关中盆地全新世黄土-土壤剖面微量元素的地球化学特征及其古气候意义

通过对老官台全新世黄土剖面12种微量元素的测定分析,结合本剖面已测定的粒度、磁化率、光释光(OSL)年龄,研究和揭示了它们在表生环境下的地球化学特征和古气候意义。微量元素在风化成壤过程中,其活动性由强至弱顺序为BaSrCdPbLiZnCuCrMnCoRbNi。其中Rb、Li、Cr、Co、Zn、Cu、Mn、Ni八种元素在土壤形成过程中相对富集,含量较高;Sr、Ba、Cd三种元素在土壤中相对淋失,含量较低;但Zn、Cu、Mn、Ni、Pb五种元素对黄土层和土壤层的区别不是很明显。因此,Rb、Li、Cr、Co的高含量反映了较温湿的成壤环境,低含量反映了较冷干的粉尘加积环境;而Sr、Ba、Cd低含量反映了较温湿的成壤环境,高含量反映了较冷干的粉尘加积环境。Pb、Zn、Cu、Mn、Ni、Cd元素含量在表土层中的富集主要与现代耕作活动或工业污染有关,反映了人类活动强度的不断增强。LGT剖面主要微量元素的变化清楚地记录了关中盆地自末次冰消期以来气候环境经历的显著波动变化。

Geochemistry of Trace Elements and Their Paleoclimatic Implications in the Loess-soil Section in Guanzhong Basin

Based on systematic experiment analysis of 12 trace elements,and combining the experimental results of magnetic susceptibility,grain size and the optical stimulated luminescence(OSL) ages for Laoguantai(LGT) section in Guanzhong Basin,this paper researched their supergene environment geochemistry and paleoclimate significance.In the process of pedogenesis,element migration intensity in the order from strong to weak was Ba>Sr>Cd>Pb>Li>Zn>Cu>Cr>Mn>Co>Rb>Ni,which identified according to their activity.Rb,Li,Cr,Co,Zn,Cu,Mn and Ni had higher contents due to relatively enriched in the course of soil formation,but Sr,Ba,Cd,and Pb had lower levels reduced from relative leaching within soil.Zn,Cu,Mn,Ni and Pb were not clearly distinguished the soil layer from loess layer.Therefore,the higher contents of Rb,Li,Cr and Co reflected the relatively higher temperature and humidity climate.On the contrary,the low content reflected the dry and cold climate.The low content of Sr,Ba and Cd indicated the higher temperature and humidity climate,and the higher levels reflected the cold and dry climate.The contents of Pb,Zn,Cu,Mn,Ni and Cd enriched in the surface soil due to the modern farming activities or industrial pollution,reflecting the increased intensity of human activities.The environment changes since the last deglaciation havd been clearly recorded by the changes in trace elements in this area.