SMX degradation by ozonation and UV radiation: a kinetic study

The rate constants of sulfamethoxazole (SMX) degradation by ozonation and UV₂₅₄ radiation were investigated under various parameters including influent ozone gas concentration, initial SMX concentration, UV light intensity, ionic strength, water quality in terms of varying anions (bicarbonate, sulfate and nitrate), humic acid (HA) and pH. The results indicated that the removal of SMX by ozonation and UV₂₅₄ radiation fitted well to a pseudo first-order kinetic model and the rate constants were in the range of (0.9-9.8) × 10⁻³ and (1.7-18.9) × 10⁻³ s⁻¹, respectively. The second-order rate constants of SMX with ozone (k_O3), under varying operational parameters, were also determined and varied in the range of (0.60-3.38) ± 0.13 × 10⁵ M⁻¹ s⁻¹. In addition, SMX degradation through UV pretreatment followed by ozonation in the presence of HA was proved to be an effective method which can remove SMX with a low ozone dose. The results suggested that ozonation of SMX was more affected by concentration of influent ozone gas, alkalinity, and HA, while incident UV light intensity, pH, and HA were the dominant factors influencing UV degradation of SMX.     

Copper tolerance in the macrolichens Cladonia furcata and Cladina arbuscula subsp. mitis is constitutive rather than inducible

In this study we assessed the degree of copper (Cu) tolerance in two common lichen species (Cladonia furcata and Cladina arbuscula subsp. mitis) that grow on both uncontaminated substrata and the surface of waste heaps from abandoned old Cu-mines. Regardless of their locality, populations of these lichens contain identical strains of photobionts (Asterochloris clade A in C. arbuscula subsp. mitis and clade D in C. furcata). Therefore, it was expected that if there were differences in Cu toxicity or tolerance between populations, that the photobiont could not be a key element of Cu tolerance in these two lichen species. In laboratory experiments samples of both lichen species (from contaminated and control sites) were incubated in Cu solutions (500 μM) for 24 h. We attempted to determine whether Cu tolerance in these lichens was constitutive, or inducible form. Based on measurements of Cu accumulation, chlorophyll a integrity, chlorophyll a fluorescence, photosynthesis, respiration, measurements of the content of thiobarbituric acid reactive substances (TBARS), the content of soluble proteins, reactive oxygen species (ROS) and the amount of extracellular secondary metabolites of both lichens we found that there were no significant differences in the response of all selected populations of both lichen species to short-term exposure to these high levels of Cu. As a result, we conclude that Cu tolerance in these two lichen species is the constitutive rather than the inducible.     

Toxicity of cobalt-complexed cyanide to <Emphasis Type="Italic">Oncorhynchus mykiss,Daphnia magna</Emphasis>, and <Emphasis Type="Italic">Ceriodaphnia dubia</Emphasis>

Background Cobalt cyanide complexes often result when ore is treated with cyanide solutions to extract gold and other metals. These have recently been discovered in low but significant concentrations in effluents from gold leach operations. This study was conducted to determine the potential toxicity of cobalt-cyanide complexes to freshwater organisms and the extent to which ultraviolet radiation (UV) potentiates this toxicity. Tests were also conducted to determine if humic acids or if adaptation to UV influenced sensitivity to the cyanide complexes. Methods Rainbow trout (Oncorhynchus mykiss), Daphnia magna, and Ceriodaphnia dubia were exposed to potassium hexacyanocobaltate in the presence and absence of UV radiation, in the presence and absence of humic acids. Cyano-cobalt exposures were also conducted with C. dubia from cultures adapted to elevated UV. Results With an LC50 concentration of 0.38 mg/L, cyanocobalt was over a 1000 times more toxic to rainbow trout in the presence of UV at a low, environmentally relevant irradiance level (4 μW/cm² as UVB) than exposure to this compound in the absence of UV with an LC50 of 112.9 mg/L. Toxicity was immediately apparent, with mortality occurring within an hour of the onset of exposure at the highest concentration. Fish were unaffected by exposure to UV alone. Weak-acid dissociable cyanide concentrations were observed in irradiated aqueous solutions of cyanocobaltate within hours of UV exposure and persisted in the presence of UV for at least 96 hours, whereas negligible concentrations were observed in the absence of UV. The presence of humic acids significantly diminished cyanocobalt toxicity to D. magna and reduced mortality from UV exposure. Humic acids did not significantly influence survival among C. dubia. C. dubia from UV-adapted populations were less sensitive to metallocyanide compounds than organisms from unadapted populations. Conclusions The results indicate that metallocyanide complexes may pose a hazard to aquatic life through photochemically induced processes. Factors that decrease UV exposure such as dissolved organic carbon or increased pigmentation would diminish toxicity.     

