Forms Of Metals In Soils Research Articles

Monitoring of Fertility and Ecotoxicological Condition of Reference Sites of Sod-Podzolic Soils of the Ivanovo Region

The results of agrochemical and ecotoxicological studies of the arable layer of reference plots of sod-podzolic soils for agricultural purposes of the Ivanovo region are presented, which were carried out in order to establish the level of fertility according to the main agrochemical indicators, the content of sulfur and trace elements, ecotoxicological state – by gross and mobile forms of heavy metals and arsenic. The deterioration of such indicators of soil fertility as the availability of ammonium and nitrate nitrogen, mobile potassium, the amount of absorbed bases and the capacity of cation exchange has been established. An increase in the content of mobile phosphorus, exchangeable calcium, magnesium and other absorbed bases was noted with an unchanged content of organic matter. The fertility of the studied soils was assessed by calculating the soil-ecological index. The provision of soils with trace elements and mobile sulfur has been established. The content of gross and mobile forms of metals in soils, with the exception of arsenic in the soils of individual sites, did not exceed the maximum permissible concentrations and clarks. The studied soils are slightly polluted and are not dangerous for cultivated plants and human health. According to the Pearson and Spearman correlation coefficients, the characters of the mutual influence of metabolic acidity, the content of organic matter and the granulometric composition of soils with the content of available forms of trace elements, gross and mobile forms of metals and arsenic are established.

Mobility indexes of Cu, Pb, and Zn in soil ecosystems with various levels of metal contamination (in Poland)

The aim of the study was to investigate and compare the soils of three groups of grassland ecosystems with varying degrees of heavy metal (Cu, Pb, and Zn) pollution as well as estimating of mobility on the basis of calculated mobility indexes (MI) expressed as a percentage of the EDTA-extracted forms of metals in their total content. A total of 55 surface soil samples were collected from various areas of Poland: urban soils, rural soils, and soils along communication routes. Heavy metal concentrations were determined in solutions after wet mineralization (using a mixture of acids) by atomic absorption spectrometry (AAS) with flame atomization. To isolate the mobile forms of metals in soils, a one-step extraction method was used with 0.05-M EDTA solution. The ranges of Cu, Pb, and Zn concentrations in soils were varied, respectively: 6.7–47.6, 61.1–563.9, and 86.4–644.5 mg·kg−1 (A); 5.7–39.8, 13.56–45.71, and 16.3–119.6 mg·kg−1 (B); and 1.0–195.8, 19.2–310.2, and 27.4–894.1 mg·kg−1 (C). The average values of mobility indexes of Cu, Pb, and Zn were at the level of 40.9, 33.5, and 22.2% (A); 23.2, 27.1, and 25.9% (B); and 37.5, 34.3, and 30.7% (C). Studies have shown that metals derived from anthropogenic sources are characterized by greater mobility compared to metals of natural origin (lithological associated with the ground). The inclusion of metal mobility indices in the environmental monitoring strategy may minimize errors in assessing the actual risk associated with the potential uptake of these metals by plants and incorporation into circulation.

Heavy metals in the system «soil - wild medicinal plant» (on the example of <i>Cichorium intybus</i> L.)

This paper discusses the features of the heavy metals content in medicinal plant raw materials Cichorium intybus L. in the conditions of the Trans-Ural region of the Republic of Bashkortostan. Variational and statistical indicators of the heavy metals content in soils and plants are calculated. The coefficients of variation of gross and mobile forms of heavy metals in soils are high (above 21%), the exception was the gross form of Fe, which is characterized by low variation (up to 10%). The content of gross forms of heavy metals in soils exceeded the maximum permissible concentrations of Cu (18 times), Zn (13 times), Cd (2 times), Co (1,2 times) in the sample area 2, and Mn (1,2 times) and Cu (2,5 times) in the sample area 3. The content of mobile forms of Fe and Pb in soils did not exceed the maximum permissible concentrations. The samples had an increased level of mobile forms in Cu (39 times), Zn (2,1-4,3 times), Ni (1,12 times), Mn (2,3-2,6 times), Co (1,3-1,5 times), Cd (2,1-5,7 times). The degree of mobility of heavy metals in soils decreases in the series Pb Co Cd Zn Mn Cu Ni Fe. According to the degree of Zc contamination, the studied soils were classified as permissible (Zc from 0,2 to 5,2), with the exception of sample area 2, which was classified as highly hazardous (Zc up to 48,2). The level of contamination of the soil cover is minimal, and the environmental situation is relatively satisfactory (Zc from 0,2 to 5,2), with the exception of test area 2, where the level of pollution is high and the environmental situation is critical (Zc up to 48,2). Plants of Cichorium intybus L. are contaminated with Ni, Cd, Fe, and concentrations of Pb and Mn in plants did not exceed the maximum permissible levels. The most absorbed elements were Fe (25,7) and Cu (65,4), which belonged to the group of elements of energetic accumulation (accumulation index 10), Ni (8,9), Pb (4,7), Zn (2,2), Cd (2,06), Co (1,1), and Mn (1,06) related to a group of elements of strong accumulation (accumulation index from 1 to 10). In plants of Cichorium intybus L. Cu, Fe, Ni, Mn, Cd, Co are distributed by acropetal type (acropetal coefficient 1,0), and Zn and Pb are distributed by basipetal type (acropetal coefficient 1,0). The value of biogeochemical activity in the plant Cichorium intybus L. varies from 47,4 to 728,3.

