Proportion Of Zn Research Articles

Mobility and Distribution of Zinc, Cadmium and Lead in Calcareous Soils Receiving Spiked Sewage Sludge

Leaching column experiments were conducted to determine the degree of mobility and the distribution of zinc (Zn), cadmium (Cd), and lead (Pb) because of an application of spiked sewage sludge in calcareous soils. A total of 20 leaching columns were set up for four calcareous soils. Each column was leached with one of these inflows: sewage sludge (only for two soils), spiked sewage sludge, or artificial well water (control). The columns were irrigated with spiked sewage sludge containing 8.5 mg Zn l−1, 8.5 mg Cd l−1, and 170 mg Pb l−1 and then allowed to equilibrate for 30 days. At the end of leaching experiments, soil samples from each column were divided into 18 layers, each being 1 cm down to 6 cm and 2 cm below that, and analyzed for total and extractable Zn, Cd and Pb. The fractionation of the heavy metals in the top three layers of the surface soil samples was investigated by the sequential extraction method. Spiked sewage sludge had little effect on metal mobility. In all soils, the surface soil layers (0-1 cm) of the columns receiving spiked sewage sludge had significantly higher concentrations of total Zn, Cd and Pb than control soils. Concentration of the heavy metals declined significantly with depth. The mobility of Zn was usually greater than Cd and Pb. The proportion of exchangeable heavy metals in soils receiving spiked sewage sludge was significantly higher than that found in the control columns. Sequential extraction results showed that in native soils the major proportion of Zn and Pb was associated with residual (RES) and organic matter (OM) fractions and major proportion of Cd was associated with carbonate (CARB) fraction, whereas after leaching with spiked sewage sludge, the major proportion of Zn and Pb was associated with Fe-oxcide (FEO), RES, and CARB fractions and major proportion of Cd was associated with CARB, RES and exchangeable (EXCH) fractions. Based on relative percent, Cd in the EXCH fraction was higher than Zn and Pb in soils leached with spiked sewage sludge.

Structure of the quaternary alloy Zn0.6Mn0.4In2S4from synchrotron powder diffraction and electron transmission microscopy

The aim of the present work was to determine the structure of the quaternary alloy Zn0.6Mn0.4In2S4and to locate the Mn2+. This was accomplished by means of powder synchrotron X-ray diffraction, high-resolution microscopy and convergent-beam electron diffraction (CBED). The powder X-ray diffraction pattern was indexed in a rhombohedral cell, with cell constantsa= 3.875 (2),c= 37.208 (4) Å, and possible space groupsR\bar{3}morR3m. Rietveld refinements using different cationic arrangements in these space groups were performed. A model in space groupR3m, in which the tetrahedral and octahedral sites were occupied by different proportions of Zn, Mn and In atoms, gave the best result. The Rietveld refinement of this model led to figures of meritRwp= 9.8%,Rp= 9.1% and χ2= 11.1. Selected-area electron diffraction patterns and high-resolution transmission electron micrographs along [001] reveal the rhombohedral configuration. CBED patterns perpendicular to [001], showing the distinctive 3msymmetry, confirmed space groupR3mand the breaking of the centrosymmetry of the parent compound, ZnIn2S4.

Influence of Metal Loading on the Mode of Metal Retention in a Natural Clay

Clay, which is a natural fine-grained soil, was subjected to various levels of contamination by the heavy metal Zn, in a series of batch sorption experiments conducted at pHs of 3–7. Zinc speciation in the soil was subsequently analyzed using a sequential extraction technique, which fractionated the retained Zn into exchangeable, carbonate, reducible, organic, and residual fractions. The results showed that when Zn loading increased, the increase in Zn sorption by the clay was rather limited in acidic conditions. The Zn distribution between the dissolved phase and each fraction of the sorbed phases could be described with either the Freundlich or the Langmuir adsorption equations. If favorable pH existed, at high Zn loadings, precipitation was the most effective process of Zn removal from the dissolved phase. At low Zn loading levels, a relatively higher proportion of Zn was retained in the more persistent fractions. These findings indicated that the predominant mode of heavy metal retention in a soil can...

