首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 78 毫秒
1.
The Ponnaiyar River is one of the largest rivers of the Tamil Nadu state (India), flowing a distance of 430 km from its point of origin to the sea. This work contributes with new data of magnetic and elemental composition of river sediments, and improves the knowledge obtained by preliminary and previous studies of rivers from Southeastern India. Magnetic susceptibility, anhysteretic and isothermal remanent magnetization and chemical determinations (major and trace metals) were measured. Magnetic results reveal the predominance of magnetite-like mineral with magnetic grain size variations along the river and in depth. Most of the uppermost samples have the major presence of trace metals and higher values of magnetic concentration. Magnetic and chemical variables were also analysed as potential pollution indicators using multivariate statistical techniques: canonical correlation and fuzzy c-means clustering analyses, which confirmed the existence of relationships, but not in a simple way, between magnetic and chemical variables. Furthermore, fuzzy analysis allows classifying the data in different well-differentiated groups regarding the trace metal load, concentration and feature-dependent parameters. The most polluted samples show high concentration of trace elements and magnetic carriers, softer and coarser magnetic minerals; on the contrary, the unpolluted samples (from the deepest sediments) have the opposite characteristics.  相似文献   

2.
Rock-magnetic techniques have become a useful tool in environmental issues; in particular, magnetic studies constitute an alternative way to study pollution in different media. The present contribution focuses on magnetic parameters as pollution indicators, especially from their relationship with contents of heavy metals. The work was carried out in two Indian rivers located in Tamil Nadu, southern India. Several sediment samples were collected and studied in the laboratory using magnetic techniques, magnetic susceptibility, anhysteric remanent magnetization, isothermal remanent magnetization, and chemical techniques to determine contents of heavy metals. Magnetic mineralogy indicates the predominance of ferrimagnetic minerals; although magnetite-like minerals are the main magnetic carriers, antiferromagnetic minerals can be present as subordinate carriers. Concentration-dependent magnetic parameters revealed noticeable differences between both rivers, e.g. magnetic susceptibility is four times higher in Cauvery than in Palaru River. Moreover, such increase can be interpreted as “magnetic enhancement” and therefore related to the pollution status. This magnetic enhancement indicated a different pollutant contribution in both rivers, and also, a different spatial distribution along these rivers, where critical (or more polluted) sites were identified. On the other hand, univariate and multivariate statistical analyses—e.g. PCoordA, Multifactorial Analysis of distance, PCA and RDA—were examined, revealing a link between magnetic and chemical variables. Among magnetic parameters, the concentration-dependent magnetic parameters (e.g. magnetic susceptibility) seem to be the most relevant for this study.  相似文献   

3.
This paper considers the magnetic properties of a range of recent and contemporary sediments from the north eastern part of the Irish Sea. Principal component ordinations of the results show a close link between magnetic property variations and particle size. The magnetic properties of a subset of samples, particles sized by a combination of sieving and pipette analysis, confirm that variations in ferrimagnetic (‘magnetite’) grain size parallel those in particle size, despite the fact that the magnetic grains in the fine grades have diameters 1–2 orders of magnitude smaller than those of the particle size fraction in which they occur. This is best explained by postulating that the fine magnetic grains occur in the clay fraction but are present in declining concentrations in the coarser grades up to 4ø as an artefact of the pipette method. Most samples have a biomodal distribution of magnetic minerals, with a coarse mode associated with heavy minerals in the sands or coarse silts, and a fine mode in the clays. Magnetic susceptibility (x) and saturation isothermal remanent magnetization (SIRM) largely pick out the coarse mode where present; anhysteretic remanent magnetization (ARM) largely picks out the fine mode. The results open up the possibility of normalizing samples from these environments for particle size and, more specifically, clay content, by means of ARM or ARM/x values. The most likely source for the uniform and almost exclusive stable single domain magnetite, which dominates the magnetic properties of the clays, is thought to be bacterial magnetosomes. The measurements as a whole do not appear to hold much promise for discriminating sediment source types.  相似文献   

