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1.
太湖MS岩芯重金属元素地球化学形态研究 总被引：21，自引：4，他引：17
采用BCR三步提取法对太湖MS岩芯沉积物中Cu、Fe、Mn、Ni、Pb和Zn等6种重金属元素的化学形态进行了研究.结果表明,有效结合态的Cu、Ni和Pb主要以有机物及硫化物结合态、Fe-Mn氧化物结合态存在,Fe和Zn主要以Fe-Mn氧化物结合态存在,Mn主要以可交换态及碳酸盐结合态存在;Fe-Mn氧化物结合态的Ni、Pb和Zn与可还原态的Mn有较好的正相关关系,有机物及硫化物结合态的Cu、Mn、Ni、Pb和Zn与有机碳含量有较好的正相关关系;重金属形态分布体现了重金属元素地球化学性质的差异,以及重金属形态含量与沉积物理化性质的关系.沉积岩芯重金属元素形态垂向变化规律及次生相富集系数表明,Cu、Mn、Ni、Pb和Zn在沉积岩芯13～4 cm有效结合态含量较稳定,为自然沉积;4～0 cm有效结合态含量明显升高,存在一定程度的人为污染.根据137Cs测年结果判断,沉积岩芯Cu、Mn、Ni、Pb和Zn等重金属污染开始于20世纪70年代末期,主要污染元素及污染历史与太湖流域污染工业类型及经济发展阶段相吻合. 相似文献
2.
Geochemical fractionation of heavy metals in Chilka Lake (east coast of India)—a tropical coastal lagoon 总被引：1，自引：0，他引：1
Chilka lake, the largest coastal lagoon of Asia is one of the most dynamic ecosystems along the Indian coast. Historically the lagoon has undergone a considerable reduction in surface area due, in part, to input from natural processes but mostly due to human activities. The purpose of this investigation is to document the heavy metals' affinity for specific geochemical phases in the recently deposited sediments in the lagoon. Thirty-three samples were collected and analyzed for different geochemical phases of Fe, Mn, Cu, Cr, Ni, Pb, and Zn utilizing a sequential extraction scheme. In the nonlithogenous fraction, the exchangeable fraction was not geochemically significant, having <2% of the total metal concentration for all the elements. However, the carbonate fraction contained the following percentages of the total concentration: <1% Fe, 13% Mn, 6% Cu, 4% Cr, 8% Ni, 13% Pb, and 12% Zn, suggesting the detrital origin of the sediments. Reducible and organic matter-bound fractions were the significant phases in the nonlithogenous fraction, containing 9% Fe, 16% Mn, 15% Cu, 16% Cr, 16% Ni, 14% Pb, and 14% Zn in the former and 4% Fe, 3% Mn, 17% Cu, 3% Cr, 14% Ni, 15% Pb, and 14% Zn in the latter. The phenomenon has been attributed to the scavenging affinity of Fe-Mn oxides and affinity for sorption into organic matter of the lagoon sediments. The lithogenous, residual fraction generally considered as a guide for natural background values was determined to contain 87% Fe, 67% Mn, 61% Cu, 77% Cr, 61.3% Ni, 56% Pb, and 60% Zn of the total concentrations. 相似文献
3.
对拜仁达坝铅锌矿矿集区3个多金属矿区的3个土壤粒级样品中Zn、Pb、Cu、Ag 4种主要成矿元素的7种赋存形式(水溶态、离子交换态、碳酸盐结合态、有机质结合态、铁锰氧化物结合态、硫化物结合态和残渣态)进行了测定。研究结果表明:1银都矿区土壤中Zn、Pb和Ag浓度最高,而道伦达坝矿区土壤中Cu的浓度最高;2拜仁达坝矿集区土壤中Zn、Pb和Cu主要以残渣态形式赋存,而Ag主要以铁锰氧化物结合态和硫化物结合态形式赋存;3拜仁达坝矿集区Zn、Pb和Cu元素在3个土壤粒级中的各个赋存形式所占的比例略有差别,但总体上大致相同,而Ag元素的赋存状态在3个土壤粒级的差异较大;4 3个矿区土壤中水溶态、离子交换态、碳酸盐结合态和有机质结合态的Zn和Pb差别不大;铁锰氧化物结合态、硫化物结合态和残渣态的Zn和Pb,以及Cu和Ag的7个赋存状态在3个矿区的差别较大。 相似文献
4.
