冻融作用对三江平原有机土吸附铵根离子及其分配系数的影响

冻融过程会影响土壤团聚体结构及微孔隙,进而影响土壤对阳离子的吸附。然而有关冻融过程对土壤吸附阳离子影响的研究很少。以典型湿地表层有机土壤为对象,通过室内模拟实验,研究了土壤饱和含水量下,冻融过程对有机土吸附低浓度铵根离子的影响。结果表明,冻融作用一般提高了有机土对铵根离子的吸附量,线性方程能较好的拟合低浓度范围氨氮的吸附,而且冻融作用降低了铵根离子吸附量为0时土壤溶液中氨氮的浓度。随着初始氨氮浓度从8.6mg·L-1升高到43.0mg·L-1,冻融条件下氨氮的分配系数从10.3L·kg-1升高到25.6L·kg-1;非冻融对照条件下氨氮的分配系数从7.0L·kg-1升高到19.8L·kg-1。冻融作用导致氨氮的分配系数增加了29.9%~47.3%,但氨氮的分配系数没有出现随冻融次数增加而升高的趋势。

Influence of Freeze-thaw on Adsorption/Distribution Coefficient of Ammonium in Organic Soils from Wetland of Sanjiang Plain, China

Freeze-thaw process might influence soil＇s aggregate and micropores, thus influence cations＇ adsorption on the soils. However, few studies had investigated the effect of freeze-thaw process on the adsorption of cations by the soils. The object of this study is to discuss the effect of freeze-thaw action on the adsorption of ammonium by organic soils from the wetland of Sanjiang Plain. Solution with different ammonium concentrations was added to the air-dried soil samples, then the soil paste was incubated under freeze-thaw treatment（FFF） （Freeze： 12 h, Thaw： 12 h ） or room temperature （NFTF） for 5 cycles. ReSults showed that freeze-thaw process generally increased the adsorption of am- monium by the organic soil, and the adsorption isotherms were well fitted by linear equation. In addition, the critical ammonium concentration when there was no adsorption happened in soils was decreased by freeze-thaw cycles. Distribution coefficient increased from 10.3 L·kg-1 to 25.6 L·kg-1 with the increase of initial ammonium concentration from 8.6 mg N. L-1 to 43.0 mg N·L-1 under freeze-thaw treatment, while it in- creased from 7.0 L·kg-1 to 19.8 L·kg-1 under room temperature. Freeze-thaw process increased ammonium distribution coefficient from 29.9% to 47.3%. However, there was no sign that ammonium distribution coefficient increased with more freeze-thaw cycles.