Nowadays,biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide attentions.However,the feasibility of using biopolymer as a green additive of cementstabilized dredg...Nowadays,biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide attentions.However,the feasibility of using biopolymer as a green additive of cementstabilized dredged sediment(CDS)with high water content is still unknown.In this study,guar gum(GG)and xanthan gum(XG)were adopted as typical biopolymers,and a series of unconfined compressive strength(UCS),splitting tensile strength(STS)and scanning electron microscopy(SEM)tests were performed to evaluate the mechanical and microstructural properties of XG-and GG-modified CDSs considering several factors including biopolymer modification,binderesoil ratio and wateresolid ratio.Furthermore,the micro-mechanisms revealing the evolutions of mechanical properties of biopolymermodified CDS were analyzed.The results indicate that the addition of XG can effectively improve the strength of CDS,while the GG has a side effect.The XG content of 9%was recommended,which can improve the 7 d-and 28 d-UCSs by 196%and 51.8%,together with the 7 d-and 28 d-STSs by 118.3%and 42.2%,respectively.Increasing the binderesoil ratio or decreasing the wateresolid ratio significantly improved the strength gaining but aggravated the brittleness characteristics of CDS.Adding XG to CDS contributed to the formation of microstructure with more compactness and higher cementation degrees of ordinary Portland cement(OPC)-XG-stabilized DS(CXDS).The micro-mechanism models revealing the interactions of multiple media including OPC cementation,biopolymer film bonding and bridging effects inside CXDS were proposed.The key findings confirm the feasibility of XG modification as a green and high-efficiency mean for improving the mechanical properties of CDS.展开更多
High-efficiency disposal of dredged sediment(DS)has become an imperative geo-environmental engineering issue due to the limited landfilling space and severe environmental burdens.This study firstly developed a novel h...High-efficiency disposal of dredged sediment(DS)has become an imperative geo-environmental engineering issue due to the limited landfilling space and severe environmental burdens.This study firstly developed a novel high-efficiency nano-modified and chemical-activated binary cement(NBC),which was composed of binary cement(BC)consisting ordinary Portland cement(OPC)and ground granulated blast-furnace slag(GGBS),chemical-activator and nano-modifier.The effects of chemical-activation and nano-modification on the strength development of BC-stabilized DS(BCDS),and the optimum mix of NBC were respectively achieved via a series of unconfined compressive strength and orthogonal tests.Then,the high-efficiency and economic applicability of NBC in DS stabilization were evaluated by comparing with OPC.Furthermore,the microstructure and mineral composition evolutions inside NBCstabilized DS(NDS)were explored by conducting X-ray diffraction(XRD)and scanning electron microscopy(SEM)tests.The results show that both chemical-activation and nano-modification could effectively improve the strength gain of BCDS,and compared with single chemical-activator and nanomodifier,the composite chemical-activators and nano-modifiers exhibited better performances.Based on BC with OPC/GGBS mass ratio of 1:1,both anhydrous sodium metasilicate/anhydrous sodium sulfate(SM/SS)and nano-SiO_(2)/nano-MgO(NS/NM)with mass ratio of 1:9 were respectively determined to be optimum chemical-activator and nano-modifier.The optimum mass ratio of BC,SM/SS and NS/NM was 20:2:1,i.e.the optimum mix of NBC.Compared with OPC,NBC exhibited higher stabilization efficiency and better economic applicability.The generation of calcium silicate hydrate(CSH),calcium aluminate hydrate(CAH)and ettringite contributed to the formation of dense cemented soil matrix inside NDS,and a conceptual micro-mechanism model characterizing the strength development under the coupling action of chemical-activation and nano-modification was proposed.展开更多
[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants in...[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants including FeCl3,Al2(SO4)3 and PAM were taken as dewatering agents which were added in dredged sediment.[Result] The results showed that Al2(SO4)3 had better dewatering effect than FeCl3 and PAM,and the optimum dosing quantity of Al2(SO4)3 in dredged sediment was 170 mg/L,in addition,the water quality of supernatant met the first class B standard of GB18918-2002 and could be directly discharged to nature water without pollution.[Conclusion] The study could provide a simple and feasible way for the rapid dewatering of dredged sediment from Dianchi Lake,which would be convenient for the disposal and resource utilization of dredged sediment.展开更多
