Visualization experiments of iron precipitates: Application for in-situ arsenic remediation     

M.I.M. Darwish  V.M. van Beek  J. Bruining 《Journal of Geochemical Exploration》2006,88(1-3):19

Laboratory experiments were carried out to acquire more insight and understanding of the phenomena associated with the in-situ arsenic remediation. Visualization techniques are the most informative for the detection of Fe(II) while flowing in soils. Green Rust (GR) was considered as representative of in-situ iron precipitates. In a visualization flat cell, the change in color of GR to orange, due to oxidation, was monitored by a digital camera and the images were analyzed giving the spatial and temporal distribution of Fe(II). Moreover, both oxygen and pH changes in time were recorded in two sections along the flow direction in the cell. The measured and calculated concentration profiles were compared and the actual reaction rates were predicted. The reaction rate constants measured in this study, under flowing conditions, are in a good agreement with the values obtained from batch experiments reported in the literature.  相似文献   

Ammonium regeneration in intertidal sediments of the Yangtze estuary during air-exposure     

L.J. Hou  M. Liu  J.J. Lu  S.Y. Xu  D.N. Ou  Y. Yang  D.G. Zheng 《Environmental Geology》2006,49(7):937-945

The influences of exposure to the atmosphere on ammonium cycle in the intertidal surface sediments were in situ studied with a geochemical approach at a typical station in the Yangtze Estuary during three tidal cycles in September 2003. During an about 8-h emersion period of each diurnal tide, six high-resolution vertical profiles of adsorbed and dissolved ammonium were measured. It was observed that both adsorbed and dissolved ammonium generally had an increasing trend in sediment cores during the exposure. The rate of ammonium regeneration in sediments was estimated using the accumulation amount of ammonium including adsorbed and soluble fractions during the daytime emersion. The calculation result showed that there was relatively high ammonification rate (˜500 nmol N cm⁻³ day⁻¹), which reflected that organic nitrogen in sediments was quickly decomposed with a residence time of ˜52.7 days. Due to the dramatic temperature difference observed in sediment profiles, free convection was considered an important mechanism of regulating the efflux of produced ammonium into overlying waters. The total estimated amount of regenerated ammonium was ˜1.35×10⁵ t N year⁻¹ in the intertidal flat of the Yangtze Estuary, which occupied 7.6% of the total inorganic nitrogen annually transported to the estuarine ecosystem.  相似文献   

长江源区生态及灾害地质调查与防治对策     

康琴  阿成业 《高原地震》2007,19(3):54-58

简述了长江源区自然地理和生态地质环境特征，分析了环境恶化的主要原因及防治对策。  相似文献   

The GW-Fauna-Index: A first approach to a quantitative ecological assessment of groundwater habitats   总被引：6，自引：1，他引：6  

Hans Jürgen Hahn   《Limnologica》2006,36(2):119-137

Between June 2001 and December 2002, 18 hyporheic and groundwater bores were sampled for fauna and environmental data using phreatic traps. The bores were situated in three different natural geographic regions in Palatinate, Southwestern Germany.Faunal data correlated with the relative amount of detritus, bacterial abundances and the standard deviation of temperature, while very few and weak correlations were found with physical–chemical variables. Dissolved oxygen was assumed to be a limiting factor for most metazoans with a critical concentration at around 0.5–1 mg l⁻¹.To quantify the strength of the hydrological exchange with surface water and its effects on fauna, a so-called GW-Fauna-Index was developed and calculated using the relative amount of detritus, standard deviation of temperature, and oxygen concentration. From all environmental data and on all spatial scales, this index best explained the total faunal abundance and taxonomic richness.To describe the availability of organic aliments in the groundwater, the terms of “alimonic” and “alimony” [from lat. alimonium=(food) supply] were proposed.Although stygofauna was different in the geographic regions investigated, the GW-Fauna-Index was independent from these regional particularities. Using the GW-Fauna-Index, three groups of groundwater habitats could be classified according to the alimonic conditions. From oligo-alimonic group I samples, fauna was mostly absent, while meso-alimonic group II samples were prevailingly populated by stygobites, and eu-alimonic group III samples by ubiquists and stygoxenes. Total abundances and taxonomic richness increased significantly from group I to group III. Group I samples were characterized by low index values, group II samples by intermediate and group III samples by high values.The GW-Fauna-Index provides promising perspectives for application, but needs some improvement. First of all, detritus should be analysed quantitatively and qualitatively, rather than semi-quantitatively. Also, a standard protocol for sampling has to be developed.  相似文献   

