The presence of heavy metals in soil negatively impacts its mechanical properties.Reactive MgO carbonation presents a promising approach to enhance the solidification of Pb-contaminated sandy soils.However,the mechani...The presence of heavy metals in soil negatively impacts its mechanical properties.Reactive MgO carbonation presents a promising approach to enhance the solidification of Pb-contaminated sandy soils.However,the mechanical properties and structural behavior of contaminated soils during carbonation can vary significantly due to differences in soil composition.This study examines the potential application and underlying mechanisms of reactive MgO carbonation in improving the mechanical properties of Pb-contaminated red clay.The findings demonstrate that Pb-contaminated red clay transitions from a plastic to a brittle state following reactive MgO carbonation.After 1 h of treatment,the strength of the red clay exceeded 3 MPa,even at high Pb^(2+)concentrations.The deformation modulus to unconfined compressive strength(UCS)ratio was calculated to be 37.761,with the failure strain primarily ranging from 1.5%to 4.0%.A strength prediction model for the reactive MgO-stabilized Pb-contaminated red clay was proposed,which showed good predictive accuracy.Furthermore,reactive MgO carbonation significantly reduced the Pb leaching concentration in the high-level Pb-contaminated soil to below 0.1 mg/L.Microscopic analysis revealed that an optimal amount of hydrated magnesium carbonates(HMCs)formed a stable and compact structure with the soil particles.However,long-term carbonation causes red clay particles to become sandy,and excessive HMCs can harm the soil structure.Therefore,to maximize the strength improvement while avoiding structural damage,the carbonation time should be controlled to 1 h.展开更多
To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with po...To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with polarity exchange technique.The variations in Pb removal efficiency and the soil p H value with the treatment time and the exchange polarity interval were determined.It is found that the removal efficiency of Pb reaches a maximum of 87.7% when the voltage gradient is 1 V/cm and the exchange polarity interval is 48 h.This value is far higher than that obtained with conventional electrokinetic remediation（61.8%）.Additionally,the ＂focusing effect＂ which appears in the conventional electrokinetic remediation can be avoided,and thus additional chemicals are not needed for the polarity exchange technique.The mechanism of Pb electromigration behavior in soil during the treatment with the polarity exchange technique was described.展开更多
Substitute planting with rapeseed offers promise for safely using large areas of Cd/Pb-contaminated farmland.Cd/Pb distributions during rapeseed oil production were investigated and health risks posed by the oil were ...Substitute planting with rapeseed offers promise for safely using large areas of Cd/Pb-contaminated farmland.Cd/Pb distributions during rapeseed oil production were investigated and health risks posed by the oil were assessed.Tests were performed using three cultivars(Brassica rapa SYH and ZS100 and Brassica napus QY-1)and four oil extraction techniques(mechanical and low-temperature pressing and n-hexane and subcritical low-temperature butane extraction).The amounts of Cd and Pb in oil were 0.73%-8.44%and 3.14%-11.76%,respectively,of the amounts in rapeseed and were strongly affected by the cultivar and oil extraction technique.The heavy metal(HM)concentrations were lower in solvent-extracted oil(particularly subcritical low-temperature butane extracted oil,in which HMs were not detected)than mechanically pressed oil.The Cd and Pb transfer indices were lower(meaning larger proportions of HMs were retained by the rapeseed meal)for B.rapa than B.napus.This was attributed to a high HM binding protein content of B.rapa seed.Health risks to humans were assessed using a probabilistic risk assessment model.The carcinogenic risk was mainly(97.1%-99.9%)caused by Cd and poses more concern than non-carcinogenic risk.Stronger health risks are posed by mechanically pressed than solvent-extracted oil,and higher carcinogenic risks are posed to people living in rural areas than urban areas.Substitute planting with B.rapa and extracting oil with organic solvent(preferably subcritical low-temperature butane)are optimal for safely utilizing Cd/Pb-contaminated soil.Attention should be paid to the health risks posed by Cd in oil to rural populations.展开更多