The Monitoring and Risk Assessment of Zn Deposition Around a Metal Smelter in Latvia

Heavy metal concentrations in Hylocomium splendens collected around a metal smelter in Latvia showed very high concentrations of Zn (>200 μg/g), and elevated concentrations of Pb (38.3 μg/g) and Cu (18.3 μg/g). In an attempt to better evaluate the potential toxicity of the high Zn concentrations, a serial elution method was used to determine the concentrations of zinc in intercellular, extracellular exchangeable cell wall, intracellular, and particle fractions. The intercellular Zn concentrations represent the water soluble component of the total concentrations, and were low with no clear trends. Zn concentrations in the extra- and intracellular and particle fractions decreased exponentially from the pollutant source. Intracellular Zn concentrations in moss close to the emission source are within the range considered to be potentially toxic, from other single element exposure studies. The proportion of Zn in the relatively insoluble particle fraction, which is least associated with environmental risk, was greater closer to the pollution source, reaching > 30% in the oldest Hylocomium splendens segments.

Alfalfa genotypes differ in their ability to tolerate zinc deficiency

Response of 13 alfalfa (Medicago sativa L.) genotypes to varied Zn supply (+Zn: 2 mg kg−1 soil, −Zn: no added Zn) was studied in a pot experiment under controlled environmental conditions. Plants were grown for four weeks in a Zn-deficient siliceous sandy soil. Plants grown at no added Zn showed typical Zn deficiency symptoms i.e. interveinal chlorosis of leaves, yellowish-white necrotic lesions on leaf blades, necrosis of leaf margins, smaller leaves and a marked reduction in growth. There was solute leakage from the leaves of Zn-deficient plants, while no solute leakage from Zn-sufficient plants. The ratios of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn in Zn-deficient plants were extremely high compared with Zn-sufficient plants indicating disturbance of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn balance within plant system by Zn deficiency. Genotypes differed markedly in Zn efficiency based on shoot dry matter production. Alfalfa genotypes also differed markedly in P:Zn ratio, Cu:Zn ratio and Fe:Zn ratio under —Zn treatment. The shoot dry weight, shoot:root ratio, chlorophyll content of fresh leaf tissue, solute leakage from the leaves, Zn uptake and distribution of Zn in shoots and roots were the most sensitive parameters of Zn efficiency. Zn-efficient genotypes had less solute leakage but higher shoot:root ratio and higher Zn uptake compared with Zn-inefficient genotypes. Under —Zn treatment, Zn-inefficient genotypes had less Zn partitioning to shoots (33–37%) and more Zn retained in roots (63–67%), while Zn-efficient genotypes had about equal proportions of Zn in roots (50%) and shoots (50%).

Characterization of a cadmium-zinc complex in lettuce leaves.

Vegetable food contributes a higher amount of daily cadmium (Cd) intake in humans than food of animal origin. The bioavailability of plant Cd depends on the content of plant zinc (Zn). The mechanism by which increased plant Zn lowers the intestinal absorption of plant Cd could be mediated by changes in the chemical speciation of Cd or Zn in plant edible tissues, including Zn-induced phytochelatin synthesis. To test this hypothesis we investigated the chemical speciation of Cd and Zn in leaf extracts of lettuce grown under 10 microM of Cd accompanied by 0.32 or 31.6 microM Zn in nutrient solution. Gel filtration chromatography of the low- or high-Zn leaf extracts yielded a major low molecular weight Cd-Zn complex that eluted at similar elution volume. Compared to low-Zn leaf extracts, high-Zn leaf extracts contained a higher proportion of Zn incorporated into high molecular weight components, and higher content of the amino acids Cys, Gly, Gly, and Asp in the low molecular weight Cd-Zn complex. The peptides isolated by high performance liquid chromatography (HPLC) of the Cd-Zn complex from the low- or high-Zn leaf extracts did not have an amino acid composition identical to phytochelatins. We concluded that 1. Sequestration of Cd or Zn via phytochelatin does not occur in leaves of lettuce containing levels of those metals representatives of Zn-Cd or Cd-only contaminated crops; and 2. Higher Cys, Glu, Gly, and Asp content in high-Zn than low-Zn leaves could lower Cd absorption in animals fed high-Zn crop diets, by enhancing metallothionein synthesis or changing Cd or Zn speciation in the animal gut.

