土地整治中底泥质耕作层土壤的构建方法及应用效果

摘要

开展底泥质耕作层土壤的构建方法研究，是确保土地整治工程质量和效益的重要举措。该研究以河流疏浚底泥土地利用为主线，从底泥质耕作层土壤构建方法的基础理论、底泥环境肥力调查评价、底泥重金属稳定化修复、底泥改造土壤工程及底泥应用案例等方面系统地探讨了土地整治工程中底泥质耕作层土壤构建方法的基础、内容、设计方法、施工工艺、工程参数。污染底泥修复后大田种植空心菜试验表明：重金属含量可达到无公害蔬菜安全标准、Cd降低率在38.61%～85.69%，稳定化修复明显降低蔬菜重金属含量；底泥质耕层土壤适宜开展种植，可提蔬菜高产量8.7%～13%，增加土壤有机质含量0.95～2.18倍。%Land treatment is to comprehensively treat the lands that are ineffectively and improperly used, or undeveloped. Soil at the tillage layer is an essential part for agriculture so its treatment is a key component for land treatment. Currently, surface soil peeling technology and soil replacement method are adopted on land treatment and reclamation engineering. However, there are problems such as limited amount of soil replacement sources, large deviation on application costs, incomplete technical methodology, irregular engineering process, and poor application efforts. Utilization of dredging sediment from rivers is one of the most emerging disposal methods. Sediment pollution and ecological risk assessment, sediment metals remediation technologies, land utilization parameters, sediment food safety assessment, are important factors affecting sediment utilization. For the scarcity issue on regional soil at the tillage layer, this study focused on dredging sediment utilization, and analyzed the related theories, scopes, design method, engineering process and application efforts on construction of tillage layer soil using the sediment. The outcome of the research was significant for both improving land treatment and maintaining the sustainability of farmland. Our results showed that tillage layer soil construction was under the scope of land treatment, using dredging sediment with proper farmland treatment process and with the aid of certain physical and chemical methods. This method must consider the principles for environment, agrology, and food safety. For sediment heavy metal stabilization remediation design, we proposed optimal stabilizers and engineering process. All of those facilitated the formulation of post-remediation soil modification engineering approach; and its related monitoring and assessment on implementation efforts. Also, to take samples according to “Sediment quality survey and Assessment Handbook”, based on the targets of sediment utilization and monitoring data and documents like “Soil environmental quality standard”(GB15618-1995); “Farmland environmental quality evaluation standards for edible agricultural products”(HJT332-2006), “National secondary soil survey related standard—fertility indicators and evaluation limits”, the sediment environmental impact and fertility were evaluated. Sediment quality less than slight pollution and fertility at the Level II can be considered for utilization. The spatial analysis on sediment environment and fertility evaluation by GIS, the strategies on integrated river sediment utilization direction, spatial distribution and stock could be identified. This provided references on stratified sediment dredging. In addition, for sediment heavy metal stabilization, typical contaminated sediment samples were selected for stabilization experiments. The test in laboratory was done by adding phosphates, magnesium oxides, or clay minerals using an orthogonal design. The results showed that both stabilized BCR(European Comuntities Burean of Reference) form of metals and leaching toxicity reached the standards. Therefore, the constituents for treatments can be considered as the optimal stabilizing agents. Considering water content and stabilization period, the effective, low-cost and operable stabilizer dosage, remediation process, and parameters were proposed to finalize the sediment heavy metal stabilization approach. Moreover, sediment modification on soil remediation process needed to consider the regional topography and landscape, irrigation system, transportation, farmland protection, and other engineering conditions. By combining sediment pavement, land peeling, sediment heavy metal stabilization remediation into the project design, the feasible measure on building the sediment phase tillage layer soil was formulated. Last, through the experiment on spinach planted, the results showed that the heavy metal content in the spinach can achieve the nuisance-free level, reducing Cd content by 38.61%-85.69%, so it can obviously reduce heavy metal in vegetables. Sediment phase tillage layer soil is suitable for cultivation, raising productivity by 8.7%-13%, improving soil organic content by 0.95-2.18 times.