The fractal model about water characteristics of solidified sediment was built according to the granular metric analysis curve of solidified dredged sediment, the measured value during the low-suction stage of the cur...The fractal model about water characteristics of solidified sediment was built according to the granular metric analysis curve of solidified dredged sediment, the measured value during the low-suction stage of the curing process was used for fitting parameters in the model to obtain the complete water characteristic curve of solidified dredged sediment. Then, the quantitative calculation model of capillary water, attached water, evaporated water and bound water was built by the water characteristic curve and from the view of quantitative angle, the paper analyzed the solidification mechanism of solidified dredged sediment. The result showed that： the model can realize the quantitative calculation about different tapes of water during the curing process, the evaporated water during the curing process mainly came from the capillary water, and the generated bound water during the curing reaction came from the attached water.展开更多
This study evaluated the feasibility of using polypropylene fiber(PF)as reinforcement in improving tensile strength behavior of cement-stabilized dredged sediment(CDS).The effects of cement content,water content,PF co...This study evaluated the feasibility of using polypropylene fiber(PF)as reinforcement in improving tensile strength behavior of cement-stabilized dredged sediment(CDS).The effects of cement content,water content,PF content and length on the tensile strength and stress–strain behavioral evolutions were evaluated by conducting splitting tensile strength tests.Furthermore,the micro-mechanisms characterizing the tensile strength behavior inside PF-reinforced CDS(CPFDS)were clarified via analyzing macro failure and microstructure images.The results indicate that the highest tensile strengths of 7,28,60,and 90 d CPFDS were reached at PF contents of 0.6%,1.0%,1.0%,and 1.0%,exhibiting values 5.96%,65.16%,34.10%,and 35.83%higher than those of CDS,respectively.Short,3 mm,PF of showed the best reinforcement efficiency.The CPFDS exhibited obvious tensile strain-hardening characteristic,and also had better ductility than CDS.The mix factor(C_(C)^(a)/C_(w)^(b))and time parameter(q_(t0)(t))of CDS,and the reinforcement index(k_(t-PF))of CPFDS were used to establish the tensile strength prediction models of CDS and CPFDS,considering multiple factors.The PF“bridge effect”and associated cementation-reinforcement coupling actions inside CPFDS were mainly responsible for tensile strength behavior improvement.The key findings contribute to the use of CPFDS as recycled engineering soils.展开更多
In this study,the dredged river sediment,soft texture and fine particles,is mixed with other materials and transformed into eco-friendly autoclaved aerated concrete(hereinafter referred to as AAC)blocks.The results in...In this study,the dredged river sediment,soft texture and fine particles,is mixed with other materials and transformed into eco-friendly autoclaved aerated concrete(hereinafter referred to as AAC)blocks.The results indicated the bricks produced under the conditions of 30%–34%dredged river sediment,24%cement,10%quick lime,30%fly ash,2%gypsum and 0.09%aluminum powder with 0.5 water to material ratio,2.2 MPa autoclave pressure and 6 h autoclave time,the average compressive strength of 4.5 MPa and average dry density of 716.56 kg/m³were obtained,the two parameters(strength&density)both met the requirement of national industry standard.At the same time,the contents of dredged river sediment,cement,lime,fly ash,gypsum and aluminum powder were 15%,48%,20%,15%,2%and 0.09%,respectively,and the non-AAC block made of 0.5 water to material ratio,the average compressive strength of 3.1 MPa and average dry density of 924.19 kg/m³were obtained,the two parameters(strength&density)also met the requirement of national industry standard.In addition,the AAC block’s phase composition and morphology were micro-analyzed by SEM and XRD,the main substances in AAC block were found to be tobermorite and CSH,Among them,the chemical bond between Si-O-Si and Al-O-Al is broken,Al-O-Si is regenerated,Al substituted tobermorite with better strength is formed,and the compressive strength of AAC is further improved.展开更多
