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Chaudhary Charan Singh Haryana Agricultural University (1988)

Exchange/adsorption studies of Zn, Cu and Co in soils of semi-arid and humid regions

Deka, Arun Kumar

Titre : Exchange/adsorption studies of Zn, Cu and Co in soils of semi-arid and humid regions

Auteur : Deka, Arun Kumar

Université de soutenance : Chaudhary Charan Singh Haryana Agricultural University

Grade : Doctor of Philosophy (PhD) 1988

Résumé présenté dans KrishiPrabha (Indian Agricultural Doctoral Dissertations Repository)

Keeping in view the significance of Cu, Zn and Co as plant nutrient and Cd as potential soil and underground water pollutant, exchange and adsorption studies of Cu, Zn, Co, and Cd were conducted in an alkaline soil sample from Hisar (H11) representing semi‑arid region of Haryana and three acidic soil samples from Beltola (AB), Kuptipara (AK) and Cinnamara (AC) representing humid region of Assam. To study the effect of organic matter on exchange/adsorption behaviour of these heavy metals alkaline sample, from Hisar, (HH) was treated with four levels of FYM i.e. 0% (HH‑0), 2.5% (HH‑1), 5% (HH‑2) and 10% (HH‑3), and acidic samples from Assam (AB and AK) with three levels i.e. 0% (AB‑0, AK‑0), 2.5% (AB‑1, AK‑1) and 5% (AB‑2, AK‑2). To study the effect of pH on exchange behaviour of Cu, Zn and Cd, alkaline soil samples (HH‑0 and HH‑3) were treated with dilute HCl to lower down their pH to around 7 (HH‑01, HH‑31) and 5 (HH‑02, HH-32). Exchange equilibria of Ca‑Cu, Ca‑Zn, Ca‑Co and Ca‑Cd systems were established on salt free Ca‑saturated samples at 10 meq/1 total electrolyte concentration and adsorption studies were made on natural soil samples with 0 to 10 meq/1 solutions of Cu, Zn, Co and Cd in 0.01 M CaCl2. The results of exchange equilibria were described in terms of selectivity coefficient (K) and app­roximate free energy ( Gr) of exchange reactions. Langmuir adsorption parameters and distribution coefficient (Rd) were used for adsorption ex­periments.

Organic matter had a distinct effect on the relative specificity of the heavy metal cations. With the application of FYM, selectivity decre­ased in alkaline soil and increased in acidic ones. The largest values of selectivity coefficients observed were in a decreasing order of Cu, Zn, Cd and Co for HH‑0, HH‑1 and HH‑2 ; Zn, Cu, Cd and Co for HH‑3 ; Cu, Zn, Co, Cd, for AK‑1 and AB‑0 samples. For alkaline sample of Hisar  Gr was negative at all levels of FYM, suggesting thermodynamic preference for Cu, Zn, Co and Cd over Ca, Cu showed thermodynamic preference over Ca in all soil samples and Ca over Co and Cd in all acidic soil sam­ples, Zn was preferred over Ca in AK‑1 and AK‑2 and Ca over Zn in other acidic samples. Interaction of heavy metals with organic matter was maximum for Cu and minimum for Cd, except in AK sample where it was just the reverse. pH had a spectacular effect on the relative specificity of Cu, Zn, Co and Cd in Hisar soil. The values of  Gr increased sharply with the artificially lowering down of soil pH suggesting a sharp decrease in pre­ference for the heavy metal cations. At existing alkaline pH, all the four heavy metals showed considerable thermodynamic preference over Ca ; Cu remained highly preferential even at pH around 7 but at pH around 5, its thermodynamic preference over Ca was only marginal. Zn, Co and Cd did not show much specificity over Ca at pH around 7. At pH around 5, Ca showed much higher thermodynamic preference over these metals. The depressive effect of pH on the, specificity of these cations was in the decreasing order of Zn, Cu, Cd, Co in no FYM and Zn, Cd, Cu, Co in FYM treated samples. Maximum pH‑organic matter interaction was observed in case of Cu, followed by Zn, Co and Cd. Adsorption maxima of Cu, Zn and Co for both parts 1 (0.01‑1 meq/1) and 11 (2‑10 meq/1) of isotherm, in general, followed the pH trend of soil samples. For Cd, it did not follow the pH trend. Adsorption maxima for all the four heavy metals increased in response to FYM application. The effect of FYM was more pronounced in the oxide rich AB sample

KrishiPrabha (Indian Agricultural Doctoral Dissertations Repository)

Page publiée le 28 janvier 2015, mise à jour le 15 février 2021