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1.
Chemical data are reported for the first time for lunar soil size fractions smaller then 2 μm. We report chemical data for 30 elements by INAA in eight size fractions (370−200, 200−94, 94−74, 74−40, 40−10, 10−5, 5−2 and <2 μm) and petrology of five size fractions (down to 40−10 μm) in two Luna 24 soils, 24176 and 24214. Consistent with our previous results for lunar soils, the compositions of coarser fractions (>10 μm) are quite similar to each other but quite different from the fine fractions (<10 μm). The finer fractions (10–5, 5–2, <2 μm) become increasingly feldspathic and enriched in large-ion lithophile elements (LILE) with decreasing grain size. Chemical data for the finer fractions provide direct evidence in favor of efficient comminution of rock mesostasis and feldspar leading to their preferential incorporation into the finer fractions. High concentrations of meteoritic indicator elements (Ni, Au, Ir) in the finer fractions are consistent with the comminution process by micrometeorite impacts. The chemical data strongly support the F3 (fusion of the finest fraction) model for agglutinate formation.Based on grain size distribution, petrology, and LILE patterns of size fractions, the Luna 24 soils are less reworked than most lunar soils. The Luna 24 regolith appears to have formed as a result of mixing more mature and fine grained material with less mature coarse material in different proportions at different depth intervals.  相似文献   

2.
The sulphur contents and δ34S values have been determined for the bulk and various grain size fractions of three 740021 lunar drive tube samples. The sulphur contents of the bulk samples ate much lower than those of other lunar soils. These samples, along with the surface orange soil 74220 analysed previously, show an increase of sulphur concentration with decreasing particle size which is more marked than for other soils and indicates that the orange and black glass droplets have a coating enriched in sulphur and other volatile elements.In sharp contrast with other soils, the orange and black glasses have slight positive δ34S values for large particles while the smallest particle sizes show negative δ34S values. This indicates that the coating of the glassy droplets is enriched in isotopically light sulphur. These observations favour the theory that the orange and black glasses were generated by a volcanic fire fountain.The anomalously high δ34S values of the fine fractions of the core bottom sample, 74001-135, combined with the results of an acid leaching experiment, indicate that these fractions are contaminated, possibly by a mature soil of high sulphur content and relatively positive δ34S value.  相似文献   

3.
The compositions of the interiors and abraded surfaces of 7 chondrules from Semarkona (LL3.0) were measured by neutron activation analysis. For nonvolatile elements, the lithophile and siderophile element abundance patterns in the surfaces are generally similar to those in the corresponding interiors. Siderophile and chalcophile concentrations are much higher in the surfaces, whereas lithophile concentrations are similar in both fractions. Most of the similarities in lithophile patterns and some of the similarities in siderophile patterns between surfaces and interiors may reflect incomplete separation of the fractions in the laboratory, but for 3 or 4 chondrules the siderophile resemblance is inherent, implying that the surface and interior metal formed from a single precursor assemblage. Metal and sulfide-rich chondrule rims probably formed when droplets of these phases that migrated to the chondrule surface during melting were reheated and incorporated into matrix-like material that had accreted onto the surface. The moderately-volatile to volatile elements K, As and Zn tend to be enriched in the surfaces compared with other elements of similar mineral affinity; both enrichments and depletions are observed for other moderately volatile elements. A small fraction of chondrules experienced fractional evaporation while they were molten.  相似文献   

4.
Classically, the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method, based on the ‘Stokes’ sedimentation rates, for the fine fractions. Results from the two methods are compared with results from laser diffraction size analysis, which is based on the forward scattering of monochromatic coherent light. From a point of view of laboratory efficiency, the laser sizing technique is far superior. Accuracy and reproducibility are shown by measurements on certified materials. It appears that laser grain size measurements of certified materials correspond very well with the certificated measurements. Tests were also done on a set of randomly selected sediments of fluvial, aeolian and lacustrine origin. Except for the (<2 μm) clay fraction, there is a coarsening of the mean diameter of one to two size classes (0.25 ?), caused by the non-sphericity of the particles. The platy form of the clay particles induces considerable differences (eight size classes) between pipette and laser measurements: the <2 μm grain size, defined by the pipette method corresponds with a grain size of 8 μm defined by the Laser Particle Sizer for the studied sediments. Using a higher grain size level for the clay fraction, when laser analysis is applied, enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique.  相似文献   

