环洞庭湖区两种典型红土理化特性比较研究

A Study on the Physi-Chemical Characteristics of Two Typical Red Soils around Dongting Lake

通过环洞庭湖区两种典型成因红土的野外勘察与取样、室内磁化率、粒度、微量元素(Li、Rb、Sr、Ba)分析,进行两种不同成因的红土理化性质的比较。研究结果表明,风成成因的红土粒度比基岩风化成因红土明显较细,风成成因红土以粉砂为主,基岩风化型红土为砂和粉砂为主;两种成因红土受到长江中游地区高温高湿的气候条件影响,磁化率均显示为低值,明显低于黄土高原黄土和长江下游下蜀黄土;微量元素Li/Ba、Rb/Sr比值显示为高值,显著高于黄土高原黄土和长江中下游地区下蜀黄土,表明两种红土均经历了强烈的风化淋溶过程,但基岩风化型红土的风化成壤强于风成成因红土,可能基岩风化型红土经历了更长的风化成壤过程。

Field investigation, magnetic susceptibility, granin-size analysis and trace elements including Li, Rb,Sr and Ba in two types of red soil around Dongting lake have revealed the differences of the Physi-Chemical characteristics. The results indicated that the grain-size of the red soil, which deposits with the dust storms and pedogenesis in the late,was finer than the red soil formed with the rock weathering. The grain-size of the red soil which formed by the aeolian dust deposition was the silt, but compound of the sand and silt of the late. Magnetic susceptibility was the lowest among two types of red soil, loess in Loess Plateau and Xiashu loess in middle and lower reaches of Changjiang River,which showed the red soil formed under the warmer and wetter environment with the higher temperature and heavy precipitation. The internal cause of the differentiation of Li, Rb, Sr and Ba was mainly due to their chemical behavior under hypergene conditions Li and Rb were relatively stable elements and remained in the soil while Sr and Ba were active elements and leached out from soil, so the value of Li/Ba and Rb/Sr could indicate the environment change. The value of Li/Ba and Rb/Sr was the highest among the red soil, loess in Loess Plateau and Xiashu loess in middle and lower reaches of CHangjiang River, those who showed the climate was warmer and wetter. However, in the same climate condition of the two types red soil developing, the value of Li/Ba and Rb/Sr of red soil of the rock weathering was higher than the red soil formed by the dust storms, which showed the former had a longer weathering time. Of coures the different sourecs of red soil had different element contents.