Micronutrient Contents of a Revegetated Saprolite Exposed by Excavation of an Oxisol

Soils of the Brazilian Cerrado biome have been found to be deficient in copper (Cu) and zinc (Zn). In this area, an Oxisol was deeply excavated in 1962 during the construction of a hydroelectrical plant, and the exposed saprolite material was abandoned, without any reclamation measures. The abandoned land was a harsh environment for plant growth, and the secondary vegetation has not recovered. A field trial was established in 1992 to assess the effects of different grass species and lime amendments on soil reclamation at the degraded site. In 2011 soil samples were collected at three depths (0–10, 10–20, and 20–40 cm) from vegetated and bare plots over tilled saprolite, from an untreated area of the saprolite, and from an Oxisol under native forest, used as external reference. Nineteen years after the reclamation effort was begun, the organic carbon (OC) content of the restored saprolite still was much lower than that of the Oxisol under natural vegetation. The undisturbed Oxisol was deficient in extractable Cu (0.16–0.10 mg kg^?1) and Zn (0.10–0.02 mg kg^?1) and exhibited rather low concentrations of extractable iron (Fe; 5.24–1.47 mg kg^?1) and manganese (Mn; 3.21–0.77 mg kg^?1). However, the saprolite under reclamation showed even lower levels of these elements compared to the native forest soil. In the natural soil, OC, N, extractable Fe, Mn, and Cu showed stratification, but this was not the case for extractable Zn. Although the reclaimed saprolite still was far from predisturbance conditions, the revegetation treatments promoted recovery of OC, N, Fe, Mn, and Cu at the surface layers, which resulted in incipient stratification. Extractable Fe, Mn, and Cu were correlated to OC, whereas no association between Zn and OC was detected. Our results also suggest that reclamation of the excavated saprolite may be constrained by micronutrient deficiencies and mostly by the extremely low levels of Zn and Cu.     

Changes in Extractable Si,Fe, and Mn as Affected by Silicon,Salinity, and Waterlogging in a Sandy Loam Soil

Silicon (Si) is one of the most abundant elements in the earth's crust, although its availability may be affected by some edaphic and abiotic factors such as soil moisture and salinity. In a laboratory experiment, effects of silicon (Si), salinity, and soil moisture on changes of extractable Si, iron (Fe), and manganese (Mn) concentrations were investigated on a sandy loam calcareous soil. The experiment was arranged as a factorial completely randomized design with three replications. Two levels of Si (8 and 200 mg per kg of soil), three salinity levels [0.46 dS m^?1, 8 dS m^?1 as sodium chloride (NaCl), and 8 dS m^?1 as four-salt combination], two soil moisture regimes (–20 kPa and waterlogged), and four incubation times (0, 7, 30, and 45 days) were applied. Salt composition consisted of sodium chloride, sodium sulfate, calcium chloride, and magnesium sulfate at a molar ratio of 4:2:2:1. Acetic acid–extractable Si, Fe, and Mn were determined after 0, 7, 30, and 45 days of incubation. Waterlogging caused significant increase in the extractable Si, Fe, and Mn. Soil salinity of 8 dS m^?1, only in the form of sodium chloride, resulted in a marked decrease in extractable Si, Fe, and Mn. Silicon addition enhanced the soil Si concentration, with no effect on Fe and Mn. Equilibrium time for Si and Fe was 30 days, whereas Mn concentration reached to a constant level after 1 week of waterlogging. It was concluded that Si, Fe, and Mn fertilizers should be applied in sufficient amounts to the saline soils to prevent their deficiencies in plants. Meanwhile, overfertilization in waterlogged conditions must be avoided, because of the probability of nutrient imbalance or toxicity.     

