非饱和土基质吸力对溶质Br~-垂向迁移影响试验研究
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摘要
研究非饱和土溶质迁移的影响因素对控制溶质污染及防治措施均有着积极意义。通过室内非饱和土柱淋溶试验,在3种质地和两种初始含水率条件下研究土中基质吸力对溶质Br~-垂向迁移的影响。结果得出,在连续降雨条件下,3种质地土的基质吸力均呈"上升—聚降—平稳"的变化趋势,其中粉黏土降雨历时比砂壤土和细砂土分别慢60、100 h,其基质吸力相比最大,最大值达84. 07 k Pa;在各含水率条件下,较低含水率土中基质吸力变幅更大,表现更为活跃;另外,溶质Br~-垂向迁移受基质吸力影响显著,在低基质吸力段内(小于20 k Pa),Br~-浓度随基质吸力的减小而骤降,而在较高吸力段上(大于20 k Pa),Br~-浓度随基质吸力的减小呈增大趋势。因此,通过调节土壤理化性质,改变土中基质吸力来控制溶质迁移,缓减或防治土壤污染。
The study on the influencing factors of solute migration in unsaturated soil has positive significance for controlling solute pollution and measures. Through indoor unsaturated soil-column leaching experiment, this paper devoted to study the influence of soil matrix suction on the vertical migration of solute Br~-under three soil textures and two types of initial water content. The result was as follows, under the condition of continuous rainfall, the matrix suction of three soil species showed the same tendency of rise-sudden drop-smooth, however, the rainfall duration of silty clay was 60 h shorter than that of sandy loam and 100 h shorter than that of fine sand, meanwhile its matrix suction was the strongest with a maximum of 84. 07 k Pa. In soils with different initial water contents, the matrix suction of soil with lower water content was more active and had a relatively wider variation range. The vertical migration of solute Br~-was distinctly effected by soil matrix suction, and the law was different among different suction scope. In low suction range( < 20 k Pa), the Br~-concentration was sharply dropping with the reduction of matrix suction. However, in higher suction range( >20 k Pa), the Br~-concentration was gradually increasing with the reduction of matrix suction. In conclusion, the soil contamination could be relieved or prevented by controlling solute migration through adjusting soil physicochemical property to change the soil matrix suction.
The study on the influencing factors of solute migration in unsaturated soil has positive significance for controlling solute pollution and measures. Through indoor unsaturated soil-column leaching experiment, this paper devoted to study the influence of soil matrix suction on the vertical migration of solute Br~-under three soil textures and two types of initial water content. The result was as follows, under the condition of continuous rainfall, the matrix suction of three soil species showed the same tendency of rise-sudden drop-smooth, however, the rainfall duration of silty clay was 60 h shorter than that of sandy loam and 100 h shorter than that of fine sand, meanwhile its matrix suction was the strongest with a maximum of 84. 07 k Pa. In soils with different initial water contents, the matrix suction of soil with lower water content was more active and had a relatively wider variation range. The vertical migration of solute Br~-was distinctly effected by soil matrix suction, and the law was different among different suction scope. In low suction range( < 20 k Pa), the Br~-concentration was sharply dropping with the reduction of matrix suction. However, in higher suction range( >20 k Pa), the Br~-concentration was gradually increasing with the reduction of matrix suction. In conclusion, the soil contamination could be relieved or prevented by controlling solute migration through adjusting soil physicochemical property to change the soil matrix suction.
引文
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[8]GRIFOLL J,COHEN Y. Contaminant migration in the unsaturated soil zone:the effect of rainfall and evapotranspiration[J]. Journal of Contaminant Hydrology,1996,23:185-211.
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[12]李洪,李鑫钢,黄国强,等.降雨蒸发条件下渗流区污染物迁移的数值模拟[J].化学工程,2007,35(9):51-54.
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[14]丁庆忠,许模,段永祥,等.成都平原粉土和粉砂土的土-水特征曲线研究[J].人民珠江,2016,37(3):29-31.
[15]黄巧云,李延轩.土壤学[M].北京:中国农业出版社,2005:52-54.
[16]WANG Q J,SHAO M G,HORTON R. A simple method for estimating water diffusivity of unsaturated soils[J]. Soil Sci.,2004,68(3):723-718.
[2]弗雷德·隆德,拉哈尔佐.非饱和土土力学[M].陈仲颐,译.北京:中国建筑工业出版社,1997.
[3]王铁行,王晓峰.密度对砂土基质吸力的影响研究[J].岩土力学,2003,24(6):979-982.
[4]栾茂田,李顺群,杨庆.非饱和土的理论土-水特征曲线[J].岩土工程学报,2005,27(6):612-615.
[5] INDRAWAN I G B,RAHARDJO H,LEONG E C. Effects of coarse-grained materials on properties of residual soil[J]. Engineering Geology,2006,82(6):154-164.
[6] KOOL J B,PARKER J C,VAN G M T. Parameter estimation for unsaturated flow and transport models-A review[J]. J of Hydrol,1987,91:255-293.
[7]左自波,张璐璐,王建华.降雨条件下非饱和土中污染物迁移的数值模拟[J].地下空间与工程学报,2011,10(7):1347-1352.
[8]GRIFOLL J,COHEN Y. Contaminant migration in the unsaturated soil zone:the effect of rainfall and evapotranspiration[J]. Journal of Contaminant Hydrology,1996,23:185-211.
[9]MARSHALL J D,SHIMADA B W,JAFFE P R. Effect of temporal variability in infiltration on contaminant transport in the unsaturated zone[J]. Journal of Contaminant Hydrology,2000,46:151-161.
[10]王福利.降雨淋洗条件下溶质在土壤中运移的初步研究[J].土壤学报,1992,29(4):451-457.
[11]王超.污染物在土壤及地下水中迁移转化规律的研究[D].南京:河海大学,1995:52-85.
[12]李洪,李鑫钢,黄国强,等.降雨蒸发条件下渗流区污染物迁移的数值模拟[J].化学工程,2007,35(9):51-54.
[13]王全九,邵明安,郑纪勇.土壤水分运动与溶质迁移[M].北京:中国水利水电出版社,2007.
[14]丁庆忠,许模,段永祥,等.成都平原粉土和粉砂土的土-水特征曲线研究[J].人民珠江,2016,37(3):29-31.
[15]黄巧云,李延轩.土壤学[M].北京:中国农业出版社,2005:52-54.
[16]WANG Q J,SHAO M G,HORTON R. A simple method for estimating water diffusivity of unsaturated soils[J]. Soil Sci.,2004,68(3):723-718.