恬矿库周围土壤中重金属存在形态特征研究 总被引：48，自引：4，他引：44
通过对大冶铜绿山铜铁矿尾矿库周围土壤中重金属形态分析实验,研究了重金属各种形态在土壤中的分布特征。由对比实验可知,尾矿库周围土壤中Ｃｕ、Ｐｂ、Ｚｎ、Ｃｄ等重金属含量都显著地高于对照样品,书经受到重金属的严重污染。土壤中重金属形态分布征为：ｗ（Ｃｒ、Ｚｎ、Ｆｅ）;可变换态〈碳酸盐态〈有机态〈铁锰氧化态〈残渣态;ｗ（Ｃｕ、Ｐｂ）：可变换态〈碳酸盐态〈有机态〈残渣态〈铁锰氧化态;ｗ（Ｃｄ）：残渣态,有机 相似文献
5.
Sediment core was collected from Tokyo Bay. The surface enrichment of heavy metals due to human activities is recognized in the sediment. Partitioning of Cu, Zn, Fe and Mn into sulfide, carbonate, organic and silicate fractions has been determined with selective chemical leaching techniques for 210Pb-dated sediment core samples. The heavy metal contents of silicate fractions without exchangeable sites are almost constant against depth in sediment core. However, the Cu, Zn and Mn contents of sulfide, carbonate and organic fractions vary with depth. Most Cu and Zn in the polluted sediment layer are associated with the iron sulfide fraction. 相似文献
6.
Axial surveys were performed in the two river tributaries of the Cochin estuary, SW India during November 1988. Surficial sediments were subjected to sequential chemical extractions to delineate five metal fractions, namely, exchangeable, carbonate bound, easily reducible, organic/sulfide bound, and residual. The results indicated selective accumulation of Mn and Ni in carbonate bound and organic/sulfide forms, along with marginal amounts of Co in the exchangeable fraction. Large portions of Fe and Cr occurred in the residual fraction, whereas composite fractionation of Zn species was noticed. The exchangeable fractions of Fe and Cr as well as of easily reducible cobalt were below detection limits. The levels of Cr and Zn indicate anthropogenic inputs in this estuary, whereas Co and Ni show regional contamination exceeding natural levels. The analytical speciation procedure helps to deduce the sedimental diagenetic processes in the estuarine environment. 相似文献
7.
Study on effective species of heavy metals in lacustrine sediment core from Xijiu Lake,Taihu Lake catchment,China 总被引：2，自引：1，他引：1
Zhaobin Sun Yanhong Wu Shuchun Yao Enfeng Liu Fuchun Li 《Environmental Earth Sciences》2009,59(2):371-377
The BCR sequential extraction procedure is applied to probe into the speciation distribution of heavy metals (Cd, Cr, Zn,
Cu and Pb) in lake sediments of Core XJ2 in Xijiu Lake, Taihu Lake catchment, China. The results showed that the effective
species concentration of this five heavy metal elements increased obviously during the past century, the proportions of organic/sulphide
fractions of Zn, Cu and Pb decreased while the Fe–Mn oxide fractions increased, and the proportion of Fe–Mn oxide fractions
of Cd decreased while the exchangeable and carbonate fractions increased. The concentrations of exchangeable and carbonate
fractions of these five elements were increased in the past century, especially the proportions of these fractions of Cd,
Zn, Cu and Pb increased prominently. These changes could be attributed to the anthropogenic pollution. Since the changes of
the heavy metal concentrations were corresponding to the history of human activities, especially the industry development,
within the catchment. 相似文献
8.
Sediment samples were collected from six springs draining the karst aquifer at Fort Campbell, Kentucky/Tennessee. These were analyzed by ICP-MS following an extraction procedure that separates the metals into exchangeable, carbonate, oxide, organic and residual fractions. Aluminum and iron are primarily present in the residual fraction while manganese may be dominantly in either the oxide or carbonate fraction. The redox-sensitive metals (Fe and Mn) have the greatest fractional distribution in the spring with the thickest sediments. Trace metals detected include Cr, Cd, Ni, Pb, and Zn in the range of a few to 200 mg/kg. In Beaver Spring, nickel is distributed between the exchangeable, carbonate and organic fractions, while in Gordon Spring, nickel is largely residual. Chromium is almost entirely associated with the organic fraction in Beaver Spring while it is largely residual in Gordon Spring. 相似文献
9.
