绰墩埋藏古水稻土中木质素特征研究

LIGNIN IN BURIED ANCIENT PADDY SOILS AT CHUODUN SITE

利用CuO氧化方法分析了苏州绰墩山埋藏古水稻土中木质素分解酚酸产物及特征,以此了解长期利用条件下水稻土中木质素的来源、保存及变化。通过比较相邻埋藏土壤剖面植稻和非植稻层次中木质素源的酚酸化合物特征,探讨水稻种植对土壤木质素结构特征的影响。结果表明,在埋藏古水稻土中木质素源的总酚酸含量在0.004～0.035 mg kg-1之间,显著低于现代水稻土(0.27～0.34 mg kg-1),而在埋藏土壤中,植稻与非植稻土壤层次中木质素无显著差异。埋藏古土壤中木质素源酚酸的组成(香草基类/紫丁香基类(S/V)及肉桂类/紫丁香基类(C/V)比分别为0.40～1.55、0.15～0.89),可证实此古土壤曾种植非木本被子植物;而S/V和C/V在植稻与非植稻土壤中没有显著差异,表明利用木质素特征难以区分同类(不同草本)有机质的具体来源。在埋藏古土壤中木质素碳占总有机碳比例很小,说明木质素在土壤中并非如通常所预期的容易被保存。

In order to know the resource,preservation and development of lignin,a useful biomarker of SOM （ soil organic matter） ,samples of lignin extracted from the buried ancient paddy soil at Chuodun ruin site, China were analyzed with the CuO oxidation method for its characteristics and catabolites of phenolic acids. The buried ancient paddy soils was identified to be more than 6 000 years old and confirmed with the archaeological method. Results showed that the total lignin-derived phenols in that soil ranged from 0. 004 to 0. 035 mg kg^-1 , decreasing with the depth and was obviously lower than those in the modern paddy soils （0.27 - 0.34 mg kg^-1 ） , but no significant difference was found between buried paddy soils that had been planted with rice or without rice. The composition of oxidized phenols in the soil with S-to-V and C- to-V ratios being 0.40 - 1.55 and 0.15 -0.89, respectively, demonstrates that non-woody angiosperms once grew in the soil; between ancient soils with rice or without rice,no significantl difference was found in S-to-V and C-to-V, suggesting that it is not easy to distinguish origin of organic matter of the same kind in the buried soils based on characteristics of lignin. Lignin carbon accounted only for a small portion of the SOC in buried ancient paddy soils,indicating lignin is not so preservable as usually expected in the soil.