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排序方式: 共有2094条查询结果,搜索用时 15 毫秒
221.
河流水体受污染后,在自然环境因素的影响下由各种物理、化学及生物作用能得到一定的净化。哈尔滨市松花江段河流水质净化作用主要包括稀释、吸附、江底沉积物的机械过滤与吸附和絮凝沉淀作用。哈尔滨市松花江断面正处于河流侵蚀与堆积交替动态平衡中,可不断提供新的活性表面,使河底沉积物的净化作用持久不衰。该特殊的地质条件是本段河流保持较强净化作用的关键,妥善利用水环境净化能力是一种经济有效的水污染控制手段。 相似文献
222.
Welton RG Cuthbert SJ Mclean R Hursthouse A Hughes J 《Environmental geochemistry and health》2003,25(1):139-145
For many years it has been realised that the weathering of stone is not merely determined by physical and chemical factors but also by biological agents. When the stone in question is a historic building or monument, the damage done constitutes an irretrievable loss of our heritage and history. Laboratory studies have commenced in Paisley to study the effect of photoautotrophs on the major sedimentary rock forming minerals, with a view to expanding this work to study the overall effect of these micro-organisms on heritage masonry. Tests were carried out on Albite, Calcite, Dolomite, Orthoclase, Siderite and Quartz, using axenic cultures of the following: Chlorella vulgaris, Chlorococcum tetrasporum, Scenedesmus obliquus, Oocystis marsonii, Stichococcus bacillaris. The rock chips were immersed in either water or bolds basal media and exposed to a mix of the micro-organisms listed above and then tested weekly for their pH, fortnightly for the waters chemical composition using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and visually utilising the universitys SEM facilities. Work so far has revealed biologically mediated etching of minerals, a well-defined pH profile over a period of 90 days, as well as a variety of elemental release patterns for the different minerals. 相似文献
223.
浙江省农业自然资源合理利用战略研究 总被引:2,自引:1,他引:1
陈庆根 《长江流域资源与环境》1998,7(2):159-163
针对浙江省自然资源利用程度高,资源环境压力大,资源浪费和污染等严重问题,根据浙江省资源构成特点,从资源,环境与经济协调发展的观点提出减少非农建设占用耕地,完善基本农田保护工作,绝不以牺牲现有耕地为调整农业产业结构。与此同时,积极开发后备土地资源,补充现有耕地面积;对于水资源必须依法治,管并重,节约与开源相结合,合理利用水资源,着重开发山,海资源和改善农业生态环境等战略措施。 相似文献
224.
根据1990-1994年调查结果表明,我国大兴岭北部现有淡水鱼类计7目5亚目14科,14亚科47属68种,其中经济鱼类22种。与80年代初期相比,有8目2亚目10科2亚科29属33种鱼类未采集到标本,经济鱼类资源少了17种。 相似文献
225.
本文以山西省为例,对省区自然资源进行了综合评价研究,分析了自然资源的相关结构,研究了各类资源的开发潜力,最后对自然资源的总体特征作了简要概括。 相似文献
226.
辽河三角洲的自然资源与区域开发 总被引:23,自引:0,他引:23
辽河三角洲有丰富的地上和地下资源,是农业综合开发和油田建设的重点地区。其区域资源开发以油田、稻田、苇田和虾田开发为核心,在土地利用主要做到全面规划与统筹兼顾;对淡水资源不足的问题要从开源与节流两方面来进行解决;对河口湿地景观生态系统要注意保护,发挥业已建立的自然保护区的功能;对河口湾水产资源更要加强保护与培育。 相似文献
227.
Metal complexation by natural ligands is important for metal transport and distribution in surface and ground water. The goal of the work was to study the ligand exchange rate for two important metal ions in natural aquatic systems (Al, Fe) was determined using EDTA and natural organic matter (NOM) of humic type as ligands. After adding EDTA to a solution containing metal-NOM complexes, these complexes dissociated and metal-EDTA complexes were formed. Metal-NOM complexes were separated from metal-EDTA complexes with the help of size-exclusion chromatography and detected by on-line inductively coupled plasma-mass spectrometry (ICP-MS). Injecting the samples into the system over time after addition of EDTA allowed us to measure the rate of the exchange of NOM by EDTA. The experiments could be well described with a first-order rate law assuming that the dissociation of the metal-NOM complexes is the rate-determining step. The exchange rate of Fe was found to be faster than that of Al. This corresponds well with the exchange rate of water molecules from the coordination sphere of the metal ions, which is also faster for Fe than for Al. Furthermore, the UV and the fluorescence signal of the chromatograms were measured. The results indicate that no disaggregation of NOM molecules took place, although about 75-85% of the aggregate-forming metal ions exchanged NOM by EDTA in their coordination sphere. This suggests clearly the fundamental role of NOM in colloidal transport of metals and in their bioavailability. 相似文献
228.
Pesavento M Biesuz R Profumo A Soldi T 《Environmental science and pollution research international》2003,10(5):317-320
SCOPE: The detection and investigation of metal ions bound in strong complexes in natural waters is a difficult task, due to low concentration of the metal ions themselves, and also of the strong ligands, which, moreover, are often not of a well-defined composition. Here, a method is proposed for the investigation of the speciation of metal ions in natural waters. OBJECTIVE AND METHOD: It is based on the sorption of metal ions on strongly sorbing ion exchange resins, i.e. complexing resins. For this reason the method is called Resin Titration. It has been shown in previous investigations that the concentration of metal ion totally sorbed by a particular resin, and its reaction coefficient in the solution phase in the presence of the resin, can be determined from the sorption data using a simple relationship. Here, a data treatment (the Ruzic linearization method) is proposed for also determining the concentration of the ligands responsible for the complex in equilibrium with the resin. RESULTS: The method was applied to data obtained by Resin Titration of a freshwater and a seawater. Copper(II) and aluminium(III) were considered, using Chelex 100 as a titrant, due to its strong sorbing properties towards these metal ions. The results were: the total metal concentration in equilibrium with the resin, the side reaction coefficients, and the concentration of ligands. In all these cases the ligands forming very strong complexes were found to be at concentration lower than that of the metals. CONCLUSION: The Ruzic linearization method allows the determination of the concentration of the ligands forming very strong complexes in equilibrium with Chelex 100. The reaction coefficient was better determined by the calculation method previously proposed for RT. The ligands responsible for the strong complexes were found to be at low concentration, often lower than that of the metal ions considered. The metal in the original sample is partly bound to these ligands, since the complexes are very strong. Only a part of the metal is linked to weaker ligands, or free. 相似文献
229.
230.