煤炭城市生态环境可持续发展研究--以淮南市为例     

邢琴琴  焦华富  尹乐 《世界地理研究》2006,15(2):54-60

根据城市生态学原理和方法,针对煤炭城市生态环境特点,构建了能够体现煤炭城市生态环境质量主要特征的,定性、定量考核的评价指标体系。利用层次分析、变权综合指数等方法,建立了煤炭城市生态环境质量综合评价模型。从自然、经济、社会三个方面对淮南市生态环境质量进行评价,并对淮南市生态环境可持续发展提出了相应对策。  相似文献   

血吸虫病的生态防治与抑螺防病林消除钉螺孳生环境机制   总被引：2，自引：0，他引：2  

费世民  周金星  张旭东  蒋俊明  陈秀明 《湿地科学与管理》2006,2(4):28-32

血吸虫病是发展中国家主要的寄生虫病之一,历史悠久,传播广泛,危害严重。研究表明,血吸虫是血吸虫病的病原体,哺乳类动物(终末宿主)和钉螺(中间宿主)是血吸虫的两个宿主。由于钉螺寄生终末宿主哺乳类动物种类多样,活动区域繁杂,人类难以控制,抑制中间寄主——钉螺的繁生便成了血吸虫病防治的有效对策。钉螺具有水陆两栖特性,其中卵的孵化、幼螺的生长发育离不开水。钉螺分布和数量受土壤和植被环境因素影响,并对栖息地具有严格的选择性。依据钉螺生物学和生态学特性,彭镇华和江泽慧提出通过林业生态工程对血吸虫病进行生态防治的思路——兴林抑螺。参照前人研究结果,综合分析了抑螺防病林改变钉螺孳生环境的机制:(1)在林木个体耗水、林分耗水、小流域耗水和林冠降低径流等方面,抑螺防病林降低了土壤水分含量,使得林地土壤水分无法满足钉螺的生长和发育条件;(2)从林木自身生物化学物质对钉螺外在生存和内部代谢环境影响角度,分析了林木自身代谢产物对抑制钉螺的生存和繁殖的作用及抑螺防病林抑制钉螺生存的生理生化机制。抑螺防病林除了具有抑制钉螺生长发育、控制血吸虫病的功能以外,还兼有人工林的多重效益。  相似文献   

益母草对钉螺化感作用的实验研究     

唐万鹏  王万贤 《湿地科学与管理》2006,2(4):47-53

本实验研究分别采用益母草的根、茎、叶的0.10、0.25、0.50、2.00、1.00g/L和水苏碱的0.20、0.40、0.60、0.80、1.00g/L5个不同浓度梯度的处理液处理钉螺,设清水和0.001g/L浓度的氯硝柳胺溶液为对照。结果表明:(1)益母草各部分的水浸液均有很好的灭螺效果,用不同浓度的处理液浸杀钉螺,在不同时间的处理下,钉螺死亡率存在差异,其钉螺死亡率是随处理浓度的增加和时间的延长呈上升趋势,0.5g/L以上的益母草根、茎、叶、化水浸液和浓度达0.60g/L以上的水苏碱处理液均可达到100%的毒杀钉螺致死效果,与通常使用浓度0.001g/L氯硝柳胺溶液的灭螺效果相当。不过益母草根、茎、叶水浸液的毒效较氯硝柳胺略慢,用0.001g/L氯硝柳胺溶液处理钉螺2～3d可达100%的死亡率,而用0.5g/L以上的益母草根、茎、叶水浸液水溶液处理需要3～5d才能达到同样的效果;灭螺效果顺序依次为:叶>茎>根。(2)钉螺趋避性研究表明,水苏碱和益母草根、茎和叶的处理液对钉螺具有明显的驱逐作用,而盐酸益母草碱几乎没有作用。(3)并对其剂量-效应与时间-效应进行了研究分析,由此获得化感作用植物益母草灭螺的化学生态学证据,为研制新的具中国特色的植物成份灭螺剂打下了基础,并为合成仿生灭螺剂以及最终构建生态工程中强化感作用植物群落灭螺提供理论依据。  相似文献   