Vergleich zwischen Total- und königswasserextrahierbaren Elementgehalten in natürlichen Böden und Sedimenten

Comparison between total- and aqua regia extractable contents of elements in natural soils and sediments Total- and aqua regia extractable contents of 19 elements from 28 soil samples with widely varying composition of the ISE ring analytical program (INTERNATIONAL SOIL-ANALYTICAL EXCHANGE) of the year 1995 to 1997 have been taken to find out the comparability between the two fractions. The relations between the two fractions and pH, organic matter and clay content were considered by means of single and multiple regressions. The correlations between the total and aqua regia extractable contents of As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, P, Pb and Zn are very close, whereas Al, Ba, K, Na and Sr are not or only weakly correlating. The multiple regressions show that the content of some aqua regia extractable elements and the proportion (in %) of the total contents is correlated with pH, organic matter and/or content of clay. In the same way the proportion of aqua regia extractable elements is closely related (except Fe and Hg) to the soil pH. Hereby the proportion of the aqua regia extractable content increases with increasing pH in the range 3,5—7,7. The determined equations are tested for As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn by using the values of certified reference material. The estimated aqua regia extractable contents are being compared with values of reference material. The average proportion of the calculated to the measured aqua regia contents of an element in percent are 99 for Zn, 98 for Co, Cu and Mn, 94 for Cd, 90 for Ni, 88 for Cr, 105 for Hg, 113 for As and 114 for Pb.     

Cobalt,copper, and manganese adsorption by aluminium and iron oxides and humic acid

Abstract

Adsorption of cobalt (Co), copper (Cu), and manganese (Mn) by synthetic aluminium oxide, ferrihydrite, goethite, extracted humic acid, and a sandy soil sample were determined as a function of metals concentration (0–1.2 mM) and pH (3.8–8.2). For each pH and adsorbent, the Langmuir adsorption maximum (adsorption capacity) was calculated. The position of the adsorption curves for Co, Cu, and Mn as a function of pH has been shown to be related to the first hydrolysis constant of the cations in solution (pK₁). The sequence of preference of the three metals to the studied adsorbents decreased in order Cu >> Co > Mn. The results obtained from this study showed that the Co, Cu, and Mn adsorption characteristics of soils are probably controlled to large extent by their organic matter and oxides contents.     

渤海湾各形态重金属的地球化学特征及其环境意义

根据2008年对渤海湾的调查,重点研究了渤海湾湾内和湾口柱状沉积物重金属的生物地球化学特征,通过剖析不同形态重金属的特征,结合渤海湾生态环境信息的综合分析,系统探讨了渤海湾沉积物重金属的演变趋势、影响控制因素以及潜在生态风险。结果表明,湾内海河口附近沉积柱重金属含量有几次突变,20～22cm段极小值可对应1939年海河北系的洪水,10～12cm段极小值可对应1963年海河南系的洪水,1963年至今重金属含量有逐渐增加的趋势。不同形态重金属百分含量从大到小为：残渣态〉铁锰氧化物结合态〉碳酸盐结合态〉有机结合态〉可交换态,且重金属在海河口附近都表现出较高的可浸取态百分含量。风险评价结果表明,重金属总量富集因子由大到小为：Pb〉Cd〉Zn〉Cr〉V〉Co〉Cu〉Ni,其中Pb、Cd和Zn的富集因子均大于1,说明其有污染,但渤海湾沉积物总体质量良好,潜在生态风险较低。从重金属形态角度评价,V和Cr无污染,Zn、Co、Cu、Ni和Pb在湾内及湾外均有不同程度的污染,而Pb的污染最为严重。     

Mineralogical and chemical properties of weathered magnetite grains from lateritic saprolite

Magnetite grains in lateritic saprolite have altered in situ to porous hematite (martite) grains. Hematite occurs as relatively large (～ 1 μm) platy crystals, triangular arrays of small (0.01–0.05 μm) lathlike crystals and very small (< 100 Å) platy anhedral particles. Titanium increased in altered grains and may substitute for Fe³⁺ in hematite. Mn, V, Cr and Zn remained approximately constant whereas the Ni content decreased. Halloysite crystallized from soil solution within pores resulting in a marked increase in the Si and Al contents of grains.     

