Chronological sequence of humic acid Pg and its validity as environmental indicator

本项目推进了以下4个课题来评价腐植酸Pg作为环境指标的有效性。1)菌核颗粒的形态特征和化学组成，Pg的来源2)表层土壤中Pg组分分布的调节因素3)土壤和黄土古土壤中腐殖酸Pg的年代顺序4)不同腐殖酸中腐殖酸Pg的组成差异在收集到的菌核颗粒中可以明显识别出铝浓度，这是Pg的来源；其发展受土壤中交换性铝含量的调控。此外，还阐明了表层土壤对Pg的吸收强度受土壤中交换性铝含量的调节。基于这些发现，我们认为Pg的形成是在土壤淋滤过程中，或在凉爽潮湿的条件下促进的。通过对日本和德国黄土古土壤的年代学分析，发现Pg存在于140 ~ 150 ka的埋藏腐殖质层中，在50 ~ 60 ka的埋藏黄土古土壤中表现出较强的Pg吸收强度。Pg的波动，称为Pg信号/，有与MIOS获得的过去温度波动曲线相对应的趋势。用高效液相色谱法对腐植酸Pg的组成进行了研究，将Pg（腐植酸绿段）分为10个部分。在不同环境下形成的Pg组分的鉴定可以在进一步的研究中讨论。

The following four subjects were promoted in this project to evaluate the validity of hurmic acid Pg as an environmental indicator.1) Morphological feature and chemical composition of sclerotia grains, the origin of Pg2) Factors regulating the distribution of Pg fraction in surface soils3) Chronological sequence of humic acid Pg in tephric and loessic paleosols4) Difference of the composition of humic acid Pg in various humic acidsAluminum concentration was significantly recognized in the collected sclerotia grains, which are the origin of Pg, and the its development revealed to be regulated by the amount of exchangeable aluminum in soils. Moreover, it was clarified that the strength of Pg absorption in surface soils was regulated by the amount of exchangeable aluminum in soils. Based on these findings, it is suggested that Pg formation is promoted under leaching process in soil, or under cool and wet condition. According to the results obtained by examining the chronological sequence of tephra and loess paleosol in Japan and Germany, Pg revealed to remain in the buried humic layers aged 140-150 ka and showed a strong Pg absorption strength in buried tephra and loess paleosols aged 50-60 ka. The fluctuation of Pg, named as Pg signal/had a tendency to correspond to the fluctuation curve of past temperature obtained by MIOS. The study on composition of humic acid Pg using HPLC performed to separate Pg (humic acid green fraction) into 10 fractions by HPLC. The identification of Pg fraction formed in different environment can be discussed in-further studies.