Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P ...Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P desorption and the relationship between phosphate sorption and desorption. Among the soil series, the Ghior soil had the highest percent clay (59.32%) and free iron oxide (15241 mg·kg–1) content. Along the catena of the calcareous soils, percent clay contents increased. For sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 mg·P·L–1 solution. For desorption, three extractants namely, SO42- (0.005 M) as Na2SO4, HCO3- (0.01 M) as NaHCO3 and distilled water were used at extractant to soil ratios of 30:1, 60:1 and 100:1 (v/w). Among the sorption equations, the Langmuir equation showed better fit to the sorption data at higher P concentrations. The amount of phosphate desorbed by all the three extractants increased significantly with the increasing extractant to soil ratios. Phosphate desorption by and water molecules was highly correlated with pH, percent clay and free iron oxide content of the soil. Significant positive correlation (r > 0.64, P L). Phosphate desorption by SO42- and water molecules was also positively correlated with Freundlich constant, N (r > 0.67, P 0 (r > 0.72, P –0.77, P L). The results suggest that freshly sorbed phosphate ions (inner-sphere complex forming species) can be readily desobed by outer-sphere complex forming species like sulphate and bicarbonate ions. Water molecules also desorbed significant amount of freshly sorbed phosphate from the soil colloids.展开更多
The effects of three electrolyte anions, ionic strength and pH on the adsorption of sulfate by two variablecharge soils, with different surface charge properties were studied. Under the conditions of the same pHand io...The effects of three electrolyte anions, ionic strength and pH on the adsorption of sulfate by two variablecharge soils, with different surface charge properties were studied. Under the conditions of the same pHand ionic strength the effect of electrolyte anions on the adsorption of sulfate was in the order of , indicating the difference of the nature among these three anions. For Ferralsol in the sameconcentration of chloride and perchloride solutions, the two sulfate adsorption-pH curves could intersectat certain pH value. When pH was higher than the intersecting point, more sulfate was adsorbed in theperchloride solution, while when it was lower than the intersecting point, more sulfate was adsorbed in thechloride solution. In different concentrations of electrolyte solution, the curves of the amount of oxy-acidanion adsorbed, which changed with pH, could intersect at a certain pH, which is termed point of zero salteffect （PZSE） on adsorption. The nature of electrolyte anions influenced obviously the appearance of PZSEfor sulfate adsorption. For ferraisol the curves of adsorption converged to about pH 7 in NaCl solution seemedto intersect in NaNO<sub>3</sub> solution and to have a typical PZSE for sulfate adsorption in NaClO<sub>4</sub> solution. ForAcrisol the three curves of adsorption were nearly parallel in NaCl and NaNO<sub>3</sub> solutions and converged topH 6.5 in NaClO<sub>4</sub> solution.展开更多
The effects of maize root exudates and low-molecular-weight-organic anions （LMWOAs） on the desorption of phenanthrene from eight artificially contaminated soils were evaluated. A significant negative correlation was...The effects of maize root exudates and low-molecular-weight-organic anions （LMWOAs） on the desorption of phenanthrene from eight artificially contaminated soils were evaluated. A significant negative correlation was observed between the amounts of phenanthrene desorbed and the soil organic carbon （SOC） contents （P 〈 0.01）, and the influences of soil pH and clay content on phenanthrene desorption were insignificant （P 〉 0.1）. Neither maize root exudates nor oxalate and citrate anions influenced desorption of phenanthrene with the addition of NaN3. A faster phenanthrene desorption occurred without the addition of NaN3 in the presence of maize root exudates than oxalate or citrate due to the enhanced degradation by root exudates. Without the addition of NAN3, oxalate or citrate at different concentrations could inhibit phenanthrene desorption to different extents and the inhibiting effect by citrate was more significant than by oxalate. This study leads to the conclusion that maize root exudates can not enhance the desorption under abiotic condition with the addition of NaN3 and can promote the desorption of phenanthrene in soils without the addition of NaN3.展开更多
文摘Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P desorption and the relationship between phosphate sorption and desorption. Among the soil series, the Ghior soil had the highest percent clay (59.32%) and free iron oxide (15241 mg·kg–1) content. Along the catena of the calcareous soils, percent clay contents increased. For sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 mg·P·L–1 solution. For desorption, three extractants namely, SO42- (0.005 M) as Na2SO4, HCO3- (0.01 M) as NaHCO3 and distilled water were used at extractant to soil ratios of 30:1, 60:1 and 100:1 (v/w). Among the sorption equations, the Langmuir equation showed better fit to the sorption data at higher P concentrations. The amount of phosphate desorbed by all the three extractants increased significantly with the increasing extractant to soil ratios. Phosphate desorption by and water molecules was highly correlated with pH, percent clay and free iron oxide content of the soil. Significant positive correlation (r > 0.64, P L). Phosphate desorption by SO42- and water molecules was also positively correlated with Freundlich constant, N (r > 0.67, P 0 (r > 0.72, P –0.77, P L). The results suggest that freshly sorbed phosphate ions (inner-sphere complex forming species) can be readily desobed by outer-sphere complex forming species like sulphate and bicarbonate ions. Water molecules also desorbed significant amount of freshly sorbed phosphate from the soil colloids.
文摘The effects of three electrolyte anions, ionic strength and pH on the adsorption of sulfate by two variablecharge soils, with different surface charge properties were studied. Under the conditions of the same pHand ionic strength the effect of electrolyte anions on the adsorption of sulfate was in the order of , indicating the difference of the nature among these three anions. For Ferralsol in the sameconcentration of chloride and perchloride solutions, the two sulfate adsorption-pH curves could intersectat certain pH value. When pH was higher than the intersecting point, more sulfate was adsorbed in theperchloride solution, while when it was lower than the intersecting point, more sulfate was adsorbed in thechloride solution. In different concentrations of electrolyte solution, the curves of the amount of oxy-acidanion adsorbed, which changed with pH, could intersect at a certain pH, which is termed point of zero salteffect （PZSE） on adsorption. The nature of electrolyte anions influenced obviously the appearance of PZSEfor sulfate adsorption. For ferraisol the curves of adsorption converged to about pH 7 in NaCl solution seemedto intersect in NaNO<sub>3</sub> solution and to have a typical PZSE for sulfate adsorption in NaClO<sub>4</sub> solution. ForAcrisol the three curves of adsorption were nearly parallel in NaCl and NaNO<sub>3</sub> solutions and converged topH 6.5 in NaClO<sub>4</sub> solution.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No. kzcx1- yw-06-03)the National Natural Science Foundation of China (No. 40730740, 20621703)
文摘The effects of maize root exudates and low-molecular-weight-organic anions （LMWOAs） on the desorption of phenanthrene from eight artificially contaminated soils were evaluated. A significant negative correlation was observed between the amounts of phenanthrene desorbed and the soil organic carbon （SOC） contents （P 〈 0.01）, and the influences of soil pH and clay content on phenanthrene desorption were insignificant （P 〉 0.1）. Neither maize root exudates nor oxalate and citrate anions influenced desorption of phenanthrene with the addition of NaN3. A faster phenanthrene desorption occurred without the addition of NaN3 in the presence of maize root exudates than oxalate or citrate due to the enhanced degradation by root exudates. Without the addition of NAN3, oxalate or citrate at different concentrations could inhibit phenanthrene desorption to different extents and the inhibiting effect by citrate was more significant than by oxalate. This study leads to the conclusion that maize root exudates can not enhance the desorption under abiotic condition with the addition of NaN3 and can promote the desorption of phenanthrene in soils without the addition of NaN3.
