【摘要】 土的颗粒粒径分布已被广泛应用于评价土壤的性质,而土的颗粒粒径分布曲线受土壤预处理的影响。为了定量评价土壤样品预处理中六偏磷酸钠的浓度和超声震荡时间对土壤颗粒粒径分布的影响,对比选取出一个表征颗粒粒径分布的定量指标并进行t检验。结果表明,分维值可以作为表征土颗粒分散效果的定量指标;六偏磷酸钠在2%的质量浓度下就可达到最大分散效果,而浓度达到12%以后分散效果显著下降;超声震荡的分散效果显示出分散与絮凝的动荡性,在很短时间内就可表现出分散性,而后随震荡时间增加,其与絮凝现象交替出现;超声震荡的最佳分散能因土壤质地的不同而表现出差异性,0.25～0.5 mm含量最高的粉质黏土最先分散,粉土次之,红黏土分散最慢。可见,六偏磷酸钠的分散效果是受其浓度影响的,超声波不可单独作为一种分散方式使用。更多还原

【Abstract】 Particle size distribution of the soil is widely used to evaluate soil properties, and the soil particle size distribution curve is affected by soil pretreatments. In order to quantitatively evaluate the influence of sodium hexametaphosphate concentration and ultrasonic vibration time on soil particle size distribution in soil sample pretreatments, a quantitative index representing particle size distribution was selected for t-test. The results show that the fractal dimension can be used as a quantitative index to characterize the dispersion effect of the soil. The dispersion effect of sodium hexametaphosphate reaches the maximum at the mass concentration of 2%, and decreases significantly when the concentration of sodium hexametaphosphate reaches 12%. The dispersion effect of ultrasonic vibration exhibits the turbulence, of which dispersion and flocculation alternate along with time. The optimal dispersion of ultrasonic shock varies with the soil texture. The silty clay with the highest content of grain group(0.25～0.5 mm) is dispersed firstly, followed by the silt and red clay. It is concluded that the dispersion effect of sodium hexametaphosphate is affected by its concentration, and the use of ultrasound alone as a means of dispersion is unreliable.更多还原