细沙和淤泥层分层土壤中微生物诱导的脱饱和与降水

IF 5.6 1区 工程技术 Q1 ENGINEERING, GEOLOGICAL
Patrick Kwon, Deepesh Karmacharya, Edward Kavazanjian Jr., Claudia E. Zapata, Leon A. van Paassen
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引用次数: 0

摘要

为了评估微生物诱导的脱饱和沉淀法(MIDP)在分层土壤条件下的效果,我们在一米的范围内进行了模拟二维平面流动条件的水槽试验。水槽设置(高 116.5 厘米、宽 122 厘米、厚 5.25 厘米)中装有两层细沙(目标层 40 厘米,非目标层 21 厘米),沙层上方(6 厘米)、中间(9 厘米)和下方(9 厘米)分别有淤泥层。多次向下部沙层注入含有钙、硝酸盐和醋酸盐的基质溶液,以刺激本地硝酸盐还原菌产生生物气体、生物矿物质和生物量。嵌入式传感器用于测量目标砂层和非目标砂层在处理周期内和处理周期之间的电导率、体积含水量和孔隙压力的变化。延时摄影机图像用于确定目标层的流速分布,并识别气体迁移模式。试验结束后,对处理过的材料的完整样本进行了水力传导性、碳酸钙含量和土壤-水特性曲线(SWCC)测量。结果表明,大部分反应产物都在目标砂层中形成。在第一个处理周期中,目标砂层中的饱和度在 5-12 天内下降到 75%,此时饱和度开始向上迁移,直至被截留并在上方淤泥层下形成透镜状。在第二个和随后的处理周期中,由于生物气体被截留,渗流速度加快,生物量积累导致反应速度加快,气体在淤泥中形成通道,并通过不规则的排气事件进一步向上迁移到上层砂层和淤泥中。经过 4-5 个周期后,达到平衡状态,饱和度从气体产生和排出时的 65% 至 80% 波动到基质耗尽时的 80-90%。经过 12 周 10 次循环后,CaCO3 含量从靠近入口处的 1.6% 到靠近出口处的 0.5%,平均为 0.68%。生物质和 CaCO3 的形成对饱和水力传导率的影响相对较大,但对 SWCC 的影响非常有限。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Microbial-induced desaturation and precipitation in stratified soils with fine sand and silt layers

Microbial-induced desaturation and precipitation in stratified soils with fine sand and silt layers

A tank test was performed simulating two-dimensional planar flow conditions at a meter scale to evaluate the effectiveness of microbial-induced desaturation and precipitation (MIDP) in stratified soil conditions. The tank setup (116.5 cm tall, 122 cm wide, and 5.25 cm thick) was filled with two layers of fine sand (a target layer of 40 cm and nontarget layer of 21 cm above) that were confined by silt layers above (6 cm), between (9 cm) and below (9 cm) the sand layers. Multiple flushes of substrate solution, containing calcium, nitrate, and acetate, were injected into the lower sand layer to stimulate indigenous nitrate-reducing bacteria to produce biogenic gas, biominerals, and biomass. Embedded sensors were used to measure the changes in electrical conductivity, volumetric water content, and pore pressure in both the target and nontarget sand layers during and between treatment cycles. Time-lapse camera images were used to determine flow velocity distributions in the target layer and identify modes of gas migration. At the end of the test, hydraulic conductivity, calcium carbonate content, and soil–water characteristic curves (SWCCs) were measured on intact samples of the treated material. The results showed that most of the reaction products were formed in the targeted sand layer. During the first treatment cycle, the degree of saturation in the target sand layer decreased to 75% within 5–12 days, at which point it started to migrate upwards until it got trapped and formed a lens underneath the silt layer above. During the second and subsequent treatment cycles, seepage velocity increased due to the entrapment of biogenic gas, the reaction rate increased due to the accumulation of biomass, and the gas formed channels through the silt and migrated further upwards into and through the upper sand and silt layers by irregular venting events. After 4–5 cycles, an equilibrium condition was reached at which the degree of saturation fluctuated from 65 to 80% when gas was being produced and vented to 80–90% when substrates were depleted. The CaCO3 content after 10 cycles over 12 weeks ranged from 1.6% close to the inlet to 0.5% close to the outlet, with an average of 0.68%. The formation of biomass and CaCO3 had a relatively large impact on the saturated hydraulic conductivity but a very limited impact on the SWCC.

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来源期刊
Acta Geotechnica
Acta Geotechnica ENGINEERING, GEOLOGICAL-
CiteScore
9.90
自引率
17.50%
发文量
297
审稿时长
4 months
期刊介绍: Acta Geotechnica is an international journal devoted to the publication and dissemination of basic and applied research in geoengineering – an interdisciplinary field dealing with geomaterials such as soils and rocks. Coverage emphasizes the interplay between geomechanical models and their engineering applications. The journal presents original research papers on fundamental concepts in geomechanics and their novel applications in geoengineering based on experimental, analytical and/or numerical approaches. The main purpose of the journal is to foster understanding of the fundamental mechanisms behind the phenomena and processes in geomaterials, from kilometer-scale problems as they occur in geoscience, and down to the nano-scale, with their potential impact on geoengineering. The journal strives to report and archive progress in the field in a timely manner, presenting research papers, review articles, short notes and letters to the editors.
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