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1.
The mineralogy of arsenic in uranium mine tailings at the Rabbit Lake In-pit Facility, northern Saskatchewan, Canada 总被引:3,自引:2,他引:3
A detailed investigation of the mineralogy of As in the tailings of the Rabbit Lake uranium ore processing facility was conducted.
The milling/ore extraction process was sampled at three different locations to obtain information about when, where and under
what condition secondary As phases form. These samples were compared with four samples of varying As content from the Rabbit
Lake in-pit tailings management facility (TMF). Up to 20% As in the tailings are present in primary minerals that reach the
tailings directly because they are not dissolved during the uranium extraction. The remaining 80% constitute As that was dissolved
during ore extraction and then re-precipitated before being discharged into the tailings pond. It was not possible to conclusively
identify any individual re-precipitated (secondary) As minerals in the Rabbit Lake TMF. Indirect evidence from sequential
extraction analyses suggests the presence of an amorphous Ca-As phase and a possible, but unlikely, minor amount of an amorphous
Fe-As phase. However, the close association between hydrous ferric oxide (HFO) and As could be clearly demonstrated. HFO was
identified to be 2-line ferrihydrite and its XRD pattern geometry indicates a substantial amount of adsorbed As. This is in
good agreement with SEM, TEM and sequential extraction analyses that all showed the close association of HFO and As.
Received: 14 February 2000 · Accepted: 9 May 2000 相似文献
2.
Enrichment of heavy metals in paddy crops irrigated by paper mill effluents near Nanjangud, Mysore District, Karnatake, India 总被引:1,自引:0,他引:1
M. S. Fazeli F. Khosravan M. Hossini S. Sathyanarayan P. N. Satish 《Environmental Geology》1998,34(4):297-302
Extensive irrigation by the effluents released from a paper mill near Nanjangud have led to the accumulation of heavy metals
in the soil and different parts of the paddy crops. In this paper, the physicochemical characteristics of paper mill effluents
and the accumulation of heavy metals (Cu, Zn, Pb, Co, Cd, Cr, and Ni) in the soil and different parts (root, leaf, and seed)
of the paddy crops growing in the irrigated area are described and compared with the soil and paddy crops irrigated by natural
waters (unpolluted). Chemical and biological oxygen demands of wastewater were found to be 437 and 1070 ppm respectively,
which are beyond the tolerance limits set by Indian standards. The total dissolved and suspended solids are 1754 and 900 ppm
respectively. The concentration of heavy metals (except Zn) in the seeds is remarkably less than that in the roots and leaves
of the paddy crops. The heavy metal uptake by plants shows the greatest accumulation of Cu, Cr, Co, and Pb in the roots; Cd
and Ni in the leaves; and Zn in the seeds of rice. The heavy metal content of the soil and their total uptake by paddy roots
has the relation: Pb>Zn>Cu>Cd and Pb>Cu>Zn>Cd. Survival of paddy crops irrigated by polluted waters indicates tolerance to
toxic heavy metals. In conclusion, since in many tropical countries the common diet of people is rice, the accumulation of
toxic heavy metals in rice may lead to health disorders.
Received: 18 July 1995 / Accepted: 24 February 1997 相似文献
3.
Time-of-flight laser-ionization mass spectrometry was applied to study the chemical composition of mineral particle surfaces
in a sulphide-rich mine-tailings impoundment. This surface-sensitive technique provides chemical information from surfaces
of irregularly shaped mineral particles (both conductive and insulators) less than 100 μm in diameter, which are considered
to be representative of particle surface coatings in the tailings pile (after drying). In addition, depth profiles in the
mineral particles were obtained. The combination of speed of analysis (1 min), small beam-diameter (2–4 μm), surface sensitivity
(2–10 nm), trace-element sensitivity, and capability to analyze rough surfaces makes this method useful as a complement to
studies of pore-water geochemistry and tailings mineralogy. As an example, the behavior of Pb and As in the Kidd Creek tailings
dam near Timmins, Ontario, Canada, was studied, using a combination of surface analyses, and pore-water geochemical data.
