豫西熊耳山地区槐树坪金矿岩石-土壤找矿指示元素的确定及其应用     

陈晶  龚庆杰  王炯辉  陈良  严桃桃  贺昕宇  李金哲 《岩石学报》2017,33(7):2302-2312

槐树坪金矿床位于河南省洛阳市嵩县境内,是豫西熊耳山地区近年来新发现的大型金矿床。本次研究对槐树坪金矿区地表及井下不同类型的较新鲜围岩、蚀变岩和矿石以及地表1∶20000面积性土壤采样,分析29项微量元素,从岩石和土壤两种采样介质来确定槐树坪金矿床的地球化学找矿指示元素。一方面基于较新鲜围岩的元素含量特征确定每个微量元素在该区岩石中的异常下限,进而分别计算了蚀变岩和矿石中微量元素平均含量与异常下限的比值,即异常衬度。按照异常衬度大于1.4的标尺确定了蚀变岩与矿石中明显富集的微量元素组合。另一方面,基于Au与28项微量元素在较新鲜围岩、蚀变岩、矿石三种介质中含量关系散点图直观确定了指示金成矿的微量元素组合。综合二者确定出槐树坪金矿区岩石地球化学找矿的指示元素组合为Au、Ag、As、Sb、Hg、Sn、Mo、Bi、Cu、Pb、Zn、Cd、Nb计13项。针对地表1∶20000面积性土壤调查,采用上述岩石中异常衬度为1.4作为土壤异常下限绘制了槐树坪金矿区微量元素的地球化学异常剖析图,以槐树坪金矿区已探明鸡公山一带的主成矿段为模型确定了土壤地球化学找矿的指示元素组合为Au、Ag、As、Sb、Hg、Bi、Cu、Pb、Zn、Cd、B计11项。综合上述结果认为在找矿指示元素组合方面土壤对岩石具有明显的继承性。基于岩石与土壤介质中共同的10项找矿指示元素,构建了归一化的综合异常指标,以鸡公山矿段为标准对整个槐树坪矿区进行了综合评价,发现槐树坪矿区内马蹄沟、秦佛爷沟、姜疙瘩和天坪西4处具有类似鸡公山矿段的找矿潜力。  相似文献   

Spatial Pattern of Benthic Diatoms and Water Quality Assessment Using Diatom Indices in a Subtropical River,China          下载免费PDF全文

Xiang Tan  Peiming Ma  Xiaoling Xia  Quanfa Zhang 《洁净——土壤、空气、水》2014,42(1):20-28

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沙漠化土地等级划分问题的初步研究   总被引：8，自引：2，他引：6  

韩广  杨文斌 《中国沙漠》1997,17(3):237-242

沙漠化土地的等级划分问题是防沙治沙工程规划设计中迫切需要解决的问题。在已有的研究工作及利用遥感技术对我国主要沙漠化地区的地表特征进行系统分析的基础上,以风沙地貌作为主导指征,植被和土壤作为辅助指征,依据它们所反映出的阶段性特征,制定了沙漠化土地等级划分方案。  相似文献   

Life history and ecology of the Maghrebian endemic Choroterpes atlas Soldán & Thomas, 1983 (Ephemeroptera: Leptophlebiidae)     

《Limnologica》2021

Knowledge of the basic life history traits of an aquatic organism such as voltinism and growth patterns is a fundamental step in understanding its potential use as indicator taxon and how it adapts to its complex environment. The distribution and life cycle of the Maghrebian endemic Choroterpes atlas Soldán & Thomas, 1983 was studied over a two year period. Random forest classification indicated that the species occupied both permanent and intermittent streams with high water depth, large river bed width and strong water flow. Density-based clustering of body measurements allowed the identification of last-instar nymphs which exhibited a significant sexual dimorphism: F-0 females were significantly larger than corresponding males. In addition, size-frequency plots and generalized additive models indicated that C. atlas exhibited a multivoltine annual cycle with three overlapping generations. Nymphal growth of the first generation happened in winter and spring with emergence occurring in June/July. The second generation grew from June/July to September whereas the third generation was completed from August/September to November. GAMs also indicated that body size varied significantly between years. The large regional distribution, habitat requirement, and phenology of C. atlas may ideally complement the potential use of Ecdyonurus rothschildi as a useful environmental indicator for North African streams and rivers.  相似文献   

