Bound Water Content of Air‐Dry Soils Measured by Thermal Analysis
Bound Water Content of Air‐Dry Soils Measured by Thermal Analysis
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DOI：
10.2136/sssaj2010.0065
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发表时间：
2011-03
影响因子：
2.9
通讯作者：
Yajing Wang;Sen Lu;T. Ren;Baoguo Li
中科院分区：
文献类型：
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作者：
Yajing Wang;Sen Lu;T. Ren;Baoguo Li
传统的烘干法不能给出土壤中结合水含量的准确信息。本研究的目的是确定分数的土壤水结合到土壤胶体使用热重（TG）技术。在室温至200 ° C的加热条件下，对原始土样和去除有机质后的土样，将结合水分为松散结合水（相当于常规烘干法测定的含水量）和紧密结合水（常规烘干法不能计算）。九个风干土壤，不同数量的粘土和OM含量，进行了测试。原始风干样品的结合水含量为0.54~5.22%，松散结合水约占80%，紧密结合水约占20%。按质量分数计算，土壤有机质的比吸水量是土壤矿物的10~40倍。然而，对于大多数矿质土壤，土壤矿物对束缚水的贡献（> 70%）远大于土壤有机质（<30%），因为矿物组分通常超过有机质组分。在有机质含量高而粘粒含量相对较低的土壤中，有机质对束缚水的贡献超过50%。土壤比表面积（SA）对束缚水含量有很大影响，SA与束缚水含量之间存在线性关系。
Conventional oven-drying method may not give accurate information of bound water content in soils. The objective of this study was to determine the fraction of soil water that is bound to soil colloids using the thermogravimetry (TG) technique. A heating program from room temperature (RT) to 200°C was developed to partition bound water into loosely bound water (equivalent to water content determined by conventional oven-drying method) and tightly bound water that was not accounted by conventional oven-drying method on original and organic matter (OM) removed soil samples. Nine air-dry soils, with varying amounts of clay and OM contents, were tested. For the original air-dry samples, bound water content ranged from 0.54 to 5.22%, and the fractions of loosely and tightly bound water were about 80 and 20%, respectively. On a mass fraction basis, the specific water adsorption capacity of soil OM was 10 to 40 times that of soil minerals. For most mineral soils, however, the contribution of soil minerals to bound water (>70%) was much larger than that of soil OM (<30%), since the mineral fraction usually dominates over the OM fraction. In a soil with high OM concentration but a relatively low clay content, OM contribution to bound water exceeded 50%. Soil specific surface area (SA) showed a strong influence on bound water content, and a linear relationship between SA and bound water content was established.