Distribution and enrichment of heavy metals in a sediment core from the Pearl River Estuary 总被引：5，自引：1，他引：4
Baolin Liu Ke Hu Zhenglong Jiang Juan Yang Ximing Luo Aihua Liu 《Environmental Earth Sciences》2011,62(2):265-275
A sediment core collected from coastal zone near the Qiao Island in the Pearl River Estuary was analyzed for total metal concentrations,
chemical partitioning, and physico-chemical properties. Three vertical distribution patterns of the heavy metals in the sediment
core were identified, respectively. The dominant binding phases for Cu, Pb, Cr, and Zn were the residual and Fe/Mn oxides
fractions. Cd in all sediments was mainly associated with exchangeable fraction. Influences of total organic carbon content
and cation exchange capacity on the total concentrations and fractions of almost all the metals were not evident, whereas
sand content might play an important role in the distributions of residual phases of Cr, Cu, Pb, and Zn. In addition, sediment
pH had also an important influence on the Fe/Mn oxides, organic/sulfide and residual fractions of Cr, Cu, and Zn. Contamination
assessment on the heavy metals in the sediment core adopting Index of Geoaccumulation showed that Cr, V, Be, Se, Sn, and Tl
were unpolluted, while Cu, Ni, Pb, Zn, Cd, and Co were polluted in different degrees throughout the core. It was remarkable
that the various pollution levels of the metals from moderate (for Cu, Pb, and Zn) to strong (for Cd) were observed in the
top 45 cm of the profiles. The relative decrease of the residual fraction in the upper 45 cm of the core is striking, especially
for Zn and Cu, and, also for Pb, and Cr. The change in fraction distribution in the upper 45 cm, which is very much contrasting
to the one at larger depths, confirms that the residual fraction is related to the natural origin of these metals, whereas
in the upper part, the non-residual fractions (mainly the Fe/Mn oxides fraction) are increased due to pollution in the last
decade. The possible sources for Cu, Pb, Zn, and Cd contaminations were attributed to the increasing municipal and industrial
wastewater discharges, agricultural runoff, atmospheric inputs, and runoff from upstream mining or smelting activities, which
may be associated with an accelerating growth of economy in the Pearl River Delta region in the past decade. 相似文献
10.
Ibtehal Fathy Mohamed 《Arabian Journal of Geosciences》2013,6(11):4145-4153
The heavy metal contents of Mn, Ni, Cu, Zn, Cr, Co, Pb, Cd, Fe, and V in the surface sediments from five selected sites of El Temsah Lake was determined by graphite furnace atomic absorption spectrophotometer. Geochemical forms of elements were investigated using four-step sequential chemical extraction procedure in order to identify and evaluate the mobility and the availability of trace metals on lake sediments, in comparison with the total element content. The operationally defined host fractions were: (1) exchangeable/bound to carbonate, (2) bound to Fe/Mn oxide, (3) bound to organic matter/sulfides, and (4) acid-soluble residue. The speciation data reveals that metals Zn, Cd, Pb, Ni, Mn, Cu, Cr, Fe, and V are sink primarily in organic and Fe–Mn oxyhydroxides phases. Co is mainly concentrated in the active phase. This is alarming because the element is enriched in Al Sayadin Lagoon which is still the main site of open fishing in Ismailia. Average concentration of the elements is mostly above the geochemical background and pristine values of the present study. There is a difference on the elemental composition of the sediment collected at the western lagoon (Al Sayadin Lagoon), junction, the shoreline shipyard workshops, and eastern beach of the lake. Depending upon the nature of elements and local pollution source, high concentration of Zn, Pb, and Cu are emitted by industrial wastewater flow (shoreline workshops), while sanitary and agricultural wastewater (El Bahtini and El Mahsama Drains) emit Co and Cd in Al Sayadin Lagoon. On the other hand, there is a marked decrease in potentially toxic heavy metal concentrations in the sediments at the most eastern side of the lake, probably due to the successive sediment dredging and improvements in water purification systems for navigation objective. These result show that El Temsah receives concentrations in anthropogenic metals that risk provoking more or less important disruptions, which are harmful and irreversible on the fauna and flora of this lake and on the whole ecobiological equilibrium. 相似文献
11.
