Adsorção mono e competitiva de Zn, Cu e Mn em diferentes solos calcários

Soil carbonate is considered an effective adsorbent to trace element retention. Many researchers have studied the preferential adsorption of those heavy metals on calcareous soils. In 2021- 2022, an experiment was conducted in agriculture college laboratories to assess the mono and competitive of three trace elements (Cu, Zn, Mn) on three calcareous soils that differ in their CaCO3 content. Calcareous representative soil samples were collected from different Nineveh governorate and north Iraq locations. The adsorption experiment was carried out using the batch method by equilibrating 2.5 gm soil with 25 ml of a solution containing concentrations of (1.5, 10, 20, 30, 40, 50, 60 and 70 mg. L-1) of all traced elements in the same concentrations. Sorption isotherms were characterized using linear Langmuir and Freundlich equations. Results showed huge differences in sorptions capacities and other studied parameters. All studied soils showed a high maximum adsorption capacity Qmax and strength binding for Cu than Zn and Mn. On the basis of Qmax and distribution coefficient values (Σkd) for each studied soil and element, the selectivity sequence was as follows Cu>Zn >Mn. Gibbs free energy (-ΔG) values were decreased as the sorption capacity decreased too. In mono and ternary adsorption system, Langmuir isotherms were of H-type whereas Freundlich isotherms were of C-type. The soil properties such as CaCO3, pH, Clay, C.E.C, and O.M were significantly related to trace elements adsorption.O carbonato do solo é considerado um adsorvente eficaz para retenção de oligoelementos. Muitos pesquisadores estudaram a adsorção preferencial desses metais pesados em solos calcários. Em 2021-2022, foi realizada um experimento em laboratório na faculdade de agricultura para avaliar a mono e a competitividade de três oligoelementos (Cu, Zn, Mn) em três solos calcários que diferem no seu teor de carbonato de cálcio (CaCO3). Amostras representativas de solo calcário foram coletadas de diferentes províncias de Nínive e locais do norte do Iraque. O experimento de adsorção foi realizado pelo método descontínuo, equilibrando 2,5 g de solo com 25 ml de uma solução contendo concentrações de (1,5, 10, 20, 30, 40, 50, 60 e 70 mg. L-1) de todos os oligoelementos nas mesmas concentrações. As isotermas de sorção foram caracterizadas usando equações lineares de Langmuir e Freundlich. Os resultados mostraram enormes diferenças nas capacidades de sorção e outros parâmetros estudados. Todos os solos estudados apresentaram maior capacidade máxima de adsorção Qmax e força de ligação para Cu do que para Zn e Mn. Com base nos valores de Qmax e coeficiente de distribuição (Σkd) para cada solo e elemento estudado, a sequência de seletividade foi Cu>Zn>Mn. Os valores de energia livre de Gibbs diminuíram à medida que a capacidade de sorção também diminuiu. Nos sistemas de adsorção mono e ternário, as isotermas de Langmuir eram do tipo H, enquanto as isotermas de Freundlich eram do tipo C. As propriedades do solo como CaCO3, pH, Argila, C.E.C e O.M foram significativamente relacionadas à adsorção de oligoelementos

Efecto del contenido de carbonato de calcio en la relación cantidad-intensidad de zinc en algunos suelos de Mosul, Irak

