Zinc Fractions Research Articles

Distribution of Zinc in Selected Benchmark Soils of South Western Nigeria

The Understanding of the different fractions of Zinc in soils is important to effectively manage fertilizer resources due to the low availability of Zinc in the native soil worldwide. Bioavailability, uptake of Zinc by plant and its fractions depend largely on the soil parent material, the type of chemical transformation the soil has been expose to over times and some anthropogenic intervention. This study examined five different Zn pools.The distribution of Zn in soil fractions was determined for seven selected soils of South Western Nigeria. A sequential batch extraction which had been modified was used to identify Zn fractions and were separated into: the extractable zinc (Ex-Zn), zinc associated with the carbonate (CO3-Zn), the organically bound zinc (Org-Zn), sesquioxide (Ox-Zn) and residual (Res-Zn) in each soil. Total Zn was estimated as a sum of all the pools.Result showed that Zinc fractions in the soils were in this order: extractible pool (3.8%) < organic pool (13.6%) < carbonate pool (14.8%) < sesquioxide pool (22.8%) < residual pool (45.1%). The residual pool amounts for almost half of the zinc that made up the total zinc in the soil. The distribution of zinc into these pools were determined by selected physical and chemical properties of the soil; the pH, organic carbon, clay, CEC, and phosphorus. However, soil phosphorus and pH had the highest influence on the zinc in the experimental soils. The stable fraction that dominated the soil was evident in the low extractable Zn fractions in the soil. Which is an indication of the inherently low levels of the bioavailability of Zn in the selected soils used in this study.

Changes in oxidative potential of soil and fly ash after reaction with gaseous nitric acid

The goal of this study was to examine the impact of simulated atmospheric aging on the oxidative potential of inorganic aerosols comprised primarily of crustal materials. Four soil samples and one coal fly ash sample were artificially aged in the laboratory through exposure to the vapor from 15.8 M nitric acid solution for 24 h at room temperature. Native and acid-aged samples were analyzed with a cellular macrophage and acellular dithionthreitol assays to determine oxidative potential. Additionally, the samples were analyzed to determine the concentration of 50 elements, both total and the water-soluble fraction of these elements by Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICMS) and crystalline mineral composition using X-ray Diffraction (XRD). The results show that reactions with gaseous nitric acid increase the water-soluble fraction of many elements, including calcium, iron, magnesium, zinc, and lead. The mineral composition analysis documented that calcium-rich minerals present in the soils (e.g., calcite) are converted into different chemical forms, such as calcium nitrate (Ca(NO3)2). The nitric acid aging process, which can occur in the atmosphere, leads to a 200–600% increase in oxidative potential, as measured by cellular and acellular assays. This laboratory study demonstrates that the toxic effects of aged versus freshly emitted atmospheric dust may be quite different. In addition, the results suggest that mineralogical analysis of atmospheric dust may be useful in understanding its degree of aging.

Partitioning and geochemical fractions of heavy metals from geogenic and anthropogenic sources in various soil particle size fractions

The size of soil particles can significantly affect the enrichment of heavy metals in soil. However, the size effect of soil particles in colloidal dimension on the partitioning and geochemical fractions of heavy metals has been rarely studied. In this study, four soils, polluted by several heavy metals, were collected from Jiangxi (JX) and Hebei (HB) Provinces and Guangxi Zhuang Autonomous Region (GX and GX′) in China, respectively. Five size fractions (>10, 10–1, 1–0.45, 0.45–0.2 and <0.2μm) were separated from the studied soils to investigate the partitioning and geochemical fractions of cadmium (Cd), cadmium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). For JX, GX and GX′ soils, Cr and Ni in JX and GX′ soils and Cr, Ni and Mn in GX soil, as geogenic elements, were comparable with their background values; whereas other heavy metals, as anthropogenic elements, were higher than their background values. For the HB soil that was only polluted by Pb, Cd, Cr, Cu, Mn, Ni and Zn were the geogenic heavy metals. Generally, the contents of most heavy metals in the soil colloids were higher than that in coarse soil particles, and the partitioning tendencies with particle size were not significantly different between geogenic heavy metals and anthropogenic heavy metals. The partitioning of heavy metals in various soil particle size fractions was closely related to the soil particle compositions, such as OM, Fe/Al oxides and clay minerals. For geogenic heavy metals (Cr, Ni), the proportion of the residual fraction, which is imbedded in the silicate crystalline structures of soil particles, was very high, and the geochemical fraction patterns of the various soil particle size fractions were comparable, whereas the bioavailable fraction of anthropogenic heavy metals, such as Cu, Mn, Pb and Zn, decreased with decreasing soil particle size and the proportion of other fractions increased with decreasing size. This result indicates that more anthropogenic heavy metals exist in their stable form in fine soil particles. Correlations between Fe, Al and TOC and the bioavailable fraction of anthropogenic heavy metals were all negative, and most were significant or very significant indicating that high contents of OM and Fe/Al oxides stabilize anthropogenic heavy metals in fine soil particles.

