Chemical defense and evolutionary trends in biosynthetic capacity among dorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia)

Summary. An evolutionary scenario incorporating recent advances in phylogenetic research begins with an opisthobranch-pulmonate common ancestor that was herbivorous and had some diet-derived chemical defense. The Nudibranchia and their closest relatives, the Notaspidea, form a lineage the ancestors of which had switched to feeding upon sponges and deriving protection from metabolites contained in them. Subsequently there have been repeated shifts in food and defensive metabolites, and trends are evident in the ability to detoxify, sequester and utilize metabolites from food, as well as to synthesize defensive compounds de novo. The Notaspidea display a minor adaptive radiation that foreshadows a more extensive one in the various lineages of nudibranchs. This review emphasizes changes that have occurred within the Holohepatica, or dorid nudibranchs (order Doridacea). Their sister-group, the Cladohepatica, consists of three other orders, Dendronotacea, Arminacea, and Aeolidiacea, in which there has been a shift from sponges to Cnidaria as food. The Dendronotacea often feed upon Octocorallia, which combine spicules, chemical defense, and stinging capsules and thereby suggest a transition from feeding on sponges. A previous diet of Octocorallia is suggested by the defensive use of prostaglandins in the dendronotacean Tethys fimbria, which eats crustaceans. A shift to bryozoans in some Arminacea is accompanied by use of different metabolites. Dorid nudibranchs evidently began as sponge-feeders, but some lineages have shifted to a variety of other food organisms, and others have specialized in the kind of sponges they feed on and how they do it. There have been shifts to bryozoans (Ectoprocta) and ascidians (Chordata: Urochordata) that track metabolites rather than the taxonomy of the food. There is a crude correlation between the genealogy and the defensive metabolites of the sponge-feeding dorids. De novo synthesis is well documented in this order and the metabolites are appropriately positioned so as to have an adaptive effect. The hypothesis that the capacity for de novo synthesis was acquired by gene transfer across lineages is rejected, partly on the basis of different chirality of metabolites in the nudibranchs and their food organisms. Instead it is proposed that there has been a preadaptive phase followed by evolution in a retrosynthetic mode, with selection favoring enzymes that enhance the yield of end products that are already present in the food. Received 5 February 1999; accepted 26 July 1999     

Whitefly wax as a cue for phoresy in the broad mite, <Emphasis Type="Italic">Polyphagotarsonemus latus</Emphasis>(Acari: Tarsonemidae)

Summary. Broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae) exhibits a specific phoretic relationship with whiteflies. Under field conditions most broad mites, caught in sticky traps, are attached to whiteflies. Under laboratory conditions, attachment occurs equally well in the dark and light. Mites do not differentiate between the sexes of their phoretic host Bemisia tabaci. However, mite attachment to B. tabaci is greatly diminished by washing the host with various organic solvents, chloroform in particular. The effect of whitefly waxy particles on broad mite behavior was studied using wax from the whitefly Aleyrodes singularis and from the mealybug Planococcus citri. Broad mites were not only attracted specifically to the A. singularis waxy particles-treated leaf areas but were also attached to leaf trichomes in this area. The results of this study suggests the importance of olfactory cues from the whitefly waxy particles in the recognition process of the phoretic host and/or the induction of the attachment behavior to whitefly legs or leaf trichomes.     

焦化污染场地土壤多环芳烃的生物强化协同降解工艺研究

以某废弃焦化厂的多环芳烃（PAHs）污染土壤为研究对象,通过耦合表活淋洗、生物降解、化学氧化等技术设计了4种修复工艺,并进行了试验验证。结果表明：针对该实际焦化污染土壤,单一的生物泥浆降解工艺21 d后PAHs可实现58.64%的降解率;采用表活增溶＋化学氧化＋生物泥浆的降解工艺,26 d降解率可达到65.68%,但前置的化学氧化会抑制生物降解效果;采用干筛分+表活分批淋洗+化学氧化的降解工艺降解率可达到85.36%,有效缩短降解时间到13 d内,但土壤中残留的PAHs与土壤颗粒结合紧密,化学氧化降解率仍难以满足大于90%的要求;采用湿筛分+表活分批淋洗+生物泥浆+化学氧化的生物强化协同降解工艺,29 d降解率可达到95.32%,实现了土壤的修复目标。生物强化协同降解工艺路线,综合了多种修复技术的优点,实现了修复技术组合优化,为焦化污染土壤中多环芳烃降解修复提供了可行的工艺路径。

     