The quantity-intensity relationship (Q/I) was used to evaluate thermodynamic parameters of zinc in soils under different agricultural management. Ten soil samples were collected from Mosul city to study zinc distribution of calcium carbonate content in these soils. Generally, Q/I relationship of zinc may provide an index for the strength and quantity of effective zinc supply to plants in soils. The Q/I parameters of zinc were studied to quantify zinc release before and after removing carbonates in the studied soils. Results showed that the zinc activity ratio (AReZn) is related to changes with labile zinc (±ΔZn) at equilibrium and increased together with increasing zinc concentrations, intensity (I) ranged between 0.8584 and 0.9972×10-3 mol/L1/2 before removing carbonates and between 0.0909 and 2.7626×10-3 mol/L1/2 after removing carbonates. The ranges of labile Zinc (ZnL) values before and after removing carbonates were between 0.5755-0.7815 and 0.0009-0.0104 cmol/kg, respectively, while the Zinc (PBCZn) before and after removing carbonates fluctuated from 0.5839 to 0.9104 and 0.00112 to 0.00990 cmol/kg(mol/L)−1/2, respectively. That means calcium carbonate increases exchangeable zinc and zinc capacity at equilibrium conditions. The free energy (−ΔF) ranged between -1.001 and -0.979 kJ/mol before removing carbonates and between -1.319 and -0.841 kJ/mol after removing carbonates. Gapon Selectivity Coefficient (kG) ranged between 0.0193835 and 0.027453 and 0.000045 and 0.00450 (mol/L)1/2 before and after removing carbonates, respectively. Therefore, these results may be used as a reference for zinc soil fertilization, whereas thermodynamic parameters values may be used to predict soil ability to supply available zinc.La relación de cantidad-intensidad-se utilizó para evaluar los parámetros termodinámicos del zinc en los suelos bajo diferentes tipos de manejo agrícola. Se recogieron diez muestras de suelo de la ciudad de Mosul, Irak, para estudiar la distribución de zinc de diferentes contenidos de carbonato de calcio en estos suelos. En general, la relación de cantidad-intensidad (Q/I) de zinc puede proporcionar un índice para la concentración y cantidad de suministro efectivo de zinc a las plantas en suelos. Los parámetros de (Q/I) de zinc se estudiaron para cuantificar la cantidad de zinc antes y después de eliminar carbonatos en los suelos estudiados. La relación de actividad de zinc (AReZn) se asoció a los cambios con el zinc lábil (±ΔZn) en equilibrio y aumentó junto con las concentraciones crecientes de zinc, a partir de 0,8584 y 0,9972 × 10-3 mol/l1/2 antes de eliminar carbonatos y entre 0,0909 y 2,7626 × 10-3 mol/l1/2 después de eliminar carbonatos. Los rangos de valores de zinc lábil (ZnL) antes y después de eliminar carbonatos oscilaron entre 0,5755-0,7815 cmol/kg y 0,0009-0,0104 cmol/kg, respectivamente, mientras que el zinc (PBCZn) antes y después de eliminar los carbonatos fluctuó entre 0,5839 cmol/kg y 0,9104 cmol/kg y entre 0,00112 cmol/kg y 0,00990 cmol/kg(mol/l)-1/2, respectivamente. Eso significa que el carbonato de calcio aumenta el zinc intercambiable y la capacidad del zinc en condiciones de equilibrio. La energía libre (-ΔF) osciló entre -1,001 kJ/mol y -0,979 kJ/mol antes de retirar carbonatos y entre -1,319 kJ/mol y -0,841 kJ/mol después de eliminar carbonatos. El coeficiente de selectividad de Gapon (kG) osciló entre 0,0193835 y 0,027453 y entre 0,000045 y 0,00450 (mol/l)1/2 antes y después de eliminar carbonatos, respectivamente. Estos resultados pueden usarse como referencia para la fertilización del suelo con zinc, mientras que los valores de los parámetros termodinámicos se podrían usar en la predicción de la capacidad del suelo para suministrar el zinc disponible

Relationship between Zn and Cd in soil and plant

Saabunud: 15.02.2022 Aktsepteeritud: 28.05.2022 Avaldatud veebis: 28.05.2022 Vastutav autor: Hudhaifa Maan Al-Hamandi E-mail: [email protected] relationship between Zn and Cd uptake by plants is somewhat controversial according to the lack of information about this subject. The objective of this study was to increase our scientific understanding of soil about plant factors controlling Zn and Cd bioavailability and uptake. This experiment was carried out in the winter season of 2019. It aimed to solve the mystery of the Zn and Cd relationship in soil and plant uptake. Five plant species were under observation (carrot – Daucus carota, radish – Raphanus sativus, wheat – Triticum aestivum L., lettuce – Lactuca sativa and bean – Vicia faba). Plants were planted in plastic pots containing 2 kg sandy loam soil with duplicate and exposure to six Zn:Cd ratios (1:0.5, 1:1, 2:1, 3:1, 4:1 and 5:1) with increasing elements molar ratio of Zn to Cd in soil. After 45 days, plants were harvested. Zn and Cd were determined in roots and shoots. Results showed, that at low molar ratios of Zn:Cd in soil, the relationship between these metals in soil is almost synergistic and both elements are accumulated easily in plant tissues, but at high molar ratios, the relationship between these metals is almost antagonistic where Cd be more competitive to Zn uptake by plants. It was concluded that the 2:1 Zn:Cd ratio in the soil is the border between synergistic and antagonistic relationships

Organic Matter and Heavy Metals Sorption

Organic matter content in soils is highly variable and includes dead and living organisms and their decomposition products. plant residue and humic substances. Thermodynamically, organic matter is unstable in soils and later will oxidize to Co2, and H2O. The effective substances of organic matter decomposition are fulvic and humic acids (FA+Hu) which contain Several functional groups that release electrons or protons during their decomposition leaving behind several radical groups that act as electron donner to ward heavy metal ions forming FA and Hu-metal soluble and insoluble complexes. Those metallic-organic Complexes are variable by their Stability constant (SC) which is absolutely pH-dependent. The less stable the metal complex, the higher mobility in soil, In contrast, a highly stable metal complex is less soluble and mobility. So, organic matter plays an important role in the accumulation, leaching, and transportation of heavy metal Cations present in water and soils as chelates of different Stability and supplying plant roots by these ions and behavior as a buffering substance to heavy metal mobility