Influence of UV-B Radiation and Temperature on Photodegradation of PAHs: Preliminary Results

The joint impact of UV-B radiation and temperature on photodegradation of polycyclic aromatic hydrocarbons (PAHs) sorbed to an organic solvent was assessed in this study. This approach was experimentally performed in a laboratory investigation by means of comparison of two different environments: Atlantic (Lancaster, UK) and Mediterranean (Tarragona, Catalonia, Spain) climatic conditions. The concentration of 10 PAHs contained in a tetradecane solution was compared under two different temperatures (10 and 20°C) and UV-B doses (6.5 and 22.5 kJ m⁻² day⁻¹). No photodegradation was observed for the heaviest hydrocarbons (benzo(a)anthracene, chrysene, benzo(a)pyrene, dibenzo(g,h,i)perylene and coronene). In general terms, the half-life of PAHs was highly dependent on their molecular weight. Significant faster photodegradation rates were detected specially for light PAHs. It indicates that a synergistic effect occurred when both temperature and UV-B dose increased. This synergism might have a great implication on the long-range transport of environmental organic pollutants taking into account that low-latitude areas are the hottest and most irradiated of the planet.     

Interactive Effects of UV-B Radiation and Chemical Contamination on Physiological Parameters in the Lichen Ramalina lacera

To assess the impact of ultraviolet B (UV-B) radiation under laboratory conditions on lichens from different biomonitoring sites, thalli of the lichen Ramalina lacera were transplanted from a clean air site to nine different polluted sites in Israel. Our objective was to determine the probability of synergistic/antagonistic effects on physiological parameters by considering two stressors: chemical contamination and UV-B. Exposure to both airborne pollutants in the field and subsequent UV-B radiation in the laboratory which led to a severe disintegration of cell membranes, followed by electrolyte leakage, indicate the probability of a synergistic effect. The impairment of the potential quantum yield of electron transfer through photosystem II (PSII) of photosynthesis indicated by a significant decrease of the ratio F_v/F_m, further demonstrated the synergistic effect of both chemical contamination and UV-B radiation. Besides enlarged amounts of stress-ethylene in lichens at contaminated sites, the reduced levels of ethylene production upon UV-B radiation in the present study suggest the likelihood of an antagonistic effect of xenobiotic elements and UV-B radiation as a result of an impaired ethylene-producing system.     

3种海洋赤潮微藻抗氧化酶活性对UV-B辐射增强的响应

利用生物化学的方法,研究了赤潮异弯藻、亚历山大藻和中肋骨条藻抗氧化酶活性对UV-B辐射增强的响应变化。结果表明:(1)不同赤潮微藻的抗氧化酶活性对UV-B辐射增强的响应变化是不同的。(2)不同的抗氧化酶活性对UV-B辐射增强的响应变化同样存在明显的差异。(3)与过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)相比,超氧化物歧化酶(SOD)活性对UV-B辐射增强的响应最敏感,谷胱甘肽过氧化物酶(GPX)活性的响应变化最不明显。3种赤潮微藻SOD活性的变化是指示UV-B辐射增强的优选生物学指标。     

Response of marine microalgae,heterotrophic bacteria and their relationship to enhanced UV-B radiation

Ozone depletion in the stratosphere has enhanced solar UV-B radiation reaching the Earth surface and has brought about significant effects to marine ecosystems. The effects of enhanced UV-B radiation on marine microalgae, heterotrophic bacteria and the interaction between them are discussed. The effects on marine microalgae have been proved to occur at molecular, cellular and population levels. Enhanced UV-B radiation increases microalgal flavonoid content but decreases their chlorophyll content and pho-tosynthesis rate; this rachation induces genetic change and results in DNA damage and change of protein content. There have been fewer studies on the effects of UV-B radiation on marine heterotrophic bacteria. Establishment of a nucroalgal ecological dynamic model at population and community levels under UV-B radiation has gradually become a hotspot. The effects of enhanced UV-B radiation on microalgae communities, heterotrophic bacterial populations and interaction between them will become a focus in the near future. This paper will make an overview on the studies concerning the effects of enhanced UV-B radiation on marine microal-gae and heterotrophic bacteria and the interaction between them.     

