Vertical Distribution Of Elements Research Articles

The vertical distribution of 27 elements in bottom sediments reflects the modern history of the hypersaline lagoon

Knowledge of the distribution of various elements in the bottom vertical cores helps to assess current levels and to reconstruct the history of a water body. There is little to no bioturbation of bottom sediments in hypersaline lagoons/lakes, and vertical distribution of elements in the sediments is not distorted. The vertical distribution of 27 elements was studied in one of the Crimean hypersaline marine lakes. Their determination was carried out in layers one centimeter thick, which were taken from a depth of 1 cm to 28 cm. Using the technogenic radionuclide 90Sr, the time intervals when various layers of bottom sediments were formed had been previously determined. The concentrations of most elements, as well as their ratio, changed quasi-cyclically. For most of the elements for which such changes were noted, the maximum peak values were in the layers that formed in 1976 and 2006. The authors concluded from this that there appears to be a natural rhythm with a period of about 30 years. Not only a concentration of technogenic radionuclide 90Sr but also Mo, Ba, Tl, Sb, Se, and Ag reacted strongly to the accident at the Chernobyl nuclear power plant in 1986 due to atmospheric fallout and transportation of elements via the Dnieper river waters through the North Crimean Canal.

Climate and soil properties regulate the vertical heterogeneity of minor and trace elements in the alpine topsoil of the Hengduan Mountains

Soil minor and trace elements are vital regulators of ecological processes that sustain alpine ecosystem functions. In this study, the vertical pattern and driving factors of element concentrations in alpine soils of the Tibetan Plateau were investigated. Three snow mountains (Meili, Baima, and Haba) part of the Hengduan Mountain range, were selected as the study area to determine the vertical distribution of 12 typical elements (Cr, Ni, Cu, Fe, Mn, Zn, Cd, Pb, Ca, Sr, As, and Se) in topsoil with increasing and decreasing elevation, as well as the dominant driving factors of their spatial heterogeneity. Results showed that all elements, except Se, showed strong vertical heterogeneity, among which Cr, Ni, Cu, and Fe showed peak concentrations at 2700–3000 m; the highest concentrations of Mn and Zn were at 3200 m and 2700 m, with Cd and Pb at 2500 m. Ca and Sr levels gradually decreased with increasing elevation. According to the structural equation model and random forest analysis, the vertical heterogeneity of soil elements is directly regulated by the variability of climate and soil properties due to changes in elevation. A three-way PERMANOVA further quantized the contributions of climate and soil properties on vertical heterogeneity of all soil elements, which were 35.2 % and 50.5 %, respectively. This study used various statistical tools to reveal the dominant factors affecting the vertical heterogeneity of soil elements. These findings provided a scientific overview of element distribution on the Tibetan Plateau and significant references for the vertical distribution of elements in the topsoil of other snow mountains worldwide.

Historical deposition of trace metals in a marine sapropel from Mangrove Lake, Bermuda with emphasis on mercury, lead, and their isotopic composition

Sapropel is an organic-rich sediment formed under conditions that can result in sequestration of trace metals. Here, we determined the concentration of total mercury (Hg), lead (Pb), and 16 other metals (Al, Ba, Ca, Cd, Cr, Cs, Cu, Fe, Li, Mn, Ni, Sr, Tl, U, V, Zn) in a sapropel core from Mangrove Lake, Bermuda that dated back nearly two millennia. The purpose was to assess historical patterns of metal deposition on this geographically remote island in the North Atlantic Ocean. Two sediment cores were collected from Mangrove Lake using a modified piston corer. Cores were age-dated with a Bayesian statistical age-depth model using a multiproxy approach relying on 210Pb and radiocarbon dates. Total Hg was determined following US EPA Method 7473 using a direct mercury analyzer. Other metals were determined by sector field ICP-MS following a microwave-assisted strong-acid digestion. Stable isotope measurements of Hg and Pb were used to better track sources of these contaminants. Sapropel Hg concentrations were low (~ 50 ng g−1) from about 1000 AD to 1600 AD, followed by a slow rise in concentration until a high point of 209 ng g−1 in the early nineteenth century. Hg levels then returned to ~ 70 ng g−1, still elevated above baseline levels, before a final sharp rise in the mid-1900s to 430 ng g−1. Pb, Zn, Cu, Cr, and Ba had similar patterns, with Pb isotope ratios showing early natural fluctuations followed by the greater influence of pollution sources. Mercury stable isotope data also show the influence of anthropogenic sources during the 1800s and suggest a mix of atmospheric, terrestrial, and possibly marine-derived Hg inputs to the lake. The vertical distribution of elements and isotopes reveals changes in deposition through time associated with pollution from industrialization, and, possibly, volcanic activity, seawater intrusion, intense hurricane events, and local pollution from ship and fortress building. Overall, this study demonstrates that organic-rich sapropel provides a good historical record of metal contamination, and that Bermuda, despite its remote location, had metal deposition profiles much like the records of other sediment cores from around the world.

