不同孔隙度土壤气体扩散系数测定  被引量:7

Determination of gas diffusion coefficient in soils with different porosities

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作  者:苏志慧[1] 吴兵[1] 龚元石[1] 

机构地区:[1]中国农业大学资源与环境学院土壤与水科学系,北京100193

出  处:《农业工程学报》2015年第15期108-113,共6页Transactions of the Chinese Society of Agricultural Engineering

基  金:农业部农业科研杰出人才及创新团队(2012);长江学者和创新团队发展计划(IRT0412)

摘  要:土壤气体扩散系数是研究土壤气体传输过程的一个重要参数,它随土壤质地、容重和孔隙的改变而变化,难以估算,为准确测定和研究其特征,依据气体扩散原理设计并研制了土壤气体扩散系数测定装置。以石英砂和砂质壤土为试验材料,利用该装置研究了气体扩散系数与不同含水量和容重下的充气孔隙度间的关系。结果表明:砂质壤土原状土和装填土的气体扩散系数差别很小;土壤相对扩散系数随土壤总孔隙度减小而变小,且粒径较小的土壤具有相对较小的气体扩散系数;原状和装填砂质壤土的相对扩散系数与充气孔隙度之间的关系均可以用幂函数方程来拟合,方程中的参数与土壤质地密切相关,原状土非活性孔隙度为0。Buckingham模型的预测值与实测结果基本一致(均方根误差=0.008),但Millington and Quirk模型(均方根误差=0.032)和SWLR模型(均方根误差=0.023)的预测结果偏差较大。Soil gas diffusion coefficient is an important parameter for describing soil gas diffusion process. Its value varies with soil texture, water content, bulk density, and thus is difficult to predict. In this study, we designed a testing apparatus of soil gas diffusion coefficient based Currie's one chamber method and investigated its relationship with air filled porosity. The apparatus was composed of 2 components: a polyvinyl chloride soil chamber on the top with cutting ring and O ring, and gas chamber below. The soil chamber was connected with air and gas chamber on both sides. The gas chamber was made of transparent resin as an observation window. A stainless steel plate was located between soil chamber and gas chamber for gas diffusion control. In addition, KE-25 O2 sensor from Figaro Inc., Japan was used to transmit voltage to computer screen. From prepared calibration curve of gas concentration and voltage, the gas concentration and the gas diffusion coefficient could be calculated. A preliminary experiment showed that the measurement error caused by gas leakage was 0.000006, smaller than measurement results, indicating that the gas leakage could be ignored and the measurements were relatively accurate. In the laboratory experiment, quartz sand of 3 particle sizes were prepared to investigate the changes of relative gas diffusion coefficient with different total porosity and undisturbed and disturbed sandy loams were used to study the changes of relative gas diffusion coefficient with air-filled porosities. Meanwhile, the relative gas diffusion coefficient estimation based on measurements was compared with 3 models(Buckingham method, Millington and Quirk method, structure-dependent water-induced linear reduction model SWLR model). The results showed that relative diffusion coefficient of quartz sand increased with increasing total porosity regardless of particle sizes and also increased with particle sizes regardless of total porosity. The relationship between relative diffusion coefficient and air-

关 键 词:土壤 孔隙度 模型 气体扩散系数 充气孔隙度 测定装置 

分 类 号:S152.6[农业科学—土壤学]

 

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