沙土不同有机组分对磷的解吸特征影响

Effect of different organic fractions on desorption characteristic of phosphorus on sandy soil

采用平衡解吸法研究了沙土不同有机组分对磷的解吸附特征影响。结果表明,通过过氧化氢去除有机质后的沙土使磷的解吸比例(Dr=0.94)大幅度增加,解吸迟滞性指数(TⅡ=0.05)显著降低;有机质是影响磷在沙土上解吸特征的重要因素;磷在橡胶态胶体(轻组有机组分)上的表面分配作用吸附是导致解吸比例(Dr=0.81)增大,解吸迟滞性指数(TⅡ=0.05)减小的原因;稳结态腐殖质中的胡敏酸在对磷的吸着和滞留过程中发挥重要作用,HⅡ+HⅢ组(Dr=0.57、TⅡ=0.30);磷在紧结态腐殖质所形成的团聚体结构中引起的团聚体结构不可逆形变是导致磷的解吸比例(HⅢ组Dr=0.24)降低,解吸迟滞性指数(HⅢ组TⅡ=0.49)增大的根本原因,考查土壤磷的解吸特征不但要考虑有机质的含量,更要考虑有机质的存在形态,它也是影响土壤磷解吸特征的重要因素,轻组有机组分、重组有机组分、以及重组有机组分中的稳结态腐殖质、紧结态腐殖质所携载的吸附态磷进入水体后对上覆水体的释放通量可分别按其饱和吸附量的81%、66%、57%和24%进行估算。

Effect of different organic fractions on desorption characteristic of phosphorus on sandy soil was investigated by batch experiments of equilibrium desorption. The results indicated that desorption ratio increased dramatically after organic matter was removed, and it increased to 0.94 after organic matter was totally removed. Furthermore, organic matter was a main factor in desorption of phosphorus on sandy soils, and surface distribution function of phosphorus on rubber-state colloid was cause of desorption ratio larger and hysteretic index smaller. On the one hand, humic acid of stably combined humus played a leading role in phosphorus sorption and retardation, desorption ratio （stably combined humus ＋ tightly combined humus） and hysteresis index were 0.57 and 0.30 respectively. On the other hand, irreversible transformation of aggregate structure on tightly combined humus was fundamental cause of desorption ratio lower （desorption ratio of tightly combined humus was 0.24） and hysteresis index higher （hysteresis index of tightly combined humus was 0.49）. Consequently, taking into account the desorption characteristic of phosphorus on sandy soil was not only the organic matter content, but also existent state of organic matter, and it was also a main factor in desorption characteristic of phosphorus on sandy soil. When regarded sorption capacity as a basic standard, releasing flux of adsorption state phosphorus on light fraction, heavy fraction, stably combined humus and tightly combined humus of heavy fraction were also estimated in accordance with 81%, 66%, 57% and 24%.