三氯异氰尿酸在模拟水生态系统中归趋的研究

利用高效液相色谱法对三氯异氰尿酸(TCCA)在微宇宙模拟水生态系统中的归趋,包括TCCA在水体、沉积物、生物体(皇冠草、河蚬、异育银鲫)等不同分配相及生物体不同组织中的分布、富集以及迁移等动态变化过程进行了研究.结果表明:TCCA进入模拟水生态系统后,除发生水解外,其余或被水生生物所吸收,或者沉降进入底泥中.水生生物对TCCA有不同程度的富集和残留.水草对TCCA的吸收较大,尤其是叶片部分;河蚬、鱼体对TCCA具有明显的吸收积累,并且在体内的残留时间较长,不同组织对TCCA的吸收积累存在明显的差别,在内脏中的积累量比肌肉组织高.不同生物对TCCA的分布和富集存在着较大的差异,其趋势为皇冠草>河蚬>异育银鲫.     

不同给药方式下环丙沙星在模拟水生态系统中的归趋

采用不同的给药方式对环丙沙星(CPFX)在模拟水生态系统中的归趋进行研究,包括环丙沙星在水体、沉积物、生物体(皇冠草、河蚬、异育银鲫)等不同分配相及生物体不同组织、器官中的含量、分布以及迁移、富集等动态变化过程。结果表明:CPFX进入模拟水生态系统后,水体中药物浓度下降迅速,3种给药方式下,最高浓度不超过15.30μg.L-1。底泥表现出明显的吸附积累,而且长时间地保持高浓度残留;在饲料给药方式下,底泥药物浓度最高可达2379.67μg.L-1。水生生物对CPFX有不同程度的富集和残留,水草对CPFX的吸收较多,尤其是叶片部分,药物浓度最高可达899.83μg.L-1;河蚬、鱼体对CPFX有一定的吸收积累,停药15d后,河蚬、鱼体内仍有明显的残留,不同组织对CPFX的吸收积累存在显著差别,在内脏中的积累量比肌肉组织高。3种给药方式导致的鱼体内药物残留量大小依次是:饲料给药>混合给药>水体给药。     

水体腐殖酸影响下河蚬对低浓度镉的蓄积和释放

研究了水体中低浓度镉(1μg?L-1)单独存在以及低浓度镉(1μg?L-1)和腐殖酸(1mg?L-1、10mg?L-1)共存情况下河蚬对低浓度镉的蓄积和释放,以了解实验室条件下水体腐殖酸对河蚬蓄积和释放的影响。在实验室中曝露15d内分别于1d、2d、3d、10d、15d取样,对比实验结果发现两种处理方式均存在镉在河蚬体内存在蓄积的现象,该蓄积效应与其蓄积时间呈显著线性正相关,但在腐殖酸影响下,河蚬对低浓度镉的蓄积减少。释放10d和20d的实验结果发现低浓度镉进入河蚬体内后难以释放。腐殖酸对镉从河蚬体内的释放效应影响极小。     

长江口潮滩大型底栖动物对重金属的累积特征

选择长江口滨岸潮滩最具代表性的4个岸段,在广泛的样方调查基础上,对比分析不同样点生物量较大的几种大型底栖动物体内的重金属含量,计算单位面积的潮滩中大型底栖动物对重金属的吸收量,并对河蚬和缢蛏的生物质量进行评价.结果表明,河蚬是长江口滨岸潮滩分布最广的大型底栖动物,其软体组织对Cu、Mn和Zn有明显的富集作用,秋季时BSAFs值分别达2.01、1.41和2.85;河蚬对Cu具有明显的选择性吸收作用,不同岸段河蚬体内Cu含量差异不大.软体动物麂眼螺和泥螺幼体以及所有甲壳动物对Cu有明显的富集作用,BSAFs值达2.97～7.97.单位面积的泥螺幼体对Cu、Pb、Fe和Cr的吸收量明显高于其它底栖动物,对Mn、Zn的吸收量仅少于浒浦的河蚬.与我国海洋生物的质量标准相比,长江口滨岸潮滩底栖贝类的生物质量总体较好.     