An experiment for studying the effects of sediment dredging on denitrification in sediments was carried out through a one-year incubation of undredged （control） and dredged cores in laboratory. Dredging the upper 30...An experiment for studying the effects of sediment dredging on denitrification in sediments was carried out through a one-year incubation of undredged （control） and dredged cores in laboratory. Dredging the upper 30 cm of sediment can significantly affect physico-chemical characteristics of sediments. Less degradation of organic matter in the dredged sediments was found during the experiment. Denitrification rates in the sediments were estimated by the acetylene blockage technique, and ranged from 21.6 to 102.7 nmol N2/（g dry weight （dw）-hr） for the undredged sediment and from 6.9 to 26.9 nmol N2/（g dw-hr） for dredged sediments. The denitrification rates in the undredged sediments were markedly higher （p 〈 0.05） than those in the dredged sediments throughout the incubation, with the exception of February 2006. The importance of various environmental factors on denitrification was assessed, which indicated that denitrification was regulated by temperature. Nitrate was probably the key factor limiting denitrification in both undredged and dredged sediments. Organic carbon played some role in determining the denitrification rates in the dredged sediments, but not in the undredged sediments. Sediment dredging influenced the mineralization of organic matter and denitrification in the sediment; and therefore changed the pattern of inherent cycling of nitrogen.展开更多
A laboratory experiment was carried out through a six-month incubation of undredged （control） and dredged cores to study the effect of sediment dredging on phosphorus （P） release from the sediment in the Taihu Lak...A laboratory experiment was carried out through a six-month incubation of undredged （control） and dredged cores to study the effect of sediment dredging on phosphorus （P） release from the sediment in the Taihu Lake. During the experiment, dredging the upper 30 cm layer could efficiently reduce the interstitial PO4^3-P concentration and different P forms in the sediment. The P fluxes of the undredged and dredged cores ranged from -5.1 to 3047.6 and -60.7 to 14.4μg·m^-2·d^-1, respectively. The fluxes of the dredged cores were generally lower than those of the control. Differences in the fluxes between the dredged and undredged cores were statistically significant （P 〈 0.05） from March to June 2006. The sediment P in the dredged cores had a lower release potential than that in the control. Dredging can be considered as a useful measure for rehabilitating the aquatic ecosystem after the external P loading in the Talhu Lake catchment was efficiently reduced.展开更多
Cd-bearing solid wastes are considered to be a serious threat to the environment,and effective strategies for their treatment are urgently needed.Ceramic sintering has been considered as a promising method for efficie...Cd-bearing solid wastes are considered to be a serious threat to the environment,and effective strategies for their treatment are urgently needed.Ceramic sintering has been considered as a promising method for efficiently incorporating heavy metal-containing solid wastes into various ceramic products.Mineral-rich dredged river sediment,especially Al and Si-containing oxides,can be treated as alternative ceramic precursors rather than being disposed of as solid wastes.To examine the feasibility of using waste sediment for Cd stabilization and the phase transition mechanisms,this study conducted a sintering scheme for the mixtures of CdO and dredged river sediment with different(Al+Si):Cd mole ratios.Detailed investigations have been performed on phases transformation,Cd incorporation mechanisms,elemental distribution,and leaching behaviors of the sintered products.Results showed that Cd incorporation and transformation in the sintered products were influenced by the mole ratio of(Al+Si):Cd.Among the high-Cd series((Al+Si):Cd=6:1),CdSiO_(3),Cd_(2)SiO_(4),CdAl_(2)(SiO_(4))_(2) and Cd_(2)Al_(2)Si_(2)O_(9) were predominant Cd-containing product phases,while Cd2Al2Si2O9 was replaced by CdAl_(4)O_(7) when the mole ratio of(Al+Si):Cd was 12:1(low-Cd series).Cd was efficiently stabilized in both reaction series after being sintered at≥900℃,with<5%leached ratio even after a prolonged leaching time,indicating excellent long-term Cd stabilization.This study demonstrated that both Cd-containing phases and the amorphous Al-/Si-containing matrices all played critical roles in Cd stabilization.A promising strategy can be proposed to simultaneously reuse the solid waste as ceramic precursors and stabilize heavy metals in the ceramic products.展开更多