Gehalte an Haupt- und Nebenelementen in Konkretionen aus Oberböden von Marschen – Untersuchungen mit einer Mikrosonde

Contents of major and trace elements in concretions of surface samples from marsh soils – Electron microprobe analysis The amounts of 14 elements (Ti, Fe, Mn, Si, Al, Ca, and P, S, Co, Ni, Cu, Zn, Cd, Pb) in concretions of four A horizons of marsh soils were determined by electron microprobe analysis on thin sections. According to the major element compositions the following types of concretions can be distinguished: Ti-Fe(-Mn) concretions (31–39% Ti; 18–29% Fe; 0,3–5,5% Mn); Fe(-Mn) concretions (31–58% Fe; ≤ 1,8% Mn); Fe-Si(-Mn) concretions (6–28% Fe; 8–42% Si; ≤ 5% Mn); Mn-Fe and Mn-Fe-Si concretions (16–40% Mn; 2–9% Fe; 2–15% Si). The formation of Ti-Fe(-Mn) concretions can be explained by adsorption of Fe²⁺ ions under reducing conditions on surfaces of Ti minerals followed by oxidation to Fe(III) oxide. In this way pseudorutile may be formed. Concretions with high Fe and/or Mn content often contain occlusions of carbonates, silicates and/or SiO₂ (bioopal) which may act as nuclei for their growth. Redox processes in marsh soils result in the formation of concretions with dominating Fe or Mn accumulation. Among the group of trace elements, P and S (like Ti and Si) reach their highest concentrations in Fe rich concretions (up to 54.000 mg P/kg and 4.200 mg S/kg). The accumulation of these elements is obviously influenced by anion competition, especially of P and Si, and probably also Ti. Likewise, high amounts of Pb were found in Fe(-Mn) concretions (up to 12.000 mg/kg). Co, Ni, Zn, and Cd show the highest amounts in Mn rich concretions (Co up to 3.400; Ni 1.800; Zn 13.200; Cd 1.000 mg/kg). Cu is also accumulated in some concretions (up to 1140 mg/kg) but no clear affinity to one of the different types of concretions was found.     

华中黄棕壤和黄褐土粘粒胶膜的微量元素地球化学特征

The relationships between the basic properties and trace elementsin soil argillans and corresponding matrix soils were studied by sampling from the B horizons of 26 Alfisols in croplands of the subtropical area in Central China. The soil elements (K, Na, Ca, Mg, Mn, Co, Cu, Cr, Cd, Li, Mo, Ni, Pb, Ti, V, and Zn) were extracted by acid digestion and their contents were measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The mean contents of clay and organic matter in the argillans were approximately 1.1 and 1.3 times greater than those in the matrix soils, respectively. The pH values and the contents of P₂O₅ and bases (K₂O, Na₂O, CaO, and MgO) in the argillans were higher than those in the corresponding matrix soils. Cu, Cd, Ti, and V were enriched in the argillans. Correlation coefficients and factor analyses showed that Co, Cu, Li, and Zn were bound with phyllosilicates and manganese oxides (Mn-oxides) in the argillans. Cr and Pb were mainly associated with iron oxides (Fe-oxides), while Ni was bound with Mn-oxides. Cd, Ti, and V were chiefly associated with phyllosilicates, but Cr and Mo were rarely enriched in the argillans. In contrast, in the matrix soils, Co and Zn were associated with organic matter and Fe-oxides, Cr existed in phyllosilicates, and Mo was bound to Fe-oxides. Cd, Ti, and V were associated with organic matter. The results of this study suggest that clays, organic matter, and minerals in the argillans dominate the illuviation of trace elements in Alfisols. Argillans might be the active interfaces of elemental exchange and nutrient supply in cropland soils in Central China.     

施硅对高锰诱发苹果粗皮病的影响

为解决辽宁等地高锰引起苹果生理粗皮病发生的问题,2004年在盆栽脱毒富士幼苗上进行施锰的同时施硅与单施锰的试验,待叶、枝发生粗皮病后再施硅矫正。结果表明,本试验条件下施锰400.mg/kg的同时施硅400mg/kg,可安全有效防治粗皮病的发生;施锰400.mg/kg诱发叶片发病后,施硅400.mg/kg可较好地控制粗皮病的发生。施锰400.mg/kg枝干发病后施硅,对粗皮病的蔓延有一定控制作用,但效果不明显。随着施硅量增加,土壤速效钾含量提高,有效铁、有效锌含量降低,说明粗皮病的发生也与上述养分有关系。     

