Soil Geochemical Survey Research Articles

Soil geochemical survey of abandoned mining sites in the Eastern-Central Peloritani Mountains, Sicily, Italy

This investigation focused on topsoils ( n = 122) and vertical profiles ( n = 6) distributed over an area of 250 km 2 in the eastern-central Peloritani Mountains, northeastern Sicily. Georeferenced concentration of 53 elements (including potentially harmful ones), determined by ICP-MS after an aqua regia leach, were used to produce geochemical maps by means of a GIS-aided spatial interpolation process. Results show that there are two distinct areas: the larger, located between the Fiumendinisi, Budali and Ali villages, and the other between C. Postlioni and Femmina Morta, which contain anomalous As (up to 727 mg/kg), Sb (up to 60 mg/kg), Ag (up to 1 mg/kg) and Au (up to 0.1 mg/kg) concentrations. Most of the investigated areas have high contamination levels for As, Zn, Sb, and Pb that exceed the threshold values (As = 20 mg/kg, Zn = 150 mg/kg, Sb = 10 mg/kg and Pb = 100 mg/kg) established for soils by the Italian Environmental Law ( Decreto Legislativo 2006 , number 152). The isotopic ratios of 206 Pb/ 207 Pb and 208 Pb/ 207 Pb have been measured in selected soils on both leaches [using 1M HNO 3 –1.75M HCl (50:50)] and residues thereof. Soil leach reflects possible anthropogenic contamination, whereas soil residues indicate geogenic contributions. Results suggest that most of contamination in the soils is related to the presence of sulphide and sulphosalt rock-forming minerals in the surveyed area. The soil fraction contains a Pb value >1600 mg/kg and has ratios of 1.1695 for 206 Pb/ 207 Pb and 2.4606 for 208 Pb/ 207 Pb. Only one soil leach isotopic composition could reflect possible anthropogenic contamination. The correlation among As, Zn, Pb contents v. Pb isotopic signatures of 206 Pb/ 207 Pb indicates that surface and deep soils collected from profiles are dominated by geogenic compositions.

Geochemistry of potentially harmful elements in topsoils around Kerman city, southeastern Iran

A multi-element geochemical soil survey was performed to assess the geochemical baseline and the environmental impacts of some potentially harmful elements in soils of the Kerman city. In doing so, a total of 175 samples, including residual (5), evaporate (6), silty–clay plain (42), urban (15), archaeological (3), road side (12), runway side (3), rail road side (7), agricultural (34), machinery battery manufacturing station (10), gasoline station (17), machinery paint working station (17) and cemetery (4) soil samples were collected on the 1:50,000 scale map of the Kerman city. The soil samples were analysed by ICP-OES for Ag, As, Bi, Cd, Co, Cr, Cu, Hg, Li, Mo, Ni, Pb, Se, Sn, V, W and Zn. The resulting elemental values in non-contaminated residual soils are similar to that of global background soil level (Salimen et al. Geochemical atlas of Europe. Part 1, Background information, methodology and maps. Finland Geological Survey, p 526, 2006; Lindsay Chemical equilibria in soils. Wiley, p 449, 1979). However, the soils close to the gasoline stations are enriched in Pb with variations up to 202 mg/kg. Soils developed around the machinery battery manufacturing stations also give a very high concentration of Pb as high as 60,445 mg/kg. The anomalous contents of Pb in soil samples close to the machinery paint working places range from 0.27 to 692 mg/kg. Some high values of Zn up to 1655 mg/kg are related to the agricultural soils in Pistachio gardens. The results highlight that the most anomalous harmful elements include Pb, Sn, Cd, Cu, Zn, Sb, As and Mo, which is supported by their high enrichment factors.

Geochemical transformation of soil cover in copper–molybdenum mining areas (Erdenet, Mongolia)