4.
Magnetic measurements made on sediment and catchment samples from two contrasting Icelandic lakes show how susceptibility and saturation isothermal remanent magnetisation alter as magnetic minerals pass from rock to soil to stream and into the lakes. There is no detectable growth of secondary magnetic minerals in Icelandic soil profiles and susceptibility peaks in the 62.5–1000 μm size range of mineral particles in the lake sediments. Changes in sediment source can be detected using combinations of magnetic measurements.  相似文献   

5.
Open-cast mining generates sediment in river systems at globally significant scales. One of the challenges in attributing measured sediment loads to upstream mining activities is establishing the source of sediments that are a mixture of natural and mining-based materials. The environmental magnetic data (mass-specific magnetic susceptibility, anhysteretic remanent magnetisation, isothermal remanent magnetisation and inter-parametric ratios) on 57 samples of suspended sediment from the Bhadra River in the Sahyadri (the Western Ghat) of India have been used in this study. Samples were collected upstream, adjacent to and downstream of Kudremukh, a mountainous and high rainfall site where the largest mechanised open-cast mine in south Asia was located. Graphical and multivariate analyses and modelling of the data show that on average ~29% of the river suspended load downstream of the mine is derived from mining and allied activities at Kudremukh although the mine occupies less than 5% of the catchment. The contribution of primary ore is the maximum (18%), followed by transitional hard weathered ore (7%) and weathered ore (4%). The model has done a fairly good job of unmixing; the sum of errors is <1 for 40 samples, 1–4,254 for five samples and >71,000 for four samples. Modelling of samples with small mass seems to produce large errors. This investigation demonstrates the utility of environmental magnetic data, which can be obtained in a simple and rapid manner, and the unmixing of such data in identifying the contribution of mining activities to the total suspended sediment load.  相似文献   

6.
武昌地区街道尘埃磁学特征及其对环境污染的指示意义   总被引：1，自引：0，他引：1  
对在武昌地区4个功能区域(青山、洪山、东湖风景区、东湖开发区)主要交通街道收集的尘埃样品进行详细的环境磁学测量,包括质量磁化率、频率磁化率、等温剩磁退磁系数以及典型样品的磁滞回线参数等。研究结果表明:尘埃样品中剩磁载体均以亚铁磁性矿物为主,样品中的磁性颗粒呈现低矫顽力的磁铁矿特征,软磁性的磁性矿物是样品剩余磁性的主要载体。尘埃样品χ、SIRM的区域分布特征受区域周围工业、车流量及道路状况等多种环境因素的影响,在4个功能区域中存在明显的磁性差异:青山工业区污染较重,东湖开发区、洪山、东湖风景区次之;硬剩磁(HIRM)的分布可能指示了道路交通来源的磁颗粒特征,东湖开发区和青山工业区由于行驶的货车和重型车辆较多,表现出硬剩磁量值较高。与其他城市(兰州、西安、南京、徐州等)相比,整个武昌地区街道尘埃样品的磁性含量仍较高,说明在城市环境方面还有待于进一步改善和保护。  相似文献   

7.
刘健  秦华峰  孔祥淮  李军 《第四纪研究》2007,27(6):1031-1039
黄东海陆架和朝鲜海峡等5个泥质沉积区全新世中期以来(自约6kaB.P.至今)的细粒沉积物主要是黄河、长江和朝鲜半岛的河流入海物质在复杂的海洋动力系统中的沉积产物.对取自山东半岛北部近岸泥质区和长江口以南的闽浙沿岸泥质区(舟山群岛近岸海区)的表层细粒沉积物(粘土质粉砂和粉砂质粘土)开展了详细的岩石磁学测试,包括磁化率、等温剩磁和样品磁化率随温度的变化等分析,并将实验数据与以往研究过的济州岛西南陆架区、南黄海东南部陆架区和朝鲜海峡西岸等3个泥质沉积区细粒沉积物的磁学特征进行比较研究.结果表明,上述5处细粒沉积物的磁性矿物主要组分为磁铁矿、磁赤铁矿和赤铁矿,其中低矫顽力磁性矿物为主,平均粒度为准单畴(PSD).根据磁性矿物的粒度和低矫顽力组分的相对含量,这5处细粒沉积物可以划分为3种类型:第1种类型是朝鲜海峡西岸细粒沉积物,其磁性矿物的粒度最粗,低矫顽力组分的相对含量为中等;第2种类型是南黄海东南部陆架细粒沉积物,其磁性矿物的粒度为中等,低矫顽力组分的相对含量最大;第3种类型是山东半岛北部近岸、闽浙沿岸(舟山群岛近岸)和济州岛西南陆架区的细粒沉积物,其磁性矿物的粒度最细,低矫顽力组分的相对含量最低.在这5处细粒沉积物中,闽浙沿岸(舟山群岛近岸)细粒沉积物的磁性矿物含量最高,其他4处细粒沉积物的磁性矿物含量都较低且大体相当.这种磁学特征的差异反映了物源的不同.从磁学特征来分析,济州岛西南陆架区的泥质沉积物主要来自黄河和长江;南黄海东南部泥质区的主要物源是朝鲜半岛进入黄海的河流,黄河和长江对其没有重要贡献.  相似文献   