To more efficiently treat the dredged contaminated sediment(DCS)with a high water content,this study proposes an integrated method(called PHDVPSS)that uses the solidifying/stabilizing(S/S)agents and prefabricated hori...To more efficiently treat the dredged contaminated sediment(DCS)with a high water content,this study proposes an integrated method(called PHDVPSS)that uses the solidifying/stabilizing(S/S)agents and prefabricated horizontal drain(PHD)assisted by vacuum pressure(VP).Using this method,dewatering and solidification/stabilization can be carried out simultaneously such that the treatment time can be significantly shortened and the treatment efficacy can be significantly improved.A series of model tests was conducted to investigate the effectiveness of the proposed method.Experimental results indicated that the proposed PHDVPSS method showed superior performance compared to the conventional S/S method that uses Portland cement(PC)directly without prior dewatering.The 56-day unconfined compressive strength of DCS treated by the proposed method with GGBS-MgO as the binder is 12–17 times higher than that by the conventional S/S method.DCS treated by the PHDVPSS method exhibited continuous decrease in leaching concentration of Zn with increasing curing age.The reduction of Zn leachability is more obvious when using GGBS-MgO as the binder than when using PC,because GGBS-MgO increased the residual fraction and decreased the acid soluble fraction of Zn.The microstructure analysis reveals the formation of hydrotalcite in GGBS-MgO binder,which resulted in higher mechanical strength and higher Zn stabilization efficiency.展开更多
In recent years,Cylindrospermopsis raciborskii blooms have been widely found worldwide.Topics dealing with the mitigation of C.raciborskii bloom is of great importance for toxins produced could threaten public health....In recent years,Cylindrospermopsis raciborskii blooms have been widely found worldwide.Topics dealing with the mitigation of C.raciborskii bloom is of great importance for toxins produced could threaten public health.The paper first investigated C.raciborskii dynamics over three years following sediment dredging in a shallow eutrophic Lake Dongqian(China).Based on rpoC1 gene copies,C.raciborskii bloom formed with average density of 1.30×10^(6) cells/L on July 2009.One year later after sediment dredging,C.raciborskii cell density decreased below 1.17×10^(5) cells/L or under detected limits during summer days on 2010.While two years later,the C.raciborskii bloom period was returned with markedly increased cell density reaching up to 4.15×10^(7) cells/L on October 2011,and the maximum peak density was shown at 20.3C that was much lower than reported optimal growth temperature.Inferred from Spearman correlation analysis,linear regression showed C.raciborskii density was significant and positive with pH and SD,whereas they were significant and negative with TP and DO.Multiple regression analysis further demonstrated that TN,TP,SRP,pH and DO provided the best model and explained 53.1% of the variance in C.raciborskii dynamics.The approaches managing nutrients reduction might not control C.raciborskii bloom as extremely low TN(avg.0.18 mg/L)and TP concentrations(avg.0.05 mg/L)resulted in the highest C.raciborskii cell density after sediment dredging.展开更多
Algae-caused black bloom （also known as black water agglomerate） has recently become a critical problem in some Chinese lakes.It has been suggested that the occurrence of algae-caused black bloom was caused by the c...Algae-caused black bloom （also known as black water agglomerate） has recently become a critical problem in some Chinese lakes.It has been suggested that the occurrence of algae-caused black bloom was caused by the cooperation of nutrient-rich sediment with dead algae,and sludge dredging was adopted to control black bloom in some lakes of China.In this article,based on the simulation of black bloom using a Y-shape apparatus for modeling natural conditions,both un-dredged and dredged sites in three areas of Taihu Lake,China were studied to estimate the effects of dredging on the prevention and control of black bloom.During the experiment,drained algae were added to all six sites as an additional organic load;subsequently,the dissolved oxygen decreased rapidly,dropping to 0 mg/L at the sediment-water interface.Black bloom did not occur in the dredged sites of Moon Bay and Nan Quan,whereas all three un-dredged sites at Fudu Port,Moon Bay and Nan Quan experienced black bloom.Black bloom also occurred at the dredged site of Fudu Port one day later than at the other sites,and the odor and color were lighter than at the other locations.The color and odor of the black water mainly result from the presence of sulfides such as metal sulfides and hydrogen sulfide,among other chemicals,under reductive conditions.The color and odor of the water,together with the high concentrations of nutrients,were mainly caused by the decomposition of the algae and the presence of nutrient-rich sediment.Overall,the removal of the nutrient-rich sediment by dredging can prevent the occurrence and control the degree of algae-caused black bloom in Taihu Lake.展开更多
基金supported by the National Key R&D Program of China(Grant No.2020YFC1908703)Funds for International Cooperation and Exchange of the National Natural Science Foundation of China(Grant No.51861165104)China Postdoctoral Science Foundation(Grant No.2022M723347).