The aim of the present study is to evaluate geochemical transformation of soil cover in the territory of Erdenet (Mongolia) and to assess the environmental risk associated with soil cover contamination. The objectives of the present study included: (1) the determination of heavy metals (HMs) and metalloids contents in surface horizons of background and urban soils and the assessment of geochemical transformation of the city’s soil cover; (2) the identification of elements’ associations and patterns of their spatial distribution in the soil cover of the city; (3) the assessment of environmental hazard, related to contamination of soils with complexes of HMs and metalloids. Soil–geochemical survey was conducted by the authors in the summer periods of 2010 and 2011. In total, 225 samples, including 32 backgrounds, were collected. Bulk contents of HMs and metalloids in soil samples were analyzed by mass-spectral method with inductively coupled plasma at All-Russian Research Institute of Mineral Raw Materials (Moscow) using Elan-6100 and Optima-4300 devices (Perkin Elmer, USA). Mo, Cu, and Se appeared to be the priority pollutants nearly in all land-use zones. The maximum accumulation of Mo, Cu, Se, As, Sb, and W is restricted to the industrial area where total pollution index of soils (Zc) equals 74.8. Three technogenic associations of elements, derived mainly from petrochemical features of Erdenet ore field and characterized by similar spatial distribution within the city, are identified. Environmental assessment of surface soil horizon geochemistry in Erdenet showed that 1/5 of its area has dangerous and extremely dangerous levels of soil pollution. Experience of the environmental–geochemical assessment of soil cover in the impact zone of mining enterprises could be useful for other fields of the non-ferrous metals with high lithological–geochemical heterogeneity of the territory. It suggests the need of accounting for the geological diversity and specific features of metallogeny of an area. Geochemical indices local enrichment factor/local depletion factor should be calculated against the individual background values for each soil-forming rock. Such approach allows more accurate assessment of the degree of technogenic geochemical transformation of soils and the environmental hazard of pollution.

Geochemical assessment of steel smelter-impacted urban soils, Ahvaz, Iran

Geochemical study of urban soils is a challenging work due to high diversity of urban areas and multiple influences of anthropogenic sources on the soil geochemical composition. In the present study, a soil geochemical survey has been performed to determine the spatial distribution and possible sources of metals in the area around the Iran National Steel Industrial Group (INSIG). Concentrations of metals (Cr, Ni, Mn, Zn, Cu, Pb, V, Co and Fe) were determined in 63 topsoil (0–20cm) and 46 subsoil (40–50cm) samples. In addition, the pH, soil organic carbon (SOC), cation exchange capacity (CEC), soil grain sizes and CaCO3 were measured for each sample. The mean concentrations of Cr, Ni, Mn, Zn, Cu, Pb, V and Co in the topsoils were 556mg/kg, 261mg/kg, 2204mg/kg, 1716mg/kg, 157/kg, 122mg/kg, 177mg/kg and 41mg/kg, respectively. This study is based on comparisons of statistical parameters, the spatial distribution of studied elements and the results of hierarchical cluster analysis (HCA) and principal component analysis (PCA). Four natural geochemical associations and one anthropogenic geochemical association were identified for the topsoil layer. Natural geochemical associations (sand, silt and CEC), (Cr, Ni and V), (Co and clay) and (pH) are mainly influenced by geogenic/pedogenic factors, while anthropogenic association (Mn, Zn, Cu, Pb, Fe, SOC and CaCO3) is related to anthropogenic activities in the study area. The principal component analysis of the subsoil data set revealed four main components: the “anthropogenic specific” association of (Zn, Cu, Pb, Fe, SOC and CaCO3) and three “natural specific” associations of (pH, sand, silt and CEC), (Cr, Ni, V and Co) and (Mn and clay). A distinct anomaly of anthropogenically introduced metals was found in soils closer to the steel smelter in the N–SE axes of the study area. The results of HCA and correlation analyses for the data sets of two soil layers suggested that chelated elements (Zn, Cu, Pb and Fe) by soil organic fraction were transported down to the subsurface layer (40–50cm). According to the Canadian Soil Quality Guidelines, Cr, Ni, Mn, Zn and Cu were the primary critical metals in the both soil layers. This study may provide decision makers with the useful information for management practices to protect human health.

Analysis and mapping of soil geochemical anomalies: Implications for bedrock mapping and gold exploration in Giyani area, South Africa

Previous exploration activities in the Giyani greenstone belt (GGB) were guided by the availability of outcrops, particularly iron formation, as this rock was considered to be the main host rock for gold mineralisation in the belt, although the majority of the known prospects/deposits are hosted by mafic rocks. However, there is no reliable lithological map available for the GGB, because most of it is covered by regolith, and thus in the early 1990s most mining and exploration companies in the GGB have abandoned their work as they were discouraged by the scarcity of outcrops, the small sizes of existing deposits and the low gold prices at that time. In the present study, major and trace element geochemical data from a high-density soil geochemical survey (1 sample/km2) have been subjected to statistical and spatial analyses to support bedrock mapping and gold exploration. Maps are presented for major oxides, trace elements and selected respective ratio maps, and principal components (PC). The PC analysis was performed on clr-transformed data of selected trace elements known to be associated with gold mineralisation. The first six PCs explain about 78% of the total variance. PC4 representing Sb–As–Te–Cr–Au association best reflects the known gold mineralisation and was, therefore, used as a thematic layer. The information provided by various composite maps of different major/trace element data, as well as PC maps, has been used to produce an interpretive bedrock map outlining major lithological units in the study area. As gold mineralisation in the Giyani greenstone belt is hosted by certain known lithologies, the map is useful in indicating potential gold bearing areas.