8.
Measurements of palaeomagnetic horizontal remanent intensity, saturation isothermal remanence, coercivity of remanence, high field remanence and magnetic susceptibility, have been made on lateglacial and postglacial sediments from two small, inter-drumlin hollow lakes from central Northern Ireland. These magnetic measurements have been compared with pollen and chemical analyses from the same profiles and with complementary mineral magnetic data from local soils. Representative sediment samples have also been divided into a range of particle size fractions and each fraction has been subjected to magnetic investigation. Five distinctive stratigraphic horizons have been identified on the basis of the magnetic mineralogy. Two horizons relate to phases of pronounced erosion. One of these is connected with solifluction processes in the lateglacial and the other to an intensive period of farming activity which started in Medieval times. Two horizons are associated with periods of very high iron and manganese deposition and are possibly related to the precipitation of magnetic minerals within the lake. Hydrological changes during periods of local anthropogenic activity appear to produce magnetic mineral assemblages indicative of stream bed/bank substrate sources. The particle size data also support the suggestion that downcore changes in the mineral magnetic record are mainly caused by changes in the sediment source rather than particle size or sedimentological effects.  相似文献   

9.
Complex studies of the mineral composition and petromagnetic properties of the rocks which compose an edifice of the Minami–Khiosi submarine volcano located in the Mariana island arc are carried out for the first time. The Minami–Khiosi Volcano is a part of the Khiosi volcanic complex within the alkaline province of the Idzu–Bonin and Mariana island arcs. All of the rocks analyzed are enriched in K2O (1.34–3.30%), Ba (370–806 ppm), and Sr (204–748 ppm). The basalt has a porhyric texture and contains mosTy olivine phenocrysts as individual crystals and growths with a size up to 2 cm; the groundmass is finecrystalline. The samples studied contain at least three Fe-bearing oxide minerals. These are predominant magnetite and less abundant ilmenite and Fe hydroxides. It is established that the samples studied are magnetically isotropic and have high values of natural remanent magnetization and Königsberger ratio. Similarly to the other island-arc Late Cenozoic submarine volcanoes in the western part of the Pacific Ocean, the samples studied are strongly differentiated by the value of natural remanent magnetization and magnetic susceptibility. The low-coercivity magnetic minerals (titanomagnetite and magnetite) of the pseudo-single-domain structure, as well as high-coercivity minerals (hematite) are the main carriers of magnetization. The high values of natural remanent magnetization are explained by the pseudo-single-domain structure of the titanomagnetite grains, whereas the high values of magnetic susceptibility result from the high concentration of ferromagnetic grains.  相似文献   

10.
The upper reaches of the Bistrita drainage system were selected as a natural test site to determine the geogenic and anthropogenic input into fluvio-lacustrine systems in humid mid-latitude morphoclimatic zones. The reason for this selection lies in the complex geology and its metallogenic evolution leading to a great variety of Fe, Mn, U, and polymetallic sulfides ore deposits. It sparked an intense mining activity during the past centuries with a strong impact on the drainage system similar to many mineralized sites in the world which are still under exploitation. Sediment samples from Bistrita River were analyzed by means of X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), near-infrared (NIR) and micro-Raman spectroscopy (μ-Raman).Our results revealed that the chemical and mineralogical built-up of the stream sediments is mainly geogenic, with most of the trace elements accumulated in the river sediments derived from the source rocks exposed in catchment area of the River Bistrita. A strong input by man has been detected in the drainage system near abandoned mining sites. The trace elements are mainly accommodated in the structure of detrital minerals representative of the clastic aureole around the source rocks, and to a lesser extent adsorbed onto the surface of clay minerals. The REE incorporated into muscovite furnish evidence of having derived from the source rocks, prevalently mica schists exposed by supergene processes in the provenance area and rule out a neoformation of clay minerals on transport and deposition.  相似文献   