元素鉛直分布および炭素・窒素安定同位体比と形態別リン分布が示す藤前干潟堆積物の生物地球化学的特徴

元素鉛直分布および炭素・窒素安定同位体比と形態別リン分布が示す藤前干潟堆積物の生物地球化学的特徴

Establishing geochemical baselines in forest soils for environmental risk assessment in the Montague and Goldenville gold districts, Nova Scotia, Canada

Mine tailings at historical gold districts in Nova Scotia, Canada, contain high concentrations of arsenic (As) and mercury (Hg), which may represent a risk to ecosystems and human health. Two sites, Montague and Goldenville, are of particular concern as tailings are located close to residences and are occasionally used for racing off-road vehicles. Risk-assessment calculations require knowledge of the naturally occurring concentrations of As and Hg in soils overlying mineralized bedrock within these gold districts. In this study, we collected samples of the top 0–5 cm of surface soil (the Public Health layer) from 46 sites near Montague, and 39 sites near Goldenville. Samples of individual soil horizons (H, Ae, B, and C) were also taken from selected sites to evaluate the vertical distribution of elements in the soil profile. Results show that the concentrations of As and Hg in all soil horizons are generally higher down-ice, southeasterly, of the ore zones in both districts, reflecting glacial erosion and transport of mineralized bedrock. Analysis of the top 0–5 cm of soils shows the following ranges in As and Hg concentrations (<2 mm size fraction): Montague: As, 4–273 mg/kg (median 42 mg/kg); Hg, 72–490 µg/kg (median 164 µg/kg); Goldenville: As, 2–140 mg/kg (median 13 mg/kg); Hg, 39–312 µg/kg (median 114 µg/kg). In general, the concentrations of As are highest in the B and C horizons, whereas Hg concentrations are highest in humus (H). Results from this study have been used to assess the distribution of tailings at these sites, and to help guide risk-management decisions.

Mineralogy and geochemistry of Late Permian coals from the Donglin Coal Mine in the Nantong coalfield in Chongqing, southwestern China

The Donglin Coal Mine, an important mine in the Nantong coalfield in southwestern Chongqing, is immediately adjacent to the Songzao coalfield. To investigate the mineralogy and geochemistry of Donglin coals, profile channel samples from the mineable Nos. 4 and 6 coals were collected. The minerals, major element oxides, and trace elements were analyzed by LTA-XRD in combination with Siroquant software, XRF, ICP-MS, ICP-CCT-MS (As and Se), ISE (F), and DMA-80 Hg analyzer (Hg). The results indicate that the Donglin low volatile bituminous coals were characterized by low ash yields and high total sulfur contents. The minerals varied between the Nos. 4 and 6 coals, differentiated by montmorillonite, calcite, ankerite, and pyrite. Despite the low boron concentration, Donglin coals were influenced by brackish water during coal accumulation. Selenium (10.9mg/kg), F (431mg/kg), Hg (0.350mg/kg), Nb (20.7mg/kg), and Ta (3.68mg/kg) in the No. 4 coals, and F (425mg/kg), Be (7.11mg/kg), Ga (14.5mg/kg), Ge (22.5mg/kg), Zr (218mg/kg), Nb (35.5mg/kg), and Ta (4.42mg/kg) in the No. 6 coals are slightly enriched. Four vertical distributions of elements were demonstrated, i.e., roof, floor, roof and floor, and middle enrichments. The slightly enriched trace elements and UCC-normalized REY distribution patterns of the Donglin coals jointly eliminated the impact of various volcanic ashes and terrigenous input from the Kangdian Oldland during the Late Permian. However, the roof rock samples shared the geochemical feature of mafic tonstein (enriched Sc, V, Cr, Co, and Ni), while the floor rock of the No. 6 coals resembles alkali tonsteins (enriched Ga, Zr, Nb, Ta, Hf, and REY). Lithium, Ga, Zr, Ag, Cd, In, Sn, Cs, Hf, Bi, Th, and U occurred in kaolinite and/or montmorillonite in the No. 4 coals, while Li, Nb, Ag, Cd, In, Cs, Ba, and Th occurred in kaolinite in the No. 6 coals. Vanadium, Sr, and Mo in the No. 4 coals, and Sr and Sc in the No. 6 coals were associated with calcite and/or ankerite. Arsenic, Se, Hg, Sb and Tl, and Hg and Mo were associated with pyrite in the Nos. 4 and 6 coals, respectively. Lithium, Be, Ge, and Sb in the No. 4 coals and Be and Ge in the No. 6 coals might be of organic affinity.