5.
在科尔沁沙地采集沙地表土样品16组,松嫩平原杜蒙沙地样品15组,同期还收集了城市道路表土样品10组,对各组样品进行粒度分级（全样、>63 μm、63~30 μm、30~11 μm和<11 μm）,分别测定碳酸盐含量和碳同位素组成。结果显示,不同区域不同性质样品各粒级组分碳酸盐含量的变化幅度不同,科尔沁沙地最小（0.8%）,其次为杜蒙沙地（1.9%）,道路表土最大（2.7%）。大部分杜蒙沙地样品（66.7%）和小部分科尔沁沙地样品（37.5%）以及全部道路表土样品的碳酸盐含量随粒度变细而增大,且变化模式各不相同。碳酸盐含量随粒度变细而增高是非匀速的,先是增幅较大（>63 μm→63~30 μm→30~11 μm）,后增幅较小（30~11 μm→<11 μm）。沙地样品碳酸盐含量与粒度的关系并不限于随粒度变细而增大这一种,风成砂和经历过强烈成壤作用改造的沙地样品中的碳酸盐含量与粒度的关系皆表现为随粒度变细而减小,沉积物中碳酸盐含量随粒径变细而增高是否是一种普遍规律还需要更多区域的更多样品来检验。大部分沙地样品和道路表土样品不同粒级组分的碳酸盐δ13C值变化范围较小（<1.8‰）,并表现出随粒度变细而趋于偏正的特征,但变化幅度很小。杜蒙沙地和科尔沁沙地碳酸盐含量的地区差异性极不明显,且各粒级组分碳酸盐含量的变化幅度大大超过了杜蒙沙地与科尔沁沙地的碳酸盐差异值,不能作为区分杜蒙沙地和科尔沁沙地风尘源区的示踪指标;而科尔沁沙地和杜蒙沙地碳酸盐δ13C组成存在明显差异（在63~30 μm粒级组分表现最为明显）,且不同粒级组分碳酸盐δ13C值差别较小,说明它是一个比碳酸盐含量更好的风尘源区示踪指标,但是不同粒级组分碳酸盐δ13C组成的差异会随离中国西部沙漠沙地风尘源区距离的加大或者风尘物质成壤作用的增强而变大,增加其风尘源区示踪的复杂性。  相似文献   

6.
Urban roadside soils are important environmental media for assessing heavy metal concentrations in urban environment. However, among other things, heavy metal concentrations are controlled by soil particle grain size fractions. In this study, two roadside sites were chosen within the city of Xuzhou (China) to reflect differences in land use. Bulk soil samples were collected and then divided by particle diameter into five physical size fractions, 500–250, 250–125, 125–74, 74–45, < 45 μm. Concentrations of metals (Ti, Cr, Al, Ga, Pb, Ba, Cd, Co, Cu, Mn, Ni, V, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) were determined for each individual fraction. These metals could be roughly classified into two groups: anthropogenic element (Pb, Ba, Cd, Cu, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) and lithophile element (Ti, Cr, Al, Ga, Co, Mn, Ni, V) in terms of values of enrichment factor. As expected, higher concentrations of anthropogenic heavy metals (Cu, Zn, Mo, As, Hg, Bi, Ag) are observed in the finest particle grain size fraction (i.e. < 45 μm). However, heavy metals Se, Sb and Ba behave independently of selected grain size fractions. From the viewpoint of mass loading, more than 30% of the concentrations for all anthropogenic heavy metals are contributed by the particle grain size fractions of 45–74 μm at site 1 and more than 70% of the concentrations for all heavy metals are contributed by the particle grain size fractions of 45–74 and 74–125 μm at site 2. These results are important for transport of soil-bound heavy metals and pollution control by various remedial options.  相似文献   

