测量土壤颗粒密度的体积置换法  

Volume replacement methods for measuring soil particle density

作　　者：马玉莹[1] 雷廷武[1,2] 庄晓晖[1] 

机构地区：[1]中国农业大学水利与土木工程学院,北京100083 [2]中国科学院水利部水土保持研究所土壤侵蚀与旱地农业国家重点实验室,杨凌712100

出　　处：《农业工程学报》2014年第15期130-139,共10页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金重点项目(41230746)

摘　　要：土壤颗粒密度测量在土壤和水的关系研究和实践中有重要意义。该文提出一种采用体积置换测量土壤颗粒密度的方法。该方法可以从2种途径进行测定。第1种途径是湿土测量法。第2种途径是干土测量法。湿土测量法：将任意质量和含水量的湿润土样装入容积已知的恒容容器后，称量得到其质量，再将恒容容器中注满水，置换出容器和土壤充气孔隙中气体的体积，再称量得到容器中土颗粒与水的总质量，进而计算得到补水置换体积。然后将土样充分烘干测量得到土颗粒的质量，计算原始土样中土壤水的体积与质量，进而计算得到土颗粒体积，由此测得土粒密度。干土测量法：将土样充分烘干测定土颗粒质量，再将烘干土样置于恒容容器中并注满水，测量并计算得到补水所置换的容器和土壤孔隙的体积，由此确定出土颗粒体积，进而由土颗粒体积和土颗粒质量计算得到土粒密度。采用4种土壤：陕西杨凌的黏黄土、北京的粉壤土、吉林的黑土和江西的黏红土，配制成5种不同土壤含水率（10%、15%、20%、25%、30%）。用上述体积置换法的2种途径，分别测定了每种土壤的土粒密度，并将测得的结果与常规比重瓶法、容量瓶法的测量结果进行比较。试验结果表明，所采用的4种土壤，持续烘干72 h（105℃），湿土法测量得到的土粒密度分别为2.6576、2.6301、2.6411和2.6687 g/cm3，采用干土法测得土粒密度分别为2.6557、2.6320、2.6423和2.6660 g/cm3。4种土壤烘干8 h（105℃）可能使测量得到的土壤颗粒密度偏小1%～2%。土壤颗粒密度测量误差随着烘干时间的延长而逐渐减小。干土法和湿土法测量土壤颗粒密度的散点都聚集在1∶1线上，表明2种方法测量得到的结果基本相同，测量结果比较的最大相对误差小于0.5%，说明体积置换法2种途径可以达到同等测量效果。�The measurement of soil particle density is of great importance for the study and application of soil and water relationships. This paper proposed a volume replacement method for accurate measurement of soil particle density. Two approaches were used. In the first approach, wet soil samples were used. In wet soil sample method, a wet soil sample of unknown volume and mass was placed into a constant volume container （CVC） and then it was weighted. The CVC was filled up with water to displace the air-filled space in the soil and then the container was weighted to determine the replaced air-filled volume and to determine the volume and mass of initial moisture and soil particles. After that the soil sample was oven-dried to determine the volume and mass of soil particles so that soil particle density （SPD） was calculated. In the other approach, dry soil sample was used. In this method, the soil was completely dried before measuring the mass of soil particles. The soil sample was put into the CVC before it was filled up with water to replace the air-filled volume. The replaced volume was computed from the volume of water used to fill the container. Four soil samples were used for the experiments： a clay loam from Yangling of Shaanxi Province （31.80% clay, 62.80% silt and 5.40% sand particles）, a silty loam from Beijing （16.75%clay, 53.00%silt and 30.25%sand particles）, a black soil from Jilin Province （12.00%clay, 86.78%silt and 1.22% sand particles） and a red clay from Jiangxi Province （47.60% clay, 45.00% silt and 7.40% sand particles）. Soil samples were prepared at 5 initial soil water contents as 10%, 15%, 20%, 25%, 30%. The two approaches discussed above were used to determine the SPD, and then the measured results were compared with the results measured by the pycnometer and volumetric flask methods. Detailed laboratory experiment procedures were made to illustrate the measurement and computational procedures. The results showed that the SPDs of the four soils were 2.6576, 2.6301, 2.64

关 键 词：土壤 体积测量 密度 体积置换 湿土法 干土法 

分 类 号：S152[农业科学—土壤学]