Vertical distribution of elements in regolith over mineral deposits and implications for mapping geochemical weak anomalies in covered areas

Several case studies are presented to demonstrate that significant migration of elements in regolith over mineral deposits can reach the earth surface through thick layers of superimposed regolith. Data obtained from drill-holes in Mo-W and Mo-Ag mineral deposits in Eastern Inner Mongolia, China using portable X-ray fluorescence (pXRF, Niton XL3t 950) and data from other areas reported in the literature have been modeled using power-law decay functions that describe the regolith decay trends with increasing distance from the underlying altered rocks or saprocks. The results demonstrate that the element concentration in the surface media can be very low due to decay and mask effects, even if a thin layer of overburden exists. In order to characterize the decay behaviour of geochemical concentration of an element in a vertical regolith profile caused by complex mechanisms, a new non-linear differential equation was proposed which assumes the decay rate of concentration is negatively proportional to the concentration itself, with a functional coefficient dependent on vertical distance from the underlying surface of mineralised rocks. Applying Taylor series expansion to the coefficient function, the differential equation can be approximated by four simple dynamic systems, each with explicit solutions including Gaussian functions, exponential functions, power-law functions and exponential functions with inverse distance. These functions can be utilized as either separate or combined models to fit observed data by means of simple linear regression or multivariate regression. The combined mode is useful for evaluating the comprehensive effect of element concentration distribution due to various mechanisms.

Spatial distribution and geochemical baselines of major/trace elements in soils of Medak district, Andhra Pradesh, India

Regional-scale variations in soil geochemistry were investigated with special reference to differences among soil groups and lithology in an area of 9,699 km2 in Medak district, Andhra Pradesh, India. The concentrations of 29 elements (major: Si, Al, Fe, Mn, Mg, Ca, Na, K, Ti, P and trace: As, Ba, Cd, Co, Cr, Cu, F, Mo, Ni, Pb, Rb, Se, Sr, Th, U, V, Y, Zn, Zr) in 878 soil samples collected (557-topsoil, 321-subsoil) at a sampling density of 1 site/17 km2 from 557 sites representative of all the soil types present in studied area were determined, and their elemental composition are discussed. The baseline levels of these elements in soils are determined over different lithological units for the identification of anomalous values relative to these. For the first time, geochemical maps for Medak district are prepared on 1:50,000 scale and the lithogeochemical database generated provides information on the lateral and vertical distribution of elements in soil. The spatial variations in the distribution of elements reflect underlying geologic characteristics. Box-plots reveal that the concentration of most of the elements in soils were not strongly dependent on the soil group but the soil-geochemistry abruptly changes with the change in the soil parent materials indicating that the distribution of elements is mostly influenced by the bedrock lithology and other natural processes acting on them. For instance, the concentrations of Co, Cu, Fe, Mn, Ti, V and Zn are high in soils developed on basaltic terrain while the soils developed on granitic and gneissic terrain exhibit high elemental concentrations of K, Pb, Rb, Si, Th and Y. Alfisols had relatively high contents of elements while entisols had lower concentrations of most of the elements. The database can be used in the chemical characterisation of different geological units as well as applications in various environmental and agricultural fields. The results indicate that regional geology is an important determinant of soil geochemical baselines for soil pollution assessment and further emphasizes the importance of determining background levels locally. The defined baselines can be used to establish background values for future soil surveys.

