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Concentrations of potentially toxic elements were determined in the soil solution of two soils (acidic sandy and slightly acidic clay loam) treated with phosphate rocks having high Cd content in a pot experiment. Relative concentrations characterizing the mobility of metals (expressed as soil solution concentrations in percentage of their “total” amounts in the phosphate rock-treated soil) decreased with increasing phosphate rock rates in the sandy soil. Mn@Sr>Cd@Co were the most, while Pb and Cr the least mobile elements. The relative concentrations in the clay loam soil were much lower than in the sandy soil and they practically remained constant with increasing phosphate rock rates. It was concluded that in the experimental time frame the environmental risk did not increase with the increase of phosphate rock rate. 

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Changes in the K, Ca and Mg contents of the soil solution were examined during the growing period to characterize the nutrient buffer capacity of sandy and clay loam soils in pot experiments set up with Italian ryegrass as indicator plant.  K, Ca and Mg concentrations in the soil solution decreased during the growth due to the nutrient uptake by plants. The normalized values of decrease (expressing the change in the concentration of the given element during unit time) were close to each other for Ca and Mg, while there was a significant difference between the sandy and clay loam soil in the case of K (0.65 and 0.11, respectively). We assumed that the normalized value was inversely proportional to the nutrient buffer capacity of soils.  For the comparison of experiments conducted under different conditions the UPI (uptake index) values were introduced. The UPI value shows to what extent the amount of the given ion calculated from concentration decrease in the soil solution accounts for the amount of element taken up by the plant. The amount of K depleted from the soil solution was 19% of the K amount taken up on the sandy soil, while on the clay loam this value was only 0.8%. Because the UPI values from experiments under different environments are comparable, they characterized the nutrient buffer capacity of soils better than the normalized values of decrease. 

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Abstract  

Field observations suggest that plutonium and americium in the environment are present in very different chemical forms in the interstitial waters of an intertidal sediment. Themodynamic modelling using the PHREEQE code predicts that plutonium is present entirely in oxidation state (V) as the PuO2CO 3 ion, whereas americium is present entirely in oxidation state (III), largely as the uncharged Am(OH)CO3 species, but with significant concentrations of the Am3+ and the AmSO 4 + ions. There are, however, differences between these predictions and others published for a very similar system which apparently arise from uncertainties in the thermodynamic data. Field data cannot resolve these differences unambiguously.

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CURTIN, D. & SMILLIE, G. W., 1983. Soil solution composition as affected by liming and incubation. Soil Sci. Soc. Am. J. 47 . 701-707. Soil solution composition as affected by liming and incubation

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1226 1231 Salmon, R. C. (1964): Cation activity ratios in equilibrium soil solutions and the availability of magnesium. Soil Sci. , 98 , 213

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Abstract  

In order to assess the behavior of Tc in flooded soil-plant systems, laboratory experiments have been done using95mTc as a tracer. Two common soil types in Japan, Andosol and Gray lowland soils, were used. Soil-plant transfer factors of Tc in rice grain were very low, i.e. 5×10–5 for Andosol and 6×10–4 for Gray lowland soil. It was found that the Tc concentrations in rice plants were influenced by those in soil solutions. Concentrations of95mTc in both soil solutions decreased rapidly in the early period of cultivation. It was observed that redox-potential (Eh) also decreased markedly following flooding. A relationship was found between the decrease of the95mTc concentrations in soil solutions and the drop of Eh in the soils. The Tc (VII) added to soil was transformed to insoluble Tc (IV) under the reduced conditions existing in flooded soil.

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Abstract  

An online analytical system using ion chromatography (IC) followed by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the separate determination of I and IO3 in aqueous solutions with a detection limit 0.1–1 μg 1/1. The total iodine concentration was also directly determined by ICP-MS. Iodine in several environmental samples (i.e., rain, river water, brine, and soil solution) was successfully determined with information on its chemical form. The release of I into soil solution with decreasing Eh was observed in an incubation experiment with flooded soil. An iodine form other than I and IO3 was observed in several environmental samples.

