scholarly journals SOIL CHEMISTRY TRENDS

2010 ◽  
pp. 64-82
Author(s):  
Yu. Vodianitsky

In modern soil chemistry, four main directions are being actively developed: 1) chemistry of organic matter, 2) biochemical processes in soils, 3) chemical basis of soil protection, 4) soil study aschemical membrane and a pool of chemical elements. Interest to the study of organic matter, soil contamination and the role of soil as a chemical component of the environment reflects pragmatic trends in modern soil chemistry. Many advances in soil chemistry are now associated with the use of new nonspecific methods of analysis, primarily physical ones. The greatest progress has been made inidentification of individual chemical compounds in soil when using synchrotron X-ray technology.

1999 ◽  
Vol 79 (1) ◽  
pp. 103-109 ◽  
Author(s):  
F. Courchesne ◽  
J.-F. Laberge ◽  
A. Dufresne

The role of soil organic matter (OM) on SO4 retention was investigated by comparing OM content, SO4 retention, and the distribution of Fe, Al and Si compounds in OM-poor (Grands-Jardins, PGJ) and OM-rich (Hermine, HER) Podzols from Québec, Canada. At both sites, four pedons were sampled by horizon; soil pH in H2O, organic C, phosphate-extractable SO4 and, sodium pyrophosphate, acid ammonium oxalate and dithionite-citrate-bicarbonate (DCB) extractable Fe, Al and Si were measured for each mineral horizon. The mineralogy of the clay (<2 µm) and fine silt (2–20 µm) fractions of selected horizons was determined by X-ray diffraction (XRD) and infrared spectroscopy (IR). Weighted mean organic C and pyrophosphate extractable Fe and Al contents were significantly higher in the HER than in the PGJ sola, while the PGJ soils were richer in amorphous inorganic Al. No trends were observed for inorganic Fe compounds. Chemical dissolution and IR allowed the identification of short-range ordered aluminosilicates, probably allophane, in the OM-poor and slightly acidic to neutral PGJ soils. These materials were absent from the OM-rich and acidic HER soils. Phosphate extractions showed that the weighted mean native SO4 content was five times higher in the PGJ than in the HER soil. Finally, native SO4 was strongly related to inorganic Fe, Al and Si (associated with allophane) at PGJ but only to inorganic Fe at HER. These results indicate that OM indirectly affects SO4 sorption through the influence organic substances exerts on the nature and distribution of pedogenic Fe, Al and Si compounds, such as allophane, in Podzolic profiles. Key words: Organic matter, sulfate, imogolite, allophane, silica, Podzol


2021 ◽  
Vol 74 (8) ◽  
pp. 1869-1875
Author(s):  
Svitlana P. Yarova ◽  
Iryna I. Zabolotna ◽  
Olena S. Genzytska ◽  
Andrii A. Komlev

The aim: Is to define dentine chemical composition of intact teeth and those with wedge-shaped defects followed by the analysis of revealed differences. Materials and methods: Longitudinal sections of 22 clinically removed teeth (12 – clinically intact ones, 10 – with wedge-shaped defects) from both jaws were studied in patients aged between 25-54 years. JSM-6490 LV focused beam electron microscope (scanning) with system of energy-dispersive X-ray microanalysis INCA Penta FETх3 was used. The chemical composition of 148 dentine areas in the incisal region (tubercle), equator, cervical area has been determined as a percentage of the weight amounts of carbon, oxygen, calcium, phosphorus, sodium, magnesium, sulfur, chlorine, zinc, potassium, aluminum. Results: Dentine chemical composition of teeth with wedge-shaped defects differed from those of intact teeth by significantly lower content: sodium, chlorine and calcium – in the incisal region (tubercle); sodium, magnesium − at the equator; sodium, chlorine and calcium – in the cervical region (p≤0.05). In the sample groups with cervical pathology there was more sulfur and oxygen in the incisal region (tubercle), phosphorus and zinc – at the equator, carbon and potassium – in the cervical region (p≤0.05). Conclusions: Differences in the chemical composition of intact teeth and teeth with wedge-shaped defects, the presence of correlation between the studied chemical elements confirm the role of macro- and microelements in the pathogenesis of non-carious cervical lesions.