11.
长江中下游干流河底沉积物环境磁性特征   总被引：8，自引：5，他引：3       下载免费PDF全文
通过多参数磁性测量,分析探讨了长江中下游干流3种不同粒级(<2mm,<0.28mm和<0.125mm)河底沉积物中磁性矿物的类型、含量、颗粒变化及空间分布特征。3种粒级中,磁性矿物主要富集在<0.125mm的细质沉积物中。对细质沉积物的分析表明,长江中下游干流河底沉积物的磁性矿物含量较长江口高近10倍,类型以亚铁磁性矿物磁铁矿为主,颗粒以假单畴-多畴为主,超顺磁性颗粒含量较低。从中游到下游,磁性矿物含量呈下降趋势,颗粒呈变细趋势。干流磁性矿物含量远高于支流,颗粒远粗于支流,支流泥沙的汇入不断影响干流沉积物的磁性特征。  相似文献   

12.
The use of mineral magnetic techniques as pollution proxy for road deposited sediment was explored using various statistical approaches. Standard techniques were adopted for measurement of mineral magnetic and geochemical parameters. The analyses of magnetic parameters revealed that the samples were dominated by ferrimagnetic minerals and multidomain grains. This implied that the magnetic fractions in the samples might be of anthropogenic origin. Results also indicate that the samples were dominated by low coercive, magnetically soft minerals. Thermomagnetic curves confirmed magnetite as the remanence bearing magnetic mineral having a Curie point temperature of ~580 °C. The strong association observed between magnetic susceptibility, susceptibility of anhysteric remanent magnetization and saturation isothermal remanent magnetization and aluminum, titanium, manganese, iron, chromium and lead demonstrated that these metals occurred as ferrimagnetic particles of technogenic origin resulting from vehicular sources. Assessment of pollution status of the road deposited sediment identified silicon and lead as the priority pollutants of concern. Generally, pollution load index was <1 (mean, 0.66 ± 0.14), indicating that the samples were not polluted in the overall, but the metals were in the buildup stage requiring constant monitoring. The sources of pollutants from principal component and cluster analyses identified the sources of pollution to be mainly from vehicular emissions such as brake linings, exhaust materials, tire wear, corroded metal parts, abrasion of lubricating oil and road construction materials. This study found that mineral magnetic techniques offer great potential as pollution proxy for soil pollution studies.  相似文献   

13.
《Applied Geochemistry》2001,16(9-10):1251-1259
Sediment samples were taken along the West, North, and East rivers of the Pearl River system at 28 locations in 1998, and a total of 49 elements were determined by ICP–AES, ICP–MS and INAA. The probability features of the datasets were studied, and the average concentrations of these elements in sediments of the three rivers were calculated. Significant differences in element concentrations among the three rivers were observed and the results were confirmed by statistical tests including analysis of variance (ANOVA), Kruskal–Wallis test, and t-test. Spatial distribution maps of element concentrations were produced using a geographical information system (GIS). The immobile trace elements (such as Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are enriched in the West River where limestone dominates the rock types in the watershed. Because of the strong weathering, immobile trace elements are enriched and reside in secondary minerals of the weathering products. All three rivers have high concentrations of rare earth elements (REEs) because of strong weathering, but relatively higher concentrations of REEs are observed in sediments of the East River where granite dominates the rock type. Granite contains high concentrations of REEs and the sediments have inherited this feature from their bedrock. Alkaline element (Li, Na, K, Rb, and Cs) concentrations are elevated in sediments of the East River, these may reside in granitic primary minerals. Relatively high concentrations of alkaline earth elements (Mg, Ca, Sr, and Ba) are observed in the West River, inherited from the limestone bedrock. High Pb and Bi concentrations are found in the North River and are caused by Pb mineralization and the discharge of a smelter in the upper reaches of the river. However, statistical tests did not indicate a significant difference between Pb concentrations in the North River and the other two rivers, which suggests that statistical results should be carefully used and explained.  相似文献   