Water-soluble chitosan(WSC)has been studied for its ability to mobilize soil Pb and promote the phytoremediation by Hylotelephium spectabile in Pb-contaminated fields.We aimed to clarify the internal mechanism by whic...Water-soluble chitosan(WSC)has been studied for its ability to mobilize soil Pb and promote the phytoremediation by Hylotelephium spectabile in Pb-contaminated fields.We aimed to clarify the internal mechanism by which wSC impacts phytoremediation by examining plant growth and Pb accumulation performance of H.spectabile as well as the Pb form,functional groups,and mineral phases of Pb-contaminated soil.WSC effectively decreased soil pH and activated Pb migration in rhizosphere soils,with a considerable increase in water-soluble and acid-extractable Pb by 29%-102%and 9%-65%,respectively,and a clear decreasing trend in reducible and oxidizable Pb.Fourier-transform infrared spectroscopy revealed a significant increase in amino and hydroxyl groups in the soil generated by WSC.The coordination of Pb with amino and hydroxyl groups may play an important role in the formation of Pb complexes and activation of Pb in soil.In field trials,the application of WSC significantly increased Pb accumulation in H.spectabile by 125.44%,reaching 92 g/hm^(2).Moreover,the organic matter and nitrogen in the soils were increased by WSc,which improved the growth conditions of H.spectabile.No obvious growth inhibition was observed in either the pot or field trials.Therefore,WSC is a promising chelating agent for mobilizing Pb in soil.Additionally,WSC can be potentially used to boost H.spectabil-mediated phytoremediation of Pb-contaminatedfarmland.展开更多
The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified...The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified with nano-silica(NS)across a continuum from nanoscale interactions to macroscopic performance.For this,a series of macroscopic experiments was conducted to evaluate the mechanical performance and lead-encapsulation efficiency,including unconfined compressive strength(UCS)and toxicity characteristic leaching procedure(TCLP).Microstructural and phase transformations were characterized using X-ray diffraction,thermogravimetric analysis,and scanning electron microscope.Molecular dynamics simulations revealed the interactions between NS-modified cement,calcium silicate hydrates(C-S-H)gel,and Illite,focusing on interaction energies,atomic density distributions and structural changes.Macroscopic analyses demonstrated that increasing NS content from 0%to 8%improved Pb-immobilization rate from 88.7%to 97.6%and enhanced UCS from 764 kPa to 1358 kPa.These improvements were attributed to NS enhancing the microstructural integrity of C-S-H gel and filling pores in samples.Nanoscale simulations elucidated that Pb-stabilization occurs through coordination bonds with oxygen atoms in the C-S-H silicon chains and on Illite surfaces,complemented by the formation of stable Pb_(3)(CO)_(3)(OH)_(2)precipitates.Additionally,the simulations revealed that Ca^(2+)migration from hydration products to mineral surfaces generated substantial repulsive interaction energies,reducing Illite layer dispersion.However,the presence of Pb impeded further Ca^(2+)migration,leading to expansion of the C-S-H gel,which collectively degraded the mechanical properties of the material.Furthermore,wet-dry and freeze-thaw cycles showed that after 10 cycles,UCS and TCLP results still met the United States Environmental Protection Agency standards,confirming long-term durability.This study provides a theoretical foundation for resource utilization of the contaminated sediments and offers a perspective for design of the cement-based curing agents,particularly in addressing variations in pollutant concentrations and environmental conditions,advancing the application of responsive and controlled release curing agents.展开更多
Aims Soil lead contamination has become increasingly serious and phytoremediation can provide an effective way to reclaim the contaminated soils.This study aims to examine the growth,lead resistance and lead accumulat...Aims Soil lead contamination has become increasingly serious and phytoremediation can provide an effective way to reclaim the contaminated soils.This study aims to examine the growth,lead resistance and lead accumulation of mulberry(Morus alba L.)seedlings at four levels of soil lead contamination with or without biochar addition under normal or alternative partial root-zone irrigation(APRI).Methods We conducted a three-factor greenhouse experiment with biochar(with vs.without biochar addition),irrigation method(APRI vs.normal irrigation)and four levels of soil lead(0,50,200 and 800 mg·kg^(-1)).The performance of the seedlings under different treatments was evaluated by measuring growth traits,osmotic substances,antioxidant enzymes and lead accumulation and translocation.Important Findings The results reveal that mulberry had a strong ability to acclimate to soil lead contamination,and that biochar and APRI synergistically increased the biomass and surface area of absorption root across all levels of soil lead.The seedlings were able to resist the severe soil lead contamination(800 mg·kg^(-1) Pb)by adjusting glutathione metabolism,and enhancing the osmotic and oxidative regulating capacity via increasing proline content and the peroxidase activity.Lead ions in the seedlings were primarily concentrated in roots and exhibited a dose–effect associated with the lead concentration in the soil.Pb,biochar and ARPI interactively affected Pb concentrations in leaves and roots,translocation factor and bioconcentration.Our results suggest that planting mulberry trees in combination with biochar addition and APRI can be used to effectively remediate lead-contaminated soils.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3707900)the National Natural Science Foundation of China(Grant Nos.42030710 and 42472337).