文摘Nowadays,biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide attentions.However,the feasibility of using biopolymer as a green additive of cementstabilized dredged sediment(CDS)with high water content is still unknown.In this study,guar gum(GG)and xanthan gum(XG)were adopted as typical biopolymers,and a series of unconfined compressive strength(UCS),splitting tensile strength(STS)and scanning electron microscopy(SEM)tests were performed to evaluate the mechanical and microstructural properties of XG-and GG-modified CDSs considering several factors including biopolymer modification,binderesoil ratio and wateresolid ratio.Furthermore,the micro-mechanisms revealing the evolutions of mechanical properties of biopolymermodified CDS were analyzed.The results indicate that the addition of XG can effectively improve the strength of CDS,while the GG has a side effect.The XG content of 9%was recommended,which can improve the 7 d-and 28 d-UCSs by 196%and 51.8%,together with the 7 d-and 28 d-STSs by 118.3%and 42.2%,respectively.Increasing the binderesoil ratio or decreasing the wateresolid ratio significantly improved the strength gaining but aggravated the brittleness characteristics of CDS.Adding XG to CDS contributed to the formation of microstructure with more compactness and higher cementation degrees of ordinary Portland cement(OPC)-XG-stabilized DS(CXDS).The micro-mechanism models revealing the interactions of multiple media including OPC cementation,biopolymer film bonding and bridging effects inside CXDS were proposed.The key findings confirm the feasibility of XG modification as a green and high-efficiency mean for improving the mechanical properties of CDS.
基金This study is supported by the National Key R&D Program of China(Grant No.2020YFC1908703)Funds for International Cooperation and Exchange of the National Natural Science Foundation of China(Grant No.51861165104)the Major Science and Technology Project of Inner Mongolia Autonomous Region,China(Grant No.2021ZD0007-02-01).
文摘High-efficiency disposal of dredged sediment(DS)has become an imperative geo-environmental engineering issue due to the limited landfilling space and severe environmental burdens.This study firstly developed a novel high-efficiency nano-modified and chemical-activated binary cement(NBC),which was composed of binary cement(BC)consisting ordinary Portland cement(OPC)and ground granulated blast-furnace slag(GGBS),chemical-activator and nano-modifier.The effects of chemical-activation and nano-modification on the strength development of BC-stabilized DS(BCDS),and the optimum mix of NBC were respectively achieved via a series of unconfined compressive strength and orthogonal tests.Then,the high-efficiency and economic applicability of NBC in DS stabilization were evaluated by comparing with OPC.Furthermore,the microstructure and mineral composition evolutions inside NBCstabilized DS(NDS)were explored by conducting X-ray diffraction(XRD)and scanning electron microscopy(SEM)tests.The results show that both chemical-activation and nano-modification could effectively improve the strength gain of BCDS,and compared with single chemical-activator and nanomodifier,the composite chemical-activators and nano-modifiers exhibited better performances.Based on BC with OPC/GGBS mass ratio of 1:1,both anhydrous sodium metasilicate/anhydrous sodium sulfate(SM/SS)and nano-SiO_(2)/nano-MgO(NS/NM)with mass ratio of 1:9 were respectively determined to be optimum chemical-activator and nano-modifier.The optimum mass ratio of BC,SM/SS and NS/NM was 20:2:1,i.e.the optimum mix of NBC.Compared with OPC,NBC exhibited higher stabilization efficiency and better economic applicability.The generation of calcium silicate hydrate(CSH),calcium aluminate hydrate(CAH)and ettringite contributed to the formation of dense cemented soil matrix inside NDS,and a conceptual micro-mechanism model characterizing the strength development under the coupling action of chemical-activation and nano-modification was proposed.
基金Supported by Scientific Research Foundation of Yunnan Provincial Education Department(09Y0292)~~
文摘[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants including FeCl3,Al2(SO4)3 and PAM were taken as dewatering agents which were added in dredged sediment.[Result] The results showed that Al2(SO4)3 had better dewatering effect than FeCl3 and PAM,and the optimum dosing quantity of Al2(SO4)3 in dredged sediment was 170 mg/L,in addition,the water quality of supernatant met the first class B standard of GB18918-2002 and could be directly discharged to nature water without pollution.[Conclusion] The study could provide a simple and feasible way for the rapid dewatering of dredged sediment from Dianchi Lake,which would be convenient for the disposal and resource utilization of dredged sediment.
基金Acknowledgments Foundation item： National Science Foundation of China （50808068） The Ph.D. Programs Foundation of Ministry of Education of China （200802941001）.