Copper, Zn and Pb soil geochemistry data from the NE domain of the Iberian Pyrite Belt in Portugal: implications for mineral exploration

The area-concentration multifractal modelling of a soil geochemical survey performed in the Alfarrobeira–Chança region (covering the Pulo do Lobo Terrane, PLT, and the Iberian Pyrite Belt, IPB) shows that the upper limit of Cu, Zn and Pb background concentrations in soils over PLT metasediments are c . 20, 55 and 20–30 ppm, respectively. In soils derived from the Volcano-Sedimentary Complex of IPB, the Cu, Zn and Pb regional threshold values are within the 25–45, 40–60 and 20–90 ppm intervals, respectively. The lower limit of Cu, Zn and Pb soil anomalies overlying metasediments are within the 30–50, 90–115 and 45–60 ppm intervals, respectively; over soils with abundant volcanic-derived components those lower limits are scattered in the 30–70, 70–90 and 33–100 ppm intervals. Proximity to mineralized rocks is indicated by Cu, Pb and Zn soil contents above c . 100, 120–150 and 250 ppm, respectively. Most of the anomalies display strong anisotropy. Separation of Cu, Zn and Pb soil anomalies reflects mostly the existence of distinct metal sources related to original compositional differences or to chemical changes developed during Variscan times. Metavolcanics represent the prevailing sources of Cu and, to a lesser extent, Pb; the prevalent sources of Zn are metasediments of the Phyllite-Quartzite (IPB) and Chança (PLT) Groups.

Urban soil geochemistry in Athens, Greece: The importance of local geology in controlling the distribution of potentially harmful trace elements

Understanding urban soil geochemistry is a challenging task because of the complicated layering of the urban landscape and the profound impact of large cities on the chemical dispersion of harmful trace elements. A systematic geochemical soil survey was performed across Greater Athens and Piraeus, Greece. Surface soil samples (0–10cm) were collected from 238 sampling sites on a regular 1×1km grid and were digested by a HNO3–HCl–HClO4–HF mixture. A combination of multivariate statistics and Geographical Information System approaches was applied for discriminating natural from anthropogenic sources using 4 major elements, 9 trace metals, and 2 metalloids. Based on these analyses the lack of heavy industry in Athens was demonstrated by the influence of geology on the local soil chemistry with this accounting for 49% of the variability in the major elements, as well as Cr, Ni, Co, and possibly As (median values of 102, 141, 16 and 24mgkg−1 respectively). The contribution to soil chemistry of classical urban contaminants including Pb, Cu, Zn, Sn, Sb, and Cd (medians of 45, 39, 98, 3.6, 1.7 and 0.3mgkg−1 respectively) was also observed; significant correlations were identified between concentrations and urbanization indicators, including vehicular traffic, urban land use, population density, and timing of urbanization. Analysis of soil heterogeneity and spatial variability of soil composition in the Greater Athens and Piraeus area provided a representation of the extent of anthropogenic modifications on natural element loadings. The concentrations of Ni, Cr, and As were relatively high compared to those in other cities around the world, and further investigation should characterize and evaluate their geochemical reactivity.

The Geological Characteristics and Potential Evaluation of Yunnan Zhenkang Luziyuan Mining Area

Luziyuan lead zinc iron metal mining area is located in the south of Baoshan-Zhenkang lead, zinc, mercury, rare metal mineralization belt of the southwest Sanjiang metallogenic belt.According to the mine tunnel drilling and logging data, that the ore bodies are controlled by strata and faults, symbiosis and Dali rock, limestone, near ore wall rock skarnization strongly, the research shows that the deposit belongs to sedimentary transformation - skarn Pb Zn Fe polymetallic deposit. [ Mining area within the range of 1:50000, 1:50000 gravity measurements of soil geochemical survey, combined with the large scale mapping of data discovery lead zinc iron copper resources are expected to find in the eastern Luziyuan area Mangxi - Head Mountain Luojiazhai resource replacement area.