TOTAL CONTENT AND AVAILABILITY OF MICRONUTRIENTS IN SOILS AND LIVESTOCK MANURE

The use of feedlot cattle manure appears as an important source of certain trace metals in soils that can be mobilized by water modifying the surface and groundwater quality. The current study is focused on assessing the availability of copper (Cu), zinc (Zn), cobalt (Co) and molybdenum (Mo) in manure from confined beef cattle systems and different soils of the Chaco-pampean plain, using a sequential extraction scheme. Soils and bovine manure coming from intensive (IS) and extensive (ES) beef cattle systems were collected. Total contents of Cu, Zn, Co and Mo were determined after microwave assisted acid digestion. Availability was evaluated through sequential extraction, including water-soluble and exchangeable fraction (EXCH), organic matter bound fraction (OM), inorganic precipitated fraction (INOR), and residual fraction (RES). Total Cu and Zn contents found in manure coming from IS were higher than the concentration of the aforementioned trace elements determined in all soils and manure analyzed from ES. EXCH-Cu only appears in IS cattle manure samples, while EXCH-Zn found in IS manure samples were higher than the soils samples analyzed. The higher levels of total and availability forms of Cu and Zn determined in IS manure compared to soils samples, require considering when this organic amendment is applied as fertilizer. These results indicate that the reuse of intensive cattle manure as fertilizer in agricultural areas could provide available forms of metals in soils and could contribute to reduce the environmental impact caused by the accumulation of excreta in pen soils during long periods in farms.

Geochemical researches of the Marmarosh massif of the Ukrainian Carpathians

Formulation of the problem. The main focus of our research is on the geochemical composition of the growth areas of beech forests in the Marmarosh Massif of the Ukrainian Carpathians, or primeval forests, which are almost unaffected by human activity. Geochemical investigations of beech forests are especially important, since the question of chemical component of environmental objects (soils, vegetation) is the basis for determining the degree of territories transformation in time. The Carpathians belong to one of the most studied metallogenic provinces. The ore occurrence contains natural gold, silver and silver minerals (sulfates, sulfides, hydrosulfides) associated with pyrite, chalcopyrite, arsenopyrite, pyrrhotite, marcasite, hematite, galena, and other. It is important to determine the background content of chemical elements in soils, which will become the basis for geochemical searches and the determination of pollution - "reference point", which should be relied upon when conducting environmental and geochemical studies in the territory of beech virgin forests. The purpose of the article. The purpose of this work is to determine the background gross content of chemical elements (Mn, Ni, Co, Ti, V, Cr, Mo, W, Zr, Hf, Rb, Ta, Cu, Pb, Ag, Sb, Bi, Zn, Cd, Sn, Ge, Ga, Be, Sc, Ce, La, Y, Yb, Th, As, Ba, Li, P) and the main mobile forms of metals - Cu, Pb, Zn in soils of forest ecosystems of beech forests of the Marmarosh Massif; determination of biogeochemical features of the concentration of chemical elements by vegetation - beech leaves, Hypericum L., Achillea millefolium, Boletus edulis, which will become the basis for monitoring studies. Methods. Lithochemical, biogeochemical testing was carried out. The gross content of chemical elements (emission spectral analysis) and mobile forms of metals (atomic absorption analysis) was determined. Results. The authors calculated the background values of chemical elements content in the soils of forest ecosystems of beech protected areas of the Marmarosh Massif. In conducting lithochemical studies, chemical elements (gross content) – Co, Ni, V, Cu, Zn, Pb, P, Mn, Ti, whose contents are higher in soils, where carbonate rocks are soil-forming and in the absence of carbonates - Cr, Mo, have been established Zr, Sn, Be. La, Y, Yb, Ba, Li. The main moving forms of metals in soils (Cu, Pb, Zn) were determined and their coefficients of mobility were calculated, on the basis of which it was established that the mobility of metals in soils where soil-forming rocks are granite-gneisses and sandstones higher than in soil-soils is 3–10 times, in addition, the pH value of soils is a dominant factor in solving the migration or concentration of metals and the formation of secondary salt halos in the presence of ore. An analysis of the chemical composition of the indicator vegetation and its parts – Hypericum L, Achillea millefolium and Boletus edulis in the area of Mount Figura was performed. Boletus edulis, St. Hypericum L, wort stems and yarrow Achillea millefolium are identified as Cu, Zn concentrators. This distinction is important when conducting biogeochemical studies with a search purpose. Scientific novelty and practical significance. The results of the conducted researches showed that the regularities of distribution of chemical elements and their mobile forms in soils and vegetation in different parts of the Trans Carpathian forest ecosystems can be the basis for the exploration, forecasting the ecological status of the territories and, in general, ecological and geochemical monitoring.

