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引用本文:陈学军,姜宝良,张晓偲.应用三维图像和数学模型对土壤团聚体内外溶质的交换速率的研究[J].灌溉排水学报,2017,36(8):.
CHEN Xuejun,JIANG Baoliang,ZHANG Xiaocai.应用三维图像和数学模型对土壤团聚体内外溶质的交换速率的研究[J].灌溉排水学报,2017,36(8):.
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应用三维图像和数学模型对土壤团聚体内外溶质的交换速率的研究
陈学军, 姜宝良, 张晓偲
济源职业技术学院,河南 济源 454650; 华北水利水电大学, 郑州 450016
摘要:
受土壤有机质和微生物的影响,大部分农业土壤都有团聚体结构。团聚体内部的孔隙一般很小,与团聚体之间的水流相比,团聚体内部的水可以视为不动的。但受质量浓度梯度和分子扩散的影响,2个水体内的溶质可以相互交换。模拟溶质在具有团聚体结构土壤中运移时,溶质在以上2个水体间的交换过程常用可动-不可动水体模型来描述。土壤溶质运移涉及的参数较多,很多参数不能直接测定,要靠观测值拟合才能获得。由于不同的参数组合可以得出相同溶质质量浓度分布,因此,即使模拟结果和实验结果吻合也不能确保该模型正确描述了2个水体之间的溶质交换过程。为了深入研究这一问题,利用三维图像技术和数学模型,计算了团聚体内外溶质交换速率。结果表明,Coats-Smith模型误差很大,2个水体之间的溶质交换速率并非与其质量浓度差成正比。作为改进,提出并证明广义γ分布函数可以准确地描述团聚体内外溶质交换过程。
关键词:  溶质运移; X射线扫描; 土壤;团聚体; 可动-不可动水体模型; 记忆函数
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Calculating Mass Transfer Between Waters inside and between Aggregates in Aggregated Soils Using Tomography and Pore-scale Modelling
CHEN Xuejun, JIANG Baoliang, ZHANG Xiaocai
Jiyuan Vocational and Technical College, Jiyuan 454650, China; North China University of Water Resources and Electric Power, Zhenzhou 450016, China
Abstract:
Most natural soils are aggregated due to the impact of soil organic matters and soil micro organisms. In aggregated soil, mass transfer between waters inside and between its aggregates is an important process for soil to retain and supply water and nutrients, but is difficult to measure experimentally. Therefore, in chemical transport modelling such mass transfer is often described using an empirical memory function with its parameters obtained by calibrating against experimental data. In practical applications, however, it is impossible to judge that a calibrated memory function correctly describes the processes occurring in soil or it is just a bridge to link model and measurements. Instead of using empirical memory function, we propose in this paper to directly calculate it using soil image and pore-scale modelling. Images of three soils are acquired using x-ray computed tomography at resolution of 30 μm with the between aggregates pores and aggregate geometries explicitly resolved. The mass transfer between solute inside and between the aggregates is calculated using a pore-scale modeling for difference solutes. The results showed that the commonly used exponential memory function associated with the mobile-immobile water model is unable to describe the mass exchange in all three soils. As an improvement, we propose and prove a generalized gamma distribution to describe the mass exchange processes.
Key words:  mass transfer; X-ray micro-tomography; aggregated soils; pore-scale modelling; mobile-immobile water model