Effect of Mn on growth,modulation, and nitrogen fixation by soybeans grown in the greenhouse

Abstract

Soybean (Glycine max (L.) Merr. cv Bragg) plants were grown in the greenhouse using a low‐Mn Leefield sand amended with 0, 2.5, 5, 20 and 50 yg Mn/g. The plants were inoculated and were primarily dependent on symbiotically fixed N. Measurements of DTPA‐extractable soil Mn, soil pH, leaf tissue Mn, top weight, top N content, and nodule weight, volume and number were made at 27, 42, 56, 63 and 69 days after planting. The DTPA extrac‐tant was a good predictor of leaf tissue Mn giving a highly significant (P = 0.01) overall correlation coefficient of 0.704 for this comparison. Because of an unexpected decline in soil pH from 6.8 to 6.0 and an associated increase in DTPA‐extractable Mn from 0.14 to 0.24 yg/g during preparation and handling prior to the first harvest time, Mn in the leaf tissue of the controls was never less than 21 yg/g. Since this concentration of Mn is above the deficient level, no significant responses in top growth, nitrogen fixation or nodule measurements were obtained from the addition of low rates of Mn. The highest Mn rate was only mildly toxic in terms of top growth and top N content, producing leaf tissue having Mn concentrations ranging from 171 to 180 yg/g at the last three harvest periods.     

The impact of redox conditions on the rare earth element signature of redoximorphic features in a soil sequence developed from limestone

Redox processes, which are widespread in soils, need to be quantified for an improved comprehension of the dynamics of Fe- and Mn-oxides and their associated trace elements. The classical methodology used to study these redox processes generally relies on the quantification of all mineral species in the various pedological features that can be related to different redox stages. However, this approach usually encounters the difficulty of precisely quantifying the different forms of poorly crystallised Fe- and Mn-oxides.In this study, we use the signature of rare earth elements (REEs) to visualise and, eventually, quantify the importance of redox processes in soils. Our approach relies on that developed by Laveuf et al. (2008) and the idea that the relative contribution to the mobilisation of REEs that is made by the primary minerals reactive to redox conditions depends on the following factors: (i) their initial proportion in the different pedological features that can be related to various redox processes, (ii) their relative mobilisation during the redox process in question, and (iii) their initial REE signatures.The catena studied is characterised by two stages of redox conditions: the first is related to the formation and subsequent dissolution of Fe–Mn concretions, and the second is related to the bleaching of the soil matrix due to morphological degradation. In this soil, the main minerals reactive to redox conditions are Mn-oxides, ferrihydrite, goethite and (fluor)apatite. The results indicate that the primary redox conditions can be characterised by a positive Ce anomaly on the REE pattern, which has been attributed to a preferential immobilisation of this element, due to its association with Mn-oxides. The results also indicate that the secondary redox conditions can be characterised by depletion in medium REEs (MREEs) in the REE pattern, which has been attributed to a preferential release of these elements during the dissolution of (fluor)apatite and, to a lesser extent, of ferrihydrite.These results emphasise the potential of REE signatures of the visualisation of the various redox processes that have been active in a soil. Additionally, REE signatures are a proxy of the frequency and intensity of the redox conditions.     

An unusual occurrence of probable Pleistocene corestone within a Cretaceous dioritic enclave,Peninsular Ranges,California

