Effects of subsurface drainage treatments on chlorine content in Mudflat Soil

摘要

To improve the soil condition in coastal area, subsurface drainage projects with different depth and space were established, and the materials were bellows combining with 40g/m~2 geotechnical cloth and forage; in the study, the economic benefits were evaluated, and the soil samples before and after one typical rainfall were taken and observed. Results showed that the subsurface drainage system was proved to be feasible, with the EIRR of about 14.3%, ENPV of about 2697 $/hm~2, and EBCR of about 1.36. On the other hand, subsurface drainage projects decreased the contents of Cl~- in different soil layers significantly, especially T4, which obtained the optimum results, decreasing Cl~- of each soil layer by more than 50% after the rainfall. From the observation results of the deeper soil, it was discovered that the lower depth was negative to the Cl~- elimination in deeper soil layer. In practical, 0.9m depth and 10m space was appropriate for the application. Besides, the management and improvement of later stage were also important, in the reality situation of project conducted, the sludge elimination of the drainage pipes should be regarded as chief issue in later utilization of the drainage project.