The ecological state of the raw material zone of the enterprises supplying beef for baby food

Subjects of the research: soils, pasture and cultivated plants, vegetable raw materials, prepared feed of the raw material zone of the Branch of the Tikhoretsky Children's Meat Canning Plant of DANON-RUSSIA JSC. The quantitative content of mobile forms of heavy metals in soils under the main feed crops and their accumulation in finished feeds was determined. The a soil with a high humus content cover in the area of the surveyed farms is mainly represented by carbonate weakly humus heavy-duty “chernozem”, which occupies 82.5 % of all land. Fodder raw materials in the autumn-winter season 2019-2020 is safe in quantitative content regulated by standards of elements of heavy metals. Their contents were established: mercury ≤ 0.01 mg / kg, cadmium ≤ 0.2 mg / kg, lead ≤ 2.0 mg / kg and arsenic ≤ 0.5 mg / kg. However, there was an insignificant (1-2%) increase in the zinc content in the silage from the green mass of corn and haylage from the green mass of alfalfa. It was established that the remains of the prohibited pesticides are in trace amounts or practically absent in the feed of the raw material zone. The monitoring results will be used in farms - suppliers of beef for the production of baby food - canned meat and meat and vegetable.

Organic matter facilitates the binding of Pb to iron oxides in a subtropical contaminated soil.

The bioavailability and potential uptake of heavy metals by crops is fundamentally influenced by the forms of metals in soils. Organic matter plays an important role in controlling the transformation of heavy metal fractionations in soils. However, long-term effects of organic matter on heavy metal speciation remains highly uncertain. In this study, rice straw was introduced to a subtropical Pb-contaminated soil for 2-year period so as to clarify the redistribution of Pb fractions and their correlations with soil properties. By combining sequential extraction and X-ray absorption fine structure spectroscopy, we find that lead is predominantly presented in Fe oxide-bound, surface adsorbed, and residual fractions in the soil. The incorporation of rice straw can effectively reduce the labile species of Pb by promoting the binding of Pb to iron oxides. Furthermore, aging leads to the transfer of considerable amounts of Pb to the association with Fe oxides and this transformation is enhanced by the presence of organic matter. Organic matter input and soil aging tend to shift Pb to amorphous Fe oxides than crystalline Fe oxides. The correlation analysis shows that Fe oxide fractions play vital roles in controlling the forms of Pb in soil. This study presents the first result regarding the long-term effect of organic matter on the redistribution of Pb in naturally polluted soil, which is useful for understanding the fate of Pb and developing remediation strategies for Pb-polluted soils.

