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101.
A sampler for collection of interstitial water from wetland sediments is described. It differs from other sampling devices because it does not have to be filled with solution to facilitate diffusion, it does not have to be removed from the wetland to collect samples, and it can be used to draw repeated samples over time from identical locations. The device facilitates in situ measurement of a wide range of abiotic parameters such as electrical conductivity, redox potential, and pH in wetland sediments. The device has application in ecological investigations of sediment-borne wildlife diseases, studies of benthic invertebrates, measurement of nutrient exchange, and other aspects of wetland ecology. 相似文献
102.
The dry summer of 1976 triggered a wholesale installation of sprinkler systems for agriculture. This dry summer also revealed areas in The Netherlands most susceptible to drought, namely sandy regions and the coastal fringe. This resulted in distribution of Rhine water to new areas, and in quantities hitherto unknown. The Second National Water Management Plan (1982) consequently focussed on enlarging the capacity of water distribution works. This distribution has led to a multitude of ecological effects, such as changes in salinity and nutrient concentration, as well as the spreading of contaminants. Consequently, the Third National Water Management Plan (1990) includes fewer distribution works because of the adverse environmental effects and the reduced feasibility due to increasing costs and decreasing agricultural benefits.A climatic change as predicted may result in climatic conditions in The Netherlands resembling those of France or the Mediterranean, implying drier summers and more precipitation in winter. An increased frequency of dry summers will no doubt revive water distribution plans now shelved and may even bring new ones to the drawing board. An increase in Rhine water distribution will have serious consequences for many aquatic and terrestrial ecosystems, as will a lowering of the groundwater table. In this paper we will discuss the dilemma of choosing between allowing increased desiccation of wetlands as the climate becomes drier or increasing the distribution of Rhinewater and the potential ecological effects of these choices. Alternative strategies to water management also are discussed.This article is largely based on Duel et al. 1989. 相似文献
103.
Summary Cuticle/water partition coefficients (Kc/w) for d-limonene, -pinene and -pinene were determined by an extrapolation and a desorption method. The sorption experiments were carried out with isolated angiosperm and gymnosperm cuticles and with [14C]-labelled monoterpenes, which were obtained biosynthetically. Both methods were suitable for the determination of the Kc/w of volatile hydrophobic compounds. For the angiosperm cuticles the partition coefficients are of the order of 104, which indicates a high accumulation of monoterpenes in the cuticle. The values of the conifer cuticles of Picea abies (L.) Karst. and Abies alba Mill., however, are lower due to their high lignin content. This is proved by the increase of the partition coefficients after removal of polar and phenolic components. The Kc/w can be estimated with good accuracy from the octanol/water partition coefficient, which was determined experimentally. 相似文献
104.
N. Bouchriti A. El Marrakchi A. Fahim S. M. Goyal 《World journal of microbiology & biotechnology》1992,8(5):546-549
A 3-year bacteriological survey of an oyster-growing area in Morocco, where the Japanese oyster (Crassostrea gigas) is grown, showed that the contamination of this lagunar ecosystem was not continuous but intermittent and that animal manure and human recreational activities were important sources of pollution. The major source of contamination was of animal origin, except during the summer, when human contamination prevailed. 相似文献
105.
106.
107.
青龙河底栖无脊椎动物群落结构及其水质评价 总被引:17,自引:3,他引:14
本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。 相似文献
108.
将去除信号肽的人肿瘤坏死因子-α(Tumor necrosis factor-α,TNF-α)cDNA插入到带有原核增强子样序列Px的新型表达载体pBV320中,使TNF cDNA 5′端直接置于大肠杆菌trp启动子下游,采用37℃恒温培养,使TNF在大肠杆菌中获得了高效表达,表达活性达1.35(±0.17)×10~6U/L菌液。表达的TNF-α对L929细胞的毒性作用可被抗人肿瘤坏死因子-α的单克隆抗体所中和。表达菌裂解液作SDS-聚丙烯酰胺凝胶电泳,显示有一条分子量与TNF分子量吻合、约为17000道尔顿的蛋白带。利用DEAE-Sepharose阴离子交换层析及Sephacryl S-200凝胶过滤对上述重组人TNF-α进行纯化,获得电泳纯产品,比活性为1.48×10~6U/mg。 相似文献
109.
酸性水和投加铝、钙对鲢鱼早期发育和鳃超微结构的影响 总被引:4,自引:1,他引:3
在实验室条件下,研究了酸性水和投加铝、钙对鲢鱼胚胎孵化和鱼苗存活以及幼鱼鳃超微结构的影响。pH4.0引起所有胚胎在24小时内死亡,暴露于pH4.5—6.0的胚胎孵化率和暴露于pH4.0—6.0的5—15日龄鱼苗存活率随pH值上升而增高。投加0.5mg Al~(3+)/L使在酸性pH暴露条件下的胚胎孵化率和鱼苗存活率进一步降低。投加3.0mg Ca~(2+)/L可显著提高暴露于pH4.5和5.0的胚胎孵化率;投加2.0mg Ca~(2+)/L可在一定程度上提高暴露于pH4.5和5.0的鱼苗存活率。幼苗经pH4.5暴露8小时后出现严重的鳃超微结构损害;投加1.0mg Al~(3+)/L使鳃结构损害加剧;投加5.0mg Ca~(2+)/L可明显缓解酸性水对鳃的损害。 相似文献
110.
Pharmacological and biochemical characteristics of the partially purified -aminobutyric acid (GABA)B receptor using baclofen affinity column chromatography have been examined. The Scatchard analysis of [3H]GABA binding to the purified GABAB receptor showed a linear relationship and the KD and Bmax values were 60 nM and 118 pmol/mg of protein, respectively. Although GTP and Mg2+ did not affect on the GABAB receptor binding, Ca2+ significantly increased [3H]GABA binding to the purified GABAB receptor in a dose-dependent manner and showed its maximum effect at 2 mM. The enhancement of the binding by Ca2+ was found to be due to the increase of Bmax by the Scatchard analysis. The treatments with pronase and trypsin significantly decreased the binding of [3H]GABA, but phospholipase A2 had no significant effect on the binding. In addition, treatment with glycosidases such as glycopeptidase A and -galactosidase significantly decreased the binding of [3H]GABA to the purified GABAB receptor. These results suggest that purification of the solubilized GABAB receptor by the affinity column chromatography may result in the functional uncoupling of GABAB receptor with GTP-binding protein. Furthermore, the present results suggest that cerebral GABAB receptor may be a glycoprotein and membrane phospholipids susceptible to phospholipase A2 treatment may not be involved in the exhibition of the binding activity.Special issue dedicated to Dr. Eugene Roberts. 相似文献