沉积物不同天然有机组分对氨氮解吸特征的影响

Effect of natural organic matter fraction on desorption characteristic of ammonium nitrogen on sediment in Western Liao River

采用平衡解吸法研究了西辽河沉积物不同天然有机组分对氨氮解吸特征的影响。结果表明,去除有机质后的沉积物氨氮解吸比例(D_r=0.70)大大增加,同时,解吸迟滞性指数显著降低(T_Ⅱ=0.016),有机质是影响沉积物氨氮解吸特征的重要因素;重组有机组分中的紧结态腐殖质(胡敏素)对抑制氨氮解吸起关键作用,它不但解吸比例较低,而且解吸迟滞性指数较大;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;考查沉积物吸附态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,它也是影响沉积物吸附态氨氮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和紧结态腐殖质所吸附的氨氮对上覆水体的扩散通量可分别按其饱和吸附量的0.97倍、0.41倍、0.25倍和0.17倍进行估算。

Effect of desorption characteristic of ammonia nitrogen on different natural organic matter from Western Liao River sediments was investigated by batch experiments of equilibrium adsorption. The results indicated that humus was a main influencing factor in desorption of ammonia nitrogen on sediment, because desorption ratio （0.70） of ammonia nitrogen on the sediment increased dramatically, while desorption hysteresis index （0.016） decreased significantly after the organic matter was removed. Tight humus （humin） in heavy fraction play an important role in restraining desorption of ammonia nitrogen. It could cause the desorption ratio to be lower and desorption hysteresis index to be larger. Distribution function sorption of ammonia nitrogen on light fraction mainly caused desorption ratio to be larger and desorption hysteresis index to be smaller. Consequently, the content of organic matter and its existing state were the main influencing factors of desorption characteristic of ammonia nitrogen on sediment and both should be considered. The diffusion flux of the adsorption of ammonia nitrogen on light fraction and heavy fraction of organic matter, stable humus and tight humus of heavy fraction to the overlying water could be roughly calculated by the percent of 97, 41, 25 and 17 of the saturated adsorption amount respectively.