Effective Vertical Solute Transport in Soils by Artificial Macropore System

Solute transport is an important factor governing soil environmental processes, such as effective fertilizer application or dispersion areas of remediation chemicals for contaminated soils. Macropores are ubiquitous in soils. In unsaturated conditions, they enhance air intrusion into soils, thus reducing the chances of clogging and surface ponding. However, their structure is hard to maintain, and they tend to collapse during long-term infiltration. In this experiment, macropore fillings were introduced into the pores to maintain their structure. Solute transport experiments were conducted for four soils with no macropores, empty macropores, macropores with paper towel fillings, and macropores with glass fiber fillings. The macropores with fillings worked as water pathways that conducted solutions to the deeper profile without saturation at the surface, thus avoiding clogging. When bio-remediation experiments were conducted using these four soil columns, soil columns with glass fiber fillings maintained 0.6-0.8 of the saturated water content, which was found to enhance biological activity. The resultant bio-remediation was best for glass fiber fillings because artificial macropores with fibrous fillings maintained a macropore structure, which gave a stable infiltration rate for 30 days. (C) 2014 American Society of Civil Engineers.