文摘The presence of heavy metals in soil negatively impacts its mechanical properties.Reactive MgO carbonation presents a promising approach to enhance the solidification of Pb-contaminated sandy soils.However,the mechanical properties and structural behavior of contaminated soils during carbonation can vary significantly due to differences in soil composition.This study examines the potential application and underlying mechanisms of reactive MgO carbonation in improving the mechanical properties of Pb-contaminated red clay.The findings demonstrate that Pb-contaminated red clay transitions from a plastic to a brittle state following reactive MgO carbonation.After 1 h of treatment,the strength of the red clay exceeded 3 MPa,even at high Pb^(2+)concentrations.The deformation modulus to unconfined compressive strength(UCS)ratio was calculated to be 37.761,with the failure strain primarily ranging from 1.5%to 4.0%.A strength prediction model for the reactive MgO-stabilized Pb-contaminated red clay was proposed,which showed good predictive accuracy.Furthermore,reactive MgO carbonation significantly reduced the Pb leaching concentration in the high-level Pb-contaminated soil to below 0.1 mg/L.Microscopic analysis revealed that an optimal amount of hydrated magnesium carbonates(HMCs)formed a stable and compact structure with the soil particles.However,long-term carbonation causes red clay particles to become sandy,and excessive HMCs can harm the soil structure.Therefore,to maximize the strength improvement while avoiding structural damage,the carbonation time should be controlled to 1 h.
基金Project(21003054)supported by the National Natural Science Foundation of ChinaProject(2013CXZDA013)supported by the Scientific Research Foundation of the Education Department of Guangdong Province,China
文摘To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with polarity exchange technique.The variations in Pb removal efficiency and the soil p H value with the treatment time and the exchange polarity interval were determined.It is found that the removal efficiency of Pb reaches a maximum of 87.7% when the voltage gradient is 1 V/cm and the exchange polarity interval is 48 h.This value is far higher than that obtained with conventional electrokinetic remediation（61.8%）.Additionally,the ＂focusing effect＂ which appears in the conventional electrokinetic remediation can be avoided,and thus additional chemicals are not needed for the polarity exchange technique.The mechanism of Pb electromigration behavior in soil during the treatment with the polarity exchange technique was described.
基金the National Natural Science Foundation of China(Nos.41907125 and 41771509)China Postdoctoral Science Foundation(No.2019M650827).
文摘Substitute planting with rapeseed offers promise for safely using large areas of Cd/Pb-contaminated farmland.Cd/Pb distributions during rapeseed oil production were investigated and health risks posed by the oil were assessed.Tests were performed using three cultivars(Brassica rapa SYH and ZS100 and Brassica napus QY-1)and four oil extraction techniques(mechanical and low-temperature pressing and n-hexane and subcritical low-temperature butane extraction).The amounts of Cd and Pb in oil were 0.73%-8.44%and 3.14%-11.76%,respectively,of the amounts in rapeseed and were strongly affected by the cultivar and oil extraction technique.The heavy metal(HM)concentrations were lower in solvent-extracted oil(particularly subcritical low-temperature butane extracted oil,in which HMs were not detected)than mechanically pressed oil.The Cd and Pb transfer indices were lower(meaning larger proportions of HMs were retained by the rapeseed meal)for B.rapa than B.napus.This was attributed to a high HM binding protein content of B.rapa seed.Health risks to humans were assessed using a probabilistic risk assessment model.The carcinogenic risk was mainly(97.1%-99.9%)caused by Cd and poses more concern than non-carcinogenic risk.Stronger health risks are posed by mechanically pressed than solvent-extracted oil,and higher carcinogenic risks are posed to people living in rural areas than urban areas.Substitute planting with B.rapa and extracting oil with organic solvent(preferably subcritical low-temperature butane)are optimal for safely utilizing Cd/Pb-contaminated soil.Attention should be paid to the health risks posed by Cd in oil to rural populations.
基金The research was financially supported by the National Natural Science Foundation of China(Nos.42277237,22206149,and 41907125)the Applied Basic Research Project of Shanxi Province(China)(No.20210302124220)the Horizontal Scientific Research Funds of Taiyuan University of Technology(Nos.RH2200002532 and RH2300002821).