Received: 22 February 1995 / Accepted: 6 January 1996 相似文献
4.
Trace element concentrations in shallow marine sediments of the Buyat-Ratototok district of North Sulawesi, Indonesia, are
affected by submarine disposal of industrial gold mine tailings and unregulated dumping of tailings and wastewater from small-scale
gold mining using mercury amalgamation. Industrial mine tailings contained 590–690 ppm arsenic, 490–580 ppm antimony, and
0.8–5.8 ppm mercury. Tailings-affected sediment As and Sb concentrations were 20–30 times higher than in muddy sediments not
contaminated with tailings, and 50–60 times higher than pre-mining average. Highest mercury concentrations were observed in
sediments affected by small-scale mining using mercury amalgamation (5–29 ppm). Concentrations of most other trace elements
were comparable in sediments affected by both types of mining and were slightly higher than regional averages for sediments
collected before the onset of industrial mining. Elevated concentrations of both As and Sb in approximately equal proportions
suggest tailings dispersal of at least 3.5 km. Mercury released from artisanal gold mining dispersed up to 4 km from river
mouths. Slight increases in concentrations of non-mercury trace elements in areas affected by artisanal mining over pre-industrial
mining concentrations were probably caused by increased rates of erosion.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
5.
Portman Bay presents elevated quantities of metals and heavy metals in the sediments and rocky outcrops. The calcitic skeletons
of the sea urchins that live there present elevated concentrations of Mn, Fe, Zn, and Pb (249, 273, 32, and 59 ppm) in comparison
with control zones (beach of La Vila) where the concentrations for these elements are 5, 7, 8, and 2 ppm, respectively. Two
species of sea urchins have been studied: Paracentrotus lividus and Arbacia lixula. The different compositions between the plates and the spines of their skeletons have also been studied.
Received: 20 November 1995 · Accepted: 25 January 1996 相似文献
6.
Hydrological and geomorphological criteria to evaluate the dispersion risk of waste sludge generated by the Aznalcollar mine spill (SW Spain) 总被引:2,自引:0,他引:2
G. Benito Alfonso Benito-Calvo Francesc Gallart Juan Pedro Martín-Vide David Regües Ernest Bladé 《Environmental Geology》2001,40(4-5):417-428
Following the Aznalcóllar pyrite mine disaster (Seville, Spain) which caused the spilling of some 4.5?hm3 of acid water, the floodplains of the rivers Agrio and Guadiamar were rapidly cleaned of waste sludge. However, despite the efficiency of cleaning activities, there is still evidence of a fine superficial layer of sludge and some soil contamination, with the consequent risk of remobilisation of the pollutants by water erosion. There is much concern that these contaminated sediments may affect the precious ecosystems of the Doñana National Park and the Guadalquivir marshlands. This report describes the evaluation of the risk of mobilisation of the waste sludge through (1) detailed geomorphological analysis, indicating potential areas of erosion-sedimentation on the floodplains of the rivers Agrio and Guadiamar, and predicted dynamics of the waste sludge, and (2) evaluation of the potential dispersion of the waste sludge provoked by future flood events, including hydraulic calculations to model channel flow and the analysis of the texture of the sludge to obtain critical transport and sedimentation values. Findings suggest that the waste sludge is likely to be transported and deposited within the Doñana National Park during future flood events. 相似文献
7.
A. M. Caredda A. Cristini C. Ferrara M. F. Lobina M. Baroli 《Environmental Geology》1999,38(2):91-100
We have studied sediments of the Piscinas beach (SW Sardinia, Italy), which is supplied by two streams that wash mine dumps
of abandoned lead and zinc mines at Montevecchio and Ingurtosu, situated inland from the supply basin of the beach itself.