7.
《Applied Geochemistry》1995,10(1):111-113
Positive identification of the origin of fine-grained quartz in highly weathered soils is not proven by routine microscopic examination. The oxygen isotope composition (δ18O vs SMOW) of quartz was determined in the albic horizon of three soils developed on the Cretaceous Nohhi rhyolite from Kiso, central Japan. Differences in the isotopic composition of quartz as a function of particle size were observed and attributed to the degree of hydrothermal alteration. One soil sample developed nearby hornblende porphyrite intrusion showed systematic increases in the δ18O values with increasing particle size, from +3.6‰ (1–10 μm) to +9.5‰ (500–2000 μm). Such a trend is indicative of the higher contribution of secondary quartz precipitated from hydrothermal meteoric fluids in fine size fractions in contrast to primary magmatic quartz in coarse size fractions. Hydrothermal activity was inferred for another soil where no lateral intrusion is mapped. The variation in the oxygen isotopic composition of quartz in different particle sizes precludes both eolian and authigenic origins for the soils. The stable isotope technology provides the only rationale for positive identification of the origin of fine-grained quartz in soils.  相似文献   

8.
The fractionation of a Recent sediment for organic geochemical analysis   总被引：1，自引：0，他引：1  
A Recent unconsolidated lacustrine sediment was separated into five size fractions which were characterized by microscopy and XRD. Higher plant detritus predominated in the coarsest fractions, but decreased in proportion in the intermediate ones in which algal debris was predominant. The overall proportion of organic debris decreased from coarse to fine fractions. Quartz and feldspar were most abundant in the intermediate size fractions, while the coarsest fraction contained chlorite with some kaolinite and quartz, and the finest fraction was composed mainly of illite.Concentrations (per fraction dry weight) of solvent extract, total long chain hydrocarbons and total fatty acids decreased from coarse to fine fractions, with the exception of the finest fraction, in which they showed an increase. The change in relative abundance of higher plant to algal debris in the coarse and intermediate size fractions was paralleled by a decrease in the relative abundance of n-C29 and n-C31 alkanes and an increase in the relative abundance of -C17 alkane. There was a progressive decrease in n-alkane carbon preference index, and a progressive increase in the unresolved envelope of hydrocarbons with decreasing grain size. The unresolved hydrocarbons, which probably originate from biodegraded lubricating oil, appear to be associated with the clay fraction. Fractionation in this way and lipid analysis of the separate fractions may give more definitive information about input sources than analysis of unfractionated sediments.  相似文献   

9.
Luna 20 soil is remarkably similar to Apollo 16 soil, in its content of 17 mainly volatile or siderophile elements: Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Like other highland soils, it seems to contain an ancient meteoritic component of fractionated, volatile-poor composition. The bulk soil has a high TlCs ratio (9.4 × 10?2), similar to that in Apollo 16 soils (5.4 × 10?2), but higher than that in samples from other sites (1.1 × 10?2). It is severely contaminated with Ag, Cd, Re, and Sb, judging from a comparison with a 1.7 mg soil breccia sample from the coarse fraction of the soil.  相似文献   

10.
The clay mineral composition, the concentrations of carbonates, the proportions of carbon and oxygen isotopes in carbonates and organic matter, as well as the concentrations of different nonanthropogenic metals were used to determine the origin of different grain size fractions of sediments and suspended matter in the Elbe estuary. Analysis of the smectite/kaolinite proportion revealed that solid material ≤2 μm from the North Sea is transported up the river, about 40 km beyond the most upstream position of the salt wedge. In the 2–20 μm fraction, the16O/18O ratio in carbonates and the kaolinite/chlorite proportion demonstrate a transport of North Sea material between 40 and 20 km upstream of the marine water limit. The transport behaviour of the 20–63 μm grain size fraction could be determined by the hafnium concentration, representative for the heavy mineral zircon. In this case, the transport distance beyond the salt wedge was up to 20 km. No information was available on the origin of the fine organic matter, whereas the coarser fractions were derived primarily from debris of salt marsh vegetation. The results demonstrate that in the Elbe estuary mixing between marine and fluvial solid material occurs upstream of the salt wedge and is significantly responsible for the observed decrease in the concentration of various pollutants in sediments and suspended matter along the estuary. The cause of the upstream particle transport is probably a scour lag mechanism based on asymmetries of the flood- and ebb-tide current distribution, especially their differing maximum velocities.  相似文献   