Statistical Studies of Soil Geochemical Data from Gbongan-Odeyinka Area, Southwestern Nigeria

Statistical Studies of Soil Geochemical Data from Gbongan-Odeyinka Area, Southwestern Nigeria In order to follow up some geochemical anomalies discovered in a regional stream sediment survey in parts of southwestern Nigeria, a medium density geochemical soil survey was carried out in Gbongan-Odeyinka area of Osun State, southwestern Nigeria. As a result, soil geochemical data on 13 elements (Ag, As, Au, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, and Zn) obtained from 186 samples from the study area were subjected to statistical analysis involving frequency distribution, Pearson correlation and R-mode varimax rotated factor analysis techniques. The frequency distribution plots revealed that all the elements investigated except Ag and Fe, which display approximately normal distribution, are positively skewed with Au and Zn being the strongest. The Pearson correlation study and factor analysis enabled separation of the 13 elements into the following three factors or metal associations: 1) Pb-Co-Ni-Fe-Cr- As-Mn-Cu; 2) Sn-Ag-Au-Cd; and 3) Zn-Cd, which are interpreted to reflect the influence of both environmental and mineralization factors on the soil of the study area. Of the three associations only the Sn-Ag-Au-Cd is considered related to metallic mineralization in the study area based on the existing knowledge of Au and Sn mineralization in the adjacent Ife-Ilesa area. The gold is believed to be hosted by schists and the tin by pegmatites. The other metal associations are interpreted in terms of environmental factors. On the basis of the presence of Fe and Mn in the Pb-Co-Ni-Fe-Cr-As- Mn-Cu association, it is inferred that the scavenging action of iron and manganese oxides was at least partly responsible for forming such trace elements association in the soil. In the case of the Zn-Cd association, both metals are considered to be anthropogenic, being possibly introduced to the soil through the application of pesticides on cocoa and kolanut plantations of the study area, although the possibility of Zn being derived from other sources cannot be ruled out.

Multivariate statistical approach to identify metal sources in Litija area (Slovenia)

A detailed soil geochemical survey has been performed in the abandoned polymetallic (Hg, Pb, Ag, Zn, Ba) mining and smelting region of Litija, central Slovenia. In an area of 30km2 the soil was systematically sampled using a 500×500m grid (120 sampling sites). Two soil horizons (0–5cm and 15–30cm) were sampled in order to distinguish between geogenic and anthropogenic metal sources. A metal dispersion halo has been mapped in a wide circle around Litija. This paper discusses its extension and characteristics, which were established on the basis of metal contents in soil. Data treatment included multivariate statistical approaches (multivariate cluster and R-mode factor analysis), which allowed the identification of two geogenic and two anthropogenic geochemical associations. The main geogenic group of element includes Ce, Cr, Fe, Hf, Nb, La, Th, Ti, Ta, U, V, W and Zr; high contents of these elements are associated with the sand fraction of the Würm terraces. The second geogenic group includes Al, Ba, K, Li, Rb, and Sc; high concentrations of these elements are related to the alluvial sediments of the Sava tributaries. The third geochemical group is partly geogenic and anthropogenic, linking typical elements (Ca, Mg, Sr) of alluvial sediments of the river Sava and some metals (Cd, Co, Cu, Ni, Mn and Zn); the source of these metals is most probably the ferrous metallurgy in the upper part of the Sava valley. The fourth and also the most important anthropogenic geochemical association (As, Mo, Hg, Pb, Sb and Sn) is typical for the areas affected by past mining and smelting activities.

REE potential of the Nordkinn Peninsula, North Norway: A comparison of soil and bedrock composition

Regional-scale, low-density sampling, geochemical surveys using a variety of different sample materials have repeatedly indicated the Nordkinn Peninsula (northern Norway) as a substantial rare earth element (REE) anomaly. Recently, a more detailed soil geochemical survey, covering about 2000km2 at a sample density of 1 site per 2km2, was carried out in the area. The new geochemical survey outlined a large area (several hundred km2) where the soil samples contained several hundred and up to over 2000mg/kg aqua regia extractable REE. In the surroundings of the highest soil anomalies, bedrock samples were collected for a mineralogical and compositional characterisation of the metasedimentary bedrock with focus on the possible economic potential.The REE concentrations obtained for aliquots of bedrock following aqua regia extraction, 4-Acid digestion and Li-borate fusion/decomposition closely match the results from soil pulps after an aqua regia extraction. Total contents for the REE determined in bedrock using the above methods range between 19 and 429mg/kg, indicating an overall limited economic REE potential and the predominance of the light REE over the heavy REE. In terms of petrography, essentially all the bedrock samples are characterised by the presence of detrital, altered and locally even decomposed allanite (a LREE-incorporating, epidote-group mineral) and minor xenotime (a HREE-incorporating phosphate) while texturally stable REE phases are scarce. It is the poor condition of the REE minerals that makes them prone towards acidic leaching and, given similar results for all of the above preparation methods, even the relatively weak AR extraction dissolved the REE almost completely from the samples. The REE anomaly observed for the soil samples thus rather reflects the state of alteration of the REE phases than ore-grade concentrations in the underlying bedrock.