文摘The fractal model about water characteristics of solidified sediment was built according to the granular metric analysis curve of solidified dredged sediment, the measured value during the low-suction stage of the curing process was used for fitting parameters in the model to obtain the complete water characteristic curve of solidified dredged sediment. Then, the quantitative calculation model of capillary water, attached water, evaporated water and bound water was built by the water characteristic curve and from the view of quantitative angle, the paper analyzed the solidification mechanism of solidified dredged sediment. The result showed that： the model can realize the quantitative calculation about different tapes of water during the curing process, the evaporated water during the curing process mainly came from the capillary water, and the generated bound water during the curing reaction came from the attached water.
基金This study is supported by the National Key R&D Program of China(No.2020YFC1908703)China Postdoctoral Science Foundation(No.2022M723347).
文摘This study evaluated the feasibility of using polypropylene fiber(PF)as reinforcement in improving tensile strength behavior of cement-stabilized dredged sediment(CDS).The effects of cement content,water content,PF content and length on the tensile strength and stress–strain behavioral evolutions were evaluated by conducting splitting tensile strength tests.Furthermore,the micro-mechanisms characterizing the tensile strength behavior inside PF-reinforced CDS(CPFDS)were clarified via analyzing macro failure and microstructure images.The results indicate that the highest tensile strengths of 7,28,60,and 90 d CPFDS were reached at PF contents of 0.6%,1.0%,1.0%,and 1.0%,exhibiting values 5.96%,65.16%,34.10%,and 35.83%higher than those of CDS,respectively.Short,3 mm,PF of showed the best reinforcement efficiency.The CPFDS exhibited obvious tensile strain-hardening characteristic,and also had better ductility than CDS.The mix factor(C_(C)^(a)/C_(w)^(b))and time parameter(q_(t0)(t))of CDS,and the reinforcement index(k_(t-PF))of CPFDS were used to establish the tensile strength prediction models of CDS and CPFDS,considering multiple factors.The PF“bridge effect”and associated cementation-reinforcement coupling actions inside CPFDS were mainly responsible for tensile strength behavior improvement.The key findings contribute to the use of CPFDS as recycled engineering soils.
基金the National Natural Science Foundation of China(NSFC)(Nos.21876025,42177119).
文摘In this study,the dredged river sediment,soft texture and fine particles,is mixed with other materials and transformed into eco-friendly autoclaved aerated concrete(hereinafter referred to as AAC)blocks.The results indicated the bricks produced under the conditions of 30%–34%dredged river sediment,24%cement,10%quick lime,30%fly ash,2%gypsum and 0.09%aluminum powder with 0.5 water to material ratio,2.2 MPa autoclave pressure and 6 h autoclave time,the average compressive strength of 4.5 MPa and average dry density of 716.56 kg/m³were obtained,the two parameters(strength&density)both met the requirement of national industry standard.At the same time,the contents of dredged river sediment,cement,lime,fly ash,gypsum and aluminum powder were 15%,48%,20%,15%,2%and 0.09%,respectively,and the non-AAC block made of 0.5 water to material ratio,the average compressive strength of 3.1 MPa and average dry density of 924.19 kg/m³were obtained,the two parameters(strength&density)also met the requirement of national industry standard.In addition,the AAC block’s phase composition and morphology were micro-analyzed by SEM and XRD,the main substances in AAC block were found to be tobermorite and CSH,Among them,the chemical bond between Si-O-Si and Al-O-Al is broken,Al-O-Si is regenerated,Al substituted tobermorite with better strength is formed,and the compressive strength of AAC is further improved.
基金supported by the National Natural Science Foundation of China (No.40730528,40901253)the Social Development Key Project and Natural Science Foundation of Jiangsu Province (No.BE2009603,BK2009333)the Knowledge Innovation Program of Chinese Academy of Sciences (No.CXNIGLAS200804)
文摘An experiment for studying the effects of sediment dredging on denitrification in sediments was carried out through a one-year incubation of undredged （control） and dredged cores in laboratory. Dredging the upper 30 cm of sediment can significantly affect physico-chemical characteristics of sediments. Less degradation of organic matter in the dredged sediments was found during the experiment. Denitrification rates in the sediments were estimated by the acetylene blockage technique, and ranged from 21.6 to 102.7 nmol N2/（g dry weight （dw）-hr） for the undredged sediment and from 6.9 to 26.9 nmol N2/（g dw-hr） for dredged sediments. The denitrification rates in the undredged sediments were markedly higher （p 〈 0.05） than those in the dredged sediments throughout the incubation, with the exception of February 2006. The importance of various environmental factors on denitrification was assessed, which indicated that denitrification was regulated by temperature. Nitrate was probably the key factor limiting denitrification in both undredged and dredged sediments. Organic carbon played some role in determining the denitrification rates in the dredged sediments, but not in the undredged sediments. Sediment dredging influenced the mineralization of organic matter and denitrification in the sediment; and therefore changed the pattern of inherent cycling of nitrogen.
