiolysis products. The model with an acetic acid salt as the radiolysis product best correlated with the experimental data.