Patrick Kwon, Deepesh Karmacharya, Edward Kavazanjian Jr., Claudia E. Zapata, Leon A. van Paassen
{"title":"细沙和淤泥层分层土壤中微生物诱导的脱饱和与降水","authors":"Patrick Kwon, Deepesh Karmacharya, Edward Kavazanjian Jr., Claudia E. Zapata, Leon A. van Paassen","doi":"10.1007/s11440-024-02324-w","DOIUrl":null,"url":null,"abstract":"<div><p>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 CaCO<sub>3</sub> 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 CaCO<sub>3</sub> had a relatively large impact on the saturated hydraulic conductivity but a very limited impact on the SWCC.</p></div>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Microbial-induced desaturation and precipitation in stratified soils with fine sand and silt layers\",\"authors\":\"Patrick Kwon, Deepesh Karmacharya, Edward Kavazanjian Jr., Claudia E. Zapata, Leon A. van Paassen\",\"doi\":\"10.1007/s11440-024-02324-w\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>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 CaCO<sub>3</sub> 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 CaCO<sub>3</sub> had a relatively large impact on the saturated hydraulic conductivity but a very limited impact on the SWCC.</p></div>\",\"PeriodicalId\":49308,\"journal\":{\"name\":\"Acta Geotechnica\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.6000,\"publicationDate\":\"2024-04-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Acta Geotechnica\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s11440-024-02324-w\",\"RegionNum\":1,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"ENGINEERING, GEOLOGICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta Geotechnica","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s11440-024-02324-w","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, GEOLOGICAL","Score":null,"Total":0}
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.
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.