Geology, geochemistry, and genesis of orogenic gold–antimony mineralization in the Himalayan Orogen, South Tibet, China

The southern Tibet AuSb metallogenic belt in the Himalayan orogen consists of more than 50 gold, gold–antimony and antimony lode deposits, and associated placer gold deposit. The deposits are hosted in a Mesozoic metamorphosed turbidite sequence of the Indian passive continental margin. The Zhemulang Au deposit, Mazhala AuSb deposit, and Shalagang Sb deposit are three typical examples of such epizonal orogenic deposits. At Zhemulang, gold-bearing quartz veins occur in the Upper Triassic Songre Formation, consisting of carbonaceous phyllite and slate. Ore minerals are native gold, pyrite, galena, chalcopyrite, and limonite. At Mazhala, the gold- and stibnite-bearing quartz vein orebodies are hosted in Lower to Middle Jurassic slate, interlayered with metastandstone, metasiltstone, and limestone of the Lure Formation. Ore minerals are native gold, stibnite, pyrite, arsenopyrite, and trace amount of cinnabar. At Shalagang, the host rocks are Lower Cretaceous sandstone, siltstone, muddy limestone, and chert of the Duojiu Formation. Orebodies consist mainly of stibnite-bearing quartz veins and locally altered fault breccia. Ore minerals are stibnite, cinnabar, valentinite [Sb2O3], limonite, and trace amount of pyrite, arsenopyrite, and realgar. For the three deposits, the wallrock alteration has produced the minerals silica, carbonates, white mica, sulfide and chlorite. The three deposits have a similar element associations, but with a few slight variations. The Zhemulang, Mazhala, and Shalagang deposits, in order of element enrichments relative to crustal abundance, are anomalous in Au, Sb, Te, Bi, As, Pb, Ag, and W; Sb, Au, Te, As, Pb, Bi, Ag and W, to Sb, Te, As, Au, Hg, W, Pb, and Ag, respectively, and all depleted in Cu, Zn, Sn, and Mo.Various aqueous, carbonic, and hydrocarbon fluid inclusions were recognized in quartz and/or stibnite at the three deposits. These include type 1a one-phase aqueous inclusions, type 1b two-phase aqueous inclusions, type 2a carbonic inclusions, type 2b aqueous-carbonic inclusion, and rare type 3 hydrocarbon inclusions that include two-phase hydrocarbon inclusions (type 3a) and dark one-phase hydrocarbon inclusions (type 3b). The three deposits have the similar low-salinity H2OCO2CH4N2 ore fluids with trace amounts of hydrocarbons. For the Zhemulang, Mazhala, and Shalagang deposits, the salinities of aqueous inclusion range mainly between 3.3 and 6.4wt.% NaCl equiv., 2.5 and 4.9wt.% NaCl equiv. and 4.1 and 6.4wt.% NaCl equiv., respectively. The ore-forming temperatures vary mainly from 180 to 320°C, 160 to 300°C and 140 to 240°C, respectively. The estimated mineralization depths are 4 to 6km, 3 to 5km, and 1 to 4km of the epizonal environment, respectively. The different mineralization temperatures and pressures led to the different element enrichments at the three deposits.For the Zhemulang, Mazhala and Shalagang deposits, ore fluid isotopic compositions are δDH2O −107.5 to −36.7‰ and δ18Ofluid 2.8 to 8.2‰, δDH2O −119.0 to −72.7‰ and δ18Ofluid 7.5 to 16.2‰, and δDH2O −173.4 to −139.2‰ and δ18Ofluid 7.5 to 12.3‰, respectively; δ13Cfluid values are −11.7 to −9.6‰, −3.5 to −2.5‰, and −6.5 to −5.1‰, respectively; and δ34S values are −4.0 to −1.1‰, −0.8 to 2.3‰, and −3.9 to 2.1‰, respectively. The ore-forming fluids were partly derived from metamorphic devolatilization of immediate or deeper level country rocks, with a deposit's corresponding metamorphic degree controlling the fluid PTX. The ore-forming fluid for Zhemulang, Mazhala, and Shalagang consisted of predominantly metamorphic water with minor involvement of meteoric water, a mixture of metamorphic fluid and meteoric water, and predominantly meteoric water, respectively. Ore metals were derived from country rocks, including synsedimentary Sedex-like sulfide layers in the Jurassic strata observed at the Mazhala AuSb deposit. Among three deposits, the variation of δ13Cfluid and δ34S reflects the fact that the Zhemulang Au deposit formed from a relatively high content of organic carbon and low ƒO2 fluid, the Mazhala AuSb deposit from a relatively low content of organic carbon and high ƒO2 fluid, and the Shalagang Sb deposit from an intermediate content of organic carbon and ƒO2 fluid. Fluid immiscibility was the main mechanism for ore metal precipitation at all three deposits. The vertical zonation of Au, AuSb, and Sb mineralization suggests that additional gold resources may exist below the antimony or gold–antimony orebodies. Stream sediment and soil geochemical surveys and the occurrence of placer gold prospects are effective for identifying areas of orogenic gold and antimony deposits in the Himalayan and other orogens.

