黄土醋酸淋溶实验及其碳酸盐组分的地球化学特征

选择性的化学淋溶实验 ,广泛用于沉积物的地球化学研究中。通过对比 1mol/L的盐酸和醋酸两种溶剂对黄土和古土壤的淋溶效果 ,发现 1mol/L的醋酸能选择性淋溶黄土和古土壤中碳酸盐组分 ,对硅酸盐、铁的氧化物等影响很小。在确定溶剂后 ,以 1mol/L醋酸溶液选择性淋溶了洛川剖面 4 3个黄土和古土壤样品 ,通过分析淋溶液的组成 ,得出黄土和古土壤中碳酸盐组分的平均成分 (wB)为 :MgO 1.71% ,MnO 670× 10 - 6 ,Sr 4 90× 10 - 6 。淋溶结果较好地反映了黄土-古土壤剖面的风化成壤程度 ,其中醋酸淋溶液中MnO含量能更好地反映当时的古气候信息。

Chemical leaching of loess deposits in China and its implications for carbonate composition

Chemical leaching is widely applied to geochemical research of sediments. In this paper, 1 mol/L hydrochloric solution (HCl) and 1 mol/L acetic acid (HAc) were used to conduct leaching experiments on loess and paleosol samples. HAc leaches mainly the carbonate fraction in the loess and paleosols but has little effect on silicates or iron oxides. In contrast, 1 mol/L HCl solution dissolves not only carbonates but also some of iron oxides and chlorites, as evidenced by higher concentrations of Mg and Fe and higher leaching percentages of elements inthe HCl leachate. Experimental results show that 1 mol/L HAc is an ideal dissolvent that caselectively leach the carbonate fraction in the loess and paleosols. On the basis of the leaching results, the average composition of the carbonate fraction, i.e., 1.71% of MgO, 490×10-6 of Sr and 6 7 0×1 0-6of MnO , was obtained . The leaching parameters reflect the degree of pedogenesis of the loess and paleosol sequence; moreover, the MnO content of HAc leachate is the best parameter to indicate the degree of pedogenesis.