A study of the texture, mineralogy and geochemistry of the sediments was conducted for the purpose of assessing the possible
influence of the mine waste on the composition of the sediments, looking for any anomalous enrichments in heavy metals. Furthermore,
to evaluate and quantify metal release into the sea, samples of Posidonia oceanica, a bioaccumulator marine plant, were also examined. The results indicate that the distribution of heavy metals in the foreshore
sediments is particularly affected by the contribution of the streams, while in the shoreface the distribution is affected
by the currents that disperse the sediments both out to sea and southwards. The metal contents of the Posidonia oceanica are correlated with the different stages of activity of the mines.
Received: 28 January 1998 · Accepted: 22 April 1998 相似文献
8.
P. J. Henderson I. McMartin G. E. Hall J. B. Percival D. A. Walker 《Environmental Geology》1998,34(1):39-58
Trace element geochemistry of humus (<0.425 mm) and till (<0.002 mm) collected in the Flin Flon-Snow Lake area, northern
Manitoba and Saskatchewan, provides a regional context for assessing smelter contamination in the environment. The area includes
a Cu-Zn smelter known to discharge As, Cd, Cu, Fe, Hg, Pb, and Zn. In this study, sequential extraction analyses, scanning
electron microscopy and x-ray diffraction analyses were used on a suite of samples to determine: (1) the chemical and physical
characteristics of heavy metals in surficial sediments related to distance from the smelter, (2) criteria for assessing the
relative contribution of these metals from natural and anthropogenic sources, and (3) the potential of these metals for remobilization
in the environment.
Humus geochemistry reflects the anthropogenic and natural component of heavy metal concentrations. Smelter-related elements
show anomalously high values adjacent to the smelter, decreasing with distance until background values are reached at 70–104 km,
depending on the element. In humus, Zn is associated primarily with labile phases; Hg with non-labile phases. Adjacent to
the smelter, high proportions and concentrations of Zn and Hg in non-labile phases, indicative of smelter-derived particulates,
are confirmed by SEM examination. The particles occur as spheres, irregular grains, and with organics. With increasing distance
from the smelter, the geochemical response to bedrock composition is more obvious than the anthropogenic input.
Till geochemistry reflects the natural variation imposed by bedrock composition. At highly contaminated sites (<3 km from
the smelter), increased percentages of smelter-related elements in labile phases suggests heavy metals are leached from humus
to the underlying sediment.
Received: 5 November 1996 · Accepted: 31 March 1997 相似文献
9.
D. Ciszewski 《Environmental Geology》1997,29(1-2):50-57
The influence of sources of effluents on pollution of bottom sediments of the small Chechło River (23 km long, mean discharge
1.5 m3 s–1) in southern Poland was examined through analysis of heavy metals distribution in transverse and longitudinal cross sections.
Underground waters from a Pb–Zn mine cause very high concentrations of Zn, Cd, and Pb in both fractions investigated (<1 mm
and <0.063 mm) of sediments in the active channel zone, whereas sedimentation of huge amounts of suspended matter discharged
from oil refinery cause concentrations of heavy metals in fine fractions rather uniform in cross sections. In the lowest reach,
with relatively reduced contamination, the highest concentration both in fine and coarse fractions occurs close to the river
banks and in the deepest points of the channel. The lowest concentrations have been found at the points of strongest reworking
and accumulation of sandy material in the riverbed.
Received: 25 April 1995 · Accepted: 11 September 1995 相似文献
10.
Removal of selected heavy metals from aqueous solutions using a solid by-product from the Jordanian oil shale refining 总被引:2,自引:0,他引:2
The potential use of treated solid by-product of oil shale to treat aqueous solutions containing several heavy metals, i.e.,
Cd(II), Cu(II), Cr(III), Ni(III), Pb(II) and Zn(II), was explored. Different experimental approaches including equilibrium
batch mode experiments and X-ray fluorescence (XRF) were used to explore the feasibility of this material as a cheap adsorbent
for the removal of these heavy metals from predetermined solutions. Results indicate that the solid by-product of oil shale
removes Cd(II), Cu(II), Ni(II), and Pb(II), from aqueous solutions by adsorption, but did not remove the other heavy metals
investigated in this study.