Chemical defense and evolution in the Sacoglossa (Mollusca: Gastropoda: Opisthobranchia)

Summary. Recent advances in both the systematics and the natural products chemistry of the order Sacoglossa (=Ascoglossa) in the gastropod subclass Opisthobranchia suggest a revised and improved historical account of the evolution of the group. Although the algal genus Caulerpa makes a suitable model for the ancestral food of the order, other siphonaceous algae are consistent with both morphological and chemical data. At an early evolutionary stage terpenoids are sequestered from the food, and used defensively, often with modification. With an evolutionary switch to different kinds of algal food, there is often a shift to other, related defensive chemicals. A switch to new food source sometimes leads to the abandonment of chemical defense, but in other cases there is de-novo synthesis of defensive metabolites. The synthesis of polypropionates, which are used defensively, occurs in some other gastropods, but otherwise is known only in fungi. The systematic distribution of the defensive polypropionates suggests that their defensive use has evolved several times among gastropods. Failure to detect them may mean that synthetic capacity has evolved more than once, or it may mean that they exist at low levels, perhaps having a non-defensive function. Received 9 February 1998; accepted 20 March 1998.     

UV-B辐射对亚历山大藻生长及其生理生化特征的影响

通过生物化学的方法,研究了UV-B辐射对亚历山大藻(Alexandrium tamarense)生长及其可溶性蛋白、叶绿素a、H2O2、丙二醛(MDA)含量和超氧化物歧化酶(SOD)活力的影响.结果表明:UV-B辐射会抑制亚历山大藻的生长并对其生理生化特征产生明显的影响;经过UV-B辐射后,可溶性蛋白和叶绿素a含量呈现降低的趋势;H2O2、丙二醛含量和超氧化物歧化酶活力呈现升高的趋势;UV-B辐射产生过量的活性氧自由基是导致亚历山大藻受损伤的主要原因.     

增强的UV-B辐射对陆地生态系统的影响

本文根据最近的文献,回顾了ＵＶ－ Ｂ 辐射对陆地生态系统的影响。ＵＶ－ Ｂ 辐射影响植物物候、形态和次生代谢,从而改变生态系统的物种结构、竞争性平衡、食物链、植物病原体、物质循环、真菌移殖与叶片分解。植物物候、形态和次生代谢的变化是ＵＶ－ Ｂ 辐射调控影响生态系统的重要途径,具有重要的生态学意义。虽然我们已经适当了解了ＵＶ－ Ｂ 辐射对植物作用的机理,但由于温室内植物个体水平的短期响应与野外条件下生态系统的长期响应具有明显的差异,到目前为止还不能预测ＵＶ－ Ｂ辐射影响生态系统的精确后果,有时甚至连变化方向也不能预测。因此,必须强调生态系统对ＵＶ－ Ｂ 辐射长期响应的野外研究的重要性。     

ZCMR法从废物中制取活性炭及在含铬废水处理中应用

采用微波照射－ 氯化锌（ZCMR） 法从废物中制取锯末活性炭及烤胶废料活性炭,用所得的两种活性炭处理含铬废水,结果表明,ZCMR法制取的废物活性炭对电镀废水中铬的吸附容量是市售一级粉末活性炭的1.72 ～1.8 倍, 过滤速度是市售活性炭的1.6 ～1.7 倍, 极限吸附量达21.5 ～22.5mg/g．     

参与光化学反应的物质对UV能量吸收的估算

在对北京紫外辐射(UV)观测资料分析的基础上,提出参与光化学反应的物质对UV能量具有吸收作用.计算了1990年12个月实际天气比晴天UV能量的减少值在64～109 W/m2之间,这一减少受臭氧、"水汽"、气溶胶等因子的衰减分别为39.1～66.3,21.5～36.5,3.2～5.5 W/m2(12月除外),12个月的平均值分别为48.3,26.6,4.0 W/m2.计算结果表明,云天大气对UV能量有衰减,其衰减能量中有26.6 W/m2是"水汽的作用",即参与大气光化学反应的物质对UV能量吸收所造成的,此计算值同国外观测与模式的研究结果比较接近.由于现有模式中还没有考虑这一部分能量,所以造成模式结果与观测结果间较大的差异.      

垂直壁面火蔓延速率的实验测量

垂直壁面火蔓延过程受材料本身的热物理性质以及外加辐射等复杂因素条件的影响很大,论文研究建立了可测量不同材料存在外加辐射条件下的垂直方向火蔓延实验台,来研究典型可燃物的垂直方向火蔓延特性,观察不同材料之间火蔓延行为的不同,同时测定可燃物的火焰到达高度随时间的变化情况,得到相应的火焰蔓延速率。同时考虑外辐射情况下对不同材料垂直方向火蔓延过程的影响,实验数据可为进一步的模拟研究工作提供很好的参考。