Synthesis of C-labelled PCB methyl sulphones

Five methylsulphonyltetrachloro-(¹⁴C)biphenyls and three methylsulphonylpentachloro-(¹⁴C)biphenyls were synthesized, 3,4-Dichloro-(¹⁴C)aniline was reacted with 2,3- and 2,6-dichlorothioanisole and 2,4,5-trichloro-(¹⁴C)aniline with 2,5-dichlorothioanisole. The PCB methyl sulphides were oxidized with hydrogen peroxide to the corresponding sulphones.     

Probabilistic approaches in the effect assessment of toxic chemicals. What are the benefits and limitations?

There is an ongoing discussion whether in the environmental risk assessment for chemicals the so called 'deterministic' approach using point estimates of exposure and effect concentrations is still appropriate. Instead, the more detailed and scientifically sounder probabilistic methods that have been developed over the last years are widely recommended. Here, we present the results of a probabilistic effect assessment for the aquatic environment performed for the pesticide methyl parathion and compare them with the results obtained with the common deterministic approach as described in the EU Technical Guidance Document. Methyl parathion was chosen because a sufficient data set (acute toxicity data for about 70 species) was available. The assumptions underlying the probabilistic effect assessment are discussed in the light of the results obtained for methyl parathion. Two important assumptions made by many studies are: (i) a sufficient number of ecologically relevant toxicity data is available, (ii) the toxicity data follow a certain distribution such as log-normal. Considering the scarcity of data for many industrial chemicals, we conclude that these assumptions would not be fulfilled in many cases if the probabilistic assessment was applied to the majority of industrial chemicals. Therefore, despite the well-known limitations of the deterministic approach, it should not be replaced by probabilistic methods unless the assumptions of these methods are carefully checked in each individual case, which would significantly increase the effort for the assessment procedure.     

催化动力学光度法测定水中痕量亚硝酸根

基于亚硝酸根对溴酸钾氧化甲基紫的反应具有催化作用，建立了测定亚硝酸根的催化动力学光度法，研究了最佳测试条件，用于测定水样和标准样品中的亚硝酸根，获得满意结果，方法检出限为０．１６μｇ．５０ｍｌ＾－１，线性范围为０．２５－１２．０μｇ．６０ｍＬ＾－１，回收率在９０％－１０８％之间。     

Form-specific fragances fromOphrys insectifera L. (Orchidaceae) attract species of different pollinator genera. Evidence of sympatric speciation?

Two closely related forms ofOphrys insectifera were observed in the field to attract different pollinator species selectively.O. i. ssp.insectifera attracted males of two species ofArgogorytes (Sphecidae, Hymenoptera Aculeata) andO. i. ssp.aymoninii attractedAndrena combinata males (Andrenidae, Apoidea, Hymenoptera Aculeata). A third form,O. aff.i. ssp.insectifera, attracted none of these three species. Volatile compounds from flowers and inflorescences of the three forms (originating from Öland, Sweden, and Aveyron, France) were collected, using entrainment, enfleurage, and solvent extraction techniques, and identified by gas chromatography — mass spectrometry. Scent differences between the three forms were confirmed in the amounts of aliphatic hydrocarbons (C₁₁–C₁₉), methyl esters (C₁₄–C₁₈), short chain aliphatic 1-alcohols (C₆–C₁₂), and monoterpene alcohols (C₁₀).     

茉莉酸甲酯(MeJA)对水稻幼苗的抗旱生理效应

茉莉酸类物质(Jas)是植物体内广泛存在的生长调节物质,它作为内源信号分子参与植物在机械伤害、病虫害、干旱、盐胁迫、低温等条件下的抗逆反应。选用抗旱性存在明显差异的两个水稻(Oryza sativa L.)品种中二欧六和丰华占作为实验材料,通过设置对照、干旱、干旱 茉莉酸甲酯(MeJA)三种处理研究了茉莉酸甲酯对水稻幼苗的抗旱生理效应。研究结果表明,干旱胁迫后两个水稻品种幼苗叶片水势均显著降低,而干旱后喷施茉莉酸甲酯能明显增加叶片的水势,改善叶片的水分状况,抗旱性强的品种水势增加幅度较大。干旱胁迫后水稻叶片的抗氧化酶活性,包括超氧化物歧化酶(SOD)、过氧化物酶(POD)及过氧化氢酶(CAT)和有机渗透调节物质,包括可溶性糖、脯氨酸及游离氨基酸含量均大幅度上升,而干旱 茉莉酸甲酯处理则能降低了这些物质的含量,两个水稻品种的变化趋势表现一致。研究结果表明外施茉莉酸甲酯在一定程度上能减缓干旱胁迫对水稻幼苗造成的伤害,有效地提高抗旱性,但这这种增强效应在不同水稻品种间存在一定差异。     