Status of Zinc Fractions in Soils of Cooch Behar District, West Bengal, India

Status of Zinc Fractions in Soils of Cooch Behar District, West Bengal, India

Nanoparticles and modified clays influenced distribution of heavy metals fractions in a light-textured soil amended with sewage sludges

We comparatively assessed the effect of modified clays (MCs) (zeolite and bentonite) and nanoparticles (NPs) (ZnO and MgO) on the distribution of cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) fractions in a light-textured soil amended with five sewage sludges (SSs) differed in chemical properties during a 92-day incubation experiment in the laboratory. Results indicated that presence of adsorbents and incubation time were critical parameters in stabilizing metals in SS-amended soil. The adsorbents that significantly decreased the easily soluble and exchangeable of metals in SS-amended soil (rate 2%) were bentonite, ZnO and MgO for Cd and Cu, ZnO and MgO for Ni, and bentonite and MgO for Zn. The calculated mobility factor of the metals at five incubation times (5, 15, 29, 57 and 92days) was found in the range of 34.7–51.8 for Cd, 16.7–20.0 for Cu, 15.0–27.7 for Ni, and 35.3–40.7 for Zn indicating a higher mobility of Cd. The addition of MCs and NPs decreased the available fraction of metals, and among them, we suggest bentonite and MgO as novel, promising and feasible adsorbents with the unique characteristics in ameliorating the toxic effects of metals by converting their form from labile to non-labile phases in the SS-amended soil.

Application of kinetic bioluminescence inhibition assay using live cultures of Aliivibrio fischeri for determination of zinc toxicity

Variation in zinc toxicity with variation in environmental conditions was studied using the kinetic bioluminescence inhibition assay conducted with live cultures of Aliivibrio fischeri. A good correlation was observed between the static assay and flash assay for colorless non-turbid samples. Color and turbidity had negligible impact on the flash assay results while the static assay caused artifacts. Naturally occurring water samples showed wide variation in the toxicity profiles. Change in zinc toxicity was determined in response to variation in hardness, alkalinity and other coexisting cations/anions in model lake water and in the presence of a solid matrix. The presence of other anions and cations in model lake water reduced and enhanced zinc toxicity, respectively, due to changes in zinc speciation, and bioluminescence inhibition was well correlated with free zinc ion concentration. Increase in alkalinity and sulfate in model lake water lowered zinc toxicity, whereas increase in ammonium ions enhanced the toxicity. Variation in toxicity with hardness was dependent on the Ca: Mg hardness ratio in the samples. The presence of solid matrix decreased toxicity of the aqueous extracts, and toxicity of the matrix was found to increase with decreasing grain size. Speciation pattern of zinc in the respective fractions, however, revealed no direct relationship between zinc associated with fraction that are considered bioavailable to higher organism and the observed toxicity. This assay may be recommended for toxicity analysis of environmental samples since most of the results obtained correlate well with observations reported in toxicity studies with higher organisms.