Statistical variability of the geochemistry and mineralogy of soils in the Maritime Provinces of Canada and part of the Northeast United States

A soil geochemical survey in the Maritime Provinces of Canada and part of the Northeast United States was completed for the North American Soil Geochemistry Landscapes Project. Soil samples, derived largely from unsorted glacial till, were collected over 349 sites, from 0 to 5 cm depth (regardless of horizon), A-, and C-horizons. The 0 to 5 cm depth interval represents the soil of interest in health risk assessments and is termed the Public Health (PH-) layer. The <2 mm fraction of each sample was analysed for a broad suite of major and trace elements using a near-total four-acid digestion, and major mineralogical components were determined by quantitative X-ray diffraction. Multivariate statistical analyses of the logcentred soil geochemistry from the PH-layer and the two soil horizons, and of the soil mineralogy from the A- and C-horizons, reveal distinctive inter-element relationships from deeper soil (represented by the C-horizon) upwards into topsoil (represented by the A-horizon and PH-layer). Statistical dispersion of several elements increases upwards in the soil profile. Maximum data dispersion occurs in the PH-layer and A-horizon soils. Elements including S, P, Pb, Hg, Cd, Se, Mo, Sb, Bi and Sn are relatively enriched in the PH-layer and A-horizon, and are positively correlated with increasing organic carbon contents. The relative enrichment of groups of elements in the C-horizon, in contrast to those elements in the A-horizon and PH-layer, suggests a composition that reflects the geochemistry of the glacial till that is derived from the local bedrock. Elements such as Ni, Mg, Cr, V, Co, Fe and Sc, represent a mafic component of the parent material, and relative enrichments of K, Rb, Zr, rare-earth elements, Li and Al indicate a more felsic component. The patterns revealed by the application of multivariate methods to the soil chemistry and mineralogy are attributed to underlying geology, soil-forming processes, and anthropogenic activity, or combinations of all three factors. Both the soil geochemistry and mineralogy were tested in their ability to predict soil horizon and underlying bedrock lithology or time-stratigraphic assemblages. The geochemistry and mineralogy of the soils are both good for predicting soil horizon; however, the soil geochemistry is better for predicting the underlying lithologies/assemblages than the soil mineralogy.

Integrating Multi‐element Geochemical and Magnetic Survey at Ancient Sagalassos (Southwest Turkey): Anthropogenic Versus Natural Anomalies

ABSTRACTSeveral studies in the field of archaeological prospection have suggested that multi‐element soil geochemical survey holds potential as an archaeological survey method, complementing more common techniques such as magnetometry and fieldwalking. Despite this, only limited research regarding this topic has been carried out. In this study, a geochemical survey was conducted in the Eastern Suburbium of the Roman to Byzantine city of Sagalassos, with the aim of investigating the possibilities and limitations of the technique in facilitating the interpretation of magnetic survey data. To explore the multivariate patterns present within the chemical dataset, the data were statistically analysed using a contiguity‐constrained spatial clustering algorithm. The resulting spatial clusters revealed that an area characterized by high‐frequency magnetic anomalies was spatially associated with a chemical cluster rich in Cu, K, P, Pb and Zn. This is interpreted as resulting from the accumulation and decomposition of occupational debris. Enhancements of Al, As and Ba helped to interpret an area with a low magnetic signal as a region where limestone bedrock was located close to the soil surface. Finally, two zones of enhanced magnetization were shown to spatially overlap with two clusters of soils containing elevated levels of Co, Cr, Mg, Mn, Ni and (Fe) and Ti, V and (Fe), respectively, indicating the presence of two different types of mafic to ultramafic ophiolitic bedrock near the soil surface. This study confirms that multi‐element geochemistry has potential as a survey technique, because it offers direct information on soil bedrock or ancient human disturbance, thereby adding an extra dimension to the interpretation of geophysical survey data. It is shown that soil chemical data are particularly valuable for distinguishing anthropogenic and natural impacts creating geophysical anomalies. Contiguity‐constrained clustering was found to be a promising data analysis technique for multivariate geochemical survey data. Copyright © 2013 John Wiley & Sons, Ltd.