Deep-penetrating geochemistry of the Tuwu copper deposit, northwestern China

Desert terrains in northern China are covered by widespread regolith sediments which mask geochemical signals from ore bodies and are major obstacles to mineral exploration. There is a critical need to study the vertical distribution of elements in this regolith and to establish optimum sampling and analytical methods. The aim of this study is to understand the dispersion and variation of elements throughout the cover in a vertical profile. The results demonstrate that the main elements show a distribution pattern of enrichment in clay layers in the vertical profile, i.e., most elements tend to be enriched in the most upper part of the profile above the orebodies except for some elements like Cu, Ca and Ag. Meanwhile, both fine (−160 mesh) and coarse (+20 mesh) fraction samples from clay-rich horizons are favorable samples and selective leaching of the elements absorbed on clays or oxide coatings is effective for localizing buried deposits. The distribution of active Cu and Mo is quite different because chalcopyrite is weathered into Cu sulfate and CuCO3, and is precipitated in alkaline environments in a layer below close to the surface. Mo is soluble in the alkaline environment so it can penetrate the caliche layer and be enriched on the surface of soil enriched with weakly cemented clay.

Vertical distribution of trace elements in the sediment cores from major rivers in east China and its implication on geochemical background and anthropogenic effects

In this study, the overbank and floodplain sediment cores were collected from the lower part of 26 large rivers in east China; 353 samples were obtained from these sediment cores; and the concentrations of 21 trace and major elements were measured for each sample. The vertical distributions of the elements exhibit the following patterns: (1) upper part enrichment; (2) complex distribution; (3) deep layer enrichment; and (4) uniform distribution. The heavy metal concentrations in the upper layer of the majority of the rivers are higher than those in the deep layer. The strong positive correlations between the heavy metals and major chemical components (Al2O3, Fe2O3, and organic carbon) indicate that the heavy metal concentrations are partly determined by sediment properties. The heavy metal concentrations and the Me/Fe values both in the upper and deep sediment layers show regional patterns. The high concentrations of As, Cd, Hg, Mn, Mo, Pb, and Zn in most of the south rivers indicate the importance of natural controlling factors from geological setting and mineralization. Significant enrichment of the heavy metals in the upper layer indicates an anthropogenic impact, particularly in some south China rivers.

Impact of microtopography on the geochemistry of soils within archaeological sites in SE Poland

The geochemical record of human impact within three archaeological sites in SE Poland was analysed. The total levels of Cd, Cu, Pb, Zn and P were defined. The content of the studied elements was found to be higher than the determined geochemical background. In all cases, significantly higher concentrations (2–3 times) of trace metals were found in sediments filling small depressions and foot-slope locations. These concentrations were often higher than in the profiles within the archaeological objects. The vertical distributions of elements were also different from soil profiles located on flat surfaces. The study thus confirms that microtopography and soil erosion may impact (diversify) the initial horizontal and vertical variation of geochemistry of soils within archaeological sites caused by human activity. This should be taken into account when using geochemical prospecting in archaeological studies in areas with varied topography.

Specific features of the vertical distribution of elements of the main biogenic cycles in waters of the Northwest shelf of the Black Sea

We study specific features of the vertical distribution of elements of the main biogenic cycle in the upper layers of waters on the northwest shelf of the Black Sea in spring and autumn and the correlation between the specific features of the vertical distributions of hydrochemical and hydrological characteristics. It is shown that the location of the halocline always specifies the location of the chemocline, whereas the effect of the thermocline on the distribution of hydrochemical characteristics is ambiguous. The vertical distribution of the hydrochemical parameters can be homogeneous in the presence of the seasonal thermocline. At the same time, in its absence, one may observe significant vertical gradients in the distributions of hydrochemical characteristics inside the upper mixed layer.

Influence of reclamation on the concentrations and chemical states of elements in tideland sediment

In order to investigate the transition of tidelands, we collected sediments in Yatsu tideland and Nekozane river mouth in Tokyo Bay. The vertical distributions of elements were determined by instrumental neutron activation analysis and prompt gamma-ray analysis. In Yatsu tideland the vertical distribution changed in a great extent, which was considered as an influence of the neighboring reclamation. They were categorized into four groups, and two parameters were created by applying principal component analysis. Chemical states of iron and sulfur were also investigated by Mossbauer spectroscopy and X-ray absorption fine structure. These results show that Yatsu tideland became an anaerobic environment.

