Statistical Analyses of La, Ce, Nd, Y, Nb, Ti, P, and Zr in Bedrocks and Their Significance in Geochemical Exploration at the Um Garayat Gold Mine Area, Eastern Desert, Egypt

A prospective lithochemical survey (scale 1:50,000) was carried out at the Um Garayat gold mine area within the central wadi Allaqi shear zone. The metavolcanic samples were analyzed for Ti, P, Zr, Nb, Y, La, Nd, and Ce. The background and threshold values were determined using histograms, box-plots, and Q-mode cluster analysis. Discriminant analysis classifies the samples into four groups: Group 1 (Au mineralization) characterizes Phase III of the hydrothermal stage; Group 2 (Cu?CAu mineralization) characterizes Phases I and II; Groups 3 and 4 comprise the least altered samples. Cubic trend surface and residual maps display groups of elements: (P, Ti, Zr), (Nb, Y), and (La, Nd, Ce) each group has similar areal distribution pattern. R-mode factor analysis, using the cubic residuals, produces a model with three factors. Factors 1 (P, Ti, Zr) and 2 (Nb, Y) are referred to the magmatic minerals of the least altered volcanic rocks. In addition, Factor 1 associates with the Au-rich site at the shafts area, whereas Factor 2 is referred to albitization western to the shafts area with high contents of Nb and Y. In Factors 1 and 2, major P and Ti with traces Nb and Y are attributed to the accessories rutile, sphene, anatase, and calcite that were developed during propylitization as well as apatite and calcite-accompanying Phase I of the hydrothermal stage. Phosphorous could be considered as an indicator element for the Au mineralization at the study area. The principal elements of Factor 3 (La, Nd, Ce) associate with the Cu?CAu-rich site at the southern adits area, and attributed to the secondary Ca-bearing accessories calcite, sphene, and apatite. In general, these elements associate with the regional propylitization and the three phases of hydrothermal stage in zones of alkali metasomatism. In these alteration zones, La, Nd, and Ce could be used as indicators during geochemical exploration at the study area. In general, the secondary accessory minerals calcite, apatite, rutile, sphene, and anatase associating with zones of alkali metasomatism are significant carriers for the investigated elements. These accessories are possible indicators during geochemical exploration in the adjacent similar mineralizations of the central Allaqi shear zone area.     

Heavy metal concentrations in surficial sediments from Wadi El Natrun saline lakes, Egypt

Heavy metal concentrations of Wadi El Natrun saline lakes were investigated. Pb, Zn, Mn, Cu, Cd, Ni, Fe and Al were measured in surficial sediments. The heavy metal concentrations largely indicate the influence of weathering of terrigenous sources on land. In comparison with the average in sedimentary rocks, the concentrations of the heavy metals studied are higher than the global average sandstone. This is also reflected in the high enrichment factors. The heavy metal concentration in lakes II and III decrease in the order Pb > Zn > Cu, while in lake I the decreasing order is Cu > Zn > Pb. Sediments with microbial mats were found to concentrate heavy metals above background sediment values.     

珠穆朗玛峰地区雪冰中重金属浓度与季节变化

The concentrations of heavy metals Ba, Pb, Cu, Zn and Co in snow pit collected in September, 2005 from the accumulation area of the East Rongbuk Glacier (6523 m a.s.l.), which lies on the northern slope of Mt. Qomolangma, were determined by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations (pg/ml) of heavy metals are Ba2-227, Co2.8-15.7, Cu10-120, Zn29-4948 and Pb14-142, respectively. The δ¹⁸O was determined by MAT-252. The time period of the snow pit spans from autumn 2005 to summer 2004. Seasonal variations of the concentrations and δ¹⁸O are observed, of which Pb, Cu, Zn and Co are much lower in summer monsoon season than that in non summer monsoon season, suggesting that different sources of heavy metals contributed to the site. EF_c (crustal enrichment factors) is Co3.6, Cu27, Pb33 and Zn180, respectively. Higher EF_c values of Pb, Cu and Zn suggest that Pb, Cu especially Zn are mainly contributed by anthropogenic sources. Foundation: National Natural Science Foundation of China, No.40501014; No.40871058 Author: Duan Jianping (1981–), Ph.D. Candidate, specialized in climate and environmental change.     

