雷州半岛玄武岩发育的时间序列土壤的发生演变

采集了广东省南部热带地区雷州半岛第四纪以来不同时代(0.58～6.12 Ma)喷发的玄武岩上发育时间序列土壤剖面样品,分析了一些理化性质的变化趋势。结果表明:(1)容重随深度增加而增大,与成土年龄有较好的相关性,说明容重在一定程度上可以指示土壤的发生层次和发育程度。(2)游离铁(Fed)、铁游离度(Fed/Fet)、活性氧化铝(Alo)和铝活化度(Alo/Ald)与成土年龄有着较好的相关性,可以指示土壤的发育程度和相对成土年龄;而无定形铁(Feo)、游离铝(Ald)和无定形硅(Sio)与成土年龄的关系不明显,尚难于指示土壤的发育程度。(3)常用的黏粒风化发育指标,如硅铝率Sa(SiO2/Al2O3)、硅铁铝率Saf(SiO2/(Al2O3+Fe2O3))、风化淋溶系数ba((Na2O+K2O+CaO)/Al2O3)、A指数((SiO2+CaO+K2O+Na2O)/(Al2O3+CaO+K2O+Na2O))、B指数((CaO+K2O+Na2O)/(Al2O3+SiO2+CaO+K2O+Na2O))、WI指数((2Na2O/0.35)+(MgO/0.9)+(2K2O/0.25)+(CaO/0.7)]×100)、CIW指数(Al2O3/(Al2O3+CaO+Na2O)]×100)、CIA指数(Al2O3/(Al2O3+CaO+Na2O+K2O)]×100,与成土年龄之间相关性不显著,难以指示土壤的风化程度,但黏粒的Sa、Saf和元素Si迁移率的变化在一定程度上揭示了土壤中生物复硅的存在。

Evolution of chronosequential soils derived from volcanic basalt on tropical Leizhou Peninsula,South China

Abstract: Chronosequential soils derived from basalts formed through volcano eruptions during different ages since the Quaternary period from 0.58Ma to 6.12M a BP on Leizhou Peninsula, South China were samples for analysis of changes in some physiochemical properties of the soils. Results show that (1) soil bulk density increased with soil depth and quite closely related to soil age, which suggests that soil bulk density could be deemed, to a certain degree, as an indicator of soil genetic horizons and development; (2) Fed, Fed/Fet, Alo and Alo/Ald, were quite closely related to soil age, as well, suggesting that they are good indicators of soil development and relative age of the soil, while Feo, Ald and Sio were not, suggesting they were not good indicators either;. and (3) the common indicators of clay weathering and development, such as Sa (SiO2/Al2O3), Saf (SiO2 / (Al2O3+Fe2O3)), ba ((Na2O+K2O+CaO) / Al2O3), A ((SiO2+CaO+K2O+Na2O) / (Al2O3+CaO+K2O+Na2O)), B ((CaO+K2O+Na2O) / (Al2O3+SiO2+CaO+K2O+Na2O)), WI ((2Na2O/0.35) + (MgO/0.9) + (2K2O/0.25) + (CaO/0.7)]×100), CIW (Al2O3 / (Al2O3+CaO+Na2O)]×100), CIA (Al2O3 / (Al2O3 +CaO+Na2O+K2O)]×100) were not significantly related to soil age, suggesting that they are not good indicators of soil weathering degree, while changes in Sa and Saf of clay and migration rate of element Si to a certain extent revealed formation and enrichment of biogenic silica, which may influence Si leaching in soil.