贵金属催化剂活性组分分布对催化湿式氧化处理非达霉素提炼废水的影响

采用均匀型和蛋白型Ru/TiO₂催化剂为湿式氧化催化剂,应用于催化湿式氧化非达霉素提炼废水,以出水COD和TOC去除率作为指标来评价2种催化剂的催化活性差异;采用实验室连续评价装置对柱状颗粒催化剂在不同pH、不同废水流量和不同温度下处理非达霉素提炼废水进行了优化评价。结果表明：在265 ℃、pH=4.1、废水流量为10 mL·h⁻¹时,催化剂的催化活性最高,故确定此条件为该废水处理的最优条件;同时对比均匀型和蛋白型2种催化剂,蛋白型催化剂具有更高的催化效率;结合SEM及N₂-物理吸附结果,推断蛋白型催化剂活性组分集中分布在催化剂颗粒的较浅层,有利于降低反应过程中的扩散阻力,提高贵金属活性组分的利用率,进而提高催化剂的催化活性。以上结果对开发高效湿式氧化催化剂,充分利用贵金属活性组分降低催化剂成本具有十分重要的意义。     

液态聚合氯化铝铁深度除磷的优化研究

以北京市生活废水为研究对象,考察了液态聚合氯化铝铁及与聚丙烯酰胺(PAM)协同作用下除磷效果及其影响因素。结果表明,液态聚合氯化铝铁与PAM复合作用时对除磷效果有一定的提高,明确了PAM的最佳投加量、最佳搅拌强度、最佳搅拌时间和pH,并得出了影响混凝效果因素的主次顺序为:pH值搅拌时间搅拌强度投加量。     

不同改性多壁碳纳米管对Cr3+的吸附性能

通过催化裂解法制备多壁碳纳米管,利用不同化学试剂对多壁碳纳米管改性,研究了不同化学改性对多壁碳纳米管表面物理化学特性的影响和Cr3＋的吸附特性。结果表明,所制备的多壁碳纳米管孔隙均匀,外径为30～50 nm,长度为0.5～2μm,经过不同化学改性表面有效地引入了含氧基团。未改性、H2SO4、HNO3、H2SO4-HNO3改性碳纳米管对Cr3＋的吸附动力学均符合Langergren模型;吸附等温线均符合Freundlich模型。温度和pH升高均有利于改性多壁碳纳米管对Cr3＋的吸附。     

厌氧-接触氧化工艺二级出水混凝除磷

为解决厌氧-接触氧化工艺处理生活污水除磷效果欠佳的问题,采用聚磷硫酸铁（PPFS）对该工艺二级出水进行混凝除磷实验研究。考察了PPFS投加量、初始pH值、温度、浊度以及与助凝剂（聚丙烯酰胺）复配对除磷效果的影响。研究表明,PPFS可有效降低出水TP浓度,当投加量为40 mg·L-1时,TP浓度能从3.71 mg·L-1降至0.34 mg·L-1左右,满足《城镇污水处理厂污染物排放标准》（GB 18918-2002）一级A排放标准限值（TP≤0.5 mg·L-1）。利用PPFS对生物除磷工艺二级出水进行化学除磷是一种有效、可行的选择。     

城市污泥的重金属生物活性及其控制

随着土壤法规的加强 ,城市污泥中的重金属严重影响着污泥的处理、处置。介绍了污泥中重金属的分配和化学形态 ,以及迄今为止几种主要的控制方法     

建立能够体现化工行业特点的行业排放标准初探

化工行业具有传统的工业类型和新兴产业交叉渗透的特点。现有的污染物排放标准因涵盖行业过多、细化内容不够、可操作性不强、行业特点不突出,故不太适应化工行业的发展,建立新的化工行业污染物排放标准势在必行。文章概要介绍了我国现有污染物排放标准,分析了美国、欧盟、日本、德国等一些国家和组织的排放标准,提议建立能够体现化工行业特点的行业排放标准,以达到淘汰落后工艺和促进清洁工艺的目的。     

利用轨迹模式模拟近地层臭氧日变化

提出在多条轨迹上应用轨迹模式,以实现对固定地区臭氧浓度日变化的模拟。应用该方法对北京燕山石化炼油厂地区的O3浓度日变化进行了模拟,结果表明模拟值和实测值十分吻和。进一步模拟了当地的臭氧生成特征,并讨论了当地的气象条件和源排放对O3生成浓度的影响,结果说明削减NOx的排放量是控制该地区光化学烟雾形成的关键,而降低烯烃和芳香烃在排放物中所占的比例也是控制该地区光化学烟雾的重要手段。