Knowledge-Driven Prospectivity Mapping for Granite-Related Polymetallic Sn–F–(REE) mineralization,Bushveld Igneous Complex,South Africa

This paper presents mineral prospectivity mapping to identify potential new exploration ground for polymetallic Sn–F–REE mineralization associated with the Bushveld granites of the Bushveld Igneous Complex, South Africa. The Lebowa Granite Suite, commonly known as the Bushveld granites, is host to a continuum of polymetallic mineralization with a wide range of metal assemblages (Sn–Mo–W–Cu–Pb–Zn–As–Au–Ag–Fe–F–U–REE), ranging from a high-temperature to a low-temperature magmatic hydrothermal mineralizing environment. The prospectivity map was generated by fuzzy logic modeling and a selection of targeting criteria (or spatial proxies) based on a conceptual mineral system highlighting critical processes responsible for the formation of the polymetallic mineralization. The spatial proxies include proximity to differentiated granites (as heat and metal-rich fluid sources), Rb geochemical map (fluid-focusing mechanism such as fractionation process), principal component maps (PC 4 Y–Th and PC 14 Sn–W, fluid pathways for both high- and low-temperature mineralization) and proximity to roof rocks (traps for fluids). Logarithmic functions were used to rescale rasterized evidential maps into continuous fuzzy membership scores in a range of [0, 1]. The evidential maps were combined in two-staged integration matrix using fuzzy AND, OR and gamma operators to produce the granite-related polymetallic Sn–F–(REE) prospectivity map. The conceptual mineral system model and corresponding prospectivity model developed in this study yielded an encouraging result by delineating the known mineral deposits and occurrences of Sn–F–(REE) mineralization that were not used to assign weights to the evidential maps. The prospectivity model predicted, on average, 77% of the known mineral occurrences in the BIC (i.e., 56 of 73 Sn occurrences, 12 of 15 F occurrences and 6 of 8 REE occurrences). Based on this validation, 13 new targets were outlined in this study.     

沅江下游入湖段河床沉积物重金属污染特征

对沅江入湖沉积物进行钻探取样,利用等离子质谱仪（ICP-MS）对沉积物重金属进行分析。结果表明：重金属Ba、Sc、V、Th、U、Cu、Co、Ni、Cr等在沉积物中含量变化相对稳定,分布相对均匀;而Mn、Zn、Pb、Mo、Cd、Tl、Bi等重金属的含量变化大,分布不均匀。重金属含量柱状剖面变化特征及富集系数（EF值）的计算结果显示：沉积物中Cd达显著富集,而Sc、V、Mn、Pb、Bi等为中等富集程度。沉积物中存在3个重金属富集层,即中下部Pb、Tl、Bi富集层;中上部Pb、Cr、Ni、Cu富集层;浅表部V、Cr、Mn、Ni、Cu、Zn、Pb、Cd、Tl、Bi等多种重金属富集层。地累积指数（I_geo）和综合富集指数（EI）评价结果显示：沅江入湖沉积物重金属污染程度自河床深部向浅部,污染程度趋于增强,污染元素组合趋于由Pb-Bi的单一元素组合向由V-Cr-Mn-Ni-Cu-Zn-Pb-Cd-Bi组成的复合元素组合变化。且自上游向下游,沉积物重金属污染程度趋于降低。这种重金属污染空间变化特征与区域人为活动有关,值得进一步研究。     