Evidence necessary for taxa to be reliable indicators of environmental conditions or impacts     

P.J. Goodsell  A.J. Underwood  M.G. Chapman 《Marine pollution bulletin》2009,58(3):323-331

Using taxa as indicators of environmental impacts is widespread. Indicators are chosen because they are considered to be easy to measure, sensitive to stresses and respond to stresses in predictable ways. Here, we review these criteria by addressing the nature of the relationships between some characteristic of taxa and the environmental variables they are supposed to indicate. It is crucial that variables measured as indicators be strongly and consistently correlated (through space and time) with levels of the environmental variables. Appropriate experiments must be done to establish that an observed correlation is causal, or the correlation cannot be considered sufficient to identify a useful indicator. Finally, it is necessary to establish that the taxa directly respond to changes in the environmental variables they are supposed to indicate. Appropriate methodologies to establish these criteria are considered and we evaluate studies in which these criteria have or have not been met.  相似文献   

What indicators can capture runoff-relevant connectivity properties of the micro-topography at the plot scale?   总被引：2，自引：0，他引：2  

Michael Antoine  Mathieu JavauxCharles Bielders 《Advances in water resources》2009

Although connectivity is acknowledged as a key factor of a catchment hydrological behaviour, it still misses reference evaluation methodologies. Therefore the objective of the paper is to evaluate different quantitative indicators of hydrological connectivity, using the concepts of structural and functional connectivity commonly used in ecology. The indicators were tested on contrasted numerical fields of micro-topography that present distinct hydrological responses.  相似文献   

The response of Clitellata (Annelida) to environmental gradients in spring fens     

《Limnologica》2016

Patterns in aquatic Clitellata assemblage composition are known to be driven by several environmental gradients, with water chemistry and substratum characteristics being particularly important. In this study we explored 54 isolated spring fens across the eastern Czech Republic and Slovakia. These fens varied in calcium and magnesium concentrations, forming a sharp and well defined environmental gradient running from calcium-poor acidic fens to extremely calcium-rich tufa-forming fens. We found that the main changes in clitellate species composition were controlled by this gradient, and/or total organic carbon content, over a wide area, including fen sites differing in other environmental conditions and historical development. However, this pattern was weakened in sites with a high organic matter content, which represented a second driver of change in assemblage composition along with water temperature. Three main types of fens were determined using cluster analysis based on clitellate assemblage composition. However, only the first type, which included tufa-forming fens, was found to fit with the previously established spring fen types based on vegetation (i.e. extremely mineral-rich fens with a tufa, brown-moss mineral-rich fens, mineral-rich Sphagnum fens and mineral-poor Sphagnum fens). The second clitellate type included sites with low temperatures and occasional desiccation, while the third type was characterised by high temperatures and trophy. Using eight environmental predictors, we were able to significantly explain changes in the population abundances of all 12 common species (i.e. recorded at 15-plus sites). The results from individual species modelling also suggests that an increase in organic matter content can trigger compositional shifts towards assemblages of common eurytopic tubificid species. Thus, human-induced eutrophication and negative changes in spring fen hydrology, mainly drying up, can represent a serious threat for species-specific assemblages of aquatic clitellates, especially at alkaline sites due to their isolated and spatially limited nature.  相似文献   

Towards the implementation of an integrated ecosystem fleet-based management of European fisheries     