Received: 20 April 1998 · Accepted: 20 November 1998 相似文献
11.
Toxic metal contamination in the lateral lakes of the Coeur d'Alene River valley, Idaho 总被引:3,自引:0,他引:3
K.F. Sprenke W.C. Rember S.F. Bender M.L. Hoffmann F. Rabbi V.E. Chamberlain 《Environmental Geology》2000,39(6):575-586
The 11 lateral lakes of Coeur d'Alene River valley in northern Idaho have received heavy metal contamination from over a
century of upstream mining. The lateral lakes lie within the flood plain of the Coeur d'Alene River, and in their bottom sediments
is preserved a stratigraphic record of the upstream mining operations. To characterize the contaminated sediments in the lateral
lakes, sampling techniques, including the Livingston piston corer and the Huttenen freeze box, have been developed by Quaternary
geologists to preserve the vertical stratigraphy in the samples. From 26 cm to over 55 cm of undisturbed tailing sediments,
commonly with “varve-like” features, have been found in each of the lateral lakes, with maximum concentrations by weight of
lead at 3.8%, zinc at 3.4%, arsenic at 340 mg/kg, cadmium at 120 mg/kg and mercury at 7 mg/kg. The contamination in the lakes
appears to be restricted to the shallow subsurface and heavy metal concentrations generally drop to background levels within
a meter of depth.
Received: 22 May 1998 · Accepted: 21 September 1998 相似文献
12.
Assessment of natural attenuation of aromatic hydrocarbons in groundwater near a former manufactured-gas plant, South Carolina, USA 总被引:1,自引:0,他引:1
J. E. Landmeyer F. H. Chapelle M. D. Petkewich P. M. Bradley 《Environmental Geology》1998,34(4):279-292
Shallow, anaerobic groundwater near a former manufactured-gas plant (MGP) in Charleston, South Carolina, USA, contains mono-
and polycyclic aromatic hydrocarbons (MAHs and PAHs, respectively). Between 1994 and 1997, a combination of field, laboratory,
and numerical-flow and transport-model investigations were made to assess natural attenuation processes affecting MAH and
PAH distributions. This assessment included determination of adsorption coefficients (K
ad
) and first-order biodegradation rate constants (K
bio
) using aquifer material from the MGP site and adjacent properties. Naphthalene adsorption (K
ad
=1.35×10–7 m3/mg) to aquifer sediments was higher than toluene adsorption (K
ad
=9.34×10–10 m3/mg), suggesting preferential toluene transport relative to naphthalene. However, toluene and benzene distributions measured
in January 1994 were smaller than the naphthalene distribution. This scenario can be explained, in part, by the differences
between biodegradation rates of the compounds. Aerobic first-order rate constants of 14C-toluene, 14C-benzene, and 14C-naphthalene degradation were similar (–0.84, –0.03, and 0.88 day–1, respectively), but anaerobic rate constants were higher for toluene and benzene (–0.002 and –0.00014 day–1, respectively) than for naphthalene (–0.000046 day–1). Both areal and cross-sectional numerical simulations were used to test the hypothesis suggested by these rate differences
that MAH compounds will be contained relative to PAHs. Predictive simulations indicated that the distributions of toluene
and benzene reach steady-state conditions before groundwater flow lines discharge to an adjacent surface-water body, but do
discharge low concentrations of naphthalene. Numerical predictions were "audited" by measuring concentrations of naphthalene,
toluene, and benzene at the site in early 1997. Measured naphthalene and toluene concentrations were substantially reduced
and the areal extent of contamination smaller than was both observed in January 1994 and predicted for 1997. Measured 1997
benzene concentrations and distribution were shown to be relatively unchanged from those measured in 1994, and similar to
predictions for 1997.