Heavy metals and phosphorus in tidal flat sediments of the Yangtze estuary

Concentrations of heavy metals (Cu, Pb, Zn, Cr and Cd), and phosphorous (P) were determined in surface tidal flat sediments of the Yangtze estuary and Shanghai coast. Results demonstrate that there were significant differences among the accumulation of the heavy metals in sediments, following the order: Zn > Cu > Cr > Pb > Cd. The spatial distribution and chemical forms of heavy metals in tidal flat sediments were closely related to the distribution of pollution resources (outlet of sewage) and the local sedimentary and hydrodynamic conditions. The dominated form of non-residual heavy metals is bound to Fe/Mn oxides, and the next form is bound to carbonates. Moreover, contents of total P in sediments range from 18.0 μmol.g⁻¹ to 31.4 μmol.g⁻¹ along the coastline, speciation of P in sediments was different, most of P in tidal flat sediments is associated with calcium phases (as Ca-P) similar to marine sediments.     

Heavy metal records in the sediments of Nanyihu Lake,China: influencing factors and source identification

In 2008, three short sedimentary cores were collected from Nanyihu Lake in the lower Yangtze River Basin using a gravity corer. Heavy metals, including Pb, Cu, Zn, Cr, Ni, Mn, and major elements, including Al, Fe, K, Na, Mg and Ti, were measured. Radionuclides, including ²¹⁰Pb and ¹³⁷Cs, were analyzed to date the sediments. The significant Mn enrichment in the uppermost sediments of the three cores did not influence the distribution of Pb, Cu, Zn, Cr and Ni. The Pb, Cu, Zn, Cr and Ni contents have increased over the past 30–40 years. The decline of ²⁰⁶Pb/²⁰⁷Pb ratios toward the surface indicated increasing anthropogenic Pb loading to the lake sediments. However, the heavy metal enrichment was low overall because of the high sediment accumulation rates and the low anthropogenic heavy metal flux into the Nanyihu Lake.     

Baseline determination,pollution source and ecological risk of heavy metals in surface sediments of the Amu Darya Basin,Central Asia

Central Asia(CA) is one of the most fragile regions worldwide owing to arid climate and accumulated human activities, and is a global hotspot due to gradually deteriorating ecological environment. The Amu Darya Basin(ADB), as the most economically and demographically important region in CA, is of particular concern. To determine the concentration,source and pollution status of heavy metals(HMs) in surface sediments of the ADB, 154samples were collected and analyzed for metals across the basin. C...     

长江流域血吸虫病的化学地理研究*

血吸虫病是一种水源性传播的寄生虫病。本文探讨了血吸虫病流行与水文化学地理因素的关系。病区水体富集微量元素,31种微量元素的平均累乘指数>1,其中亲铜元素、亲石元素和稀土元素的含量较高,而亲铁元素和Hg、As的含量较低,钙镁摩尔比值接近毛蚴最造钙镁摩尔比值(0.8)。     

澜沧江河床沉积物重金属污染评价

河床沉积物是河流水体与泥沙环境中重金属的主要积存载体,能反映水环境的重金属污染状况。本文选取澜沧江为对象,通过对澜沧江干流西藏和云南境内22个河段的河床沉积物重金属测定分析,得到了8种主要的重金属元素(Cr、Mn、Ni、Zn、As、Pb、Cu和Co)的含量,并采用沉积物富集系数法与地质积累指数法分别对所测得沉积物的重金属污染程度进行了评价。结果表明:①澜沧江干流大部分河段污染情况并不明显,但在中游的旧州和功果桥河段,因该区域的地质金属背景值和支流沘江流域铅锌矿开采,地表的重金属元素被雨水冲刷到该河段,导致沉积物重金属富集现象明显,出现了轻度到较强度污染;②澜沧江流域受人为干扰的区域集中于中游与下游,部分河段(功果桥附近)Cu、Pb和Zn等元素呈轻度或偏中度污染;③大坝对河流的阻隔效应使得干流沉积物重金属污染呈现片段化分布,河流沿岸城市化等人类活动对附近河段沉积物重金属污染状况也有较明显的影响。     

