污水灌溉下土壤孔隙特征的CT定量分析

污水中的悬浮物、盐分和有机营养物对土壤孔隙状况产生了深刻的影响.通过室内模拟和CT(computed tomography)扫描的方法, 定量研究污水灌溉条件下土壤孔隙数、孔隙度及形态特征.结果表明: 与对照点相比, 污水灌溉区上层土壤总孔隙数和大孔隙数(当量直径≥1.00 mm)均显著升高, 而下层土壤总孔隙数、大孔隙数、粗孔隙数(当量直径为0.26~1.00 mm)、总孔隙度、大孔隙度和粗孔隙度均显著降低(p＜0.05);在模拟悬浮液和盐液灌溉条件下, 土壤总孔隙数、粗孔隙数和粗孔隙度均有所升高, 而大孔隙数、总孔隙度、大孔隙度和孔隙成圆率均有所降低; 在模拟营养液灌溉条件下, 土壤总孔隙数、大孔隙数、粗孔隙数和粗孔隙度均有所增加, 而孔隙成圆率有所降低; 对于研究区土壤来说, 悬浮液灌溉对土壤孔隙的影响效应强于盐液灌溉; 对于同种性质的污水灌溉来说, 污灌对对照点土壤孔隙的影响效应强于污灌区土壤. 

Quantitative Analysis of Soil Pores under Sewage Irrigation Using Computerized Tomography

The suspension solids, salts and organic nutrients in sewage efflunts can significantly affect soil porosity condition. Based on the laboratory simulation and computed tomography, the numbers of soil pores, porosity and shape were quantitatively studied under the condition of irrigation with sewage. The results show that the soils irrigated with sewage effluents exhibited higher total pore numbers and macropore numbers(≥1.00 mm in diameter) in the upper layer but lower total pore numbers, macropore numbers, coarse pore numbers (0.26-1.00 mm in diameter), total porosity, macroporosity and coarse porosity in the subsoil layer when compared with the soils irrigated with groundwater (p < 0.05). Under the condition of irrigation with suspension or with salt solution, total pore numbers, coarse pore numbers and coarse porosity increased, while macropore numbers, total porosity, macroporosity and cycle rate decreased. Under the condition of irrigation with nutrient solution, total pore numbers, macropore numbers, coarse pore numbers and coarse porosity increased, while macroporosity and cycle rate decreased. For the soil in the study fields, the effect of irrigation with suspension on the soil pores was stronger than that with salt solution. For the same irrigation with suspension or with salt solution, the effect of sewage irrigation on pores in groundwater irrigated soils was stronger than that in sewage irrigated soils.