基金Project supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (No.KZCX3-SW-348)the National Natural Science Foundation of China (Nos.20577053 and 40730528)the National High Technology Research and Development Program (863 Program) of China (No.2005AA60101005).
文摘A laboratory experiment was carried out through a six-month incubation of undredged （control） and dredged cores to study the effect of sediment dredging on phosphorus （P） release from the sediment in the Taihu Lake. During the experiment, dredging the upper 30 cm layer could efficiently reduce the interstitial PO4^3-P concentration and different P forms in the sediment. The P fluxes of the undredged and dredged cores ranged from -5.1 to 3047.6 and -60.7 to 14.4μg·m^-2·d^-1, respectively. The fluxes of the dredged cores were generally lower than those of the control. Differences in the fluxes between the dredged and undredged cores were statistically significant （P 〈 0.05） from March to June 2006. The sediment P in the dredged cores had a lower release potential than that in the control. Dredging can be considered as a useful measure for rehabilitating the aquatic ecosystem after the external P loading in the Talhu Lake catchment was efficiently reduced.
基金financially supported by the National Key R&D Program of China(No.2018YFC1902904)the National Natural Science Foundation of China(Nos.21707063 and 41977329)+2 种基金the Research Grants Council of Hong Kong(China)(Project T21-771/16R)Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control(China)(No.2017B030301012)The authors are sincerely grateful for the assistance of SUSTech Core Research Facilities(China).
文摘Cd-bearing solid wastes are considered to be a serious threat to the environment,and effective strategies for their treatment are urgently needed.Ceramic sintering has been considered as a promising method for efficiently incorporating heavy metal-containing solid wastes into various ceramic products.Mineral-rich dredged river sediment,especially Al and Si-containing oxides,can be treated as alternative ceramic precursors rather than being disposed of as solid wastes.To examine the feasibility of using waste sediment for Cd stabilization and the phase transition mechanisms,this study conducted a sintering scheme for the mixtures of CdO and dredged river sediment with different(Al+Si):Cd mole ratios.Detailed investigations have been performed on phases transformation,Cd incorporation mechanisms,elemental distribution,and leaching behaviors of the sintered products.Results showed that Cd incorporation and transformation in the sintered products were influenced by the mole ratio of(Al+Si):Cd.Among the high-Cd series((Al+Si):Cd=6:1),CdSiO_(3),Cd_(2)SiO_(4),CdAl_(2)(SiO_(4))_(2) and Cd_(2)Al_(2)Si_(2)O_(9) were predominant Cd-containing product phases,while Cd2Al2Si2O9 was replaced by CdAl_(4)O_(7) when the mole ratio of(Al+Si):Cd was 12:1(low-Cd series).Cd was efficiently stabilized in both reaction series after being sintered at≥900℃,with<5%leached ratio even after a prolonged leaching time,indicating excellent long-term Cd stabilization.This study demonstrated that both Cd-containing phases and the amorphous Al-/Si-containing matrices all played critical roles in Cd stabilization.A promising strategy can be proposed to simultaneously reuse the solid waste as ceramic precursors and stabilize heavy metals in the ceramic products.
基金Financial support for this investigation was provided by the National Key Research and Development Program of China(Grant No.2019YFC1806000)Changjiang River Scientific Research Institute Open Research Program(Grant No.CKWV2019730/KY)+1 种基金the National Natural Science Foundation of China(Grant Nos.51678268 and 51878312)and the Hubei Province Postdoctoral Advanced Programs(Grant No.0106240048).This support is gratefully acknowledged.