Overview of trace metals in the urban soil of 31 metropolises in China

This overview provides an up-to-date assessment of the trace metal contamination (As, Cd, Cr, Cu. Hg, Ni, Pb, Sb, Se, and Zn) in urban soils of 31 metropolises in China. This systematic soil geochemical survey summarizes the characteristics of trace metals in Chinese urban soils, including concentration, accumulation, spatial distribution, and major sources. Mercury was ranked first followed by Cd and Se in geo-accumulation among all of the contaminant metals in urban soils in China; this finding is likely due to the Hg and Se emissions from fossil fuels. However, the lack of studies on Se contamination in urban soils, not only in China but also in the rest of the world, implies that Se contamination may have been unobserved for a long time. Shanghai, Kunming, Shenyang, and Changsha may be some of the most heavily contaminated Chinese cities based on the concentrations, spatial dimensions, and associations among the contaminant metals. Numerous hotspots with high concentrations of metals were found in Changsha, Shanghai, and Shenyang, clearly indicating a significant contribution from both the metallurgical industry and smelt mining to the contamination of urban soils. Conversely, the levels of Sb, Cu, and Cd in Kunming originated from their naturally high geochemical background in soils. Heavy Se contamination was found in Guiyang and Taiyuan. The natural source of Se may be important in defining the pattern of pollution in Guiyang, whereas anthropogenic sources are likely more accurate than is the natural background in Taiyuan city. We review the existing limits and types of pollutants in the current soil guidelines and find that an international agreement on the range of the limits and the types of pollutants contained in the soil guidelines is urgently needed.

Analysis on mineralisation potential of copper and uranium in Luamala area, northwestern province, Zambia

Luamala area is in the middle of Lufilian arc and western of copper belt in middle Africa, which is beneficial for ore-forming. Because this area is covered by thick soil and plants, it is difficult to appraise the resources. According to the study of regional mineralization characteristics, it is considered to be a perspective area for exploration of copper and uranium minerals. Two copper anomalies were delineated by soil geochemical survey in a scale of 1∶25000 and a radioactive anomaly was delineated by Radon survey and gamma spectrum survey. This area is considered to be an perspective area with high potential based on geology,geophysical,Geochemical and radiometric survey. No.5 and No.3 anomaly area are preferable targets for prospecting for copper or uranium minerals in depth.

Ecological-geochemical state of soils in Ulaanbaatar (Mongolia)

Based on the results of the soil-geochemical survey, the assessment of the soil cover pollution in different Ulaanbaatar functional zones is given. The soils of the industrial and traffic zones concentrating a wide spectrum of pollutants (Zn, Mo, Cr, Cr, Cd, Pb, and Cu) are characterized by the strongest technogenic transformation. The soils of the residential areas accumulate Pb and Zn, while those of the recreation zone, Mo, Ni, and Cr. The geochemical mapping allowed distinguishing four groups of elements with similar distribution patterns determined by the common pollution sources, the specific features of the parent rocks, and the intensity of the migration. Among the natural and technogenic factors responsible for the accumulation of microelements in soils, the basic ones are the soil physical and chemical properties: the contents of organic matter (for As, Cd, Cu, Mo, Zn), physical clay (Ni, Co), sulfates (Pb, Sr), and the pH (Cr). The character of the land use noticeably affects the concentration of many elements. The soils of the city are assessed as weakly polluted (Zc = 11). The contents of As, Zn, Mo, and Pb exceeded their MPC in 100, 34, 20, and 16% of the city’s territory, respectively. As compared to the state of the soil cover in 1990, no significant changes were revealed.