14.
龙昱 《沉积学报》2005,23(2):291-296
通过中山舰沉积物的纹层、磁化率、铁磁性物质与长江水位、大气污染的磁性物质来源关系等,并结合文史资料,得出沉积物磁化率的显著变化可作判别沉积物相对年代的指标,而沉积物中与现代工业发展相关的圆球状磁性金属废渣可作为判别沉积物确切年代的标志。沉积物磁化率的明显增强的原因是环境变化引起的铁磁性物质的增多,圆球状金属废渣的首次出现是武钢投厂对大气环境污染的结果,其指示年代为1959年。磁化率相对较低的沉积物沉积年代为1938-1958年,而磁化率明显增强的沉积物年代为1959年以后。研究表明,采用的沉积物磁性特征与文史相结合的断年方法,具有原理简明、操作方便、研究成本低等特点,适合内陆人口密集地区大尺度沉积环境普查研究的需要,并且不受沉积环境、沉积类型差异的影响。  相似文献   

15.
武汉市东湖沉积物的磁性特征与重金属含量之间的关系   总被引：6，自引：0，他引：6  
对武汉市东湖主湖区的郭郑湖和塘林湖114个沉积物样品的磁化率与代表性样品的频率磁化率系数、磁滞回线参量和重金属元素进行系统分析, 综合区域环境背景, 探讨应用岩石磁性方法技术评价大型城市内陆湖泊沉积物污染程度的可行性及其效果.结果表明, 在主成分中, 郭郑湖沉积物没有一个主成分占绝对优势, 仅有少数重金属元素含量与磁化率相关, 磁化率χ与重金属富集强度的相关性较差; 而塘林湖沉积物有一个“工业源”的主成份占绝对优势, Fe (全铁)、Co、V、Mn、Ti、Ba、Cr、Ni、Cu等元素与饱和等温剩磁SIRM、χ关系密切(相关系数大于0.87).郭郑湖与塘林湖的沉积物的饱和等温剩磁与重金属富集强度的相关程度高于磁化率, 因此, 可以用其(SIRM) 作为环境污染程度的指示参量.   相似文献   

16.
长江中下游第四纪沉积物发育土壤磁性增强的环境磁学机制   总被引：25，自引：2，他引：23  
对长江中下游第四纪沉积物 (Q3 黄土,Q2 红土和Q3 红土 )发育土壤的磁性增强现象及其物理机制进行了讨论。结果表明 :(1)铁磁性矿物是土壤磁性的主要载体,它们是成土过程中形成的稳定单畴 (SSD)和超顺磁性 (SP)态的次生磁性矿物,没有显示重要的反铁磁性矿物的贡献;(2 )土壤磁化率 (χ)的高低与成土过程产生的稳定单畴和超顺磁性颗粒呈极显著正相关,指示了风化成土作用的强度,磁化率可作为反映成土环境变化的代用指标;(3)频率磁化率 (χfd) 5 %可作为土壤中的超顺磁性颗粒存在与否的临界值,土壤 χfd值的高低同样反映了风化成土作用的强度,可用作研究第四纪环境变化的有用工具之一。  相似文献   

17.
Multivariate canonical correlation analysis has been carried out taking physical variables (mean, standard deviation, skewness, kurtosis) as predictors and chemical variables (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) as responses from the soils and sediments of Thane Creek and Ulhas River areas in Bombay, India. Soil samples provide the first canonical correlation to the presence of more clay fractions, which controls the concentration of trace elements such as Co, Fe, and Ni. In sediment samples, the first canonical correlation explains the role of mean particle size in controlling the concentration of Pb and Ni. The second correlation shows the role of clay minerals in controlling the concentration of the trace elements such as Fe and Zn. The plot of transformed scores of first canonical correlation for soil illustrate the high correlation between sets of variables as all points are grouped closely within an ellipsoidal field. The plot of transformed scores of first canonical correlation illustrate that there is a clear distinction between the type of sediments collected from Thane creek and the Ulhas river region.  相似文献   