以深港西部通道填海区淤泥为研究对象,研究了重金属的化学形态特征,分析了填海工程活动带来的填海区地下水物理化学条件变化对重金属各个形态的影响。结果表明:除残留态外,填海区重金属存在形态主要为铁锰结合态、碳酸盐结合态和硫化物及有机结合态,其中,Pb和Ni以铁锰氧化物结合态和碳酸盐结合态为主,Cu以碳酸盐结合态和有机结合态为主,Zn以有机结合态和铁锰氧化物结合态为主,而Cd则以碳酸盐结合态为主。各金属在深港西部通道填海区淤泥的潜在迁移能力序列如下:Pb(39.68%)>Cu(31.59%)>Zn(20.49%)>Cd(12.80%)>Ni(10.98%)。 相似文献
12.
The distribution of Si, Al, Fe, Mn, Cu, Zn, Ni and Cr in different grain-size fractions and geochemical association of Fe,
Mn, Cu and Zn with <63-μm size fraction of bed sediments of Damodar River has been studied. In general, concentrations of
heavy metals tend to increase as the size fractions get finer. However at two sites, near mining areas, the coarser particles
show similar or even higher heavy metal concentrations than finer ones. The higher residence time and/or presence of coarser
particles from mining wastes are possibly responsible for higher metal content in the coarser size fractions. The chemical
fractionation study shows that lithogenic is the major chemical phase for heavy metals. Fe and Mn are the major elements of
the lithogenic lattice, constituting 34–63% and 22–59%, respectively, of total concentrations. Fe-Mn oxide and organic bound
fractions are significant phases in the non-lithogenic fraction. The carbonate fraction is less significant for heavy metal
scavenging in the present environment and shows the following order of abundance Zn>Cu>Mn>Fe. The exchangeable fraction of
the Damodar sediments contains very low amounts of heavy metals suggesting poor bioavailability of metals.
Received: 18 August 1998 · Accepted: 1 December 1998 相似文献
13.
The water ecosystem of the Vyshny Volochek Reservoir is characterized based on the study of the distribution of heavy metals speciations in the solid phase and pore waters of bottom sediments. Using the sequential extraction procedure, it is shown that Mn is mainly present in exchangeable and carbonate-bound forms; significant roles for Fe, Zn, Pb, and Co are played by forms that are bound to iron and manganese hydroxides and Cu and Ni are mainly bound to organic matter. Thermodynamic calculations have established the prevailing share of the following forms in pore waters: free ions for Zn, Ni, Co, and Cd, carbonate complexes for Pb, and fulvic complexes for Cu. It has been revealed that the speciation forms of heavy metals in bottom sediments depend on the lithological features and content of organic matter in sediments. 相似文献
14.
A field study was conducted to clarify the effect of rhizosphere processes on the accumulation and partitioning of heavy metals
(Pb, Zn, Cu, Cr, Cd and Ni) in mangrove sediments. Metals were fractionated by a sequential extraction procedure into three
chemically distinct fractions: water soluble, exchangeable and carbonate bound (B1), Fe–Mn oxide bound (B2), and organic and
sulfide bound (B3). Results indicate that rhizosphere processes tend to increase the metal concentrations in the rhizosphere
sediments. However, plant uptake may result in the decrease of the metal concentrations in the rhizosphere sediments when
the metal concentrations are relatively low in the bulk sediments. Compared with the bulk sediments, the rhizosphere sediments
have low concentrations of heavy metals in the B1 and B2 fractions and high concentrations in the B3 fraction. Either an increase
or decrease in the residual fraction of heavy metals in the rhizosphere sediments may appear, depending on whether the formation
of the refractory metal-organic compounds or the activation of the residual fractions dominates. Results also indicate that
mangrove plants absorb and store non-essential metals in the perennial tissues, thus reducing the export of non-essential
metals via leaf litter transport. Mangrove plants are excellent candidates for phytostabilization of heavy metals in intertidal
substrates. 相似文献
15.
