风沙土不同有机组分对氨氮的解吸特征影响

Effect of organic matter fraction on desorption characteristic of ammonium nitrogen on sandy soil in western Liao River

采用平衡解吸法研究了风沙土不同有机组分对氨氮的解吸特征影响。结果表明,去除腐殖质后的风沙土氨氮解吸比例增加(由0.58增加到0.68),同时,解吸迟滞性指数显著降低(由0.067降低到0.021),说明腐殖质是影响风沙土氨氮解吸特征的重要因素;氨氮在轻组有机组分上的表面分配作用吸附是导致解吸比例增大,解吸迟滞性指数减小的原因;重组有机组分中的紧结态腐殖质(胡敏素)对氨氮的解吸起关键作用,它不但解吸比例较低(Dr=0.23),而且解吸迟滞性指数较大(TⅡ=0.458);氨氮在紧结态和稳结态腐殖质所形成的团聚体颗粒微孔隙中的不可逆吸附是导致解吸比例降低、解吸迟滞性指数增大的根本原因;考查土壤对氨氮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,它也是影响土壤氨氮解吸特征的重要因素,轻组有机组分、重组有机组分及重组有机组分中的稳结态加紧结态腐殖质(HⅡ+HⅢ组)和紧结态腐殖质(HⅢ组)携载的吸附态氨氮进入水体后,对上覆水体的扩散通量可分别按其饱和吸附量的0.94、0.58、0.33和0.23倍估算。

Effect of organic matter fraction on desorption characteristic of ammonium nitrogen on sandy soil was investigated by batch experiments of equilibrium adsorption.The results indicated that desorption ratio on the sediment increased dramatically after organic matter was removed（from 0.58 to 0.68）.Meanwhile,desorption hysteresis index decreased significantly（from 0.067 to 0.021）.Humus was a main factor in desorption of ammonium nitrogen on sandy soil.Distribution function of ammonium nitrogen sorption on light fraction was main cause of desorption ratio larger and hysteresis index smaller.On the one hand,tightly combined humus（humin） of heavy fraction played a leading role in restraining desorption of ammonium nitrogen.Furthermore,desorption ratio was relatively lower,and desorption hysteresis index was relatively higher.On the other hand,irreversible sorption of micro-hole aggregate on tightly combined and stably combined humus was fundamental cause of desorption ratio lower and hysteresis index higher.Consequently,taking into account the desorption characteristic of ammonium nitrogen on sandy soil was not only organic matter content,but also existent state of organic matter,and it was also a main factor in desorption characteristic of ammonium nitrogen on sandy soil.When regarding sorption capacity as a basic standard,diffusion flux of adsorption state ammonium nitrogen on light fraction、heavy fraction、HⅡ＋HⅢ（stably combined humus ＋ tightly combined humus） and HⅢ（tightly combined humus） were also estimated in accordance with 0.94,0.58,0.33 and 0.23 times.