Zonation in primary halos and geochemical prospecting pattern for the Guilaizhuang gold deposit, eastern China

The Guilaizhuang gold deposit, with an average grade of 8.10 g/t Au and reserves of over 30 mt, is a subvolcanic epithermal deposit. The deposit is hosted in Paleozoic carbonate rocks in the western Shandong metallogenic terrane of the littorine Pacific metallogenic domain, eastern China, and is associated spatially with an early Mesozoic subvolcanic alkalic intrusive complex (188–190 Ma). The orebody was discovered at the end of the 1980s based on anomalies of Au in stream sediment samples at a map scale of 1∶200,000. The ore is rich in Au, Ag, Te, V, F, As, Sb, Tl, W, and Mo but poor in Cu, Pb, and Zn. The ore is similar in its trace elements to Carlin-type Au deposits. The transverse element association zonation of the deposit is as follows: (on the hanging wall) F⟸ W−Mo−As−Tl⟸Se−Sb−Bi⟸Au−Ag−Te (orebody) ⟹ Se−Sb−Bi (on the foot wall). The axial zonation is as follows: Au⟹Ag⟹Sb⟹V⟹Zn ⟹W⟹F⟹Mo⟹Tl⟹As. Indexes such as (Au+Sb) _d / (As+Tl) _d and (Au+ Ag) _d /(As+Tl) _d decrease with depth but dramatically increase at the level where the orebody pinches out, which indicates another orebody might exist at depth. Multivariate statistical analysis suggests that the ore (halo)-forming process can be divided into two stages: alteration and mineralization. The former includes: potash feldsparization, albitization, silicification, and fluoritization. The latter includes the following substages: arsenopyritization and scheelitization; pyritization, chalcopyritization, and sphaleritization; and native gold, electrum, and calaveritization. The last substage is considered to be the main ore-forming stage in the formation of the deposit.     

Human-induced change in sedimentary trace metals and phosphorus in Chaohu Lake,China, over the past half-millennium

We present a sedimentary geochemical record of human perturbation in the watershed and related changes in trace metals (Cr, Ni, Zn and Pb), phosphorus and abundant rock-forming elements (Al, Fe, K, Mg, etc.) in Chaohu Lake over the past 500 years, a period spanning historical agricultural expansion and modern economic development. The record exhibited a stable terrestrial detrital input to Chaohu Lake before ca. 1540 AD, a period with less human perturbation of the watershed, which resulted in low and constant values of trace metals and phosphorus (TP) concentrations as well as Al, Fe, K, Mg, fine silt (<16 μm), the chemical index of alteration (CIA) and K/Na ratio. Two periods of successive marked increases in Al, Fe, K, Mg, fine silt, chemical index of alteration (CIA) and K/Na ratio occurred after ca. 1540 AD and 1950 AD. The former period apparently resulted from enhanced well-weathered topsoil erosion in the watershed related to the expansion of arable land, and the latter resulted from further enhancement of human perturbation in the watershed during the modern period. Concentrations of trace metals and TP were positively correlated with that of the rock-forming elements and fine silt. Trace metal pollution was limited during 1540–1950 AD, according to the low enrichment factors (EFs = 0.8–1.1), when an increase in trace metal concentrations was also linked to changes in detrital input. In addition to detrital regulation, pollution also contributed to an increase in TP concentrations (average EF 1.4) during 1540–1950 AD and the average accumulation rate of anthropogenic phosphorus was 87.3 mg m⁻² a⁻¹. Anthropogenic phosphorus increased further and Pb and Zn pollution also occurred after 1950 AD, reaching maximum values after 1980 AD, when the average accumulation rates of anthropogenic Zn, Pb and phosphorus (mainly in the form of NaOH-P) were 242.2, 43.3 and 811.8 mg m⁻² a⁻¹, respectively. The increase in phosphorus pollution in recent decades is probably from the domestic sewage sources of Hefei City and non-point sources related to agricultural utilization of commercial fertilizer, whereas Zn and Pb pollution is probably derived mainly from industrial sources of Hefei City, as deduced from their spatial variations in the sediments of the river mouths.     