The influence of physicochemical parameters on bioaccessibility-adjusted hazard quotients for copper, lead and zinc in different grain size fractions of urban street dusts and soils

When the hazard quotient for ingestion (HQI) of a trace element in soil and dust particles is adjusted for the element's bioaccessibility, the HQI is typically reduced as compared to its calculation using pseudo-total element concentration. However, those studies have mostly used bulk particles (<2mm or <250µm), and the reduction in HQI when expressed as bioaccessible metal may not be similar among particle size fractions, the possibility probed by the present study of street dusts and soils collected in Tehran. The highest Cu, Pb and Zn near-total concentrations occurred in the finest particles of dusts and soils. Bioaccessible concentrations of Cu, Pb and Zn in the particles (mgkg-1) were obtained using simple bioaccessibility extraction test (SBET). The bioaccessibility (%) did not vary much among near-total concentrations. In the bulk (<250µm) sample, the bioaccessible concentration of Cu and Pb increased as the pH of sample increased, while Zn bioaccessibility (%) in the bulk particles was influenced by organic matter and cation exchange capacity. X-ray diffraction identified sulfide and sulfate minerals in all of the size-fractionated particles, which are insoluble to slightly soluble in acidic conditions and included most of the Cu and Pb in the samples. The only Zn-bearing mineral identified was hemimorphite, which would be highly soluble in the SBET conditions. The calculated HQI suggested potential non-carcinogenic health risk to children and adults from ingestions of soils and dusts regardless of particle size consideration, in the order of Zn>Pb≥Cu. The HQI calculated from near-total metal was not much different for particle size classes relative to bulk particles; however, the bioaccessibility percent-adjusted HQI for Pb was higher for the smaller particles than the bulk. This work is novel in its approach to compare HQI for a bulk sample of particles with its composite particle size fractions.

Selective recovery of copper and zinc from mine dump waters of mining enterprises in precipitates

The acid mine dump waters at mining companies that mining the copper and copperzinc sulphide ore have the high concentrates of metals and classified in our view as the raw materials for selective recovery of metals in precipitates comparable in quality with concentrates of ores enrichment and suitable for further metallurgical processing. Authors have implemented three two-stage schemes for sequential extraction of copper and zinc: cementation-sulphide precipitation, galvanocoagulation-sulphide precipitation, precipitation-precipitation. Moreover, parameters of processes and quality of the obtained precipitates have described. The achieved copper recovery is 89% and 94% respectively with the application of cementation and galvanocoagulation, in sulphide precipitate exceeded 75%. Furthermore, the copper recovery from decoppering in precipitates amounted to more than 65%. Zinc-containing precipitates because of coprecipitation of iron, magnesium and calcium contain zinc from 14% to 28%, in two to three times less than the quality of conditioned zinc concentrates. The content of precipitates allows to apply them for additional charging to concentrates of enrichment or for the production of metals in metallurgical treatment. As a result of the studying the effect of reduced total salinity (S) on mass fraction of zinc in precipitate (β) with the constant concentration of zinc (SZn), the changes in concentration with constant salinity and reduction in total salinity (S) with constant ratio S/CZn, the following dependencies have obtained: , in the range of an index S from 4.5 to 90.0 g/L , where is a partial derivative of x to y, whereas the value z is fixed.

Availability of zinc from infant formula by in vitro methods (solubility and dialyzability) and size-exclusion chromatography coupled to inductively coupled plasma-mass spectrometry.

Zinc bioaccessibility from infant formula was estimated by in vitro methods (solubility and dialyzability) and size-exclusion chromatography (SEC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Infant formula samples were first characterized in terms of Zn bound to lipids and proteins and Zn distribution in the aqueous soluble protein fraction. We found that Zn is not incorporated into the lipid fraction of the samples, being mainly associated with the protein fraction (around 100%). Fractionation of Zn-containing proteins in the soluble protein fraction was achieved by SEC-ICP-MS after performing protein extraction with a solution of 100mM (pH 6.8) Tris-HCl. The percentages of zinc in the soluble protein fraction in the soy-based and lactose-free infant formula were very low, around 7 and 24%, respectively, whereas the content of Zn in the soluble protein fraction of milk-based formula was around 90%. By SEC-ICP-MS, we found that Zn is associated with low-molecular weight compounds (around 10kDa) in all the infant formulas tested. The percentages of Zn estimated in the in vitro gastrointestinal digests of the infant formula ranged from 30 to 70% and from 1 to 10% for solubility and dialyzability assays, respectively. The dialyzability test resulted in lower than expected scores, as SEC-ICP-MS analysis of the gastrointestinal extracts revealed that Zn is bound to biomolecules with a molecular weight ranging from 1 to 7kDa, which suggests that dialysis data should be interpreted with caution. Speciation studies are a valuable tool for establishing availability of nutrients and for validating data from dialyzable in vitro methods.