Sequential extraction procedure for fractionation of Pb and Cr in artificial and contaminated soil

AbstractMetal contamination of soil is due to mining, manufacturing and use of synthetic products (e.g. pesticides, paints, batteries, industrial waste and industrial or domestic sludge) which is a serious environmental problem. Hence, determining chemical forms of metals in soils is important to evaluate their mobility or bioavailability. Both artificial and contaminated soils were sequentially extracted to fractionate metals into the water soluble fraction (WSF), exchangeable fraction (EF), bound to carbonate fraction, bound to metal oxide fraction, organically bound fraction (OBF) and residual fraction (RF). In the case of contaminated soil, Pb and Cr are found to be associated with the carbonate fraction while in artificial soil, Pb bound to WSF and Cr with the Fe/Mn fraction. Chemical properties such as pH, electrical conductivity (EC) and textural classification of concerned soils were also analyzed. Percentage recovery was calculated to check the reliability of processes both in Pb and Cr, and it was found to be more in Cr (66% and 84%) in both artificial and contaminated soil than Pb (5% and 34%) in both soils. Analyses of extracts were carried out by atomic absorption spectrometry (AAS). Results were interpreted in terms of environmental mobility or bioavailability of metals.

Total polyphenols content in fruits of selected cultivars of strawberries in relation to concentrations of cadmium and lead in soil

The key aim of our study was to define the correlation of total polyphenols contents in seven cultivars of strawberries (Clery, Sonata, Alba, Korona, Ázia juh, Anthea, Joly) grown in the parcels with exceeded levels of pseudo-total Cd and mobile Pb in soil. Strawberries were grown in rows long 200 m, the distance of the plants was 0.35 m and inter-row distance was 1 m. Following fertilizing was applied - at the beginning of vegetation period the doses of elements (in kg.ha-1) were: N48.2 +P78.3 +K66.3 +Mg7.2, afterwards 23 days of elements were applied in liquid irrigation in amount: N46.5 +P34.8 +K118.7. Heavy metals in contamination soil were analysed by the method of atomic absorption spectroscopy and total contents of polyphenols spectrophotometrically. The highest content of all monitored parameters (pseudo-total and mobile Cd and Pb, as well as the amount of total polyphenols) was found in Ázia juh cultivar. There was statistically significant positive relation of total polyphenols contents in Anthea cultivar to levels of all monitored forms of metals in soil and contrary, in Clery cultivar there was found non-correlation of total polyphenols contents on levels of monitored heavy metals in soil (mainly of mobile contents of Cd and Pb contents). Contents of mobile forms of individual heavy metals positively correlated with total polyphenols (except of Clery and Ázia juh cultivars). Varietal relation on levels of total polyphenols was confirmed in experiment prior to relation of these organic compounds to the presence of monitored heavy metals in soil.

Chemical Fractionation of Copper, Manganese and Zinc in Dumpsite Soil Samples in Kaduna Metropolis, Nigeria

Aims: In this research, sequential chemical extractions were performed to fractionate copper, manganese and zinc in dumpsite soil samples into six geochemical fractions with varying mobility and bioavailability. Study Design: Determination of chemical forms of metals in soils and evaluation of their mobility and bioavailability. Place and Duration of Study: This study was conducted between March, 2011 and June, 2013 in the Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria. Methodology: Collection of soil samples from Kawo (KW), Rafin Guza (RG), Angwan Dosa (AD), Badarawa (BD), Malali (ML), Angwan Shanu (AS), Kurmi Mashi (KM), Tudun Wada (TW), Kakuri (KK) and Trikania (TK) dumpsites; sequentially extraction of samples into six fractions and determination of metal concentrations in extracts. Results: Copper had high mobility factor values in the rainy season at TK (43.76%), TW (13.51%), AS (13.48%) and ML (0.14%); and in the dry season at TK (44.79%), KW (14.65%), AS (14.18%), ML (13.43%) and TW (13.31%). Manganese in the rainy season recorded relatively high mobility values at KK (2.18%), AD (2.07%), and TW (1.67%) and in the dry season at ML (2.57%), BD (2.23%), KK (2.06%) and TW (1.51%) while Zinc had Original Research Article American Chemical Science Journal, 4(2): 138-150, 2014 139 high mobility values in the rainy season at BD (54.14%), AS (26.62%), KM (18.08%), TK (16.11%), ML (5.88%) and KK (3.54%) and in the dry season at RG (145.79%), BD (44.59%), AS (31.08%), KM (21.65%) and TK (18.19%). Copper and zinc were distributed evenly across the non-residual and residual fractions, while manganese was predominantly retained by residual fractions. The mobility and potential bioavailability of the metals in decreasing order is: zinc > Copper > Manganese. Conclusions: The amount of metals bound to each fraction differed significantly according to metal type, dumpsites and seasons. The study indicates the tendency for bioavailability of the metals studied for plant uptake from soil.

