生物炭对东北草甸黑土水力特性影响的数值化研究

Numerical Investigation on Effects of Biochar on Hydraulic Characteristics of Northeast Meadow Black Soil

为探究生物炭对东北草甸黑土水力学特性的影响,建立适用于添加生物炭后的土壤模型,以5种生物炭体积比(0、2%、4%、6%、8%)施入土壤,对土壤水分运动参数进行了试验和数值分析研究。结果表明,添加生物炭后土壤持水能力的增加主要是生物炭大于2 200 cm吸力范围持水能力的提升,土壤导水性能的改善是由于生物炭在小于35.82 cm吸力段具有良好的导水特性。饱和导水率试验结果表明,添加生物炭后土壤的饱和导水率接近于生物炭层状分布的理论结果,最大偏差为8.9%。采用毛细管模型模拟了添加生物炭的土壤在渗水24 h后的水分分布情况,模拟计算的饱和度与实际测量值相比偏低11%左右,这说明毛细管模型很好地导出添加生物炭后土壤的非饱和导水特性。该研究结果可为不同生物炭施加量、施加面积、地势、渗透时间的土壤水力学特性研究提供方法与保障。

In order to study the effect of biochar on the hydraulic characteristics of northeast meadow black soil,establish the model suitable for the soil with addition of biochar,and the ratio（ 0,2%,4%,6% and 8%） biochar was applied to soil,and the soil hydraulic parameters were tested and numerically analyzed. The results showed that the increase of soil water holding capacity was due to the high ability of water holding capacity of biochar greater than 2 200 cm suction range,and the improvement of hydraulic conductivity was due to the hydraulic conductivity of biochar at low suction range that lower than35. 82 cm. Compared saturated hydraulic conductivity test data with theoretical estimate value,it was showed that the actual measurement values were closed to layered distribution,the max difference was about 8. 9%,added biochar soil should be considered as layered distribution. The difference between experimental data and theoretical values was due to the increase of gap in soil by biochar. The water distribution of the soil after infiltrated 24 h was simulated by capillary model. The saturation of simulation was 11% lower than actual measured value,which showed that the unsaturated hydraulic conductivity of soil with addition of biochar was fit in capillary model. According to the results of capillary model,the hydraulic conductivity of soil that added biochar was mainly due to the characteristics of biochar,it mainly changed the hydraulic conductivity of soil under low suction. The results showed that application of biochar can improve the hydraulic conductivity of northeast meadow black soil of China,the higher content of biochar added was,the higher hydraulic conductivity was increased. The results also showedthat the number of different aperture of capillary was not evenly distributed in biochar,the smaller the aperture was,the more number of capillary was. The capillary model was simple and effective,when the volume ratio of biochar in soil was less than 8%,the numerical analysis results were in good agreement with those obtained with the test data of soil,and it was showed that the model can provide accurate method for numerical calculation. The results can provide a method and guarantee for the study of soil hydrodynamic characteristics under certain biochar application,different areas,different terrains and different permeation times.