酸改性纳米TiO_2降解模拟污染物的研究

用溶胶-凝胶法制备了酸改性纳米二氧化钛,并用XRD、UV-vis等测定技术对所制得的粉体试样进行了表征,同时以甲基橙为模拟污染物,评价了改性后纳米二氧化钛的光催化性能,发现其光催化活性大大高于未改性二氧化钛粉体。并从酸改性的样品中筛选出了光催化活性最好的粉体,以光催化降解苯酚为模型反应,确立了降解的最优条件。     

Combined effects of two sulfonylurea herbicides on soil microbial biomass and N-mineralization

ＩｎｔｒｏｄｕｃｔｉｏｎＡｇｒｏｃｈｅｍｉｃａｌｓｈａｖｅｂｅｅｎａｃｔｅｄａｖｅｒｙｉｍｐｏｒｔａｎｔｒｏｌｅｉｎａｇｒｉｃｕｌｔｕｒａｌｐｒｏｄｕｃｔｉｏｎ .Ｆｏｒａｖｏｉｄｉｎｇｄａｍａｇｅｏｆｃｒｏｐｓ,ｍａｎｙｋｉｎｄｓｏｆｐｅｓｔｉｃｉｄｅｓａｒｅａｐｐｌｉｅｄｆｏｒｔｈｅｒｅａｓｏｎｏｆｉｎｓｅｃｔ,ｄｉｓｅａｓｅｓａｎｄｗｅｅｄｃｏｎｔｒｏｌｉｎＣｈｉｎａ .Ｓｃｉｅｎｔｉｓｔｓｈａｖｅｄｏｎｅａｌｏｔｏｆｗｏｒｋｏｎｔｈｅｆａｔｅａｎｄｍｅｔａｂｏｌｉｓｍｏｆｐｅｓｔｉｃｉｄｅｓ,…     

Direct hydride derivatization of methyl- and ethylmercury chlorides in aqueous solution with KBH4

ＩｎｔｒｏｄｕｃｔｉｏｎＲａｐｉｄａｎｄｓｅｎｓｉｔｉｖｅａｎａｌｙｔｉｃａｌｍｅｔｈｏｄｓｆｏｒｔｈｅｄｅｔｅｒｍｉｎａｔｉｏｎｏｆｍｅｒｃｕｒｙａｎｄｒｅｌａｔｅｄｃｏｍｐｏｕｎｄｓｉｎｅｎｖｉｒｏｎｍｅｎｔａｌｓａｍｐｌｅｓａｒｅｉｍｐｅｒａｔｉｖｅｌｙｄｅｍａｎｄｅｄｓｉｎｃｅｖａｒｉｏｕｓｃｈｅｍｉｃａｌｆｏｒｍｓｏｆｍｅｒｃｕｒｙｉｎｔｈｅｎａｔｕｒａｌｅｎｖｉｒｏｎｍｅｎｔｃａｎｂｅｈａｖｅｄｉｆｆｅｒｅｎｔｌｙ ,ｔｈｅｒｅｂｙａｆｆｅｃｔｉｎｇｉｔｓｂｉｏｇｅｏｃｈｅｍｉｃａｌｂ…     

Fe-Ce/ZSM-5复合催化剂的制备及其催化性能

采用浸渍法制备了Fe-Ce/ZSM-5复合催化剂,并将其用于甲基橙的催化降解。利用单因素实验考察了溶液pH、初始甲基橙质量浓度、催化剂加入量、初始H_2O_2浓度及反应温度对准一级动力学方程反应动力学常数的影响,对催化剂的稳定性进行了测试,并探讨了甲基橙的催化降解机理。实验结果表明:在溶液pH 5.0、初始甲基橙质量浓度100 mg/L、催化剂加入量1.0 g/L、初始H_2O_2浓度20 mmol/L、反应温度20℃的优化条件下反应60min,反应动力学常数高达0.034 min~(-1),甲基橙降解率高达87%,铁离子流失量仅为0.019 mg/L;催化剂重复使用3次后,甲基橙降解率仍高于80%,保持了较高活性。     

植物法改性类Fenton反应催化剂降解甲基橙

采用银杏叶和桑叶提取液制备了改性类Fenton反应催化剂并进行了表征分析,研究了溶液初始p H、反应温度、催化剂加入量、甲基橙初始质量浓度等因素对甲基橙降解率的影响,同时考察了催化剂的重复使用效果。表征结果表明:制备出的催化剂为Fe_2O_3和Fe OOH的混合物;桑叶改性催化剂的粒径分布较银杏叶改性催化剂均匀,粒径较小,比表面积较大。实验结果表明:在初始p H为6.23、反应温度60℃、催化剂用量1 g/L、甲基橙初始质量浓度100 mg/L的条件下,银杏叶改性催化剂的甲基橙降解率为99.40%,桑叶改性催化剂的甲基橙降解率为99.96%;碱性条件下,甲基橙降解率仍接近100%,扩宽了反应的p H适用范围,为碱性条件下处理偶氮染料提供了新思路;催化剂重复使用6次之后,甲基橙降解率仍可达到99%。根据反应前后溶液的紫外-可见吸收光谱,初步探讨了降解机理。