Effect of Fe/Al Hydroxides on Desorption of K+ and NH4+ from Two Soils and Kaolinite

WANG Yan-Ping; XU Ren-Kou; LI Jiu-Yu

摘要

Potassium (K) and nitrogen (N) are essential nutrients for plants.Adsorption and desorption in soils affect K+ and NH4+ availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges.We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH4+ from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles.Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides,as amorphous Al(OH)3 or Fe(OH)3,and negatively charged surfaces from an Ultisol,an Alfisol,and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative.Thus the adsorption affinity of these negatively charged surfaces for K+ and NH4+ declined as a result of the incorporation of the Fe/Al hydroxides.Consequently,the release of exchangeable K+ and NH4+ from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added.The greater the positive charge on the surfaces of Fe/Al hydroxides,the stronger was the interactive effect between the hydroxides and soils or kaolinite,and thus the more release of K+ and NH4+.A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite.As a result,more K+ and NH4+ were desorbed from the soils and kaolinite.This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH4+ in the soils and thus increase their leaching loss.

机译：钾（K）和氮（N）是植物必需的营养素。土壤中的吸附和解吸会影响植物对K +和NH4 +的利用率，并可能受到带相反电荷的粒子上的双电荷层之间相互作用的影响，因为这种相互作用会减少表面通过正负电荷的中和作用使颗粒的电荷密度增加。我们研究了铁（Fe）/铝（Al）氢氧化物对土壤和高岭石中K +和NH4 +的解吸的影响，并基于两层之间扩散层的重叠提出了解吸机理结果表明，带正电的Fe / Al氢氧化物之间的电双层扩散层重叠，为非晶态Al（OH）3或Fe（OH）3以及Ultisol，Alfisol和高岭土标准品带负电的表面导致土壤上的有效负表面电荷密度因此，由于Fe / Al氢氧化物的结合，这些带负电的表面对K +和NH4 +的吸附亲和力下降。结果，土壤和土壤中可交换的K +和NH4 +释放出来。高岭石随Fe / Al氢氧化物添加量的增加而增加。Fe/ Al氢氧化物表面上的正电荷越大，氢氧化物与土壤或高岭石之间的相互作用越强，因此K +和NH4 +的释放越多pH值的降低导致铁/铝氢氧化物表面正电荷的增加，并增强了氢氧化物与土壤/高岭石之间的相互作用。结果，更多的K +和NH4 +从土壤和高岭石中解吸。可变电荷土壤中带相反电荷的颗粒之间的相互作用可以增强土壤中K +和NH4 +的迁移率，从而增加其淋失损失。

Effect of Fe/Al Hydroxides on Desorption of K+ and NH4+ from Two Soils and Kaolinite

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