Author(s):  
Intizar Aliyeva Intizar Aliyeva ◽  
Rasul Hajıyev Rasul Hajıyev

The article discusses various limited considerations and assumptions on the positive or negative impact of geochemical features chemical elements found in rocks, ores, soil, plants, water and in the air of the territories of populated areas, factories, the mining and agro-industrial complexes to the environment and the role of analytical geochemistry in this process. According to the author, one of the main points on which the light should be shed is the role of finding elements (independent, combination or isomorphic mixture) rather than their existence in different amounts in the environment. Thus, the chemical elements can be more or less hazardous to environment regardless its amount, but the finding methods. Chemical and natural combinations can be either very hazardous or very useful to all living creatures depending on their characteristics, so it’s better to determine their environmental hazardousness via their impact to a particular human or animal organ which in turn facilitates the solution of the problem. Moreover, it should be noted that the most environmentally dangerous and active chemical elements are the ones with fluctuating valence. Some elements are not so hazardous when they are independent or in solid form since they change weakly. But they are very dangerous when they turn into liquid or gas forms and create mineral compounds with other elements such as halkofil group of elements which in turn can easily decompose and dissolve in water by causing dangers to all living creatures in the nature. Approximately any chemical element can either react negatively or in most cases stimulate the life functions of the organs of animals and plants depending on its finding forms. The study of geochemical parameters in different natural objects such as surface and subsoil water, air, rocks and ores can be very helpful in organizing the protection of environmetal and the solution of its problems. X-ray Spectral analysis is particularly highlighted in this article for identifying various chemical elements in geological and ecological objects. There are several advantages of X-ray Spectral analysis such as its productiveness and low cost, the expressiveness and simplicity of analysis operations, having slightly high sensitivity, universality, high range of elements identification features, etc. To conclude some authors claim that the following problems can be solved with the help of analytic geochemistry: Identifying the main source of pollution and the evaluation of its impact on the environment; Identification of quantitative and qualitative parameters of sources of natural, techno and agro genic pollution in the settlements, industrial objects and in the regions of developed mining complexes; Eco-geochemical and biochemical evaluation of the negative impact of water, weather and harmful geochemical anomalies on live organisms. We hope the elimination of this type of problems can pave the way to the ecologically clean environment. Keywords: ore, soil, plant, water, weather.


2021 ◽  
Author(s):  
Mike C. Rowley ◽  
Stephanie Grand ◽  
Jorge E. Spangenberg ◽  
Eric P. Verrecchia

AbstractGeochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values.


2021 ◽  
Vol 895 (1) ◽  
pp. 012025
Author(s):  
A N Makhinov ◽  
A F Makhinova ◽  
Sh Liu

Abstract Inhomogeneity of the concentrations of chemical elements in the cross-section of the Amur River is considered as a function of the state of their soluble and suspended forms. Flooding of wetlands and urbanized areas contributes to the removal of pollutants into the river channel. The wide spread of fens on the left bank contributes to the concentration of organic matter along the left bank of the river. Terrigenous material mostly comes from the right bank, where agricultural fields are concentrated. The ratio of their concentrations is maintained by the duration of the flood. The mechanisms of redistribution of elements between their suspended and soluble forms have been studied. The mechanisms of sorption of chemical compounds on mineral and organic colloids are described. It was found that mineral colloids with a negative charge due to electrostatic attraction sorb electrically neutral compounds (hydroxoaqua complexes [Mn(OH)2(OH2]0, ammonia [Cu(NH3)4(OH)2]0. The role of organic material in the redistribution of chemical compounds between soluble and suspended forms is shown. Organic colloids with molecular mass > 5.0 kDa precipitate complex cations – [FeHSO4]+, [FeHSO4]2+, [CuHSO4]+. An organic substance with a molecular mass of <2.0 kDa has a greater complexing ability for Fe(2)3+, Cu2+, Zn2+, Mn2+ ions. They bind metals to organo-mineral complexes by chemical interaction and form mobile organo-mineral complexes and heteropolar salts.