18.
Tin-mine tailings containing high concentrations of Sn, Cu, Zn, Fe, Mn, As, and W are discharged into the Red River of cornwall, England and are then transported into St. Ives Bay under normal flow conditions. Most of the tin-bearing particles in the fluvial sediments are smaller than 170 μm, but tin-bearing composite grains or mineral grains with tin interspersed in the crystal lattices also occur in coarser size fractions. Tin distribution in the sediments is controlledby: (1) the distance from the source of the tailings, and (2) the concentration processes operating on the river bed. Suspended sediment and sediment transported by saltation filtered from river water samples also showed high concentrations of metals although, in contrast to the bottom sediments, they vary within a narrow range. Distributions of Cu, Zn, Fe, As, and Pb in the filtered sediments probably are related to the physical and chemical behavior of their sulphide minerals during fluvial transportation. A regional stream-sediment geochemical reconnaissance survey for tin did not show the highest concentration in the Red River; this indicated that in other rivers and streams tin reconcentration by selective removal of light minerals had taken place in the bottom sediments after mining operations had ceased. These rivers and streams also can transport large quantitiies of land-derived sediment including tin-mine tailings discharged into them when mines were operating. The minimum distance of tin transported by the Red River is at least 10 km; however, most of the tin was derived from mine tailings and is considered to be unnatural.  相似文献   

19.
对辽河三角洲大凌河河口湿地地区ZK3钻孔的58个沉积物样品中碎屑矿物和黏土矿物进行鉴定和分析,结果显示:碎屑矿物中轻矿物占比大,平均含量为95.7%,主要包括斜长石(43.89%)、钾长石(28.10%)和石英(22.45%);重矿物平均含量仅为4.3%,主要为普通角闪石(38.03%)、绿帘石(27.51%)和自生重晶石(12.01%)。黏土矿物中伊利石平均含量(50.3%)最高,其次为蒙脱石(24.5%)、绿泥石(12.7%)和高岭石(12.6%),黏土矿物组合为伊利石-蒙脱石-绿泥石-高岭石型。ZK3孔晚更新世以来沉积物的物源有所差异,但总体上来说,除河道和湖相沉积时期物源主要来自大凌河外,其它沉积环境中沉积物主要来自辽河和大辽河,物源相对稳定。黏土矿物组合特征所指示的气候变化过程与本区域的孢粉数据有很好的对应关系:45~31 ka BP处于庐山—大理的间冰期阶段,蒙脱石/(伊利石+绿泥石)比值较大,指示气候温和湿润;31~11 ka BP为大理冰期阶段,蒙脱石/高岭石比值较低,指示气候寒冷干燥;11 ka BP至今为冰后期阶段,随着新仙女木事件(YD)的结束,温度逐渐回升,蒙脱石/(伊利石+绿泥石)比值升高,指示气候温暖湿润。  相似文献   

20.
Variations in sediment input and distribution to the Laptev Sea continental margin during the Holocene and Termination I could be identified based on radiocarbon dated magnetic susceptibility logs and sediment thickness in high-resolution seismic profiles. Magnetic susceptibility of surface samples reveals an increased input of magnetic grains to the Laptev Sea deriving from the Anabar and Khatanga river catchments. Exposed magnetite schists and volcanic rocks of the Anabar shield and Putoran Plateau, respectively, function as major source of magnetic material. The distribution of magnetic susceptibility in association with the thickness of the Holocene sediments indicates bottom-current induced sediment transport guided by major submarine valleys on the Laptev Sea shelf. The sites of filled paleoriver channels identified in the seismic profiles suggest that during the Late Weichselian sea-level lowstand river runoff continued through four of the major valleys on the exposed Laptev Sea shelf. The sediments at the top of the lowstand deposits in front of the Anabar-Khatanga valley, represented in the seismic profiles by prograding deltas, are characterized by outstandingly high magnetic susceptibility values. Radiocarbon datings approximate the deposition of these high magnetic sediments between 10 and 13.4 ka. It is suggested that this increased input of magnetic material is related to the deglaciation of the Anabar shield and the Putoran Plateau and thus support their glaciation during marine isotope stage (MIS) 2.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号