Received: 26 June 1997 · Accepted: 25 August 1997 相似文献
13.
Dreissena polymorpha is an exotic freshwater bivalve species which was introduced into the Great Lakes system in the fall of 1985 through the release
of ballast water from European freighters. Utilizing individual growth rings of the shells, the stable isotope distribution
(δ18O and δ13C) was determined for the life history of selected samples which were collected from the western basin of Lake Erie. These
bivalves deposit their shell in near equilibrium with the ambient water and thus reflect any annual variation of the system
in the isotopic records held within their shells. Observed values for δ18O range from -6.64 to –9.46‰ with an average value of –7.69‰ PDB, while carbon values ranged from –0.80 to –4.67‰ with an
average value of –1.76‰ PDB. Dreissena polymorpha shells incorporate metals into their shells during growth. Individual shell growth increments were analyzed for Pb, Fe, Mg,
Mn, Cd, Cu, and V concentrations. The shells show increased uptake of certain metals during periods of isotopic enrichment
which correspond with warmer water temperatures. Since metals are incorporated into the shells, the organism may be useful
as a biomonitor of metal pollution within aquatic environments.
Received: 31 October 1996 · Accepted: 21 May 1997 相似文献
14.
Mercury in lake sediments of the Precambrian Shield near Huntsville, Ontario, Canada 总被引:10,自引:0,他引:10
P. E. Rasmussen D. J. Villard H. D. Gardner J. A. C. Fortescue S. L. Schiff W. W. Shilts 《Environmental Geology》1998,33(2-3):170-182
Long sediment cores (>1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for
mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment
Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the
whole of Canada. Strong areal correlations between Hg concentrations and LOI (r
2
=0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration
profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals
in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (>20 cm) was found to mirror
the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r
2
=0.85;n=25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences
in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in smallmouth
bass normalized to 35 cm length (R
2
=0.63;n=15 lakes). The latter relationship suggests that smallmouth bass and lake sediment indicators provide mutually supportive
information regarding Hg loading to the lacustrine environment from geological sources in the watershed system.
Received: 31 October 1996 · Accepted: 27 May 1997 相似文献
15.
污染指数法用于碳酸盐型尾矿(指富含碳酸盐的金属硫化物尾矿)重金属污染评价存在局限性。通过研究湖南黄沙坪铅锌矿尾矿中Zn、Cd、Pb、Cu及As等元素赋存状态(包括尾矿铅垂剖面结构、元素总量及其水溶态分量的分布和影响因素以及次生胶结物纤铁矿与元素结合作用等),结合元素迁移活性(水溶取率)和污染指数分析,得出如下结论:1该尾矿发育层(带)状结构,即浅表胶结硬化层(中褐色,氧化/酸化)→中部弱胶结层(黄褐色,次氧化)→深部尾砂层(橄榄灰-绿灰色,弱/未氧化),重金属元素在尾矿中浅部的胶结层中富集;2纤铁矿为主要次生胶结物,纤铁矿与元素结合作用的差异性影响尾矿中元素的稳定性/迁移活性;3尾矿中Zn、Cd的迁移活性和污染指数均较高,是主要的污染因子,应重点防控;As的污染指数虽高,但因其迁移活性较低,仍属次要污染因子;Pb、Cu的迁移活性及污染指数均较低,对环境影响可能较小。采用污染指数与元素赋存状态分析相结合的方法,对(黄沙坪)碳酸盐型尾矿的重金属污染危险进行综合评价,可避免污染指数法的局限性。 相似文献
16.
