不同前处理方法对南方红土粒度测量的影响——以安徽宣城第四纪红土剖面为例

INFLUENCE OF PRETREATMENTS ON GRAIN-SIZE DISTRIBUTION OF THE RED EARTH IN SOUTHERN CHINA——A CASE STUDY ON THE QUATERNARY RED EARTH PROFILE IN XUANCHENG,ANHUI PROVINCE

以安徽宣城官塘村第四纪红土剖面为例,研究了不同前处理方法对南方红土粒度测量的影响。结果表明:(1)南方红土中所含的有机质对粒度测量结果会产生明显影响,在进行粒度测量前处理时,必须加入双氧水去除有机质;(2)南方红土因淋溶强烈,碳酸钙含量极低,对粒度测量结果无影响,无需加入盐酸进行去钙处理。加入盐酸反而使得所测粒径偏粗;(3)与六偏磷酸钠相比,氢氧化钠作为分散剂因其强碱性产生的复杂化学反应,会导致所测得的粒度频率曲线峰态出现异常,且<1μm的黏粒组分含量减少,故不宜用作南方红土粒度测量的分散剂;(4)在对南方红土进行粒度测量时,建议使用H2O2+(NaPO3)6的前处理方法,即先使用双氧水去除有机质,再使用六偏磷酸钠作为分散剂,并用超声波清洗仪震荡后上机测试。

Taking the Quaternary red earth profile in Xuancheng as an example,we studied the influence of different pretreatment methods on grain size distribution of the red earth in southern China,The results indicate that：（1） The southern red earth contain a little amount of organic matter,which will influence the grain size distribution,so it’s necessary to use hydrogen peroxide（H2O2） to remove the organic matter during the pretreatment.（2） Due to the strong leaching,carbonate content in red earth is extremely low,which has no effect on the result of measurement.So it doesn’t need to add hydrochloric acid（HCl） to remove carbonate.The input of HCl may lead to flocculation,which will make the results coarser.（3） Compared with sodium hexametaphosphate（（NaPO3）6）,sodium hydroxide（NaOH） leads to an abnormal shape of grain size frequency curves,and the decrease in grain content of size 〈1 μm,so NaOH is not an appropriate dispersant agent for the red earth.（4） According to the experiment,we find the pretreatment method of（H2O2＋（NaPO3）6） is the best.It is recommended using H2O2 to remove organic matter,and（NaPO3）6 as a dispersant,finally dispersing the sample by ultrasonic cleaning instrument.