土壤胡敏素各组分数量及结构特征初步研究

QUANTITIES AND STRUCTURAL CHARACTERISTICS OF VARIOUS FRACTIONS OF SOIL HUMIN

土壤胡敏素(HM)是与矿物质紧密结合的腐殖物质,具有碱不溶性及大分子结构的特性,并呈现不均一性,被认为是土壤中的惰性物质。由于HM的非溶解性和结构复杂性,目前国内外学者对于HM结构特征的研究还很少。对加入大量有机物料培养后新形成的HM数量及性质的研究尚未见报道。本研究选用风沙土、草甸土、黑土、黑土底土加玉米秸秆培养土为材料,根据Pallo分组法,将土壤HM分为铁结合胡敏素(HMi)、粘粒结合胡敏素(HMc)和不溶性胡敏素(HMr)三个组分;对自然土壤中HM各组分以及加入玉米秸秆后新形成的HM各组分的数量及结构特征进行初步研究,为丰富腐殖质化学提供基础性资料。实验结果表明:在自然土壤HM各组分中以HMr为主,其次是HMi,含量最少的是HMc。通过HMi和HMc的光学性质比较得出HMi的分子结构较简单,HMc分子结构相对较复杂,加玉米秸秆培养后新形成的HMi、HMc的分子结构比自然土壤中的简单。红外光谱结果表明,与自然土壤相比加玉米秸秆培养后新形成的HMi、HMc的脂族性最强,自然土壤中HMi、HMc的脂族性强弱顺序为:风沙土>黑土>草甸土。

Humic substance （HS） can be divided into humic acid （HA）, fulvic acid （FA） and humin （HM） according to solubility in alkali or acid solution. HM is a fraction tightly combined with soil minerals and hardly extracted. In recent years, researchers have conducted a series of research on HM and advanced some means of separating, fractionating and purifying the substance. Among them the Pallo method is quite complicated to operate, but capable of fractionating HM into iron-linked HM （HMi）, clay-combined HM （HMc）, inherited HM（IH） and highly developed HM （DH）. As the fraction of inherited HM is very limited in quantity, it was ruled into the fraction of highly developed HM, which was then called insoluble humin residues （HMr） in this paper. In the experiment, samples of cultivated black soil and meadow soil were collected from the Jilin Agricultural University Campus （N43°48＇, E125°23＇）, and samples of Aeolian sandy soil from the Yaojingzi Grassland Research Station （N44°45＇, E123°45＇） , Northeast Normal University, Jilin Province, China. The above samples were all taken from 0 ～20 cm topsoil layers, except the samples of black subsoil, which was collected from the soil layer, 70 ～100 cm in depth in the tableland. The black subsoil （2 mm mesh） was mixed with powdered corn stalks （0.42 mm mesh） and some bacteria of normal soil bacterial groups. Then the mixture was put under incubation at 25 ℃ for 90 days. Results show that HMr is the dominant fraction of humin, accounting for 30% ～60% of the total organic carbon（TOC） in quantity, and followed by HMi and HMc, accounting for 3.1% ～ 5.5 % and 1.5 % ～4.1%, respectively. The content of HMi is a little bit higher than that of HMe in all the soils, except in the incubated soil. The E4/E6 and △LogK of HMi is higher than that of HMc in all the soils. The IR of HMi is almost the same as that of HMc regardless of difference in soil, but the new-formed HMi in the incubated soil showed stronger aliphatic C-H vibration （2 920 cm^- 1 ）. In terms of 2 920/1 620 ratio of both HMi and HMc, a decreasing order of incubated soil 〉 Aeolian Sandy soil 〉 black soil 〉 meadow soil is found. From the above results, it can be concluded that HMi is simpler and more aliphatic than HMc in molecular structure, and HMi and HMc are simpler and more aliphatic in the incubated soil than in the normal soils.