Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studi...Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.展开更多
The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated...The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated either by actively metabolizing cells of anaerobic microbes and aerobic halophilic archaea or by their inactive biomass.Aerobic halophilic bacteria are widely distributed in(proto-)dolomite-depositing evaporitic environments and their biomass might serve as a template for the crystallization of protodolomite.To test this hypothesis,carbonation experiments were conducted using dead biomass of an aerobic halophilic bacterium(Exiguobacterium sp.strain JBHLT-3).Our results show that dead biomass of JBHLT-3 can accelerate Mg2+uptake in carbonate mineral precipitates.In addition,the amount of Mg incorporated into Ca-Mg carbonates is proportional to the concentration of biomass.High Mg-calcite is produced with 0.25 or 0.5 g/L biomass,whereas protodolomite forms with 1 g/L biomass.This is confirmed by the main Raman peak of Ca-Mg carbonates,which shifts towards higher wavenumbers with increased Mg substitution.Microbial cells and their imprints are preserved on the surface of high Mg-calcite and protodolomite.Hence,this study furthers our understanding of the dolomitization within buried and dead microbial mats,which provides useful insights into the origin of ancient dolomite.展开更多
基金supported by the National Parks Board,Singapore,and the Cities of Tomorrow R&D programme(Grant No.COT-V1-2020-4)by Ministry of National Development and National Research Foundation,Singapore.
文摘Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.
基金jointly supported by the National Natural Science Foundation of China(Nos.42272046,42072336 and 41772362)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB26000000)+1 种基金the 111 Project of China(No.BP0820004)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGCJ1703)。
文摘The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated either by actively metabolizing cells of anaerobic microbes and aerobic halophilic archaea or by their inactive biomass.Aerobic halophilic bacteria are widely distributed in(proto-)dolomite-depositing evaporitic environments and their biomass might serve as a template for the crystallization of protodolomite.To test this hypothesis,carbonation experiments were conducted using dead biomass of an aerobic halophilic bacterium(Exiguobacterium sp.strain JBHLT-3).Our results show that dead biomass of JBHLT-3 can accelerate Mg2+uptake in carbonate mineral precipitates.In addition,the amount of Mg incorporated into Ca-Mg carbonates is proportional to the concentration of biomass.High Mg-calcite is produced with 0.25 or 0.5 g/L biomass,whereas protodolomite forms with 1 g/L biomass.This is confirmed by the main Raman peak of Ca-Mg carbonates,which shifts towards higher wavenumbers with increased Mg substitution.Microbial cells and their imprints are preserved on the surface of high Mg-calcite and protodolomite.Hence,this study furthers our understanding of the dolomitization within buried and dead microbial mats,which provides useful insights into the origin of ancient dolomite.