11.
Lead concentrations and stable isotopic measurements were examined in the different chemical fractions of Czech forest soils to investigate the mechanisms of Pb partitioning. A method of selective sequential dissolution (SSD) was employed that distinguished between five different fractions: exchangeable, surface bound, organic matter, Fe-oxides, and silicates (non-labile).From an analysis of the concentrations and isotopic compositions associated with the different fractions, it is apparent that Pb in the deep Czech mineral soils is of predominantly natural origin and is primarily associated with silicates (69-81%) and Fe-oxides (11-19%). Natural Pb associated with surface bound and organic matter fractions in mineral soils accounts for only 7 to 15%. Anthropogenic Pb in the Czech soils is concentrated primarily in the organic horizons and is strongly associated with the surface-bound and organic matter fractions in which the proportion of total Pb is 33 to 50% and 23 to 47%, respectively.At high and low levels of contamination, Pb isotopic signatures within the labile fractions of the same soil samples are generally homogenous, although a degree of heterogeneity among these fractions is noted in samples of intermediate degrees of contamination. Such heterogeneity probably reflects different levels of natural and anthropogenic Pb mixing.Determination of the mass-normalized affinity of Pb to the primary components using solid-solution distribution coefficients suggests that in Czech forest soils, the order of affinity may be summarized as Fe-oxides > organic matter > silicates. A similar treatment of the data reported for semiarid Mediterranean soils indicates the prevailing order to be Fe-oxides > carbonates > organic matter > silicates. The general similarity of the behaviour of Pb with respect to the different soil components in both temperate and semiarid soils suggests that these orders of affinity may have wider significance for a variety of other soil types.  相似文献   

12.
青藏高原土壤有机碳储量（soil organic carbon stocks, SOCS）对于区域生态环境演替具有重要作用, 但是其空间分布数据还比较缺乏, 特别是季节冻土区的数据较少。基于378个土壤剖面数据, 结合与土壤有机碳（soil organic carbon, SOC）相关的地形、 气候以及植被等环境因子, 使用地理加权回归（geographically weighted regression, GWR）模型模拟了青藏高原季节冻土区0 ~ 30 cm、 0 ~ 50 cm、 0 ~ 100 cm和0 ~ 200 cm深度的SOC总量和空间分布。结果表明： 青藏高原季节冻土区SOCS自东南向西北递减, 表层0 ~ 200 cm的SOC总量约15.37 Pg; 季节冻土区不同植被类型SOC从大到小依次为森林、 灌丛、 高寒草甸、 高寒草原和高寒荒漠; 各土壤类型中棕壤、 黑钙土和泥炭土的SOC最大, 而棕钙土、 棕漠土、 灰棕漠土、 风沙土、 石质土、 盐土、 冷钙土、 寒漠土以及冷漠土的SOC最小。研究结果给出了青藏高原季节冻土区SOC的总量、 空间分布及规律, 可为相关地球模式的发展提供基础数据。  相似文献   

13.
Polycyclic aromatic hydrocarbons’ (PAHs) concentrations in bulk samples are commonly used to assess contamination but PAHs are unevenly distributed among particle-size fractions. Seventeen urban surface soil samples from the city of Xuzhou, China, were collected and then fractionated into five size fractions (2,000–300, 300–150, 150–75, 75–28, and <28 μm). The concentrations of 12 US EPA PAHs were measured using gas chromatograph/mass spectrometry in various fractions, and the bulk soil samples and distribution patterns of PAHs in different particle-size fractions were investigated. The mean concentration of total PAHs in bulk soil samples was 1,879 ng/g. The median concentrations for all individual PAH were higher for the 75–2,000 μm fraction than for the <75 μm fraction. The distribution factors for various PAHs in <28 μm soil fraction were closely correlated (r = ?0.661, p < 0.019) to bulk soil fugacity capacity. The values of PAH isomer indicated that traffic emissions might be the major origin of PAHs in Xuzhou surface soils. Spearman correlation analysis was performed and the result suggested that soil organic carbon might be a factor controlling the concentrations of PAHs in soils.  相似文献   