非生物因子对河蚬重金属富集量的影响

对影响长江口滨岸带河蚬体内重金属富集量的4个主要非生物因子依次进行分析。结果表明,较高温度有助于河蚬对Cu、Zn、Cr、Ni的吸收;盐度对河蚬的重金属累积量影响比较复杂,仅在秋季表现出一定相关性,春季盐度影响不大;河蚬体内Cu含量与沉积物粒径存在显著正相关,Zn与沉积物中有机质含量存在一定正相关,Pb与沉积物中有机质含量存在着负相关;河蚬体内重金属元素两两间的相关性明显,多种元素间的相互作用机理值得进一步探讨。     

中国主要流域河蚬[Corbicula fluminea(Müller,1774)]形态及其对环境的适应性

双壳动物形态变化是适应环境变化的一个重要方面.但不同环境条件下的适应机制可能存在差异.河蚬是一种底栖双壳类动物,原产东南亚,现分布于世界许多地区.本研究采集了我国江、淮、黄河和西江等主要流域的河蚬样品,进行了三度空间尺度分析,以认识壳体形态的区域变化及其影响因素.结果表明,长江上游和西江上游等高山与峡谷地区河蚬的相对高度、圆度和凸度均小于黄淮、汉水流域和西江中下游等低山和平原地区.水流速度是造成这种形态适应性变化的主要原因.流速的增加使河蚬向相对长、矮和扁的方向发展,这种形态利于个体在底质中固定下来而不被水流冲走;而缓慢的水流使河蚬向相对宽圆的方向发展.环境温度、水体化学与河蚬形态之间不存在相关性,表明二者对河蚬形态的影响不明显.上述结果不仅有助于认识双壳动物对环境变化的适应性,而且对我国的河蚬养殖和捕捞也具有指导意义.     

长江口滨岸带河蚬的时空分布特征及其指示作用

以长江口滨岸湿地生态系统习见的大型底栖动物河蚬为对象,研究了河蚬种群密度、生物量的时空分布特征,分析了河蚬及环境中悬浮颗粒物和沉积物中的重金属含量.结果表明,不同季节、不同采样点以及相同采样点的不同断面河蚬的分布都有差异.河蚬种群密度、生物量的季节分布趋势是春、秋两季＞夏季;其中,浒浦河蚬的年度平均种群密度与平均生物量最高;河蚬在崇明中潮滩的种群密度、生物量高于低潮滩和高潮滩.研究表明,河蚬对沉积物中的重金属元素Cu、Zn富集能力强,对Pb、Cr的富集能力弱,其中,河蚬体内Pb含量与沉积物中Pb含量呈显著负相关(R=-0.924,P<0.01).     

巢湖富营养化对河蚬和环棱螺分布及种群密度影响

2001年9月和2002年9月两次对巢湖河蚬和环棱螺的调查表明,在富营养化程度较重的西湖区,河蚬生物量分别为17.87和47.29g·m^-2;环棱螺生物量分别为4.4和12.6g·m^-2.而在富营养化程度较轻的东湖区,河蚬的生物量分别为67.86和96.18g·m^-2;环棱螺的生物量分别为32.00和31.21g·m^-2.河蚬和环棱螺的种群密度和生物量均随水体富营养化的加剧而下降.近岸带河蚬和环棱螺的密度和生物量明显高于敞水区.河蚬的分布型为核心型,而环棱螺更接近随机性分布.河蚬和环棱螺的种群密度和生物量与水深均无明显相关(P＞0.05).环棱螺生物量与总氮TN、硝态氮NO₃-N、总磷TP和溶解性磷PO₄-P浓度呈显著负相关,而河蚬生物量仅与PO₄-P呈负相关.现有河蚬资源量与1981年相比有较大幅度的下降.探讨了其它环境因子对河蚬和环棱螺分布和生长的影响.     