文摘Water-soluble chitosan(WSC)has been studied for its ability to mobilize soil Pb and promote the phytoremediation by Hylotelephium spectabile in Pb-contaminated fields.We aimed to clarify the internal mechanism by which wSC impacts phytoremediation by examining plant growth and Pb accumulation performance of H.spectabile as well as the Pb form,functional groups,and mineral phases of Pb-contaminated soil.WSC effectively decreased soil pH and activated Pb migration in rhizosphere soils,with a considerable increase in water-soluble and acid-extractable Pb by 29%-102%and 9%-65%,respectively,and a clear decreasing trend in reducible and oxidizable Pb.Fourier-transform infrared spectroscopy revealed a significant increase in amino and hydroxyl groups in the soil generated by WSC.The coordination of Pb with amino and hydroxyl groups may play an important role in the formation of Pb complexes and activation of Pb in soil.In field trials,the application of WSC significantly increased Pb accumulation in H.spectabile by 125.44%,reaching 92 g/hm^(2).Moreover,the organic matter and nitrogen in the soils were increased by WSc,which improved the growth conditions of H.spectabile.No obvious growth inhibition was observed in either the pot or field trials.Therefore,WSC is a promising chelating agent for mobilizing Pb in soil.Additionally,WSC can be potentially used to boost H.spectabil-mediated phytoremediation of Pb-contaminatedfarmland.
基金the supports from the National Natural Science Foundation of China(Grant Nos.42177163 and 42307232)the China Postdoctoral Science Foundation of China(Grant No.2022M723347).
文摘The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified with nano-silica(NS)across a continuum from nanoscale interactions to macroscopic performance.For this,a series of macroscopic experiments was conducted to evaluate the mechanical performance and lead-encapsulation efficiency,including unconfined compressive strength(UCS)and toxicity characteristic leaching procedure(TCLP).Microstructural and phase transformations were characterized using X-ray diffraction,thermogravimetric analysis,and scanning electron microscope.Molecular dynamics simulations revealed the interactions between NS-modified cement,calcium silicate hydrates(C-S-H)gel,and Illite,focusing on interaction energies,atomic density distributions and structural changes.Macroscopic analyses demonstrated that increasing NS content from 0%to 8%improved Pb-immobilization rate from 88.7%to 97.6%and enhanced UCS from 764 kPa to 1358 kPa.These improvements were attributed to NS enhancing the microstructural integrity of C-S-H gel and filling pores in samples.Nanoscale simulations elucidated that Pb-stabilization occurs through coordination bonds with oxygen atoms in the C-S-H silicon chains and on Illite surfaces,complemented by the formation of stable Pb_(3)(CO)_(3)(OH)_(2)precipitates.Additionally,the simulations revealed that Ca^(2+)migration from hydration products to mineral surfaces generated substantial repulsive interaction energies,reducing Illite layer dispersion.However,the presence of Pb impeded further Ca^(2+)migration,leading to expansion of the C-S-H gel,which collectively degraded the mechanical properties of the material.Furthermore,wet-dry and freeze-thaw cycles showed that after 10 cycles,UCS and TCLP results still met the United States Environmental Protection Agency standards,confirming long-term durability.This study provides a theoretical foundation for resource utilization of the contaminated sediments and offers a perspective for design of the cement-based curing agents,particularly in addressing variations in pollutant concentrations and environmental conditions,advancing the application of responsive and controlled release curing agents.
基金funded by the Innovative Foundation of Mulberry and Silkworm Research Institute,Chinese Academy of Agricultural Sciences(16JK005).
文摘Aims Soil lead contamination has become increasingly serious and phytoremediation can provide an effective way to reclaim the contaminated soils.This study aims to examine the growth,lead resistance and lead accumulation of mulberry(Morus alba L.)seedlings at four levels of soil lead contamination with or without biochar addition under normal or alternative partial root-zone irrigation(APRI).Methods We conducted a three-factor greenhouse experiment with biochar(with vs.without biochar addition),irrigation method(APRI vs.normal irrigation)and four levels of soil lead(0,50,200 and 800 mg·kg^(-1)).The performance of the seedlings under different treatments was evaluated by measuring growth traits,osmotic substances,antioxidant enzymes and lead accumulation and translocation.Important Findings The results reveal that mulberry had a strong ability to acclimate to soil lead contamination,and that biochar and APRI synergistically increased the biomass and surface area of absorption root across all levels of soil lead.The seedlings were able to resist the severe soil lead contamination(800 mg·kg^(-1) Pb)by adjusting glutathione metabolism,and enhancing the osmotic and oxidative regulating capacity via increasing proline content and the peroxidase activity.Lead ions in the seedlings were primarily concentrated in roots and exhibited a dose–effect associated with the lead concentration in the soil.Pb,biochar and ARPI interactively affected Pb concentrations in leaves and roots,translocation factor and bioconcentration.Our results suggest that planting mulberry trees in combination with biochar addition and APRI can be used to effectively remediate lead-contaminated soils.