徐闻南山镇红树林沉积物及红树植物中重金属的累积特征与迁移规律

为探究重金属在红树林沉积物及红树植物中的分布累积及迁移规律,选取了徐闻南山镇红树林为研究对象,通过测定红树林沉积物及红树植物不同部位（根、茎、叶）的重金属质量分数,运用富集因子、生物富集系数、转移系数及相关性分析等方法进行分析。结果表明：1）红树林沉积物重金属质量分数表现为铬（Cr）＞锌（Zn）＞镍（Ni）＞铜（Cu）＞铅（Pb）＞砷（As）＞汞（Hg）＞镉（Cd）,为中等变异程度;除了镍（Ni）元素外,其余7种重金属未超过国家一级标准,除了铅（Pb）元素外,其余7种重金属均超过广东省土壤环境背景值,说明研究区沉积物中重金属具有一定的积累效应。2）沉积物中砷（As）、铜（Cu）、锌（Zn）、汞（Hg）、镍（Ni）、铬（Cr）富集因子值均＞1.5,说明受到轻微人为活动影响;各站位镍（Ni）富集因子值均＞5,结合研究区背景,反映了镍（Ni）受到自然和人为输入的共同影响。3）白骨壤体内重金属主要集中在根部,而红海榄体内重金属在根茎叶中分布相对均匀。白骨壤根茎叶部位的大多数重金属质量分数远高于红海榄,说明白骨壤对重金属的吸附能力比红海榄强。汞（Hg）集中分布在植物的叶片部位,且与其他重金属之间相关性不明显;推测汞（Hg）主要通过叶片吸收进入植物体内,与交通运输污染有关。4）不同红树植物对不同重金属富集能力各异,白骨壤对重金属的富集能力表现为：镉（Cd）＞砷（As）＞铜（Cu）＞锌（Zn）＞汞（Hg）＞铅（Pb）＞镍（Ni）＞铬（Cr）,红海榄表现为：镉（Cd）＞铜（Cu）＞汞（Hg）＞锌（Zn）＞铅（Pb）＞砷（As）＞镍（Ni）＞铬（Cr）。白骨壤和红海榄对汞（Hg）的运移能力都较强;红海榄对镉（Cd）的富集能力和转运能力都较强,而白骨壤对镉（Cd）富集能力较强,转运能力却较弱,这说明红树植物对重金属元素的富集能力与转运能力不存在正比关系。     

澜沧江水系底沙重金属含量空间分布及其污染评价

流域内矿山开采引起的河流系统重金属污染是流域开发及资源利用过程中的主要环境问题之一.本研究选取澜沧江水系底沙沉积物为介质,考察其干流及11 条主要支流的5 种重金属元素铜(Cu)、砷(As)、铅(Pb)、锌(Zn) 和铬(Cr) 含量的空间变化,并综合采用了单因子指数法和潜在生态危害指数法评价澜沧江干支流底沙沉积物中重金属污染分布现状.结果显示: (1) 澜沧江水系自上游至下游,底沙重金属含量呈减弱趋势,但各支流重金属含量分布差异较大;(2) 单因子指数法评价结果表明,干流最上游的旧州断面因区域背景值较高而致使As、Pb 呈现重污染.支流黑惠江河口的As及勐戛河的Cu为重污染,沘江断面的Pb、Zn污染指数最大,属严重污染.其它干支流样点除了少数重金属元素有中度污染外,均为无污染状态;(3) 潜在生态危害指数法指出,干流旧州断面的As及支流沘江断面Pb 的E_rⁱ 值较高,其它各采样点值均未超出40,且各支流潜在生态危害指数(RI) 值均小于150,属于低潜在生态危害的范围.本研究对澜沧江干流及其主要支流底沙沉积物中重金属污染状况进行分析与评价,分析干流主要的污染来源及各支流主要污染物,为澜沧江干支流的污染治理提供科学依据.     