Nutritional Composition of Iron, Zinc, Calcium, and Phosphorus in Wheat Grain Milling Fractions as Affected by Fertilizer Nitrogen Supply

Fe and Zn deficiencies are global nutritional problems. N supply could increase Fe and Zn concentrations in wheat grain. This study was conducted to determine the impacts of different N rates (0, 122, 174, and 300 kg/ha) on the distribution and speciation of Fe and Zn in wheat grain milling fractions under field conditions. Zn and protein concentrations were increased, whereas Fe was less affected in the flour fractions with increasing N rates. Further analysis with size‐exclusion chromatography coupled with inductively coupled plasma mass spectrometry revealed that Fe and Zn bound to low‐molecular‐weight (LMW) compounds in the flour fractions (probably Fe‐nicotianamine [NA], Fe‐deoxymugineic acid, or Zn‐NA) were less affected by increasing N supply, representing 3.5–10.9% of total Fe and 2.5–56.6% of total Zn. In the shorts fraction, LMW‐Fe was absent, and LMW‐Zn with higher N supply was over twice as high as that in control and 3–27 times as high as that in the other milling fractions. In the flour fractions, the molar ratios of phytic acid (PA)/Fe and PA/Zn (both less than 30.5) decreased, whereas soluble LMW‐Fe/Zn was not affected with increasing N rates.

Laser-induced local phase transformation of CIGSe for monolithic serial interconnection: Analysis of the material properties

The change of electrical conductivity in chalcopyrite (i.e., Cu(Inx, Ga1−x)Se2 or CIGSe) solar cells induced by nanosecond laser pulses is investigated as a function of the elemental composition and its spatial distribution. The underlying laser induced phase transformation process, which results in a decomposition of the CIGSe semiconductor and a modification of its elemental composition, is utilized to form the monolithic series interconnection between front and back contact in CIGSe based thin film solar cells. The results show a dependence of the composition of the CIGSe layer and the resulting series resistance on the applied laser fluence. Lower series resistance is primarily related to an enhanced fraction of copper, gallium and zinc in the laser transformed zone resulting from selective vaporization of absorber elements. For intermediate laser fluences (~0.36J/cm2) a patterning process is established that allows reliable and high-quality series interconnection. Both, lower and higher laser fluences result in high series resistances due to incomplete phase transformation or damages of the back contact, respectively.

Evonik to commission additional R&D operations at its Marl site

In Vienna approximately 1 million tons of waste is incinerated annually. Therefore 13 lines of waste incineration, including fluidized bed incinerators, rotary kilns and grate furnaces, are in operation. Beside municipal solid waste, hazardous waste as well as communal sewage sludge are utilized. All incinerator lines use a wet flue gas cleaning system. Based on the zinc, lead and copper concentrations in its solid residues and knowledge on the mass flow of the residues, a detailed material flow analysis is carried out, that determines the total throughput of these metals. It turns out that 800 t of zinc, 300 t of lead and 550 t of copper pass through Vienna's waste incineration cluster annually. Approximately half of the zinc can be found in the fly ashes of the waste incinerators investigated. In Switzerland a process that recovers pure zinc (> 99.99%) as well as a mixed fraction of lead, copper, zinc and cadmium out of waste incineration fly ash, has been realized at full scale. A comparison between the expected operational costs, on the one hand, and the anticipated revenues from recovered metals and reduced disposal costs resulting from the application of this technology to the investigated waste incinerators, on the other, is discussed within this work. Main drivers responsible for the economical non-applicability to Vienna, are examined.

