黄土包气带中氨氮吸附/解吸机理研究

以关中盆地黄土为研究对象,综合野外采样、室内模拟试验和数据统计分析,系统分析了黄土包气带中不同深度典型物质成分(有机质含量、CaCO_3、氧化物)变化趋势以及氨氮的吸附/解吸特征,并选取黄土(L_1)和古土壤(S_5)为例,探讨黄土包气带中典型物质成分对氨氮吸附/解吸行为的影响机理。研究结果表明:黄土包气带吸附量的变幅(300～1 100 ug·g~(-1))较解吸量的变幅(100～380 ug·g~(-1))大,其吸附量随深度增加呈波浪下降,解吸量在浅层(-20 m以上)波动较大而在深层稳定;对于不同深度土壤,相邻古土壤对氨氮的吸附能力基本均大于黄土,整体而言黄土的平均解吸率比古土壤高8.65%。黄土包气带中物质成分对氨氮的吸附/解吸行为影响最为显著的是有机质和CaCO_3,其与氨氮的吸附/解吸呈正相关,而氧化物的影响较小。因此,不同深度黄土包气带中典型物质成分含量变化是引起氨氮吸附/解吸差异的主控因素。

Adsorption/desorption mechanism of ammonia nitrogen in aerated zone of loess soil

This paper took loess in the Guanzhong Basin as the research object, combined field sampling, indoor simulation experiments, and statistical analysis of data, and systematically analyzed the change trends of typical material components at different depths in the aeration zone of loess (organic matter content, CaCO₃, and oxides) and the adsorption/desorption characteristics of ammonia nitrogen (N). On this basis, the article selects loess (L₁) and paleosol (S₅) as examples to reveal the influence mechanism of the typical material components in the aeration zone of loess on the adsorption/desorption behavior of ammonia N. The study showed that the amplitude of adsorption (300~1 100 ug·g^-1) in the aeration zone of loess was larger than the amplitude of desorption (100~380 ug·g^-1), and the adsorption capacity decreased with increasing depth, and the desorption capacity fluctuated greatly in the shallow (-20 m) and was stable in the deep layers. For soils at different depths, the adsorption/desorption capacity of adjacent paleosols for ammonia N is basically greater than that of loess soils. On the whole, the average desorption rate of loess was 8.65% higher than that of paleosols. The most significant influence on the adsorption/desorption behavior of ammonia N by the constituents of the loess zone was organic matter and CaCO₃. Organic matter and CaCO₃ had a positive correlation with the adsorption/desorption of ammonia N. In addition, oxides had little effect on the adsorption/desorption behavior of ammonia N. Therefore, the changes in the content of typical substances in the aeration zone of loess at different depths were the main factors that caused the difference in ammonia N adsorption/desorption. The research further indicated the influence mechanism of ammonia N adsorption/desorption in the aeration zone of loess, and provided the scientific and technological support for agricultural fertilization and soil pollution control on the Loess Plateau.