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

本课题从以下四个方面对腐植酸Pg作为环境指示剂的有效性进行了评价：1）菌核颗粒的形态特征和化学成分，Pg的来源2）表层土壤中Pg组分分布的调控因素3）火山灰和黄土古土壤中腐殖酸Pg的年代序列4）不同腐殖酸中腐殖酸Pg组成的差异在所采集的菌核颗粒中发现了明显的铝含量，这是腐殖酸Pg的来源，其发展受土壤中交换性铝含量的调节。土壤交换性铝的含量对土壤吸附Pg的强度有一定的影响。根据这些结果，我们认为在土壤中的淋溶过程中，或在凉爽潮湿的条件下，促进了Pg的形成。根据对日本和德国火山灰和黄土古土壤年代序列的研究结果，Pg在140-150 ka的埋藏腐殖层中残留，在50-60 ka的埋藏火山灰和黄土古土壤中表现出较强的Pg吸附强度。Pg的波动（称为Pg信号/）与米奥斯获得的过去温度的波动曲线有对应的趋势。利用高效液相色谱法对腐殖酸Pg的组成进行了研究，将Pg（腐殖酸绿色组分）用高效液相色谱法分离成10个组分。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.