Investigation of the origin and distribution of heavy metals around Ebenezer Dam, Limpopo Province, South Africa

This study was based on the outcome of the soil geochemical survey which was conducted by the Council for Geoscience around Ebenezer Dam during 1995-1996, the results of which indicated high concentrations of lead (Pb), zinc (Zn) and arsenic (As). The current study therefore focused on the origin and distribution patterns of Pb, Zn, Cu, As and Cr within the environs of Ebenezer Dam and their potential impacts on the environment and human health. The work involved soil, sediment, rock and water sampling and analysis. Atomic absorption and x-ray fluorescence spectrometry were used to determine the metal concentrations. The occurrence of anomalous concentrations of these metals in the study area was established. The anomalies registered maximum concentrations of (mg/g): 57 for Pb, 157 for Zn, 313 for Cu, 73 for As and 888 for Cr. The concentrations of these metals in sediments along the streams were high near the anomalies, but decreased downstream. Concentrations of heavy metals in water around the Ebenezer Dam were found to be less than 0.01 mg/g , except for As which was less than 1.0 mg/g. Thus Pb, Zn, Cu and Cr values were below the target water quality ranges for domestic, irrigation, livestock watering and aquatic ecosystem use. The study confirmed that the distribution of heavy metals in this area is localised within and around the source rocks that are felsic in nature, namely; granites and pegmatites that formed domes in the area.

Dispersion of antimony from oxidizing ore deposits

Abstract The solubilities of brandholzite, [Mg(H2O)6][Sb(OH)6]2, and bottinoite, [Ni(H2O)6][Sb(OH)6]2, at 25 °C in water have been measured. Solubilities are 1.95(4) × 10-3 and 3.42(11) × 10-4 mol dm-3, respectively. The incongruent dissolution of romeite, Ca2Sb2O7, and bindheimite, Pb2Sb2O7, at 25 °C in 0.100 mol dm-3 aqueous HNO3 was also investigated. Equilibrium dissolved Sb concentrations were 3.3 ± 1.0 × 10-7 and 7.7 ± 2.1 × 10-8 mol dm-3, respectively. These values have been used to re-evaluate the geochemical mobility of Sb in the supergene environment. It is concluded that the element is geochemically immobile in solution and in soils. This was in part validated by an orientation soil geochemical survey over the Bayley Park prospect near Armidale, New South Wales, Australia. Anomalous soil Sb levels are confined to within 100 m of known stibnite mineralization.

A regional-scale study of chromium and nickel in soils of northern California, USA

A soil geochemical survey was conducted in a 27,000-km2 study area of northern California that includes the Sierra Nevada Mountains, the Sacramento Valley, and the northern Coast Range. The results show that soil geochemistry in the Sacramento Valley is controlled primarily by the transport and weathering of parent material from the Coast Range to the west and the Sierra Nevada to the east. Chemically and mineralogically distinctive ultramafic (UM) rocks (e.g. serpentinite) outcrop extensively in the Coast Range and Sierra Nevada. These rocks and the soils derived from them have elevated concentrations of Cr and Ni. Surface soil samples derived from UM rocks of the Sierra Nevada and Coast Range contain 1700–10,000 mg/kg Cr and 1300–3900 mg/kg Ni. Valley soils west of the Sacramento River contain 80–1420 mg/kg Cr and 65–224 mg/kg Ni, reflecting significant contributions from UM sources in the Coast Range. Valley soils on the east side contain 30–370 mg/kg Cr and 16–110 mg/kg Ni. Lower Cr and Ni concentrations on the east side of the valley are the result of greater dilution by granitic sources of the Sierra Nevada. Chromium occurs naturally in the Cr(III) and Cr(VI) oxidation states. Trivalent Cr is a non-toxic micronutrient, but Cr(VI) is a highly soluble toxin and carcinogen. X-ray diffraction and scanning electron microscopy of soils with an UM parent show Cr primarily occurs within chromite and other mixed-composition spinels (Al, Mg, Fe, Cr). Chromite contains Cr(III) and is highly refractory with respect to weathering. Comparison of a 4-acid digestion (HNO3, HCl, HF, HClO4), which only partially dissolves chromite, and total digestion by lithium metaborate (LiBO3) fusion, indicates a lower proportion of chromite-bound Cr in valley soils relative to UM source soils. Groundwater on the west side of the Sacramento Valley has particularly high concentrations of dissolved Cr ranging up to 50 μg L−1 and averaging 16.4 μg L−1. This suggests redistribution of Cr during weathering and oxidation of Cr(III)-bearing minerals. It is concluded that regional-scale transport and weathering of ultramafic-derived constituents have resulted in enrichment of Cr and Ni in the Sacramento Valley and a partial change in the residence of Cr.