Impacts of river impoundment on dissolved heavy metals in floodplain soils of the Lahn River (Germany)

The effects of changing soil moisture conditions and oxidation–reduction (redox) processes on dissolved fractions of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn) were studied in floodplain soils in the Lower Lahn Valley (Germany). Multiple weirs and locks affect the groundwater levels in the adjacent river banks by modifying the river’s discharge rate. Redox conditions act as a key factor for sorption and desorption processes and are strongly regulated by groundwater levels. Hence, floodplain soils situated up- and downstream of impounded river segments were characterized by various contents of their mobile heavy metal fraction. To quantify the variations of the dissolved heavy metal concentrations during seasonal and periodic fluctuations of the groundwater levels, a 2-year field study was conducted. The results indicated that higher seasonal changes of river discharge downstream of a weir caused higher amplitudes of groundwater levels, redox changes and variations in dissolved As, Fe and Mn in soil depths (50–60 cm) with a strong groundwater influence. Upstream of a weir, higher dissolved concentrations and more smooth variations of As, Fe and Mn dominated within the same depths. A high rise of capillary waters within the same study site caused significant enrichments of dissolved Cd and Zn in the middle (25–35 cm) of the soil profile. The comparison of floodplain soils along the Lahn River showed how the stream regulations influence heavy metal concentrations of soil pore waters, which may in turn influence the quality of the river water.

Of zinc fractions in relation to properties of some soils of Bangladesh

An investigation was conducted to determine the distribution and concentrations of different forms of Zn in the soils of Gazipur. Gerua, Kalma and Khilgaon soil series were identified in three land types, named as highland, medium high land and medium low land, respectively. Soil samples were collected from each soil series at three different depth such as surface (0 -15 cm), subsurface (15 -40 cm) and substratum (40 cm+) to determine soil characteristics and the distribution pattern of Zn fractions. Results indicated that amount of total Zn varied significantly, ranges from 14.99 to 36.11 ?g/g at different depth of different land types. Moreover, the purpose of the sequential extraction or fractionation was to find out the Zn in the exchangeable (Exch.), organic matter (Org.) bound, Mn oxide (Mn-O), amorphous Fe oxide (Am. Fe-O), crystalline Fe oxide (Crys. Fe-O) and residual (Res.) fractions. In Gerua, Kalma and Khilgaon soils, Zn concentrations predominated in Res. followed by Crys. Fe-O and Am. Fe-O fractions. Results reflected that soil properties influence the distribution of different Zn fractions in soils.Dhaka Univ. J. Biol. Sci. 25(1): 19-25, 2016

Temporal variation of total and DTPA-extractable heavy metal contents as influenced by sewage sludge and perlite in a calcareous soil

ABSTRACTContinuous application of sewage sludge (SS) as a source of organic matter, may increase available heavy metals (HMs) up to their critical levels. As a consequence their uptake by plants, risks of accumulation in food chain and groundwater pollution increases. To evaluate the effects of perlite and SS on total content and available fraction of iron (Fe), manganese (Mn), lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd) and zinc (Zn) over 45 and 90 days a completely randomized pot experiment was conducted. Treatments consisted of SS (0, 2 and 4%) and combined SS and perlite levels (1:1, 1.5:0.5 and 0.5:1.5% SS:perlite). Mean available Fe, Ni, Cd, Mn and Zn fractions decreased over time by 7–27%, whereas, total contents did not change. Available HMs in SS-treated soils increased by 0.5–25%; whereas, only total Zn, Cu and Pb concentrations increased with SS application (although concentrations fall in the range of critical levels). The lowest (1.6 fold) and highest (22.1 fold) increases obtained for available Cu and Zn, respectively. Perlite could mitigate the adverse effect of high rate application of SS on amplification of HMs extractability. Therefore, their concomitant applications can be suggested considering the perlite durability and its positive effects on soil physical properties.

Distribution of different fractions of Iron, Zinc, Chromium, lead and Nickel in Soils around Petrol filling stations in selected Areas of Delta State, Nigeria

