Study On The Vertical Variation Of Soil Organic Matters Characteristics And Influencing Factors In The Soil Profile

The study on characteristics of soil organic matters in the soil profiles was the bases of researching the organic pollutants migration and transformation in the vadose zone. The vertical profiles at the middle and upper area of alluvial-proluvial fan in the south of Beijing were selected as study objects, since the work has been done in the down stream. It is to verify the preliminary conclusion obtained and better understand the vertical variation of soil organic matters characteristics and influencing factors. After sampling and extractions, the vertical variation of soil humification degree, the organic matter contents, structures and compositions were evaluated and summarized. Results show that:1) Humic acids and fulvic acids were the main humus in the soil and the vadose zone, their contents account for 80%~90% of the total extraction amount. While the extraction amount increased, their percentage decreased. This demonstrated that the percentage of the additional organic matte(rAOM) increased, which may be relevant to the impaction sequences of all kinds of functions to the humus formation and decompose .2) It is simple and effective to determine the soil humification degree with the alkali extractions method. The soil humification degree was relatively high in topsoil and decrease with the depth increasing in both Daxing Yinghai and Tongzhou Ciqu profile because of the contents of the soil organic matter obviously decreasing. Besides, the soil humification degree and the rate of E4/E6 had a good relationship with each other by correlation analysis.3) The contents of C and O vertically varied on the contrary in humic acids and AOM generally, while they had the same trend in fulvic acids. When the TOC, clay content and moisture content were higher than others, the oxidation of the humic acids and AOM increased, but the aromatic degree, polymerization degree and chemical stability decreased in the humic acids correspondingly. As a whole, the oxidation decrease with the depth increasing , the chemical stability increased correspondingly in the humic acids and fulvic acids. The aromatic degree, polymerization degree and chemical stability decreased in AOM, though. 4) The humus included the hydroxyl, carbonyl, aliphatic hydrocarbon, aromatic groups and amino-groups mainly. The semi-quantitative analysis indicates that the functional groups were hydroxyl >carbonyl and aromatic groups>aliphatic hydrocarbon groups by contents order. The contents of carbonyl, aliphatic hydrocarbon and aromatic groups were gradationally higher from fulvic acids to humic acids and to AOM, which means that their structures enhanced gradationally. It was helpful to form the phenolic hydroxyl groups and increased the acidity of the humus when the TOC, clay content and moisture content were higher than others, but not in favor of aliphatic hydrocarbon and aether, especially in humic acids and fulvic acids.5) The SEM study indicates that the surface morphology of the humus had more forms in the Daxing Yinghai profiles than that in the Tongzhou Ciqu profile. In brief, the fulvic crystal surface was mostly in the shape of the little crumbs. The humic acids mostly had regular shapes and densely-structured crystals.AOM had both the plumed and blocky crystals.