Vertical variations and dispersion of elements in arid desertregolith: a case study from the Jinwozi gold deposit,northwestern China

Desert terrains in northern China are covered by widespread regolith sediments which mask geochemical signals from ore bodies and are major obstacles to mineral exploration. There is a critical need to study the vertical distribution of elements in the regolith, and to determine potential mechanisms for transferring elements from the ore body upwards through regolith cover to the surface, and to establish appropriate sampling media and analytical methods. The Jinwozi gold deposit, which is covered by four to several tens of metres of regolith sediment, was selected for this study. Samples were taken from different regolith horizons in two vertical profiles over the deposit. Gold and associated elements showed crescent-shaped distribution patterns in the vertical profile, i.e. elements tend to be enriched in lower and upper parts of the profile over the ore body. Enrichment of elements in weathered rocks is derived from the ore body, whereas enrichment at or near surface is due to adsorption by clays or oxide coatings. For gold, the greatest contrast between anomalous and background concentration is in the fine fraction of soils, and the Au anomalies are located directly over the ore body. Gold appears to migrate vertically to the surface to be trapped in clays and oxide coatings to produce superimposed anomalies in the regolith near or at the surface. Fine fraction samples (−120 mesh; 125 μm) from clay-rich horizons or selective leaching of elements adsorbed on clays or oxide coatings are effective for locating buried deposits.

Estimation and relevance of bark proportion in a willow stand

Abstract We studied bark proportion of a willow ( Salix viminalis ) plantation established to produce biomass for energy, the vertical distribution of elements (N, P, K, Mg, Ca, Co, Cu, Zn, As, Si, Cd, Cr, Pb, Hg and Ni) in bark and in wood of the shoots and the content of elements in the standing biomass. The study is based on 5-year-old shoots (clone 77-683) from a 12-year-old plantation. The bark proportion of the whole willow stand was 19% ( 9 tDM ha - 1 ) . The bark proportion of single shoots was constant after they had reached the size of 20 mm at stem diameter at 55 cm height. Compared to wood, bark had significantly higher concentrations of N, P, K, Mg, Ca, Cd, Pb, Co and Zn. The nutrient element (N, P, K, Mg) concentrations in the bark and in the wood of the current year shoot fractions (twigs) were significantly higher compared to the bark and the wood of other fractions. The accumulation of heavy metals occurred due to the accumulation of tree biomass and not due to the increase of heavy metal (Cd, Cr, Pb and Hg) concentrations in plant tissues over time. In summary, different management regimes give a possibility to influence shoot size frequency distribution of the crop and the chemical composition of biomass. For minimizing element removals from the soil and corrosion processes in power plants, energy willow stands should be managed in a way that promotes low bark proportion and thereby as little nutrient removal from the site by biomass harvest as possible.

A study on vertical distribution of elements and their chemical states in Yatsu tideland sediments

We have clarified vertical distribution of thirty and more elements in the Yatsu tideland sediment by instrumental neutron activation analysis (INAA) and prompt g-ray analysis (PGA). The distributions of elements were categorized into three groups according the tendency of each vertical distribution. Chemical states of iron in the sediments were investigated by Mossbauer spectroscopy. In the distribution of iron species, maximum pyrite distribution was found in the middle layer. Paramagnetic high-spin Fe2+ distributed complementarily to pyrite, suggesting that the Fe2+ was used for pyrite formation.