The geochemical forms of some heavy metals in soils around selected petrol filling stations were studied in order to assess the mobility and bioavailability of the metals and hence their potential environmental risk. Water soluble fraction (F1) contained an average of 0.97% iron, 1.40% zinc, 2.37% chromium, 2.08% lead and 41.96% nickel with the abundance trend of Ni &gt; Cr &gt; Pb &gt; Zn &gt; Fe. Metal bound to exchangeable phase followed the same abundance trend with an average of 6.46% nickel, 5.48% chromium, 2.64% lead, 2.55% zinc and 0.62% iron. Lead was predominantly associated with carbonate fraction with an average of 52.32% followed by iron with an average of 15.41%. Other metal average levels in the carbonate fractions were 9.66% for nickel, 8.78% for chromium, and 8.73% for zinc giving the abundance trend of Pb &gt; Fe &gt; Ni &gt; Cr &gt; Zn. The most important metal in iron-manganese oxide phase was zinc with an average of 42.49%, followed by iron with an average of 32.82%. The averages of the other metals bound to this phase were 30.39%, 13.24% and 6.46% for chromium, lead and nickel respectively. The organic bound metals were in the abundance trend of Fe &gt; Zn &gt; Cr &gt; Pb &gt; Ni with average of 39.48% for iron, 30.87% for zinc, 23.03% for chromium, 8.54% for lead and 4.94% for nickel. Nickel with an average of 51.58% was predominantly associated with the residual fraction. The other metals bound to this phase in order of their importance to the fraction had the average of 22.75% for chromium, 13.96% for zinc, 12.24% for lead and 10.97% for iron. The mobility factor values of the metals were moderately high with the abundance trend of Pb &gt; Ni &gt; Cr &gt; Fe &gt; Zn. The generally low levels of the metals in the residual fraction coupled with the mobility factor trend suggest potential risk for the metals.Keywords: Soil pollution, speciation, petrol filling stations, heavy metals, Delta State

Zinc and iron concentrations in grain milling fractions through combined foliar applications of Zn and macronutrients

Agronomic biofortification of wheat with Zn and Fe can correct micronutrient deficiency in humans who consume wheat. In this study, two field experiments were conducted to investigate the effects of foliar Zn application combined with (1) macronutrients and Zn-amino acid chelates and (2) different soil N levels on Zn and Fe concentrations in whole grain and flour grown with straw incorporation. The results of the first experiment showed that flour Zn concentrations increased by 60.5%, 39.9%, and 56.2% due to the foliar application of ZnSO4 combined with N (urea), PK (KH2PO4), and K (K2SO4), respectively, compared to the control, and the corresponding increases in whole grain were 65.6%, 38.1%, and 50.1%, respectively. Compared with foliar Zn application alone, foliar N and K applications caused similar increases in grain Zn and Fe concentrations, whereas the foliar application of Zn combined with PK resulted in a significant decrease (approximately 12.1% across the two cropping years) in whole-grain Zn concentrations. Flour Zn concentrations, however, were unaffected by foliar Zn combined with PK fertilization and significantly increased due to the foliar application of Zn combined with N or K (in the first cropping year) compared to foliar Zn application alone. Foliar Zn combined with macronutrient fertilization tended to increase flour and grain Fe concentrations. Additionally, reducing the soil N application rate generally had a small effect on flour and grain Zn and Fe concentrations. The results of the second experiment showed that the application of Zn(Gly)2, alone or in combination with N(urea), caused similar increases in Zn and Fe concentrations in flour and whole grain. Foliar ZnSO4 combined with macronutrient fertilization under 15% reduced soil N supply and straw incorporation is an economical, effective, practical, and environmentally friendly agronomic practice for enhancing Zn and Fe concentrations in flour.

