煤矿区重构土壤剖面水气变化及其对温度梯度的响应

Variation of water and air in reconstruction soil profile and its response to temperature gradient in coal mine area

  • 摘要: 煤矿区用煤矸石作为基质进行土壤重构,恢复生态环境和土地复垦的立地条件工程大量存在。但是,煤矸石氧化放热过程会对重构土壤剖面的水气变化产生影响,进而影响矿区生态修复的效果。为了研究重构土壤的水气运动特征及其对温度梯度的响应,设计了一种重构土壤水气热耦合运移室内模拟装置。在重构土壤不同深度布设温湿度传感器连续监测重构土壤剖面含水量和温度,利用CO2体积分数检测仪测定不同深度CO2体积分数,并通过底部的加热装置对重构土壤进行加热,研究重构土壤温度分布及其对水气运动的影响。结果表明:Hydrus-1D软件能较好地模拟重构土壤剖面体积含水量分布,但水分入渗过程存在明显的滞后性,水分在土壤层累积。气体在扩散过程中也表现出了明显的滞后性,在80 cm矸石层累积。当底部加热时,重构土壤剖面会形成稳定的温度梯度。在温度梯度的作用下,重构土壤中的水分会从底部向上运动,导致底层含水量明显降低,而其他层的含水量均明显上升,其中60 cm层的含水量增速最大,为0.057%/h。此时,气体易在矸石层及层间界面累积,并且累积效应随着温度梯度的增加而增强。温度和含水量均会影响重构土壤气体的扩散,但温度梯度的增加会削弱含水量对气体扩散的影响。另外,在重构土壤层间界面可能存在一个“障碍带”,当水分和气体接触到层间界面“障碍带”时开始受阻,从而导致水分在土壤层开始累积,气体在矸石层及层间界面累积。

     

    Abstract: There are a large number of engineering projects that use coal gangue as a substrate for ecological en-vironment restoration and land reclamation in coal mine area.However,the process of coal gangue oxidation and heat release will affect the water and gas changes in reconstruction soil profile,which can affect the effects of ecological restoration.An experimental simulation system in laboratory for studying water transport and gas-heat diffusion of the reconstruction soil was designed to study the characteristics of water and air movement of recon-structed soil and its response to temperature gradient.The system could be used for constantly measuring soil content,temperature and soil CO2 concentration by laying sensors and detectors in different depth of reconstructed soil and heating the reconstruction soil at the bottom to study the influences of gradient temperature on water and air movement.The results showed that the Hydrus-1D software could better simulate the water content distribution in reconstruction soil.However,the water infiltration process had an obvious hysteresis,which leaded to water accumulate in the soil layer.The gas also showed an obvious hysteresis during the diffusion process,which accumulated in gangue layer at 80 cm.When the bottom was heated,the reconstruction soil profile will form a stable temperature gradient.Under the action of temperature gradient,water moved up from the bottom,leading to a significant decrease in the water content of the bottom layer,while the water content of other layers increased significantly in the reconstructed soil.Among them,the water content of the 60 cm layer was fastest growing at 0.057%/h.In addition,the air accumulated in the coal gangue layer and the interlayer interface,and the cumulative effect increased with the temperature gradient increase.Temperature and water content all can affect the air diffusion in the reconstruction soil,but the increase of temperature gradient will weaken the influences of water content on the air diffusion.In addition,there may be a “barrier belt” in the interlayer interface of the reconstructed soil.Thus,water and air are blocked,causing the accumulation of water in soil layer and air in coal gangue layer and interlayer interface.

     

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