We here document an unusual occurrence of probable Pleistocene corestone within an ∼ 5 m by ∼ 5 m dioritic enclave contained within a Cretaceous tonalitic pluton, Santa Margarita Ecological Reserve, SW California. The enclave lies within ∼ 3.5 km of the seismically active ∼ 1.5–2 Ma Elsinore fault zone, and may have been subjected to ∼ 70–90 ground shaking events since ∼ 22,000–18,000 years ago. The studied corestone is elliptical with major axis measuring ∼ 55 cm and minor axis ∼ 26 cm in length. It is surrounded by a discontinuous ∼ 7 cm thick rind that breaks apart under slightly greater finger pressure than does the surrounding saprolite. In order to assess changes in the physical and chemical properties of the corestone, rind, and saprolite we collected along an ∼ 66.5 cm long traverse 4 samples from the corestone, 1 from the rind, and 5 from the saprolite for bulk and grain density, porosity, and major and trace element analyses. Textural and clay mineral data, along with the redistribution of elemental mass, indicate that the weathering of biotite, and to much lesser degrees apatite and the An-rich cores of plagioclase, played critical roles in the production of saprolite especially in a narrow ∼ 20 cm wide zone adjacent to the rind of the corestone. Within this zone bulk densities reach their minimum values, while porosities and positive volume strains reach their maximums. In addition, the maximum loss of K, Fe, Mn, and Ca mass occurred just inside this region, and is paralleled by the highest CIA values and highest additions of Si and Rb mass. In contrast, the masses of Na and Sr are progressively increased and decreased, respectively along the entire sampling traverse while the loss of Mg, Ti, and P mass is episodic with the greatest losses occurring within the narrow zone adjacent to the rind and at the end of the traverse. The above observations indicate that the conversion of biotite to expandable mixed-layered clay minerals, aided by the alteration of the An-rich cores of plagioclase, produced sufficient stress on grain boundaries that a weakening or loss of intercrystalline cohesion occurred. However, unlike the well documented isovolumetric development of saprolite in other areas, at the study site saprolitization was accompanied by a volume expansion. We speculate that repeated ground shaking in response to earthquakes generated in the nearby Elsinore fault zone may be responsible for this difference. Important byproducts of ground shaking would include additional weakening or loss of intercrystalline cohesion, and the production and enhancement of new and older fluid pathways respectively. The fact that the most intensely altered material at the study site lies adjacent to the boundary between the rind and saprolite, suggests that this interface acted to guide fluid flow around the corestone and rind and into the adjacent saprolite where elemental mass was redistributed down various paths leading to the underlying water table. Most of the leached elemental mass was removed from the area of the sampling traverse, but small increases in Si, Rb, and Na mass suggest redistribution of these elements from elevated areas outside the area sampled during this study. The result of the above complex set of processes is a variably porous and chemically altered saprolitic enclave that is still undergoing modification as it adjusts to the vicissitudes of the paralithic environment and continuing ground shaking during earthquakes generated along the Elsinore fault.     

Effects of pasture‐applied biosolids on forage and soil concentrations over a grazing season in north Florida. II. microminerals

Abstract

The experiment rationale was to determine forage micromineral concentrations as effected by biosolids fertilization. We determined the effects of two exceptional quality biosolids on bahiagrass trace mineral concentrations as related to beef cattle requirements. Twenty‐five 0.8‐ha pastures were divided into five blocks. Two biosolids were applied as normal and double agronomic rates. The control received NH₄NO₃. Forages were analyzed for total copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), molybdenum (Mo), cobalt (Co), and selenium (Se), and soils were analyzed for Mehlich I extractable Cu, Mn, and Zn. Some significant increases (P<0.05) in forage Co, Cu, Fe, Zn, and Se were observed at various sampling times, but the increases were generally small and biologically insignificant. Although forage Mo samples from pastures with the Tampa biosolids applied were consistently higher than the control (P<0.05), at no time did they approach levels considered toxic. Similar results were seen in forage Mn concentrations, with treatment Baltimore‐2X elevating (P<0.05) Mn concentrations as well. Deficiencies of Co, Cu, Zn, and Se are common in this Florida region and slight elevations due to biosolids treatment could be beneficial. Biosolids applied at the highest rates improved soil Cu and Zn concentrations above control soils and soil Mn was increased over the control at both sampling times for Baltimore‐2X. In relation to beef cattle requirements, the majority of forages were deficient in Co, Cu, Se, and Zn. In summary, biosolids fertilization slightly improved the micromineral status of forage and soil, without creating toxicity.     