Determination of Heavy Metals and Their Speciation in Street Dusts by Inductively Coupled Plasma-Optical Emission Spectrometry after a Community Bureau of Reference Sequential Extraction Procedure

Sequential selective extraction techniques are commonly used to fractionate the solid-phase forms of metals in soils. This procedure provides measurements of extractable metals from media, such as acetic acid (0.11 M), hydroxyl ammonium chloride (0.1 M), hydrogen peroxide (8.8 M) plus ammonium acetate (1 M), and aqua regia stages of the sequential extraction procedure. In this work, the extractable Pb, Cu, Mn, Sr, Ni, V, Fe, Zn, and Cr were evaluated in street dust samples from Sakarya, Turkey, between May and October 2009 using the three-step sequential extraction procedure described by the Community Bureau of Reference (BCR, now the Standards, Measurements, and Testing Programme) of the European Union. The sampling sites were divided into 10 categories; a total of 50 street dusts were analyzed. The determination of multielements in the samples was performed by inductively coupled plasma-optical emission spectrometry. Validation of the proposed method was performed using BCR 701 certified reference material. The results showed good agreement between the obtained and the certified values for the metals analyzed.

Content of available forms of some micronutrients in soil after long-term differentiated fertilization

The objective of this study has been to follow modifications in the content of Cu, Zn and Mn in the topmost layer of soil which had been fertilized for many years with farmyard manure and mineral fertilizers or with mineral fertilizers alone. Soil samples were collected in 2002-2005 from a trial established in 1986 on proper brown podsolic soil, according to the random block design with four replication. The first factor consisted of organic fertilization (manure applied every two years or without manure). The second factor involved different rates of mineral fertilization. Rates of nutrients in the mineral fertilizers were identical in both experimental series – with or without manure. In each year, the same crop was grown on both fields, in a crop rotation system: sugar beet (2002), spring barley (2003), maize (2004) and spring wheat (2005). Plant available forms of nutrients were extracted from soil in 1 mol HCl dm -3 solution. After extraction, the content of metals was determined by atomic absorption spectrophotometry. The results underwent statistical processing using analysis of variance for a two-factor experiment. The content of available forms of copper, zinc and manganese in soil regularly amended with manure was evidently higher than analogous concentrations determined in soil receiving only mineral fertilization since 1986. Manure most strongly improved the concentration of Cu (nearly 1.7-fold), while producing the weakest influence on manganese (over 1.3-fold more). In absolute values, however, the increase in availability of manganese was the highest, reaching on average 52 mg kg -1 of soil. Differentiated mineral fertilization with nitrogen or potassium as well as manganese and liming to a lesser extent than manure modified the availability of Cu, Zn and Mn in soil. Among these nutrients, nitrogen most often increased the content of plant assimilable forms of metals in soil, which may have been caused by its acidifying influence.

A study on the characteristics of heavy metals in orange ecosystem

An investigation was conducted to identify the characteristics of heavy metals in orange ecosystem in three areas in the Three Gorge Reservoir Region by using the modified Tessier sequential extraction procedure. The contents of Cu and Pb in different speciation fractions of the soils can be ordered as the Residual (F6)>Reducible (F4)>Oxidable (F5)>Water soluble (F1)>Carbonate (F3)>Exchangeable (F2), and the contents of Zn and Ni follow the order of the Residual (F6)>Oxidable (F5)>Reducible (F4)>Water soluble (F1)>Carbonate (F3)> Exchangeable (F2), and those of Cd follow the order of the Reducible (F4)>Oxidable (F5)>Exchangeable (F2)>Carbonate (F3)>Residual (F6)>Water soluble (F1). The concentrations of Cu in the different organs of oranges follow the increasing sequence of pulp>leaf>pericarp, those of Zn and Ni following the increasing sequence of leaf>pulp>pericarp, and those of Pb and Cd follow the increasing sequence of leaf>pericarp>pulp. Correlation degrees of different forms of same heavy metals in soils are according to the order of Cu>Zn>Cd>Pb>Ni. Correlation degrees of different heavy metals in same forms are according to the order that the forms of Reducible (F4), Oxidable (F5) and Residual (F6) are higher than the forms of Water soluble (F1), Exchangeable (F2) and Carbonate (F3). There are either positive or negative correlations between heavy metals in leaves and in pulp, while there are all positive correlations between heavy mentals in leaves and in pericarp. There are significant correlations between the concentrations of some heavy metals in leaves, pericarp or pulp, and those in speciation fractions in the soils.