Zinc Fractions and their Availability to Wetland Rice in Acidic Soils of Assam

Distribution of various fractions of soil zinc (Zn) and their relationships with soil properties in rice growing soils of Assam were studied with twenty five geo-referenced soil samples (0-30 cm) with variable Zn status from rice growing areas of Assam, representing 3 major soil orders viz., Entisol, Inceptisol and Alfisol. The distribution of different forms of Zn in rice soils revealed that water soluble and exchangeable Zn (WSEx-Zn) fraction in soils ranged from 0.32 to 1.92, complexed Zn (COMP-Zn) from 1.46 to 4.5, amorphous sesquioxide bound Zn from 1.30 to 6.21, crystalline sesquioxide bound Zn (CBD-Zn) from 0.45 to 2.25 and residual Zn (Res-Zn) from 101.7 to 285.2 mg kg-1 with mean values of 0.87, 2.71, 2.92, 1.12 and 186.98 mg kg-1, respectively. Residual Zn was the dominant fraction among all Zn fractions studied, which ranged from 101.7 to 285.2 mg kg-1 and the mean value was 186.9 mg kg-1. The WSEx-Zn, COMP-Zn, amorphous sesquioxide bound Zn, CBD-Zn and Res-Zn constituted 0.45, 1.57, 1.62, 0.63 and 95.7 per cent of total Zn. Multiple regression of physicochemical properties of soil with different Zn-fractions showed the highest R2 value (0.616) with COMP-Zn. Multiple regression of different Zn fractions with plant parameters showed the highest contribution of WSEx-Zn to plant Zn concentration (76.7%), Zn-uptake (63.0%) and dry matter yield (36.1%) of rice. Path coefficient analysis of different Zn-fractions with Zn-concentration in rice plant showed the highest direct effect (0.5610) of WSEx-Zn on Zn concentration and indirect effect of COMP-Zn (0.3731) and amorphous sesquioxide bound Zn (0.2508) via WSEx-Zn. Significant positive correlation was also observed between WSEx-Zn and plant Zn uptake (r=0.668**), plant Zn concentration (r=0.647**) and drymatter yield (r=0.401*), suggesting that water soluble plus exchangeable Zn fraction is of great importance in Zn nutrition of lowland rice. Major portion of Zn was in the residual fraction which contributed very little to plant uptake. Significant positive correlation among WSEx, organic complex and amorphous sesquioxide bound Zn indicated that they are possibly in dynamic equilibrium with each other.

Fast and simple procedure for fractionation of zinc in soil using an ultrasound probe and FAAS detection. Validation of the analytical method and evaluation of the uncertainty budget.

A new fast method for determination of mobile zinc fractions in soil is proposed in this work. The three-stage modified BCR procedure used for fractionation of zinc in soil was accelerated by using ultrasounds. The working parameters of an ultrasound probe, a power and a time of sonication, were optimized in order to acquire the content of analyte in soil extracts obtained by ultrasound-assisted sequential extraction (USE) consistent with that obtained by conventional modified Community Bureau of Reference (BCR) procedure. The content of zinc in extracts was determined by flame atomic absorption spectrometry. The developed USE procedure allowed for shortening the total extraction time from 48 h to 27 min in comparison to conventional modified BCR procedure. The method was fully validated, and the uncertainty budget was evaluated. The trueness and reproducibility of the developed method was confirmed by analysis of certified reference material of lake sediment BCR-701. The applicability of the procedure for fast, low costs and reliable determination of mobile zinc fraction in soil, which may be useful for assessing of anthropogenic impacts on natural resources and environmental monitoring purposes, was proved by analysis of different types of soil collected from Podlaskie Province (Poland).Electronic supplementary materialThe online version of this article (doi:10.1007/s10661-015-5020-6) contains supplementary material, which is available to authorized users.

Mobility and eco-risk of trace metals in soils at the Hailuogou Glacier foreland in eastern Tibetan Plateau.

The concentrations and fractions of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in soils collected from Hailuogou Glacier foreland in eastern Tibetan Plateau were analyzed to decipher their mobility, and their eco-risk was assessed combined with multiple environmental indices. The concentrations of Cd were more than ten times higher than its local background in the O horizon and nearly three times higher in the A horizon. The concentrations of Pb and Zn were relatively high in the O horizon, whereas that of Cu increased with soil depth. The main fractions of metals in the surface horizons were reducible and acid-soluble for Cd, oxidizable and residual for Cu, reducible and oxidizable for Pb, and reducible and residual for Zn. The metal mobility generally followed the order of Cd > Pb > Zn > Cu in the O horizon and Cd > Pb > Cu > Zn in the A horizon. Sorption and complexation by soil organic matters imparted an important effect on the mobilization and transformation of Cd, Pb, and Zn in the soils. The oxidizable Cu fraction in the soils showed significant correlation with organic matters, and soil pH mainly modulated the acid-soluble and reducible Cu fractions. The concentrations and other environmental indices including contamination factor, enrichment factor, geoaccumulation index, and risk assessment index revealed that Cd reached high contamination and very high eco-risk, Pb had medium contamination but low eco-risk, Zn showed low contamination and low eco-risk, and Cu was not contaminated in the soils. The data indicated that Cd was the priority to concern in the soils of Hailuogou Glacier catchment.