风沙土不同有机组分对氨氮的吸附特征影响

Effect of Organic Matter Fraction on Sorption of Ammonium Nitrogen on Sandy Soil

采用平衡吸附法研究了风沙土不同有机组分对氨氮的吸附特征影响。结果表明,去除腐殖质后的风沙土对氨氮的吸附能力大大降低,其碳标化饱和吸附量Гmoc和吸附分配系数Koc分别只能达到原样的68.58%和28.24%,说明腐殖质是影响氨氮在风沙土上吸附特征的主要因素;轻组有机质是一类橡胶态胶体,氨氮在橡胶态胶体上的吸附以分配作用为主,其碳标化吸附分配系数为81.58;重组有机质对氨氮的吸附起主导作用,其碳标化饱和吸附量为3350.55mg.kg-1;重组有机质是一类玻璃态胶体,氨氮在玻璃态胶体上的吸附除分配作用外,还存在孔隙填充方式的吸附;重组有机组分中的紧结态腐殖质(胡敏素)对氨氮的吸附起关键作用,其碳标化饱和吸附量可达6626.30mg.kg-1,影响机制主要为稳、紧结态腐殖质是形成土壤疏松多孔团聚体结构的重要胶结物质。在其所形成的有机-无机复合体中存在着孔隙填充方式的氨氮吸附。考查土壤对氨氮的吸附能力不但要考虑有机质的含量,更要考虑有机质的存在形态,它也是影响土壤对氨氮吸附特征的重要因素。以重组为基准,轻组有机质、稳结态腐殖质和紧结态腐殖质携载吸附态氨氮可分别按重组的0.59、1.05倍和2.50倍估算。

Effect of organic matter fraction on sorption of ammonium nitrogen on sandy soil was investigated by batch experiments of equilib- rium adsorption. The results indicated that the sorption capacity on the sandy soil reduced dramatically after humus was removed, normalized sorption capacity and partition coefficient only accounted for 68.58% and 28.24% of original sample, humus was a main factor in the sorp- tion of ammonium nitrogen on sandy soil.On the one hand, light fraction of organic matter was rubber-state colloid, and distribution function was main process in ammonium nitrogen sorption on rubber-state colloid, normalized partition coefficient was 81.58. On the other hand, heavy fraction was glass-state colloid, it played a leading role in the sorption of ammonium nitrogen and the normalized sorption capacity was 3 350.55 mg.kg^-1. The sorption mechanism of ammonium nitrogen on the glass-state colloid was micro-hole function filling except distri- bution function. Furthermore, normalized sorption capacity of tightly combined humus （humin） of the heavy fraction was 6 626.30 mg. kg^-1. Stably combined humus and tightly combined humus were important adhesive material in the formation of loose and porous structure on sandy soil aggregate. Consequently, there was a micro-hole filling function in ammonium nitrogen sorption on organic and inorganic complexes. Taking into account the adsorption capacity was not only organic matter content, but also existent state of organic matter, and it was also a main factor in sorption characteristic of ammonium nitrogen bn sandy soil. When regarding heavy fraction as a basic standard, adsorption state ammonium nitrogen on light fraction of the organic matter, stably combined humus and tightly combined humus were estimated in accordance with 0.59, 1.05 times and 2.50 times.