The application of an oral zinc tolerance test to assess zinc absorption from three different dietary sources in the dog

Zinc (Zn) is a key nutrient for dogs, playing an important role in many metabolic functions. It has been estimated that 91% of the minimum maintenance requirement for Zn is needed to support hair growth. Coat condition is perceived as being important by pet owners and is thus of fundamental concern when evaluating the adequacy of a diet for dogs.Zn absorption has been shown to vary as a function of the amount and source of the Zn in the diet and as a function of the presence of elevated calcium and / or phytate levels in the diet.It has been suggested that when dietary Zn is supplied in the form of a chelate with amino acids, rather than from inorganic sources, a greater proportion of Zn is absorbed an is thus available to the animal. Further, the undesirable effects that dietary antagonists, such as calcium, exert on Zn absorption may be negated

Fate of zinc applied to calcareous soils using Zn‐65 as a tracer: II. Extraction and particle size association

Abstract Extraction of Zn by EDTA, DTPA 1.0 N NH4OAc, and 0.1N HCl was made on soil samples taken from eight calcareous soils of varied physical and chemical properties. Zinc‐65 was applied as carrier‐free and carrier to soil samples incubated for 1, 15, and 30 d. Zinc associated with each size of soil particles was accomplished through pipetting on the same treated soils. Based on the mean values, the efficiency in Zn extraction followed the order EDTA > DTPA > NH4OAc ≫ HCl for the carrier‐free treatments. However, for the carrier treatments, the order had changed to NH4OAc > HCl > EDTA > DTPA for the 1 d and to NH4OAc > EDTA > HCl > DTPA for the 15 and 30 d incubation. The greater power of the acidic NH4OAc in extracting Zn (84 to 92%) is attributed to its capability of dissolving the carbonate‐metal phase as well as the exchangeable forms. In general, neither soil texture nor the incubation period had an important influence on the proportion of Zn associated with each soil particle size. Nearly 60% of ...

Effect of cycloheximide on the induction of metallothionein and acute toxicity of cadmium in mice.

Using male mice of ICR strain, the effect of cycloheximide on metal-lothionein production and the acute toxicity of Cd were studied. Followiug ad-ministration of Cd alone (2.5 mg/kg body weight), most of the Cd accumulated in the lives and kidney was found in the metallothionein (MT) region. Zn was also detected in this region, being enhanced with increasing time after Cd injection. Following combined treatment with Cd and cycloheximide (total dose 2.0 mg), the proportions of Cd and Zn in the cell sap were slightly decreased. In the MT region, the proportion of Cd was markedly decreased by cycloheximide. In par-ticular, in the Cd + Cy-10 hr group, this proportion in the liver and kidney was half of that in the Cd-10 hr group treated with Cd only. The proportion of Cd increased at 24 hr after Cd injection, even though the mice were treated with cycloheximide. Simultaneously, the proportion of Zn in the MT region also in-creased. Mice injected with 2.5 mg Cd/kg body weight did not die up to 24 hr after this metal injection. Following the combined treatment with Cd and cycloheximide, however, 6 out of 10 mice died within 24 hr after Cd injection. These results suggest that the toxicity of Cd is modified by cycloheximide, and MT synthesis contributes to the appearance of this toxicity.

Supply of trace elements to ruminants in the German Democratic Republic. 3. Supply of zinc

The supply of zinc to ruminants as influenced by and depending upon the geological origin of soils was investigated using the hair test and the technique of indicator plants. A total of 1276 samples of red meadow clover and 3022 samples of red field clover and 4184 hair specimens from cows were analyzed. The following statistically well-established results were obtained which appear to be generalizable: Red meadow clover contained significantly more Zn than red field clover (48 ppm/38 ppm). Red meadow clover and field clover grown on loamy soils (59%), weathered soils of less (59%), red sandstone (57%) basalt (53%), shell limestone (47%) and Keuper (41%) contained only 59%-41% of the amount of Zn found in indicator plants that were grown in locations were the highest Zn level (weathered soils of porphyry). Zn concentrations in red meadow and field clover grown on soils of the same geological origin correlated with r = 0.87. A positive correlation (B = 0.53) was found to exit between the relative proportions of Zn contained in indicator plants grown on a particular soil and the proportions of Zn contained in hair specimens from Zn-deficient cows (less than 100 ppm of Zn). The largest number of hair specimens containing less than 100 ppm of Zn were found in cows from areas with soils of basalt (17%), and loess (18%), areas with loamy soils (24%), and sandy diluvial soils (25%), or with alluvial pastures (23%), or with soils of Keuper (27%), shell limestone (22%) or red sandstone (29%). Ruminants in these areas are liable to suffer from Zn deficiencies.