红树植物秋茄对PCBs污染沉积物的修复

通过盆栽试验,研究了红树植物秋茄(Kandelia candel)对污染沉积物中系列浓度的PCB47(2,2′,4,4′-tetrachlorobiphenyl)和PCB155( 2,2′,4,4′,6,6′, -hexachlorophenyl)的修复作用与累积机理.结果表明:(1)经过180d处理,栽种了秋茄的沉积物中PCB47的残留浓度为53.99～528.37μg·kg-1,PCB155的残留浓度为68.25～682.90μg·kg-1,分别比对照1(加二氯化汞)低10.40%～15.46% 和6.10%～11.94%;比对照2(无二氯化汞)低7.70%～12.85% 和5.28%～8.27%;(2)秋茄对沉积物中PCB47和PCB155均具有较强的吸收积累作用,并随沉积物中PCB47和PCB155含量的增加而增大,不同种类PCBs在秋茄体内不同部位的积累趋势相同,不论是PCB47还是PCB155的累积量均是根> 叶> 茎.秋茄叶片中多氯联苯来自根部传输和空气吸收两部分,较低浓度的处理中,主要来自空气吸收,较高浓度的处理中,主要来自根部传输;(3)秋茄根对PCBs的生物富集系数(BCFs) 随着沉积物中PCB47和PCB155含量的增加而减小.不同种类PCBs 以及植物不同部位间BCFs 差异较大, PCB47的生物富集系数大于PCB155, 秋茄不同部位对PCBs生物富集系数大小不同,无论是PCB47还是PCB155,生物富集系数均是根＞叶＞茎.总体看来,秋茄能积累与去除污染沉积物中的PCB47和PCB155,表明用红树植物秋茄修复PCBs污染沉积物是一种有效、可行的方法.     

巢湖富营养化对河蚬和环棱螺分布及种群密度影响

2001年9月和2002年9月两次对巢湖河蚬和环棱螺的调查表明,在富营养化程度较重的西湖区,河蚬生物量分别为17.87和47.29 g·m^-2;环棱螺生物量分别为45.45和12.56 g·m^-2.而在富营养化程度较轻的东湖区,河蚬的生物量分别为67.86和96.18 g·m^-2;环棱螺的生物量分别为32.00和31.21 g·m^-2.河蚬和环棱螺的种群密度和生物量均随水体富营养化的加剧而下降.近岸带河蚬和环棱螺的密度和生物量明显高于敞水区.河蚬的分布型为核心型,而环棱螺更接近随机性分布.河蚬和环棱螺的种群密度和生物量与水深均无明显相关(P>0.05).环棱螺生物量与总氮TN、硝态氮NO₃-N、总磷TP和溶解性磷PO₄-P浓度呈显著负相关,而河蚬生物量仅与PO₄-P呈负相关.现有河蚬资源量与1981年相比有较大幅度的下降.探讨了其它环境因子对河蚬和环棱螺分布和生长的影响.     

长江口潮滩生态系统氮微循环过程中大型底栖动物效应实验模拟

依据长江口滨岸潮滩大型底栖动物的自然分布特征,选取了两段典型的研究区域——崇明东部潮滩和浒浦岸段边滩,运用实验模拟和对比分析方法,定量地研究了大型底栖动物谭氏泥蟹和河蚬对潮滩生态系统中氮营养盐的界面扩散及其早期成岩变化的影响。研究表明,谭氏泥蟹主要通过掘穴活动增加沉积物-水-气三相接触界面,促进沉积物中的无机氮(NH 4- N、NO- 2 -N和NO- 3- N)向上覆水体中扩散,并且也加快了沉积物中氮的氨化作用和硝化作用速率,而河蚬则主要通过生理活动机制影响潮滩生态系统内氮素的迁移转化过程。研究结果深刻揭示了大型底栖动物通过生物扰动和生理活动作用机制,促进了长江口潮滩生态系统内氮素的生物地球化学循环过程速率。     

A Preliminary Laboratory Investigation of PCB Flux from Dredge Resuspensions and Residuals

A preliminary laboratory investigation was conducted to understand the relative contributions of major dredge resuspension and residual processes on the releases of polychlorinated biphenyl (PCB) contaminants from sediments to water column. Sediments from New Bedford Harbor were used as test samples. Six sets of experiments were run for simulated resuspension and residual scenarios. During the experiments, water above the sediments was recirculated by peristaltic pumping or orbital shaking and the levels of two PCBs, Aroclor 1248 (PCB-1248) and Aroclor 1254 (PCB-1254), were monitored for 15 days. Analysis of the model predicted data indicated that resulting water column PCB concentrations differed with sediment surface, residual, and resuspension type. Highest PCB water column concentrations were observed for a condition which used a settled fluff from thin sediment slurry as a residual source and the column water was recirculated by orbital shaking. Lowest water column PCB levels were observed for a thick sediment deposit placed over clean sand. The PCB levels in the water column for all six simulated conditions were several orders higher than the USEPA ambient water quality criteria concentrations for aquatic environment and human consumption.     