文摘To more efficiently treat the dredged contaminated sediment(DCS)with a high water content,this study proposes an integrated method(called PHDVPSS)that uses the solidifying/stabilizing(S/S)agents and prefabricated horizontal drain(PHD)assisted by vacuum pressure(VP).Using this method,dewatering and solidification/stabilization can be carried out simultaneously such that the treatment time can be significantly shortened and the treatment efficacy can be significantly improved.A series of model tests was conducted to investigate the effectiveness of the proposed method.Experimental results indicated that the proposed PHDVPSS method showed superior performance compared to the conventional S/S method that uses Portland cement(PC)directly without prior dewatering.The 56-day unconfined compressive strength of DCS treated by the proposed method with GGBS-MgO as the binder is 12–17 times higher than that by the conventional S/S method.DCS treated by the PHDVPSS method exhibited continuous decrease in leaching concentration of Zn with increasing curing age.The reduction of Zn leachability is more obvious when using GGBS-MgO as the binder than when using PC,because GGBS-MgO increased the residual fraction and decreased the acid soluble fraction of Zn.The microstructure analysis reveals the formation of hydrotalcite in GGBS-MgO binder,which resulted in higher mechanical strength and higher Zn stabilization efficiency.
基金The National Key Research and Development Program of China(2017YFA0605003)the National Natural Science Foundation of China(51922010,91751114,41521003,31700404),supported this study.
文摘In recent years,Cylindrospermopsis raciborskii blooms have been widely found worldwide.Topics dealing with the mitigation of C.raciborskii bloom is of great importance for toxins produced could threaten public health.The paper first investigated C.raciborskii dynamics over three years following sediment dredging in a shallow eutrophic Lake Dongqian(China).Based on rpoC1 gene copies,C.raciborskii bloom formed with average density of 1.30×10^(6) cells/L on July 2009.One year later after sediment dredging,C.raciborskii cell density decreased below 1.17×10^(5) cells/L or under detected limits during summer days on 2010.While two years later,the C.raciborskii bloom period was returned with markedly increased cell density reaching up to 4.15×10^(7) cells/L on October 2011,and the maximum peak density was shown at 20.3C that was much lower than reported optimal growth temperature.Inferred from Spearman correlation analysis,linear regression showed C.raciborskii density was significant and positive with pH and SD,whereas they were significant and negative with TP and DO.Multiple regression analysis further demonstrated that TN,TP,SRP,pH and DO provided the best model and explained 53.1% of the variance in C.raciborskii dynamics.The approaches managing nutrients reduction might not control C.raciborskii bloom as extremely low TN(avg.0.18 mg/L)and TP concentrations(avg.0.05 mg/L)resulted in the highest C.raciborskii cell density after sediment dredging.
基金supported by the Industry-Academia Cooperation Innovation Fund Project of Jiangsu Province(No.BY2011165)the Innovation Program of the Chinese Academy of Sciences(No.KZCX2-EW-314)+1 种基金the Key Project of"One Three Five"Strategic Developing Plan(No.NIGLAS2012135008)the National Water Pollution Control and Management Technology Major Project(No.2012ZX07103-005,2012ZX07101-010)
文摘Algae-caused black bloom （also known as black water agglomerate） has recently become a critical problem in some Chinese lakes.It has been suggested that the occurrence of algae-caused black bloom was caused by the cooperation of nutrient-rich sediment with dead algae,and sludge dredging was adopted to control black bloom in some lakes of China.In this article,based on the simulation of black bloom using a Y-shape apparatus for modeling natural conditions,both un-dredged and dredged sites in three areas of Taihu Lake,China were studied to estimate the effects of dredging on the prevention and control of black bloom.During the experiment,drained algae were added to all six sites as an additional organic load;subsequently,the dissolved oxygen decreased rapidly,dropping to 0 mg/L at the sediment-water interface.Black bloom did not occur in the dredged sites of Moon Bay and Nan Quan,whereas all three un-dredged sites at Fudu Port,Moon Bay and Nan Quan experienced black bloom.Black bloom also occurred at the dredged site of Fudu Port one day later than at the other sites,and the odor and color were lighter than at the other locations.The color and odor of the black water mainly result from the presence of sulfides such as metal sulfides and hydrogen sulfide,among other chemicals,under reductive conditions.The color and odor of the water,together with the high concentrations of nutrients,were mainly caused by the decomposition of the algae and the presence of nutrient-rich sediment.Overall,the removal of the nutrient-rich sediment by dredging can prevent the occurrence and control the degree of algae-caused black bloom in Taihu Lake.