Silicon nutrition of rice is affected by soil pH,weathering and silicon fertilisation

Silicon (Si) is a beneficial element for tropical grasses such as rice (Oryza sativa) and responses to applications of Si are common on highly weathered soils. However, the importance of pH (and hence Si speciation), weathering and fertilisation on Si uptake is still poorly understood. The responses of rice to Si fertilisation were studied in two variably weathered basalt soils (Red Ferrosol, Grey Vertosol) adjusted at different pH values (5.5–9.5) with three levels of acidulated wollastonite. Soil Si was extracted using deionised water (H₂O), 0.01 M CaCl₂, or 0.5 M NH₄OAc. Significant increases in Si uptake and rice biomass were observed in the Red Ferrosol following fertilisation (p < 0.01). Greater biomass production was observed at lower pH, due to decreased Si sorption and higher solution Si concentrations. Silicon uptake by rice was greater at low pH, despite similar extractable Si concentrations; suggesting a relationship between Si speciation and uptake. In contrast, Si uptake and rice shoot dry matter in the less weathered Grey Vertosol were unaffected by Si fertilisation (p > 0.05) except at the highest rate and lowest pH (5.5). Solution Si concentrations were controlled by precipitation/polymerisation reactions in equilibrium with specific soil pH values rather than adsorption processes. Silicon speciation effects (monosilicic acid vs. silicate ions) were unable to be measured due to an induced phosphorus deficiency in both soils at pH values > 8.5. In conclusion, weathered soils are more responsive to Si fertilisation and Si uptake is increased at low pH.     

Pedogenic and biogenic alkaline‐extracted silicon distributions along a temperate land‐use gradient

The primary source of dissolved silicon (Si: DSi) is the weathering of silicate minerals. In recent years, it has been shown that Si cycling through vegetation creates a more soluble Si pool in the soil, as amorphous Si (ASi) deposits in plants (phytoliths) are returned to the soil through litter. Amorphous Si accumulation in soils depends on a number of factors, including land use. In addition to the biogenic ASi fraction, soils contain other non‐biogenic amorphous and sorbed Si fractions that could contribute significantly to DSi export to rivers, but hitherto these Si fractions have been difficult to separate from each other with traditionally applied extraction methods. The objective of this paper is to understand better how land use affects the distribution of the different extractable Si fractions. We re‐analysed samples from the land‐use gradient studied previously by Clymans et al. ( 2011 ) with a continuous Si and aluminium (Al) extraction technique. Different extractable Si fractions of biogenic or pedogenic origin were successfully separated on the basis of their dissolution in alkaline solutions (Na₂CO₃ and NaOH) and Si:Al ratios. We show that forests store almost all alkaline extractable Si (AlkExSi) in the pedogenic fraction while the importance of phytoliths increases with human disturbance to become the dominant fraction in the AlkExSi pool at the arable site. The pedogenic AlkExSi pool is also more reactive than the phytolith‐bound Si. Conversely, pastures and croplands tend to preserve phytoliths in the soil, which are less reactive, decreasing the potential of DSi export relative to forested ecosystems.     

Selenite adsorption by a variety of oxides

Abstract

Selenite adsorption by a variety of oxides consisting of iron (Fe), aluminum (Al), titanium (Ti), manganes (Mn), and silicon (Si), and by two humic acids were investigated in order to grasp selenite behavior and fixation mechanisms in soil. It was found that selenite was apparently adsorbed even by the Mn oxides on which surface negative charge was dominant in normal pH range (pH <4). No selenite adsorption was observed in the silicon dioxide (SiO₂) and the two humic acids. A sequential extraction of adsorbed selenite with competitive anions showed the differences of binding force or stability of adsorbed selenite among the minerals. While the goethite fixed selenite strongly, selenite adsorbed on the Mn oxide was easily released to the liquid phase with other anions, such as phosphate. Each mineral had its inherent characteristic in ligand exchange reactions accompanied with selenite sorption. Selenite sorption by the Mn and the Ti oxides resulted in large increase of surface negative charge, while only a little increase in the Fe and Al oxides. Proton consumption with selenite sorption was extremely smaller for the Mn oxide than for the others.     

