长期再生水灌溉后土壤孔隙分布的多重分形特征

Multifractal characteristics of soil pore distribution after long-term recycled water irrigation

土壤结构是表征土壤质量的重要指标之一.为了定量表征长期再生水灌溉后土壤孔隙分布的非均匀性,以不同年限再生水灌溉后的土壤为研究对象,采用KYKY-2800B型扫描电子显微镜获取土壤数字图像,利用数字图像处理技术测定了土壤的孔隙分布特征,运用多重分形谱参数描述了土壤孔隙分布的非均质性,探讨了土壤孔隙分布多重分形曲线对称性的意义.结果表明:多重分形谱可以定量描述土壤孔隙分布的非均质性,土壤孔隙分布的多重分形奇异谱函数α-f(α)表现为非对称连续性分布,奇异谱宽度Δα表征了土壤孔隙分布的非均质特征;大兴区北野厂灌区农田土壤孔隙分布的多重分形谱宽度Δα普遍大于石景山衙门口灌区土壤,即具有30 a再生水灌溉历史的土壤其孔隙分布的非均匀性较50 a再生水灌溉历史的土壤孔隙分布的非均匀性大,且北野厂灌区土壤小孔隙的数目小于石景山衙门口灌区土壤小孔隙数目.多重分形参数可以作为定量表征土壤孔隙分布非均匀性的重要指标.

Soil structure is one of important indicators for characterizing soil quality. For quantitative characterization of heterogeneity of soil pore distribution after long term recycled water irrigation, the characteristics and heterogeneity of soil pore distribution after recycled water irrigation for various years were analyzed based on KYKY-2800B scanning electron microscope, digital image processing technology and multifractal theory, and then the significance of symmetry of multifractal curve was discussed. The result show that the multifractal spectrum can quantitatively describe the heterogeneity of soil pore distribution, and its multifractal singularity spectrum function α-f（α） is continuous and asymmetric, the width of multifractal spectrum Δ α can reflect the heterogeneous charac- teristics of the pore distribution. The width of multifractal spectrum Δ α in Beiyechang Irrigation District is generally greater than that in Yamenkou Irrigation District, i.e. the pore distribution is more heterogeneous after 30 years recycled water irrigation compared with 50 years recycled water irrigation, and the number of small pores in Beiyechang Irrigation District is more than the number in Yamenkou Irrigation District. As a result, multifractal parameters can be used as important indicators to characterize the heterogeneity of soil pore distribution quantitatively.