14.
The relationships between soil texture, plant growth, and anaerobic microbial activity in two tall-formSpartina alterniflora marshes on Sapelo Island, Georgia, were compared. The soil of one marsh was composed of typical silt-clay-sized particles; the soil of the other marsh consisted of >90% sand-sized particles. The two soils supported similar biomasses ofS. alterniflora, however, plants were taller and more robust in the silt-clay-soil than in the sand soil. Total microbial adenosine triphosphate concentrations in the silt-clay and sand soils averaged 5.71 and 1.64 μg per cm3, respectively. Seawater slurries of both soils exhibited potential for microbial sulfate reduction, methanogenesis, and glucose fermentation; rates for the processes averaged 2.03 and 0.33 nmol S-cm3 per h; 1.20 and 0.87 μmol CH4 per cm3 per h; and 0.04 and 0.12 per min (rate constant) for the sand and silt-clay soils, respectively.  相似文献   

15.
Grain‐size data from different climatic zones across the Chinese Loess Plateau show that the loess generally contains an ultrafine component, which has a consistent modal grain size of ca 0·37 μm and a variable proportion of 4 to 10%. The variation of the ultrafine component through a loess section is characterized by a high proportion and fine grain size in palaeosols, and by a low proportion and coarse grain size in loess layers. Its proportional content in a stratum roughly increases from north‐west to south‐east across the Loess Plateau. Quantitative X‐ray diffraction analysis indicates that the ultrafine component is composed mainly of clay minerals (ca 70%), which are mostly illite (ca 80%), and with significant amounts of kaolinite (ca 8%) and chlorite (ca 2%). The temporal and spatial variations of the ultrafine component, and the degree of illite crystallinity, suggest that this component in aeolian sediments is linked closely to the process of pedogenesis. Weakly altered loess on the north‐western margin of the Loess Plateau contains considerable amounts of detrital clay minerals derived from the aeolian source areas. Results from a loess section with a basal age of 7·6 Ma in the central Loess Plateau show that the ultrafine component increased from 7·6 to 5 Ma, and progressively decreased thereafter. This trend was punctuated by two abrupt changes at 2·6 and 0·6 Ma. These variations reflect to a considerable extent the history of pedogenesis during the Late Cenozoic.  相似文献   

16.
 Understanding the mechanisms of mercury evaporation from soil to the atmosphere is necessary for tracing the fate of mercury in the biological environment and for assessing potential health effects and the impact of anthropogenic mercury emissions on the environment. In this article an integrating overview of the current knowledge of the mechanisms of mercury evaporation is presented. Abiological and biological formation of Hg(0) and/or (CH3)2Hg in the uppermost soil layers are the rate limiting processes of mercury evaporation from soils in background areas; the evaporation rate in background areas is probably strongly influenced by deposited airborne mercury. The evaporation rate limiting factors in mercury enriched mineralized areas with large fractions of total mercury being volatile mercury species (relative to background soil in the non-mineralized vicinity) meteorological variations and the transport characteristics of soils for volatile mercury species. Mercury evaporation rates from background soils are usually <0.2 μg·m–2·h–1 and significantly smaller than from mercury-enriched mineralized areas. Received: 20 November 1995 / Accepted: 24 July 1996  相似文献   

17.
[研究目的]对土壤中硒元素的有效吸收是水稻富硒的关键,而土壤中硒的形态则是影响水稻吸收能力的直接影响因素之一,为了探讨影响富硒土壤中硒的形态与水稻籽实中硒含量的关系,本文对陕西省安康市西部土壤开展了定量研究.[研究方法]本文对研究区土壤硒的形态以及水稻富硒状况进行测定,获得了土壤中各形态硒的赋存状态分布特征.[研究结果...  相似文献   