Spatial and vertical distributions of elements in sediments of the Colorado River delta and Upper Gulf of California

The abundance of major components (Fe, Ca, K, and organic carbon) and trace elements was analyzed in surface sediments and core samples from the Colorado River delta (CRD) and the Upper Gulf of California (UGC) using instrumental neutron activation analysis . The spatial distribution patterns of the elements studied are consistent with the model of sedimentary dynamics proposed for this area [Mar. Geol. 158 (1999) 125]: intense tidal resuspension of sediments in the delta with subsequent transport of suspended particulate matter in a southerly direction, followed by sedimentation of fine-grained material in a depocenter near the southwestern margin of the UGC. Concentrations of most of the elements are higher in the surface sediments of this depocenter. The gradual mixing of terrigenous and marine biogenic materials , normally expected for the estuarine sediments , was not detected in the CRD–UGC system because of homogenization of the sediments by tides and wind. Vertical profiles of element contents in samples of the sediment core collected in the depocenter area revealed (i) almost no anthropogenic contamination of the area by environmentally important trace elements such as Cr, Co, Sb, and As; (ii) a twofold decrease of Fe, Sc, Cr, and Co in upper core sediments; and (iii) the enrichment of the sediments at 60–62 cm depth in the core, in calcium carbonate , Ca, Sr, and the Eu n /Sm n shale-normalized ratio along with a depletion in this layer of Fe, Sc, Cr, Co, light rare-earth elements (REEs), and some other elements of terrigenous origin, presumably caused by the dilution of fluvial terrigenous material by biogenic carbonates, which were probably introduced at this level in the sediments by the action of a strong episodic winter storm, followed by the advective transport of shell fragments from the coastal clam banks or as a result of strong planktonic bloom.

Trace element contents in marls of the Ptolemais - Amynteon lignite basin, Western Macedonia, Greece

Sixty-five marl samples were collected from the outcrops of six active and one abandoned mine of Ptolemais-Amynteon Lignite Center, Northern Greece. Core samples were also collected from the West Field, a Neogene lignite deposit located at the same area. The concentrations of 39 trace elements were determined using Instrumental Neutron Activation analysis (INAA) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Carbon and sulfur contents and the loss on ignition of the samples were also determined. The classification of the trace elements concentrations in each mine and their statistical processing allows determining the horizontal and vertical distribution in the coal deposits and in the entire basin. Regarding the vertical distribution of elements and geochemical groups, significant variations of the concentrations in both the different marl seams and the upper, intermediate and lower lignite seams were determined. The mining, processing, transportation, storage and utilization of marls release, among others, some amounts of trace elements into the environment. However, the low concentrations of all trace elements, except Pb in the South field, compared to the upper mean values of world rocks Crust (W.C-U.M.V) (enrichement factor <0.8) is of great environmental concern and prove the non hazardous role of the marl during mining, beneficiation and usage.

Vertical distribution of elements in non-polluted estuarine sediments determined by neutron induced prompt gamma-ray and instrumental neutron activation analyses

Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments.

Mobilization and attenuation of metals downstream from a base-metal mining site in the Mátra Mountains, northeastern Hungary

Regional geochemical baseline values have been established for Hungary by the use of low-density stream-sediment surveys of flood-plain deposits of large drainage basins and of the fine fraction of stream sediments. The baseline values and anomaly thresholds thus produced helped to evaluate the importance of high toxic element concentrations found in soils in a valley downstream of a polymetallic vein-type base-metal mine. Erosion of the mine dumps and flotation dump, losses of metals during filtering, storage and transportation, human neglects, and operational breakdowns, have all contributed to the contamination of a small catchment basin in a procession of releases of solid waste. The sulfide-rich waste material weathers to a yellow color; this layer of `yellow sand' blankets a narrow strip of the floodplain of Toka Creek in the valley near the town of Gyöngyösoroszi. Contamination was spread out in the valley by floods. Metals present in the yellow sand include Pb, As, Cd, Cu, Zn, and Sb. Exposure of the local population to these metals may occur through inhalation of airborne particulates or by ingestion of these metals that are taken up by crops grown in the valley. To evaluate the areal extent and depth of the contamination, active stream sediment, flood-plain deposits, lake or reservoir sediments, soils, and surface water were sampled along the erosion pathways downstream of the mine and dumps. The flood-plain profile was sampled in detail to see the vertical distribution of elements and to relate the metal concentrations to the sedimentation and contamination histories of the flood plain. Downward migration of mobile Zn and Cd from the contaminated upper layers under supergene conditions is observed, while vertical migration of Pb, As, Hg and Sb appears to be insignificant. Soil profiles of 137Cs which originated from above-ground atomic bomb tests and the Chernobyl accident, provide good evidence that the upper 30–40 cm of the flood-plain sections, which includes the yellow sand contamination, were deposited in the last 30–40 years.