Concentrations Of Exchangeable Zn Research Articles

Zinc and copper fractions in Oxisols of different textures fertilized with pig slurry

HIGHLIGHTS Higher concentrations of exchangeable Zn were found in areas with pig slurry application. No higher concentrations of Cu were found in the exchangeable fraction in areas using pig slurry. In all study areas, it was observed that more than 70% of Cu is in recalcitrant forms.

Zinc fractions and availability to soybeans in representative soils of Northeast China

Limited information exists about the zinc (Zn) status of major soils in northeast China, and their ability to supply Zn to soybeans. This study aims to establish the critical concentrations of Zn in soil for plant growth, to characterize the Zn forms in soil, to correlate the concentration of various Zn forms with Zn uptake by soybeans, and to identify the most effective means of Zn application. Thirty-three soil samples were collected from farmland in 11 districts/sites (covering six soil groups) of northeast China. Zinc fractions and DTPA-extractable Zn concentrations of the soils were determined. A pot experiment was also carried out to study the effects of Zn application method on Zn uptake, yield and use efficiency of soybeans. The concentrations of total Zn in these soils ranged from 60 to 84 mg kg−1 while the DTPA-extractable Zn concentrations ranged from 0.77 to 2.16 mg kg−1 and were highly correlated positively with both concentrations of exchangeable Zn (Ex-Zn) and organically bound Zn (OM-Zn). Soybean yields correlated positively and best with concentrations of Ex-Zn, followed by those of OM-Zn. In addition, soybean growth correlated positively with concentrations of all Zn forms except for Fe-oxide bound Zn. When concentrations of DTPA-extractable Zn were less than 1.0 mg kg−1, Zn deficiency occurred and the application of Zn fertilizer increased the yield of soybeans significantly. Foliar sprays and seed coatings resulted in greater yield responses and Zn-use efficiency than other methods. Surface application of Zn after flowering was ineffective. The soils at seven out of 11 field sites were deficient or marginally deficient in Zn. DTPA-extractable Zn provides a good indicator of Zn availability to soybeans with a critical concentration of 1.0 mg kg−1 soil. Foliar sprays and seed coatings should be recommended for the correction of Zn deficiency.

Imaging Zinc in Brain Slices: Figure 1.

INTRODUCTIONThis protocol provides a practical guide to imaging zinc within synaptic vesicles and the extracellular space of brain slices. Certain glutamatergic synaptic terminals in the brain have high concentrations of exchangeable Zn(2+) within their synaptic vesicles. Classically, these terminals have been revealed by Timm's histochemical stain. More recently, a number of fluorimetric probes have become available that allow Zn(2+) to be detected in live preparations. This protocol describes two methods, one for visualizing Zn(2+) in synaptic vesicles, and another for detecting Zn(2+) in the extracellular space. These methods are applicable to any tissue with the high levels of loosely bound Zn(2+) that are typically found in vesicles, and tissue that might have Zn(2+) associated with macromolecules in the extracellular space.

Zinc distribution in soils amended with different kinds of sewage sludge

Sewage sludge (SS) can be applied to cropland to supply and recycle nutrients and organic carbon. Potentially toxic elements in the sludge, however, are of environmental concern. This study evaluates the changes in chemical speciation of Zn in three representative pristine soils of the Pampas Region, Argentina, measured with sequential extraction over a one-year period. Pure SS or SS containing 30% (DM) of its own incineration ash (AS) was applied to the soils at an application rate of 150 Mg ha −1. Zn was sequentially fractionated into exchangeable, organically bound, inorganic and residual fractions. The application of the SS and AS amendments significantly increased Zn concentration in all soil fractions at each sampling date. At day 1, Zn was mainly found in the residual fraction. A year after the application of the amendments, redistribution towards the inorganic fraction was observed (41–76% of total Zn content). Zn found in exchangeable and inorganic fractions depended on soil pH rather than on the type of soil used. A negative and significant correlation was found between exchangeable Zn concentrations and soil pH ( r=0.94), and a positive and significant correlation between inorganic Zn concentrations and soil pH ( r=0.92). For each amended soil and sampling date, no significant differences were observed between SS or AS treatments for the exchangeable fraction. Moreover, the use of AS did not cause significant differences in Zn concentration in the other soil fractions compared to SS. Based on these results, land spreading of AS may be similar to SS diaposal in terms of Zn mobility.

Effect of solid-phase speciation on metal mobility and phytoavailability in sludge-amended soil

Sequential extraction was utilized for partitioning Cd, Cr, Ni, and Zn, in soil and sludge samples into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The highest amounts of Cd, Ni, and Zn, expressed as per cent of the total, were found in the Fe-Mn oxide fraction of the sewage sludge. Chromium was significantly associated with the organic fraction of the sludge. The residue was the most abundant fraction for all metals studied in the untreated soil, and for Cd and Ni in the sludge-treated soil. The concentration of exchangeable Cd and Cr was relatively low in the untreated soil and did not change much after sludge application, whereas the concentrations of exchangeable Zn increased about 50 times and the concentrations of exchangeable Ni doubled in the sludge-treated soil. The lysimetric experiment revealed an increase in Zn and Ni uptake by ryegrass and in the percentage of metals leached from the soil profile after massive sludge application. In contrast only negligible changes were observed for Cd and Cr. The assumption that mobility and biological availability are related to metal speciation was confirmed by the agreement between the distribution pattern of Cd, Cr, Ni and Zn in the soils, the uptake of the metals by plants and their capacity for leaching out from the soils.

THE EFFECTS OF ADDITIONS OF CaCO3 AND P ON THE SOIL SOLUTION CHEMISTRY OF A PODZOLIC SOIL

The surface horizon from a Humo-Ferric Podzol was amended with both CaCO3, and P to investigate the changes in the ionic composition of the soil solution and the charge characteristics of the horizon. Addition of CaCO3 increased the concentrations of Ca and [Formula: see text] and decreased the total concentrations of Mg, Na, K, Al, Zn, Mn, Si and [Formula: see text] in the soil solutions. In addition, the pH of the soil solutions, the content of negatively charged sites on the soil surfaces, the relative proportion of Mn2+ and Zn2+ of sulfate ion pairs were raised. In contrast, the concentrations of exchangeable Zn and Mn, the amount of positively charged sites and the proportion of metals linked with the "modelled" fulvate ligands were reduced. The addition of increasing rates of P reduced the total concentrations of Mg, K, Al, Si, and the concentrations of [Formula: see text] and [Formula: see text] in solution but did not affect the pH or the CEC of the soils appreciably. The concentrations of Si, phosphate-P, [Formula: see text] and of the sulfate ion pairs in solution were increased by increasing P additions to the soil. Key words: Liming, phosphorus fertilization, soil solution, GEOCHEM, ion speciation