Effects of sterilization on the chemical forms of heavy metals in soils

We used sequential extraction to investigate changes in the amounts of six chemical forms of manganese, cobalt and cadmium in soil samples after chloroform fumigation. The six forms were designated as follows: exchangeable, dilute-acid-soluble, manganese-oxide-occluded, organically bound, iron-oxide-occluded and residual. For all three metals, the decreases in the amounts of manganese-oxide-occluded forms were equivalent to the sum of the increases in the amounts of exchangeable and dilute-acid-soluble forms. The amounts of the other three forms did not change significantly after fumigation. These results indicate that some of the cobalt and cadmium in the manganese oxides was converted into exchangeable and dilute-acid-soluble forms, which suggests that soil sterilization may increase the availability of these heavy metals to plants.

Determining mobile forms of metals in soil by the use of the sorption-kinetic method

A kinetic model has been designed for considering sorption accumulation in mobile forms of metals from soil suspension by the use of filters with immobilized chelate groups. The advantages of the method were demonstrated for use in large-scale analysis during soil testing.

Fuzzy divisive hierarchical clustering of soil data using Gustafson–Kessel algorithm

In this paper we discuss the clustering results of 304 soil samples based on the concentration of 13 chemical elements (Cd, Co, Cr, Cu, Eu, Fe, Mn, Ni, Pb, Sb, Se, Y, and Zn) determined according to a four-step sequential extraction procedure: acetic acid ( 1), hydroxyl ammonium chloride ( 2), hydrogen peroxide/ammonium acetate ( 3) and aqua regia ( 4). The use of a sequential extraction procedure is the only objective method to determine the present binding forms of metals in soils and sediments. The mobility of chemicals in the environment is of a large interest for scientists because their mobility in soils and sediments, for example, is strongly associated to their toxicity effects. Considering the enormous data flood and their complexity it appears evident that chemometric techniques are the most suitable methods of investigation and as a direct consequence fuzzy clustering could be one of the best solution. In this order we have applied different fuzzy clustering algorithms, namely hierarchical and horizontal fuzzy clustering including Gustafson–Kessel algorithm which may detect clusters of different geometrical shapes in a data set by introducing an adaptive distance norm for each cluster. The present assessment has shown that the Gustafson–Kessel algorithm is the superior and effective method for clustering soil samples. This conclusion has been also clearly supported by the values of some conventional cluster validity indices.

Use of sequential extraction to assess the influence of sewage sludge amendment on metal mobility in Chilean soils

In Chile, the increasing number of plants for the treatment of wastewater has brought about an increase in the generation of sludge. One way of sludge disposal is its application on land; this, however involves some problems, some of them being heavy metal accumulation and the increase in organic matter and other components from sewage sludge which may change the distribution and mobility of heavy metals. The purpose of the present study was to determine the effect of sewage sludge application on the distribution of Cr, Ni, Cu, Zn and Pb in agricultural soils in Chile. Three different soils, two Mollisols and one Alfisol, were sampled from an agricultural area in Central Chile. The soils were treated with sewage sludge at the rates of 0 and 30 ton ha(-1), and were incubated at 25 degrees C for 45 days. Before and after incubation, the soils were sequentially extracted to obtain labile (exchangeable and sodium acetate-soluble), potentially labile (soluble in moderately reducing conditions, K4P2O7-soluble and soluble in reducing conditions) and inert (soluble in strong acid oxidizing conditions) fractions. A two-level factored design was used to assess the effect of sludge application rate, incubation time and their interaction on the mobility of the elements under study. Among the metals determined in the sludge, zinc has the highest concentration. However, with the exception of Ni, the total content of metals was lower than the recommended limit values in sewage sludge as stated by Chilean regulations. Although 23% of zinc in sludge was in more mobile forms, the residual fraction of all metals was the predominant form in soils and sludge. The content of zinc only was significantly increased in two of the soils by sewage sludge application. On the other hand, with the exception of copper, the metals were redistributed in the first four fractions of amended soils. The effect of sludge application rate, incubation time and their interaction depended on the metal or soil type. In most cases an increase in more mobile forms of metals in soils was observed as the final effect.