PRINCIPLES OF RIVER TRAINING AND MANAGEMENT     

Zhaoyin WANG Shimin TIAN Yujun YI Guoan YU 《国际泥沙研究》2007,22(4):247-262

River regulation and river training have been performed for various purposes and negative effects have been shown in numerous cases. In some cases the negative effects are so serious that humans have to consider to "renaturalize" the regulated rivers. Only by using the strategy of integrated river management the diverse river uses and natural fluvial processes and ecological systems may be harmonized. Based on analysis of case studies and data collected from literatures this paper presents the concept of integrated river management and four principles of river training. The integrated river management comprises: 1) taking the watershed, upper stream basin including the tributaries, middle and lower reaches and the estuary as an integrated entity in the planning, design and management; and 2) mitigating or controlling the negative impacts on hydrology, erosion and sedimentation, fluvial processes, land use and river use, environment and ecology while in achieving economic benefit from water resources development, flood safety management and hydropower exploitation. River training and management should be in accordance with the four principles: 1) extending the duration of river water flowing on the continent, which may be achieved by extending the river course or reducing the flow velocity; 2) controlling various patterns of erosions and reducing the sediment transportation in the rivers; 3) increasing the diversity of habitat and enhancing the connectivity between the river and riparian waters; and 4) restoring natural landscapes.  相似文献   

水稻免耕栽培的减灾效应研究     

熊传伟  黄国勤 《气象与减灾研究》2007,30(2):33-37

为探索稻田保护性耕作技术——水稻免耕的减灾效应,将免耕与传统稻作方法相结合组成常耕移栽、常耕抛秧、免耕移栽、免耕抛秧4个处理进行试验,并运用生态学原理对试验结果进行了分析研究。结果表明,稻田保护性耕作能提高作物产量,降低部分生育期间水稻病虫害,抑制农田杂草的生长。  相似文献   

Modelling of oxygen and nitrogen cycling as a function of macrophyte community in the Thau lagoon     

M. Plus  A. Chapelle  P. Lazure  I. Auby  G. Levavasseur  M. Verlaque  T. Belsher  J. -M. Deslous-Paoli  J. -M. Zaldívar  C. N. Murray 《Continental Shelf Research》2003,23(17-19):1877

A three-dimensional model coupling physical and biological processes for the whole Thau lagoon (Mediterranean coast of France) was developed in order to assess the relationships between macrophytes and the oxygen and nitrogen cycles. Ten species have been inserted as forcing variables in the model. Plankton dynamics, shellfish cultivation impact and mineralization of organic matter are also considered, as well as nutrient and oxygen exchanges between the sediment and the water column.Simulations with and without the macrophytes have shown that the system can be characterized as having a highly structured pattern involving lagoon nitrogen and oxygen cycles. This pattern is created by the combined influence of macrophytes, watershed and oyster farming.The model has been also used to assess the total annual macrophyte production at the whole lagoon scale. Comparisons with phytoplankton production and with results from other temperate lagoons have underlined the high productivity of the Thau lagoon supported by active nutrient regeneration.  相似文献