西南极乔治王岛长城站区晚第四纪燕窝湖岩芯元素地球化学特征

本文阐述了乔治王岛长城站区燕窝湖沉积物中微量元素及某些常量元素的含量、分布、富集系数和相关系数的变化规律 ,探讨了该湖岩芯物质来源及气候环境的阶段性变迁 ,认为一方面燕窝湖周围碎屑沉积岩 (包括火山沉积岩 )是进入沉积体系的主要物源 ;另一方面 ,地幔物质也是其物源之一 ;同时 ,并不排除南极大陆冰进期搬运来的陆源物质进入沉积体系。     

Use of Factor Analysis to Study the Distribution of Metalliferous Bauxitic Tailings in the Seabed of the Gulf of Corinth,Greece

In 1994, a detailed marine environmental survey was carried out in surface sediments of the northern flank (Antikyra Bay) and the basin floor of the Gulf of Corinth. Metalliferous tailings (red-mud slurry) of a bauxite processing plant are discharged through a pipeline at a water depth of 100 m, in the Antikyra Bay, covering an area of 16 km². The bauxitic tailings are detached from the main deposit at the outfalls, flow as turbidity currents downslope, and are redeposited on the basin floor of the Gulf of Corinth, where they cover an area of about 277 km². One hundred sediment samples, that were collected from red-mud deposits and the surrounding natural sediments, were analyzed for Ag, Al, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Si, Ti, V, and Zn concentrations. Statistical analysis of the heavy metals concentrations using factor analysis allowed (i) an examination of the interrelations among metals and (ii) distinguishing possible sample groups on the basis of metal concentrations in order to study the mechanisms of transport of the red mud and the degree of mixing with natural sediments. Factor 1 (Al, Cr, Ti, Fe, Co, Ni, Pb, Ag, Hg, V, Cd, and Cu) and the positive pole of Factor 2 (Cu, Ag, Cd, and Hg) are red-mud factors, reflecting different metal behaviors, which are related to processes that take place during the transport and redeposition of the red mud. The negative poles of Factors 2 and 3 and the positive pole of Factor 4 are related to natural sediment supply processes. Q-mode factor analysis identifies three distinct sediment groups located in different areas, on the base of the degree of mixing of red mud with natural sediments.     

Past atmospheric Pb deposition in Lake Qinghai,northeastern Tibetan Plateau

Two short sediment cores were recovered from sub-basins of Lake Qinghai, China and were analyzed for concentrations of Pb and 16 other elements to determine historic, regional atmospheric Pb deposition on the Tibetan Plateau. Core chronologies, dating back to the eighteenth century, were established using activities of ²¹⁰Pb and ¹³⁷Cs. The 17 elements were divided into three principal components. Variations in concentrations of PC1 elements (Al, Cr, Cu, Fe, K, Mn, Ni, and Ti) demonstrate different patterns between the two cores, and are attributed to different sediment sources in the two sub-basins. PC2 elements (Ba, Ca, Na, and Sr) may be associated with the degree of catchment weathering and/or water chemistry. Four elements (Pb, Zn, P, and Co) are related to both PC1 and PC2, and reflect a mixture of natural and anthropogenic sources. The PC3 element is Mg in the north sub-basin, and is perhaps related to aragonite precipitation and/or increased farming. Elevated Pb concentrations in uppermost sediments of both cores signify a recent regional/global increase in anthropogenic Pb release into the environment. After subtracting lithogenic Pb, derived from rock weathering and/or dust and normalized to the background immobile element Ti, results suggest that excess, anthropogenic Pb is transferred to the lake and its sediments predominantly via the atmosphere. This anthropogenic atmospheric Pb is comparable in magnitude and displays similar variation patterns in the two cores, reflecting regional atmospheric deposition and local erosion. The average anthropogenic Pb deposition rate in Lake Qinghai since the 1960s has been ~12.2 ± 3.5 mg/m²/a, comparable with atmospheric Pb fluxes reported for sites elsewhere in the northern hemisphere.     