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Abstract  

In this work, soil-soil solution distribution coefficients (K d) of Sr and Cs were obtained for 112 Japanese agricultural soil samples (50 paddy soil and 62 upland soil samples) using batch sorption test. The relationships between Sr-or Cs-K d values and soil properties were discussed. Furthermore, the amount of Cs fixed in soil was estimated for 22 selected soil samples using a sequential extraction method. Then, cross effects of some soil properties for Cs fixation were evaluated.

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Agrokémia és Talajtan
Authors:
Krisztina Végh
,
J. Csillag
,
A. Lukács
,
B Panwar
, and
Gy. Füleky

Potassium uptake is the result of numerous simultaneous processes influencing the potassium dynamics in the rhizosphere.The presented research has focused on plant-soil interactions in the potassium supply of soil in the root environment of maize. It was assumed that: 1. roots promote the mobilization of K by the acidification of the rhizosphere soil, 2. roots increase wetting-drying cycles in their environment, and 3. soil total K content affects K release and fixation in the bulk of soil and the root environment.The promoting effect of root activity was detected on K release from soil when feldspar was added as K source to the root environment. A 2-unit reduction of soil pH multiplied K concentration in the soil solution, depending on the feldspar rate. Feldspar application significantly increased the solubility and release of potassium into the soil solution.The effect of pH reduction on the K concentration of soil solution was several magnitudes higher than that of the wetting-drying cycles both in the untreated and feldspar treated soils.Potassium uptake by maize over two generations greatly exceeded the exchangeable pool in the growing media. As a consequence of the exhaustive K uptake K release slowed down to the soil solution, as reflected in the H2O extractable K and ExK contents.Significant K fixation was detected after the K removal of maize in feldspar treated soils. On the contrary, in the treatments without plants increasing feldspar rates increased both H2O extractable K and ExK contents.One-term Langmuir equation, corrected with the originally sorbed amount of K, was fitted to measured data. The maximum amount of potassium adsorption (Kmax, mg∙kg−1) and the equilibrium constant (k) were calculated. The potassium buffering capacity was estimated at zero equilibrium concentration. Both K buffering capacity and the energy of K fixation were high for the rhizosphere soil. In rhizosphere soil samples the energy of K fixation was one magnitude higher as compared to the bulk soil and decreased substantially with feldspar addition. In soils without plants the k equilibrium constant did not change as the result of drying-wetting process only in the case of the 50% soil/feldspar mixture.In the liquid phase of the soil without feldspar application potassium concentration decreased in the one-year drying-wetting cycle, presumably it got into more strongly bounded forms in the low K status soil. In 50% feldspar enriched soil samples potassium concentration in the soil solution increased, likely as a consequence of a slow dissolution of the K content of feldspar.

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In the hydrogeologically closed Carpathian Basin subsurface waters have particular importance in the salinization/alkalization processes. In the poorly-drained low-lying areas the capillary flow transports high amounts of water soluble salts from the shallow, „stagnant” groundwater with high salt concentration and unfavourable sodium-carbonate(bicarbonate) type ion composition to the overlying soil horizons. Due to the strongly alkaline soil solution, the Ca and Mg salts (mostly carbonates and bicarbonates) are not soluble and Na + became absolutely predominant in the migrating soil solution which leads to high ESP even at relatively low salt concentration. High Na + saturation of heavy-textured soils with high amount of expanding clay minerals results in unfavourable physical-hydrophysical properties and extreme moisture regime of these soils, which are their main ecological constrains and the limiting factors of their fertility, productivity and agricultural utility. The simultaneous hazard of waterlogging or overmoistening, and drought sensitivity in extensive lowland areas, sometimes in the same places within a short period, necessitates a precise, “double function” soil moisture control against their harmful ecological/economical/social consequences. Most of the environmental constrains (including salinity/alkalinity/sodicity) can be efficiently controlled: prevented, eliminated, or - at least - moderated. But this needs permanent care and proper actions: adequate soil and water conservation practices based on a comprehensive soil/land degradation assessment. It includes continuous registration of facts and changes (monitoring); exact and quantitative knowledge on the existing soil processes, their influencing factors and mechanisms.

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