土壤硼吸附热及温度对硼滞后解吸特性影响的研究

THE STUDIES ON SOIL BORON ADSORPTION HEAT AND TEMPERATURE EFFECT ON PROPERTIES OF BORON HYSTERETIC DESORPTION

对棕红壤（9701）、黄棕壤（9702）和灰潮土（9703）在25℃和40℃条件下，硼吸附一解吸特性，土壤硼吸附热以及温度对土壤础滞后解吸的影响进行了研究。结果表明，9701、9702和9703号土壤用的吸附热分别为－15．4、－15．6和－22．6kJ／mol，处于化学吸附热的范围，从热力学上证明了棚在土壤上专性吸附的存在。与25℃相比，40℃时土壤硼滞后解吸得到加强。与此相应，施入土壤中的外源硼，夏季与春季相比，其解吸率分别下降了38％、19％和7％。这些结果可以解释在夏季，土壤缺硼并不在于硼在土壤上的吸附减弱，而是土壤用滞后解吸在高温下得到加强的缘故。

The properties of adsorption-desorption, adsorption heat and hysteretic desorption of boron effected by temperature in brown-red soil (9701), yellow-brown soil (9702),and calcareous alluvial soil (9703) collected in Hubei Province of China have been studied, The results showed that the adsorbed boron was more in 25℃ than that in 40℃, i. e., boron adsorption reaction was exothermic. The boron adsorption heat of 9701, 9702, and 9703 calculated with equilibrium constant of the Langmuir adsorption equation in 25℃ (K1) and 40℃ (K2) were - 16.4, - 15.6, and - 22.6kJ/ moL,respectively. These values were within the range of chemical adsorption heat and it was testified in thermodynamics that boron adsorption in soil is mainly a kind of chemical specific adsorption. In comparison with 25℃, that hysteretic desorption of boron in the experimental soils was higher in 40℃, the hysteretic coefficients of boron of 9701, 9702, and 9703 were enhanced to 67%, 21%, and 62%, respectively.Being corresponding with the propenies of soil boron adsorption-desorption, the desorption ratio of added boron of 9701, 9702, and 9703 in the summer were lowed by 38%,19%, and 7% than in the spring, respectively. These may explain that lack of soil boron in the summer was caused by increase of boron hysteretic desorption in soil in higher temperature, not by decrease of boron adsorption in soil.