Magnetic susceptibility measurements were conducted on 24 vibrocores obtained from an area located off the northeastern coast
of Lantau Island in Hong Kong. High intensities of magnetic susceptibility were detected in the uppermost sections of the
majority of the cores. Several magnetic parameters measured for one of the cores suggest that the variations in the magnetic
characteristics over depth are mainly due to varying concentrations of the magnetic minerals. Since a strong correlation has
been found between magnetic susceptibility and the heavy metals Pb, Cu, Zn and Cr, an anthropogenic contamination origin is
thought to be the cause. The present study shows that magnetic susceptibility is a fast, inexpensive and non-destructive method
for the detection and mapping of contaminated sediments.
Received: 12 August 1997 · Accepted: 18 November 1997 相似文献
17.
Heavy metals in freshly deposited sediments of the Gomati River (a tributary of the Ganga River): effects of human activities 总被引:10,自引:0,他引:10
The concentrations of various metals (Cr, Cu, Co, Fe, Mn, Ni, Pb, Zn, and Cd) were determined in recently deposited surface
sediments of the Gomati River in the Lucknow urban area. Markedly elevated concentrations (milligrams per kilogram) of some
of the metals, Cd (0.26–3.62), Cu (33–147), Ni (45–86), Pb (25–77), and Zn (90–389) were observed. Profiles of these metals
across the Lucknow urban stretch show a progressive downstream increase due to additions from 4 major drainage networks discharging
the urban effluents into the river. The degree of metal contamination is compared with the local background and global standards.
The geoaccumulation index order for the river sediments is Cd>Zn>Cu>Cr>Pb. Significant correlations were observed between
Cr and Zn, Cr and Cu, Cu and Zn and total sediment carbon with Cr and Zn. This study reveals that the urbanization process
is associated with higher concentrations of heavy metals such as Cd, Cu, Cr, Pb, and Zn in the Gomati River sediments. To
keep the river clean for the future, it is strongly recommended that urban effluents should not be overlooked before their
discharge into the river.
Received: 16 February 1996 · Accepted: 29 February 1996 相似文献
18.
A comparative mineralogical and geochemical study of sulfide mine tailings at two sites in New Mexico, USA 总被引:5,自引:0,他引:5
A comparative study of sulfide mine tailings from two sites near Silver City in southwest New Mexico has shown the need for environmental monitoring in a geological context. The Cyprus-Piños Altos and Cleveland deposits consist of Cu and Zn skarn mineralization in the Piños Altos Mountains of New Mexico. Primary ore minerals in both deposits include chalcopyrite, sphalerite, and galena. The Cyprus-Piños Altos Mine ceased operation in 1995 and the Cleveland Mill closed in 1950. The deposits have similar mineralogical characteristics; however, the tailings are different in terms of age, degree of oxidation and method of disposal. The Cyprus-Piños Altos tailings (CPAT) are stored in a lined, bermed impoundment. They are dominantly water-saturated and exhibit no secondary-phase formation. The grains are not cemented and show no evidence of primary-mineral dissolution. The geochemical data show a predominantly primary signature. The tailings pond water is neutral to slightly alkaline (pH?from 7 to 8.3), partly as a result of processing methods. The Cleveland mill tailings (CMT) were deposited in a valley at the headwaters of an ephemeral stream. They are highly oxidized and differentially cemented. They have undergone numerous wet/dry cycles resulting in extensive oxidation. Secondary minerals predominate, and consist mainly of jarosite, goethite, hematite, and Fe-oxyhydroxides and -oxyhydroxysulfates. The pH of the stream draining the CMT is as high as 2.15. Maximum metal contents in the stream immediately downstream from the tailings are 5305?ppm Zn, 454?ppm Cu, 1.16?ppm Pb, 17.5?ppm Cd, 1.4?ppm As, and 0.01?ppm Hg. 相似文献
19.