Fractionation studies of trace elements in contaminated soils and sediments: a review of sequential extraction procedures

Sequential selective extraction techniques are commonly used to fractionate the solid-phase forms of metals in soils. Many sequential extraction procedures have been developed, particularly for sediments or agricultural soils, and, despite numerous criticisms, they remain very useful. This article reviews the reagents used in the various schemes, with their advantages and disadvantages. The particular case of elements giving anionic species is also developed. Finally, there is discussion of the limits of sequential extraction procedures.

Copper speciation and microbial activity in long-term contaminated soils.

Most soil quality guidelines do not distinguish among the various forms of metals in soils; insoluble, nonreactive, and nonbioavailable forms are deemed as hazardous as highly soluble, reactive, and toxic forms. The objective of this study was to better understand the long-term effects of copper on microorganisms in relation to its chemical speciation in the soil environment. Carbon mineralization processes and the global structure of different microbial communities (fungi, eubacteria, actinomycetes) are still affected after more than 50 years of copper contamination in 20 soils sampled from two different agricultural sites. The microbial respiration lag period (LP) preceding the beginning of mineralization process increases with the level of soil copper contamination and is not significantly affected by other environmental factors such as soil pH and soil organic matter (SOM) content. The total copper concentration showed the best correlation with the LP when each site is considered separately. However, when considering the whole set of data, soil solution free Cu2+ activity (pCu2+) is the best predictor of Cu toxicity determined by LP (quite likely because pCu2+ integrates the soil physicochemical variability). The maximum mineralization rate (MMR), even if well correlated with the pCu2+, appears not to be a good biomonitor of copper contamination in soils since it is highly sensitive to soil characteristics such as SOM content. This study emphasizes the importance of the physicochemical properties of the environment on soil heavy metal toxicity and on soil toxicological measurements. These properties must be characterized in soil toxicological studies with respect to (1) their interactions with heavy metals, and (2) their direct impact on the selected biological test. The measurement of pCu2+ to characterize the level of soil contamination and of lag period as a bioindicator of metal effects in the soil are recognized as useful tools for the evaluation of the biological quality of soils.

Redistribution of forms of zinc, cadmium and nickel in soils treated with EDTA

Organic amendments are often added to soils in the form of waste materials which increase the soluble organic ligands in soil. To study the interaction of these soluble organics with metals in soil, Ethylenediaminetetraacetic acid (EDTA) can be used as a model compound for natural organics. The addition of EDTA to soil may alter the physicochemical forms of metals in soil because of its strong chelating capacity. In this work, samples of eight agricultural soils collected in Georgia were spiked with soluble salts of Zn, Cd, and Ni in proportions of 75.9, 1.62, and 4.30 mg kg−1, respectively. Both natural and metal-amended soils were treated with Na2-EDTA (disodium ethylenediamine tetraacetate) solution at amounts of 0, 1.0 and 2.0 g kg−1. After five months incubation in a greenhouse, the soil samples were fractionated into exchangeable (EXC), organic matter (OM), Mn oxide (MNO), amorphous Fe oxide (AFEO), crystalline Fe oxide (CFEO), and residual (RES) fractions. The added Zn was distributed among all fractions in the soils, and added Cd and Ni were found predominantly in the EXC and OM fractions with some of the added Ni occurring in the RES fraction. Increasing the amounts of EDTA significantly raised Zn concentrations in the EXC fraction in both natural and metal-amended soils, and the EDTA also increased Ni and Cd concentrations in the EXC fraction of the metal-amended soils. The results suggested that added EDTA enhanced the solubility of these metals in these soils. The OM-fraction metals decreased with increasing amounts of EDTA, except for Ni in the natural soils. The increase in Zn and Cd associated with the EXC fraction may have been related to solubilization of metals from the OM fraction by EDTA. In the metal-amended soils, EDTA not only removed Ni from the OM fraction, but also from the MNO, AFEO and CFEO fractions, and redistributed it into the EXC fraction. Based on relative percent, Cd in the EXC fraction was higher than Zn, while Ni in this fraction was lowest. This suggests that the order of solubility was: Cd>Zn>Ni for metals added to soils, but when EDTA was present, added Ni may be more vulnerable to solubilization than added Zn and Cd.