D. Gascuel  G. Merino  R. Döring  J.N. Druon  L. Goti  S. Guénette  C. Macher  K. Soma  M. Travers-Trolet  S. Mackinson 《Marine Policy》2012

Using the Celtic Sea and the North Sea as case studies, the fleet-based approach is shown to be the pathway to implement an effective ecosystem approach to fisheries management (EAFM) in European seas. First, a diagnostic on the health of each ecosystem is proposed based on the reconstruction of long time-series of catch, the analysis of mean indicators or stocks trajectories derived from ICES stock assessment results, and the analysis of ecosystem indicators. Then, a fleet-based synthesis is presented using indicators of both the ecological impact and the economic performances of the major fleets operating within each ecosystem. In particular, assessment diagrams show whether each fleet segment, on average, sustainably exploits the stocks. Although results are preliminary due to the poor quality of available data, the analysis shows that simple indicators can be estimated and clearly highlight contrasts between fleet segments. Such an approach contributes to the evolution from a stock-based to a fleet-based management, which reflects the ecological, economical and social pillars of the sustainable development of fisheries.  相似文献   

Fish assemblages in forest drainage ditches: Degraded small streams or novel habitats?     

《Limnologica》2014

Artificial drainage of forested wetlands to increase timber production has profoundly altered the hydrology of North-European landscapes during the 20th century. Nowadays, drainage ditches and small dredged streams can comprise most fluvial water bodies there, but the resulting ecological effects are poorly documented. In the current study, we explored, using fish as an indicator group, consequences of the transformation of natural stream networks to a mixture of natural and artificial watercourses. We asked whether the transformation results in impoverishment, enrichment or re-assembling of the communities both at watercourse and the landscape scales. We sampled fish in 98 sites in five well-forested regions in Estonia where ditches formed 83–92%, dredged streams 4–7%, and natural streams 3–10% of the total length of small watercourses. Based on a total of 6370 individual fish of 20 species, we found that, compared to natural streams, ditches had an impoverished fauna at both scales and both in terms of species richness and assemblage composition. Only natural streams hosted characteristic species (with Barbatula barbatula, Lampetra planeri and Lota lota emerging as significant indicators), while dredged streams had intermediate assemblages. The habitat factors explaining those drainage-related differences included a reduced flow velocity, loss of stream channel variability, less transparent water, and abundant aquatic vegetation. Hence, for stream-dwelling fish, drained forest landscapes represent degraded habitats rather than novel ecosystems, which contrasts with the transformation of terrestrial assemblages. Future studies should address whether that reflects the situation for whole aquatic assemblages, and how is the functioning of the hydrological systems affected. We suggest that the critical management issues for environmental mitigation of ditching effects on fish include basin scale spatial planning, protecting of the remaining natural streams, and rehabilitation of ditch channels in flat landscapes lacking beavers.  相似文献   

多种建模方法耦合建立冲积扇三维构型模型:以克拉玛依油田六中东区下克拉玛依组为例     

李君  李少华  张敏  许长福  吴小军 《现代地质》2013,27(3):662-668

以克拉玛依油田六中东区下克拉玛依组为例,通过对8口小井距的密闭取心井及周围24口井的构型特征分析,建立了研究区目的层段的三维构型模型。分析得到冲积扇不同亚相实用的构型建模方法：冲积扇扇根为泛连通体,各级构型展布范围不大,主要为片流砂砾体,三维构型建模适合用基于目标的模拟方法;扇中主要构型单元为漫流细粒、辫流水道和漫流砂体,辫流水道与漫流砂体有明显的接触分带关系,适合用截断高斯模拟方法;扇缘主要构型单元为漫流细粒,少量分布径流水道和漫流砂体,适合用序贯指示及基于目标的模拟方法。最终建立的三维构型模型能较好地体现了各级构型单元在平面上和垂向上的展布范围和接触关系。为后期剩余油分布的预测、井网调整及剩余油挖潜提供了准确的依据。  相似文献