Seasonal variations in heavy metals concentrations in Mt. Qomolangma Region snow

The concentrations of heavy metals Ba, Pb, Cu, Zn and Co in snow pit collected in September, 2005 from the accumulation area of the East Rongbuk Glacier (6523 m a.s.l.), which lies on the northern slope of Mt. Qomolangma, were determined by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations (pg/ml) of heavy metals are Ba2-227, Co2.8-15.7, Cu10-120, Zn29-4948 and Pb14-142, respectively. The δ18O was determined by MAT-252. The time period of the snow pit spans from autumn 2005 to summer 2004. Seasonal variations of the concentrations and δ18O are observed, of which Pb, Cu, Zn and Co are much lower in summer monsoon season than that in non summer monsoon season, suggesting that different sources of heavy metals contributed to the site. EFc (crustal enrichment factors) is Co3.6, Cu27, Pb33 and Zn180, respectively. Higher EFc values of Pb, Cu and Zn suggest that Pb, Cu especially Zn are mainly contributed by anthropogenic sources.     

The use of heavy metal concentrations and dendrochronology in the reconstruction of sediment accumulation, Ma a Panew River Valley, southern Poland

Heavy metal concentrations were investigated in overbank sediments of the Mala Panew River, southern Poland. Samples were collected from seven vertical profiles located within channel infills of a 20th century floodplain at three sites, each up to 50 m wide. In each profile, 15–24 samples were collected and analysed for Ba, Cd, Cu, Pb, and Zn. Sequential extraction of these elements was carried out in the 0.063-mm fraction of selected samples. Additionally, the age of the oldest trees growing close to the profiles has been used to estimate the initiation of sediment accumulation there. Ba, Cu, and Pb, which occur mostly in less mobile, moderately reducible, and residual fractions, were used for sediment dating. Zn and Cd, which in 50–75% occur in the mobile exchangeable fraction, were not suitable for dating. Correlation of Ba, Cu, and Pb concentrations in vertical profiles with changes in the load of effluents discharged to the river showed abrupt changes in the thickness of the strongly polluted sediments across the floodplains. A comparison of the relative changes between heavy metal peaks in sediments of similar age in the different profiles suggests a variable rate of downward metal migration. In general, none of the heavy metals investigated seems to have been mobilised within the stratigraphic layers above the water table. In layers located at stratigraphically lower levels, the Zn and Cd peaks seem to migrate several centimetres to several decimetres down in the profile. In profiles inundated for several weeks every year, Zn and Cd, as well as the relatively less mobile Ba, Cu, and Pb, have migrated downward by several decimetres. The investigation shows that frequent fluctuations of the water table have blurred the original depositional metal patterns of metal concentrations within a period of less than 40 years.     

湘江沉积物重金属元素环境地球化学特征

在前人研究的基础上,对湘江干流河道表层沉积物及入湖三角洲地区沉积物中的重金属富集特征、赋存状态等进行了总结;对湘江沉积物中重金属的污染来源进行了分析,湘江沉积物重金属的富集种类主要受流域富集矿产的控制,重金属污染主要是人为活动导致的点源污染集中和高排放引起的;另外,运用Hakanson潜在生态风险指数和地累积指数对湘江沉积物中重金属的潜在生态风险和污染程度进行了评价,结果显示Cd、Pb、As、Zn、Cu、Hg等重金属在湘江沉积物中存在不同程度的污染,其中Cd、Hg、As、Pb、Cu污染严重同时潜在生态危害也大,应引起重视。