Distribution and immobilization of heavy metals in Pliocene aquifer sediments in Wadi El Natrun depression, Western Desert 总被引：2，自引：0，他引：2
The Pliocene aquifer receives inflow of Miocene and Pleistocene aquifer waters in Wadi El Natrun depression. The aquifer also receives inflow from the agricultural activity and septic tanks. Nine sediment samples were collected from the Pliocene aquifer in Wadi E1 Natrun. Heavy metal (Cu, Sr, Zn, Mn, Fe, Al, Ba, Cr, Ni, V, Cd, Co, Mo, and Pb) concentrations of Pliocene aquifer sediments were investigated in bulk, sand, and mud fractions. The determination of extractable trace metals (Cu, Zn, Fe, Mn, and Pb) in Pliocene aquifer sediments using sequential extraction procedure (four steps) has been performed in order to study environmental pathways (e.g., mobility of metals, bounding states). These employ a series of successively stronger chemical leaching reagents which nominally target the different compositional fractions. By analyzing the liquid leachates and the residual solid components, it is possible to determine not only the type and concentration of metals retained in each phase but also their potential ecological significance. Cu, Sr, Zn, Mn, Fe, and Al concentrations are higher in finer sediments than in coarser sediments, while Ba, Cr, Ni, V, Cd, Co, Mo, and Pb are enriched in the coarser fraction. The differences in relative concentrations are attributed to intense anthropogenic inputs from different sources. Heavy metal concentrations are higher than global average concentrations in sandstone, USEPA guidelines, and other local and international aquifer sediments. The order of trace elements in the bulk Pliocene aquifer sediments, from high to low concentrations, is Fe?>?Al?>?Mn?>?Cr?>?Zn?>?Cu?>?Ni?>?V?>?Sr?>?Ba?>?Pb?>?Mo?>?Cd?>?Co. The Pliocene aquifer sediments are highly contaminated for most toxic metals, except Pb and Co which have moderate contamination. The active soluble (F0) and exchangeable (F1) phases are represented by high concentrations of Cu, Zn, Fe, and Mn and relatively higher concentrations of Pb and Cd. This may be due to the increase of silt and clay fractions (mud) in sediments, which act as an adsorbent, retaining metals through ion exchange and other processes. The order of mobility of heavy metals in this phase is found to be Pb?>?Cd?>?Zn?>?Cu?>?Fe?>?Mn. The values of the active phase of most heavy metals are relatively high, indicating that Pliocene sediments are potentially a major sink for heavy metals characterized by high mobility and bioavailability. Fe–Mn oxyhydroxide phase is the most important fraction among labile fractions and represents 22% for Cd, 20% for Fe, 11% for Zn, 8% for Cu, 5% for Pb, and 3% for Mn. The organic matter-bound fraction contains 80% of Mn, 72% of Cu, 68% of Zn, 60% of Fe, 35% of Pb, and 30% of Cd (as mean). Summarizing the sequential extraction, a very good immobilization of the heavy metals by the organic matter-bound fraction is followed by the carbonate-exchangeable-bound fraction. The mobility of the Cd metal in the active and Fe–Mn oxyhydroxide phases is the highest, while the Mn metal had the lowest mobility. 相似文献
16.
17.
Heavy metal mobility assessment in sediments from the Odiel River (Iberian Pyritic Belt) using sequential extraction 总被引：1，自引：1，他引：0
Rafael Beltrán J. D. de la Rosa J. C. Santos M. Beltrán J. L. Gómez-Ariza 《Environmental Earth Sciences》2010,61(7):1493-1503
The Tessier sequential extraction scheme (SES) was applied to sediments from the Odiel river catchment (Iberian Pyritic Belt,
SW of Spain), one of the most acid rivers on Earth, to assess the chemical association (exchangeable, carbonatic, bound to
manganese and iron oxides, bound to organic matter and residual mineral) of heavy metals (Zn, Cd, Pb, Cu, Cr, Mn, Ni, Fe,
and Hg). Sediments are very heterogeneous in their textural characteristics, showing different grain size. Twenty-seven samples
were studied from from areas along the Odiel River, from the source to the mouth, with special interest in the Odiel Marshes
Natural Park due to its ecological significance. Samples were classified as sandy (especially at the river mouth with low
iron oxide and organic matter content) and clay-silty (in the middle of the river catchment with high iron oxide content).
The numerous sandy samples with low pH values explain the low levels of metals upstream, although potential metals contributions
arise from mining and ore. However, the presence of sulfate in the mining area and carbonate at the mouth may explain the
high presence of lead and iron in these sandy zones. Some percentage of mobile Ni, Cu, and Zn were detected in the mining
area, but the elevated relative percentage of exchangeable Cd in the estuary is even more remarkable. The percentage of Zn
bound to carbonate is considerable in the catchment but especially in the estuary. However, Cu is only detected in the carbonate
phase downstream, in spite of the low concentration of carbonate, which represents a drawback in the application of the Tessier
SES to these types of samples. Finally, relatively high percentages of residual, non-mobile, Hg and Pb were observed, in the
estuarine and mining areas, respectively. Sand, lime, and clay fractions of representative samples from Areas I, II, and III
were used in a metal speciation study. Mainly, the elements analyzed had accumulated in the non-residual fractions. In the
mining area of the Pyrite Belt, the elements analyzed are mainly bound to Fe–Mn oxides (Fe + Mn + Cu + Cr + Pb + Mn ± Zn)
and the organic matter/sulfide fraction (Ni + Zn + Hg ± Cd), independent of sediment grain size. In conclusion, we show that
the results of the study of chemical speciation in sediments from acid rivers are independent of the sediment grain size considered. 相似文献
18.