3种赤潮微藻对UV-B辐射处理的敏感性

通过实验生态学的方法,研究了赤潮异弯藻(Heterosigma akashiwo)、亚历山大藻(Alexandrium tamarense)和中肋骨条藻(Skeletonema costatum)的生长对UV—B辐射增强的响应。结果表明,UV—B辐射处理对赤潮异弯藻的生长始终表现出抑制效应,而低剂量的UV—B辐射处理对亚历山大藻和中肋骨条藻的生长有刺激作用,高剂量的UV—B辐射处理对亚历山大藻和中肋骨条藻的生长仍然显示出抑制作用。UV—B辐射对赤潮异弯藻、亚历山大藻和中肋骨条藻的96h半抑制剂量分别为1．63、2.34和2．58J／m^2。     

A Possible Photochemical Link Between Stratospheric and Near-Surface Ozone on Swiss Mountain Sites in Late Winter

Record high near-surface ozone concentrations at two elevated sites (Chaumont, 1140 m asl, and Rigi, 1030 m asl) in Switzerland were observed simultaneously with extremely low total ozone during a fair weather period in mid-February 1993. An analysis of ozone, temperature, humidity, and wind profiles suggests that the surface ozone peaks were most possibly generated within the region in a layer between about 1000 and 1500 m asl. Mean diurnal cycles of ozone concentration during the period shows a strong increase from late morning to late afternoon at Chaumont and at the same time a decrease at the high alpine site Jungfraujoch (3580 m asl). The different diurnal ozone cycles can both be explained photochemically by taking into account the large difference in NOx concentrations (about two orders of magnitude) between the sites. Photochemical processes are also indicated by the diurnal cycles of NO2 and NO concentration. As a strong photochemical activity is not expected in mid-February at 47°N, we hypothesize that the extremely low total ozone played a role. Total ozone controls the amount of UV-B radiation reaching the troposphere and thus influences photochemical processes. Using a radiation model, we calculated an increase in ozone photolysis at Chaumont and Jungfraujoch of 73% and 83%, respectively, on the day with the lowest total ozone (243 DU) compared to average February conditions (335 DU). It is suggested that total ozone changes have the potential to stimulate photochemistry sufficiently to produce the observed surface ozone peaks at Chaumont and Rigi of 61 and 64 ppbv, respectively. A fog layer just below Chaumont during these days probably also influenced photochemistry, but on a smaller spatial scale. Our empirical results on the influence of changing UV radiation on tropospheric photochemistry are in close agreement with model studies of other groups. Although this case study represents unique conditions, a distinct anticorrelation between near-surface ozone at Chaumont and total ozone also appears in other years (1992–1997) when selecting fair weather days in mid-February. However, other influences cannot be excluded. The selected days provide evidence of a significant photochemical source of ozone in the mid-latitude lower troposphere in late winter.     

阿克达拉紫外线B波段辐射强度特征浅析

通过对阿克达拉站2005年7月至2010年11月紫外线B波段实测资料的分析得出：阿克达拉UV-B 的日曝辐量年平均在26 159J/㎡左右。夏季值最高,为42 090J/㎡,次高是春季,为33147J/㎡,第三是秋季,为17476 J/㎡,最低是冬季,为11921J/㎡,呈现出较明显的季节性特征。无论是晴好天气还是其它正常天气条件下, 这几年的UV-B强度总体上呈现出上升趋势。紫外线辐射强度日特征:中午强,早晚弱,关于一天中最大值出现的时间呈对称分布,日变化特征曲线的斜率,夏季最大,其次是春季和秋季,冬季最小,一天中紫外辐射的止时间随着季节的变化而变化。     

南极冰藻Chlorophyceae L-4抗氧化酶活性对UV-B辐射增强的响应

为了了解在UV B辐射增强的胁迫下,南极冰藻ChlorophyceaeL 4细胞内保护酶系统对活性氧自由基的清除作用,对不同辐射强度下ChlorophyceaeL 4细胞中丙二醛含量的变化、自由基的产生速率和相应的保护酶系统的变化进行了测定。结果表明,在UV B辐射增强的初期(1～3d),ChlorophyceaeL 4中丙二醛含量的迅速提高,但随后很快降低,在低强度UV B(35μW·cm-2)辐照下保护酶活性能够恢复到基本水平。在UV B辐射增强的胁迫下,ChlorophyceaeL 4中的超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性明显比对照组的高,而且在高强度(70μW·cm-2)的辐照下,酶活性更高。ChlorophyceaeL 4中的抗坏血酸过氧化物酶的活性在UV B辐射增强的胁迫下略有升高或变化不大。本研究结果表明,保护酶系统在南极冰藻适应南极强辐射环境中起着非常重要的作用。