Mine waste dumps and heavy metal pollution in abandoned mining district of Boccheggiano (Southern Tuscany, Italy) 总被引:11,自引:1,他引:11
M. Benvenuti I. Mascaro F. Corsini P. Lattanzi P. Parrini G. Tanelli 《Environmental Geology》1997,30(3-4):238-243
Mining activity in the Boccheggiano-Fontalcinaldo area (Southern Tuscany) dates back at least to the 16th century AD and
lasted up to very recent times. Copper-rich hydrothermal veins, massive pyrite deposits, and their gossans were exploited.
Two mine waste dumps (Fontalcinaldo, Fontebona), one flotation tailings impoundment (Gabellino), and one roasting/smelting
waste dump (Merse-Ribudelli) in the study area were selected to ascertain the environmental effects of such protracted mining
activity. Primary waste mineralogy is mainly characterized by pyrite, gypsum, quartz, carbonates, chlorites, and micas. Secondary
oxidation mineralogy includes Fe and Cu sulfates and hydroxy sulfates, Cu carbonates, Fe and Al oxyhydroxides, and other phases
[neogenic cassiterite at Fontalcinaldo; probable calkinsite, (Ce,La)2(CO3)3· 4H2O, at Fontebona]. Mine waste samples show extremely variable contents of toxic elements (Cu, Pb, Zn, Bi, Cd, As), with average
values in the order of hundreds to thousands of parts per million (except for Bi and Cd). In some samples, the abundance of
proper minerals of these metals cannot account for the entire metal load. Conceivably, either solid solution substitutions
or adsorption processes contribute to the intake of released metals into newly formed minerals. Release and transport of pollutants
was affected to variable degrees by acid-neutralization processes. The highest metal and acid concentrations occur close to
the investigated wastes and rapidly decrease moving downstream some hundreds of meters or less, with the partial exception
for Mn and Fe. Other than dilution effects, this phenomenon may be ascribed to metal adsorption and precipitation of solid
phases.
Received: 16 April 1995 · Accepted: 14 December 1995 相似文献
20.
Distribution and fractionation of heavy metals in the surface sediments of the Ganges- Brahmaputra-Meghna river system in the Bengal basin 总被引:1,自引:0,他引:1
The lower Ganges-Brahmaputra-Meghna (G-B-M) drainage basin occupies the total Bengal Basin, which is one of the unique basins
of the world because of its location and size, density of population, and catastrophic deposition of sediments. The increased
heavy metal concentration in the 63 m fraction of surface sediments shows similarity among major segments of the G-B-M system
in the basin, which reflects the homogenization of lithologic and chemical diversity of the greater denudation regime by the
river processes. The differences in heavy metal concentation in the lower G-B-M system with that of its upper and middle counterpart
is mainly related to the contrast between Himalayan rivers and the other major South Asian rivers, and may be due to the geological
differences of their denudation regime. Heavy metals in the Lower G-B-M system have an affinity towards the clay fraction
of the sediments. The correlation matix of heavy metals in the lower Brahmaputra and Meghna suggests the importance of Fe-Mn
oxyhydroxides in their accumulations. Iron, Ti and Mn are higher in the Meghna main channel, Zn is higher in the Meghna tributaries,
and Cr is higher in both the Brahmaputra and Meghna compared to the value for standard shale. The enrichment factor is ≤1
for most of the metals except Mn which is relatively higher in the Meghna and lower Ganges main channels. The geoaccumulation
index (Igeo) for most of the heavy metals lies below grade zero, suggesting unpolluted sediment quality. The lower Ganges system shows
relatively higher concentration in the nondetrital fraction of heavy metals, probably due to the presence of petroleum refinery,
industrial and mining effluents, and agricultural runoff in the drainage basin. The relative uniformity in concentration of
heavy metals in vertical profiles may be due to the uniformity in sediment grain size and catastrophic deposition of sediments,
where the time period represented by the vertical sediment column is not enough to reflect the cultural accumulation of heavy
metals. The Bengal basin thus represents a relatively unperturbed alluvial basin with regards to heavy metal pollution.
Received: 21 July 1997 · Accepted: 13 October 1997 相似文献