18.
Tl and Pb isotopic abundances have been measured in various phases from Allende and the distribution and siting of these elements in the matrix phase investigated. Matrix fractions, prepared by sieving, sedimentation, magnetic separation and acid etching, were further characterised by X-ray diffraction and SEM. Tl concentrations range from 1 ppb in coarse grained inclusions to 1560 ppb in the acid-etched carbon residues and from 32 ppb to 194 ppb in the 16 matrix fractions. Pb concentrations which range from 0.1 ppm to 3.1 ppm, are enhanced in magnetic phases and depleted in Allende pentlandite relative to the whole meteorite. The Tl-204Pb abundance diagram is described near the origin by the inclusions and chondrules and extends through sulphide to the non-magnetic and magnetic matrix fractions. Abundances in the finest grained matrix fractions form a linear trend which passes through the origin and the Orgueil and Murchison whole meteorite data. The deviation of magnetic matrix fractions from the above linear trend is probably related to the presence of an intimate association of an awaruite-sulphide-carbon species. 92% of the Tl in the carbon residues, which is released on hydrolysis with HCl, probably resides in an organic host molecule(s) on the macromolecular carbonaceous material, whereas the surface film of organics on the matrix grains shows no apparent enrichment of Tl.Tl and 204Pb abundances revealed an inverse correlation with grain size and a distribution within the grains rather than as a surface layer, is indicated. Constraints placed by the data on the formational environment of the matrix grains are considered. Interstellar shock heating and rapid radiative cooling is a possible mechanism for the establishment of the observed inverse correlation of volatile abundance with grain size. Matrix data do not lend support for a recent redistribution of lead as an explanation for the apparent excess Pb in Allende. The apparent initial Pb isotopic compositions of the matrix fractions are heterogeneous and not attributable to terrestrial contamination. The very magnetic fractions have high abundances of Pb and the least radiogenic apparent initial Pb compositions, whereas the non-magnetic fractions have lower Pb abundances but more radiogenic apparent initial Pb compositions. The data also indicate that use of the predicted Tl-204Pb cosmothermometer, to infer accretion temperatures, is apparently not valid for individual phases of Allende.  相似文献   

19.
The Nickel Plate deposit, in which gold occurs as <25 μm blebs associated with arsenopyrite in garnet-pyroxene skarns, is in the subalpine zone near the southern limit of the Thompson Plateau. During the last glaciation the Cordilleran ice sheet moved south-southwest across the deposit and deposited a stony basal till. A dispersion train with anomalous concentrations of gold in tills and soils now extends 2 km down ice from the deposit.Gold contents of samples of humus (LFH horizon) and the −212 μm fraction of mineral soils (A, B and C horizons) was determined by instrumental neutron activation and fire assay-atomic absorption, respectively. Selected samples were examined in detail to determine distribution of gold between different size and density fractions.Despite erratic variability, Au contents of the −212 μm fraction generally decrease from 200–400 ppb close to the mine site to <50 ppb at distal sites. At most sites there is also a twofold increase of gold values down the soil profile. Within samples concentrations of Au in the −420 + 212 μm, −212 + 106 μm, −106 + 53 μm and −53 μm fractions are usually roughly constant. However, because of its abundance, the −53 μm fraction contains more than 70% of the gold. Amenability of gold in this fraction to cyanidation suggests that it is largely free gold. For size fractions > 53 μm the contribution of the heavy mineral (SG > 3.3) fraction to total gold content increases with decreasing grain size.Distribution of gold between size and density fractions is consistent with its release from the bedrock or pre-glacial regolith by glacial abrasion. The bulk of the gold was incorporated into the fine fractions of the till at or close to the source. However, differences between down ice dilution ratios for gold in different heavy mineral size fractions suggest that comminution of host minerals continued to transfer gold to the finer size fractions during glacial transport.For exploration purposes, B and C horizon samples provide the best anomaly contrast. Estimates of the abundance of gold particles in different size fractions indicate that the nugget effect, which causes erratic gold values in the −212 μm fraction, can be avoided by analysis of 30 g of −53 μm material.  相似文献   

20.
This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration.  相似文献   

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