Beziehungen zwischen Mangan-Gehalten in Haferpflanzen und Böden

Relationship between Mn in Oat Plants and Soils The Mn concentration of oat plants in the stage of appearing panicles from agricultural fields were put in relationship to extractable Mn. With soils of sandy texture (clay < 4%, pH 4,7–6,6) a correlation existed between Mn in plants and n-MgCl₂ extractable Mn, however, no additional relationship with the easyly reducible Mn. A negative correlation between pH and Mn in plants was traced to the pH dependence of exchangeable Mn. With soils of loess (clay 5–28%, pH 6,6–7,7) a significant correlation existed between Mn in plants and easyly reducible Mn fractions (methods by Schachtschabel: extracting solutions containing Na₂SO₃, pH 8,0, or Na₂SO₃ + NaHSO₃, pH 5,5), however, only if an interrelationship with the pH of the soil was allowed for. The higher the pH of the soil the lower its level of extractable Mn might be, to reach a certain concentration of Mn in plants. This relationship seems to be caused through a modifying influence of the soil pH on the reducing power of the extracting solutions.     

Evaluation of Decomposition Procedure to Determine Ba,Co, Cr,Cu, Ni,Mn, V,and Zn Total Content in Soil Samples

Different procedures have been proposed to decompose soil samples. Most of them regard determination with fertility aims. In this case, the contents available to the plants are considered. On the other hand, there are procedures to determine total content. The objective of this work was to propose a new decomposition procedure to determine barium (Ba), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), vanadium (V), and zinc (Zn) total content in tropical soils with high content of oxides and silicate. According to the results, the digestion procedure proposed in this study provided satisfactory results for the contents recovery for the elements Ba, Co, Cr, Cu, Mn, Ni, V, and Zn, above 90%, and the use of inverted aqua regia, hydrogen peroxide (H₂O₂), hydrofluoric acid (HF), pre-digestions and agitation was shown as a new alternative for the high silicate content soil sample total digestion, such as the oxisols.     

Cu,Co und Mo in Sesquioxid-Anreicherungshorizonten

Cu, Co and Mo in sesquioxide accumulation horizons Fe, Mn, Cu, Co and Mo were determined in 1) a podzol-gley- and 2) a pseudogley brownearth — stagnogley — ?ochre earth”?-landscape. In landscape 1) the accumulation of Fe in the gley — G_o is pronounced and the translocation Mn>Cu, whereas landscape 2 is characterized by the accumulation of Mn in the ?ochre earth”? and by a translocation Co>Cu (Mo shows just small differences in 1) and 2)). The relation between the distribution of Cu, Co and Mo and of sesquioxides is overlapped by the influence of organic matter. From larger concentration differences for both Mn and Co in landscape 2 as compared to 1 a special role of manganese oxides for the accumulation of Co can be concluded. This accumulation however is not connected with a stronger immobilization.     

宝鸡市某工业园区灰尘重金属含量、形态及生态风险分析

利用X射线荧光光谱法(XRF)和原子荧光分光光度法(AFS)分析了宝鸡市某工业园区灰尘中重金属的含量。结果表明,宝鸡市某工业园区灰尘中As,Co,Cr,Cu,Hg,Mn,Ni,Pb和Zn的平均含量分别为23.3,16.4,1 591.8,178.2,0.243,346.5,40.2,1 586.2和1 918.8mg/kg,其中,Cr,Cu,Hg,Pb和Zn累积比较明显;铅锌冶炼厂周边灰尘中As,Cu,Hg,Pb和Zn的含量高于电厂。采用修正BCR法(欧洲共同体标准物质局)和原子吸收分光光度法(AAS)研究了灰尘中重金属的形态特征。结果表明,灰尘中Cu主要以残渣态和可氧化态的形式存在,Pb主要以可还原态的形式存在,Zn主要以乙酸可提取态的形式存在,Mn和Co主要以乙酸可提取态和残渣态存在,Ni和Cr主要以残渣态存在。灰尘中Pb,Zn,Co,Mn和Cu有55%~85%可以发生移动,易被生物利用,危害较大。潜在生态风险评价表明,灰尘中重金属的污染及潜在生态风险达到严重水平,铅锌冶炼厂周边灰尘中重金属的污染和潜在生态风险高于电厂。