Author(s):  
Russell G. Egdell ◽  
Elizabeth Bruton

Just over 100 years ago, Henry Moseley carried out a systematic series of experiments which showed that the frequencies of the X-rays emitted from an elemental target under bombardment by cathode rays were characteristic of that element and could be used to identify the charge on its atomic nucleus. This led to a reorganization of the periodic table, with chemical elements now arranged on the basis of atomic number Z rather than atomic weight A, as had been the case in previous tables, including those developed by Mendeleev. Moseley also showed that there were four ‘missing elements’ before gold. With further measurements up to uranium Z = 92, the Swedish physicist Manne Siegbahn identified two more missing elements. This paper provides an introduction to Moseley and his experiments and then traces attempts to ‘discover’ missing elements by X-ray spectroscopy. There were two successes with hafnium (Z = 72) and rhenium (Z = 75), but many blind alleys and episodes of self-deception when dealing with elements 43, 61, 85 and 87. These all turned out to be radioactive, with extremely small natural abundances: all required synthesis by a nuclear reaction, with radiological characterization in the first instance. Finally, the paper moves on to consider the role of X-ray spectroscopy in exploring the periodic table beyond uranium. Although the discovery of artificial radioactive elements with Z > 92 again depended on nucleosynthesis and radiological characterization, measurement of the frequencies or energies of characteristic X-rays remains the ultimate goal in proving the existence of an element. This article is part of the theme issue ‘Mendeleev and the periodic table’.


Author(s):  
S. K. Essa ◽  
Raid Shaalan Jarallah

To study role of gypsum and corn cobs in linkage of fractions in cracking soils. Three soils (Al-Diwaniya , Al-Wihda and college of Agriculture / Abu Ghraib) were chosen for this study . They were  treated with two levels of gypsum (0.5 and 1) % with one level (4%) of corncobs . In this experiment , 2 kg of each studied soil were treated with same levels of corn cobs and gypsum above and incubated at 30 + 2 °C for 90 days and 80% relative moisture content at 33 kpa. And then the soils were sieved with 1 mm sieve to measured the x-ray diffractions . The results showed : The intensity of clay minerals peaks which treated with gypsum and corn cobs were decreased comparing with control sample. We believed that the gypsum should be facculated on clay minerals surfaces and mask them to appear clearly , and suggested that the gypsum was played an important role in conjugated of soil particles. Results of X-ray diffractions showed that there was no evidence of interaction between organic matter (corn cobs) and clay mineral inter layers.  


Vestnik RFFI ◽  
2019 ◽  
pp. 26-45
Author(s):  
Almir S. Gazizov ◽  
Yulia M. Sadykova ◽  
Elmira M. Gibadullina ◽  
Alexander R. Burilov ◽  
Lyudmila K. Kibardina ◽  
...  

In the popular science review, dedicated to the 150th anniversary of the first publication of the Periodic Table of chemical elements by D.I. Mendeleev, the elements of the 5th (main) Group (namely nitrogen, phosphorus, arsenic, antimony, and bismuth) are considered. The history of these elements discovery and some their properties are shortly described. The elements of the fifth group are also called “the elements of life”, which is linked with both the development of living organisms themselves and their compounds importance for human life. The review confirms this thesis in a popular-science form, using the available literature data on the role of chemical compounds of Group 5th elements in the development of living nature as well as in the progress of human civilization.


Author(s):  
L. T. Germinario

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.


Author(s):  
Janet H. Woodward ◽  
D. E. Akin

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.


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