YUAN Xuyin DENG Xu SHEN Zhiyong GAO Yun 《中国地球化学学报》2007,26(4):384-393
The species of Cu, Pb, Zn, Cd and Cr in sediments of the Taihu Lake, China, have been analyzed using the sequential chemical extraction method. Variations in the chemical fractions of these metals and their geographic distributions have also been studied. For all five metals, the residual fraction is highest but the exchangeable fraction is lowest among all the fractions. Compared to other metals, Cd has the highest percentage in the exchangeable fraction, and Cr is associated mainly with the residual fraction. Cu in the organic fraction and Pb in the Fe-Mn fraction are the important species, whereas the lowest percentages are found for Cd in the organic fraction, Cu in the Fe-Mn oxide fraction and Pb in the carbonate fraction. With respect to spatial differences, the total contents in the non-residual fractions of the metals in bay sediments are found to be higher than those in other sediments. The fractions of Cd, Cu and Cr showed significant variations in different regions. The fractions of Pb and Zn, however, did not show significant variations in spatial distribution, suggesting different amounts and different paths of anthropogenic input for the metals. Comparisons of the metal speciation indicated that Cd might be the most bioavailable metal, followed by Pb. 相似文献
19.
太湖沉积物中重金属的地球化学形态及特征分析 总被引：24，自引：2，他引：22
用连续提取法分析了太湖沉积物5种重金属的地球化学形态,对地球化学形态的组成和地理特征进行了分析研究.重金属地球化学形态配分的共同特点是可交换态最低,残渣态最高.两种形态中Cd的可交换态最高,Cr的残渣态最高,可交换态最低.Cd的碳酸盐态较高,Cr的最低;Pb、Cd的Fe-Mn氧化态较高,Cu的偏低;Cu的有机态最高,Cd的最低;Zn的地球化学形态比例大都处于中间.地域上变化较大的元素是Cd和Cu,变化不明显的元素有Pb和Zn.化学成分中Fe2O3、MnO与重金属地球化学形态的相关性最好,TOC与Cu的形态相关系数最高.综合对比分析表明,太湖沉积物重金属的生物有效性以Cd为最高,其次为Pb. 相似文献
20.
Chemical partitioning of trace and major elements in soils contaminated by mining and smelting activities 总被引：4，自引：0，他引：4
Soils from historical Pb mining and smelting areas in Derbyshire, England have been analysed by a 5-step sequential extraction procedure, with multielement determination on extraction solutions at each step by ICP-AES. Each of the chemical fractions is operationally defined as: (i) exchangeable; (ii) bound to carbonates or specifically adsorbed; (iii) bound to Fe–Mn oxides; (iv) bound to organic matter and sulphides; (v) residual. The precision was estimated to be about 5%, and the overall recovery rates were between 85 and 110%. The carbonate/specifically adsorbed and Fe–Mn oxide phases are the largest fractions for Pb in soils contaminated by both mining and smelting. Most of the Zn is associated with Fe–Mn oxide and the residual fractions. Cadmium is concentrated in the first 3 extraction steps, particularly in the exchangeable phase. The most marked difference found between soils from the mining and smelting sites is the much higher concentrations and proportions of metals in the exchangeable fraction at the latter sites. This indicates greater mobility and potential bioavailability of Pb, Zn and Cd in soils at the smelting sites than in those in the mining area. The most important fraction for Fe and Al is the residual phase, followed by the Fe–Mn oxide forms. In contrast, the Fe–Mn oxide fraction is the dominant phase for Mn in these soils. In the mining area, most of the Ca is in the carbonate fraction (CaCO3), while the exchangeable and residual phases are the main fractions for Ca at the smelting sites. Phosphorus is mainly in the residual and organic fractions in both areas. The exchangeable fractions of Pb, Zn and Cd in soils were found to be significantly related to the concentrations of these metals in pasture herbage. 相似文献