Exposure of pig oocytes to PCBs during in vitro maturation: effects on developmental competence, cytoplasmic remodelling and communications with cumulus cells

Polychlorinated biphenyls (PCBs) are one of the most persistent and widespread groups of endocrine disrupting compounds in the ecosystem. These substances are present in sewage sludge that is spread in increasing amounts on arable land and pasture as fertilizer, and are ingested by farm animals with food and drinking water. This study investigated the effect of different PCB concentrations on pig oocyte in vitro maturation and developmental competence as well as examined the possible mechanisms involved. A concentration ranging from 0 to 1 mg/mL of Aroclor 1254 (A1254), a pool of more than 60 PCB congeners, was added to the maturation medium, as its composition is considered environmentally relevant. A1254 had no effect on maturation of pig oocytes and on the number of oocytes that cleaved following parthenogenetic activation at any of the doses tested. By contrast, a significant decrease in the number of zygotes that developed to blastocyst stage became evident at a concentration of 10 ng/mL. The number of blastocysts obtained decreased significantly, and in a dose response manner with higher concentrations. Exposure to PCBs altered mitochondria relocation during maturation and this was associated with the lack of a cytoplasmic microtubule network. No effect on mitochondria activity was observed. A1254 exposure also perturbed gap-junction mediated communications between oocytes and cumulus cells. In conclusion, PCB exposure of pig oocytes during in vitro maturation significantly decreased oocyte developmental competence, altered both their cytoplasmic remodelling and the communication with the somatic compartment. These data indicated that accumulation of PCBs in the pig organism may have a detrimental effect on the reproductive efficiency in this species.     

Polychlorinated biphenyls in alfalfa: Accumulation,sorption and speciation in different plant parts

The accumulation, chemical speciation and distribution of polychlorinated biphenyls (PCBs) were investigated in various parts of alfalfa. Moreover, the adsorption characteristics for PCB 28 by alfalfa and the influencing factors of the adsorption characteristics were studied. There were different degrees of PCB accumulation in alfalfa roots, root nodules and shoots. The decreasing order of the accumulation of PCBs in plant tissues was root nodules > roots > shoots, and the decreasing order of the total PCB contents was roots > shoots > root nodules, indicating that the roots were the main sink for PCB accumulation. There were three modes of PCB speciation in alfalfa roots and root nodules, comprising strong sorption (78%) and weak sorption (19%) on tissue surfaces and absorption within tissues (2%). The adsorption isotherms of PCB 28 indicate that the adsorption capacities of root nodules and shoots were both significantly higher than that of the roots. Both lipids and carbohydrates, and especially lipids, affected the PCB adsorption capacities of the tissues. These results may help in the elucidation of the mechanisms of sorption and accumulation of PCBs in the plants and their main influencing factors and thus contribute to the development of phytoremediation technologies for PCB-contaminated soils.     

Detailed Structure of the Skeleton,Muscles, and Connective-Tissue Elements in the Head of Silver Carp Hypophthalmichthys molitrix (Cyprinidae) in Relationship with the Functional Features of Its Visceral Apparatus

Journal of Ichthyology - The structure of some muscles, ligaments, the aponeurotic system, and osteological traits of the visceral apparatus in silver carp Hypophthalmichthys molitrix is considered...     

Muscular alteration of gill geometry in vitro: implications for bivalve pumping processes

In bivalves, water-pumping potential is determined both by ciliary activity and by the geometry of the system of passageways that acts as a conduit for water flow. Smooth muscles intrinsic to the gills of eulamellibranch bivalves possess the anatomical organization needed to regulate the dimensions of these water passageways. The tone of these muscles can be controlled experimentally using excitatory neurotransmitters to elicit muscle contraction and by removing Ca++ from the Ringer's solution to induce muscular relaxation. These experimental methods were used to investigate the effects of smooth muscle tone on the gill dimensions of two freshwater bivalves, Dreissena polymorpha and Corbicula fluminea, and one marine bivalve, Mercenaria mercenaria. In addition, endoscopic observations were made from the suprabranchial chamber of a freshwater unionid, Lampsilis anodontoides. Contraction of gill muscles led to a significant reduction in interfilament width, internal ostial area, and the cross-sectional area of the water tubes. Endoscopic observation from minimally disturbed L. anodontoides revealed rapid constriction of the water tubes upon contraction of the muscles of the gill and gill axis. Taken together, these data support the idea that alteration of smooth muscle tone in the gill provides a mechanism for controlling water-pumping activities.