Field investigation and greenhouse experiments were conducted to study the tolerance of Pteris vittata L. （Chinese brake） to cadmium （Cd） and its feasibility for remediating sites co-contaminated with Cd and arsen...Field investigation and greenhouse experiments were conducted to study the tolerance of Pteris vittata L. （Chinese brake） to cadmium （Cd） and its feasibility for remediating sites co-contaminated with Cd and arsenic （As）. The results showed that P. vittata could survive in pot soils spiked with 80 mg/kg of Cd and tolerated as great as 301 mg/kg of total Cd and 26.8 mg/kg of diethyltriaminepenta acetic acid （DTPA）-extractable Cd under field conditions. The highest concentration of Cd in fronds was 186 mg/kg under a total soil concentration of 920 mg As/kg and 98.6 mg Cd/kg in the field, whereas just 2.6 mg/kg under greenhouse conditions. Ecotypes of P. vittata were differentiated in tolerance and accumulation of Cd, and some of them could not only tolerate high concentrations of soil Cd, but also accumulated high concentrations of Cd in their fronds. Arsenic uptake and transportation by P. vittata was not inhibited at lower levels （〈20 mg/kg） of Cd addition. Compared to the treatment without addition of Cd, the frond As concentration was increased by 103.8% at 20 mg Cd/kg, with the highest level of 6434 mg/kg. The results suggested that the Cd-tolerant ecotype of P. vittata extracted effectively As and Cd from the site co-contaminated with Cd and As, and might be used to remediate and revegetate this type of site.展开更多
It is important to research the rules about accumulation and distribution of arsenic and cadmium by tea plants,which will give us some scientific ideas about how to control the contents of arsenic and cadmium in tea.I...It is important to research the rules about accumulation and distribution of arsenic and cadmium by tea plants,which will give us some scientific ideas about how to control the contents of arsenic and cadmium in tea.In this study,by field investigation and pot trial,we found that mobility of arsenic and cadmium in tea plants was low.Most arsenic and cadmium absorbed were fixed in feeding roots and only small amount was transported to the above-ground parts.Distribution of arsenic and cadmium,based on their concentrations of unit dry matter,in tea plants grown on un-contaminated soil was in the order:feeding roots>stems≈main roots>old leaves>young leaves.When tea plants were grown on polluted soils simulated by adding salts of these two metals,feeding roots possibly acted as a buffer and defense,and arsenic and cadmium were transported less to the aboveground parts.The concentration of cadmium in soil significantly and negatively correlated with chlorophyll content,photosynthetic rate,transpiration rate and biomass production of tea plants.展开更多
Ferrihydrite, prepared in the presence of different amount of As and Cd in the solution, was used to study the combined effect of As and Cd coexisted in the same system on the transformation of ferrihydrite into crys...Ferrihydrite, prepared in the presence of different amount of As and Cd in the solution, was used to study the combined effect of As and Cd coexisted in the same system on the transformation of ferrihydrite into crystalline products at pH & and pH 12. The data showed that there was apparent interaction between As and Cd in the transformation process. At pH 8, the transformation product was hematite with 1% As and different percent Cd (mole fraction, so as the follows), but the size of particles formed with different amount of Cd was different. At pH 12, the transformation products varied from sole hematite with 1% As and less than 2% Cd to a mixture of hematite and goethite with more than and equal to 2% Cd, and the percentage of goethite in the transformation products increased with the increasing level of Cd in the system. XRD (X-ray diffraction) and chemical analysis data showed that almost all As and part of Cd initially present in the system were retained in the crystalline products. The presence of As increased the amount of Cd retained in the structure of iron oxide. SEM (Scanning Electron Microscope) examination showed that the presence of As and Cd also altered the morphology of cry stalline products.展开更多
Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES）...Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES） and electrothermal atomic absorption spectrometry （ETAAS）, Due to the potential spectral interferences of As and Fe in the quantification of Cd, two methods were used for the background compensation. The first method was based on the use of a deuterium lamp （BGCD2 mode）. The second one required a Cd hollow cathode lamp pulsated with a current for which the intensity varies in the course of time （BGCSR mode）. The results showed that the choices of the analytical technique and the method used for the background compensation depend on the Cd, As and Fe concentrations in the solution and the concentration ratios As/Cd or/and Fe/Cd. In comparison with the ICP-AES and the ETAAS in combination with the BGCD2 mode, it was shown that the high-speed self-reversal method （HSSR） was a more appropriate method to correct As and Fe spectral interferences during the Cd measurements. On the other hand, depending on the Cd concentration, it was established that no significant Fe interference occurred during the Cd determination even if Fe concentration was 50 mg/L, reflecting the efficiency of the HSSR method to overcome the Fe interferences in the determination of Cd concentration by ETAAS without any matrix modifier in water extracts.展开更多
To investigate the effects of“Runbang”soil conditioner on simultaneously decreasing cadmium(Cd)and arsenic(As)in early-season paddy field,a typical red mud field in Hunan Province was selected for monitoring the dyn...To investigate the effects of“Runbang”soil conditioner on simultaneously decreasing cadmium(Cd)and arsenic(As)in early-season paddy field,a typical red mud field in Hunan Province was selected for monitoring the dynamic changes of Cd and As contents in early-season rice plants and soils,plus the soil physical-chemical properties and rice yields.Results of the field experiments indicated that the soil conditioner could significantly reduce Cd and As contents in soil and rice grain,whereas it could increase rice yield.Applying Runbang soil conditioner(1500~2100 kg/hm^2)to paddies brought about a reduction of 23.7%~44.8% and 24.3%~40.5% in available Cd and As contents of the soil,an increase of 0.9~1.1 units in soil pH value,a decline of 35.6%~51.1% and 22.0%~40.6% in Cd and As contents of rice grains,and a rise of 2%~5% in rice yields,respectively.展开更多
Although Brassica juncea (Indian mustard) is reported to be a good accumulator of metals, little is known of the selected varieties of B. juncea (cvs. Rai and BARI-11). This paper investigates the phytoaccumulation of...Although Brassica juncea (Indian mustard) is reported to be a good accumulator of metals, little is known of the selected varieties of B. juncea (cvs. Rai and BARI-11). This paper investigates the phytoaccumulation of arsenic, cadmium and lead by B. juncea (cvs. Rai and BARI-11) parents and F1 hybrids. The experiment was conducted in the hydroponic media in the greenhouse of University of Southampton under a Randomised Block Design. Sodium arsenite, cadmium sulphate and lead nitrate with 0 ppm, 0.5 ppm and 1 ppm were used. The cadmium treated plants were analysed by Varian Atomic absorption spectrophotometer-200. The samples of arsenic and lead were analysed by Inductively Coupled Plasma Atomic Emission Spectrophotometer. The results suggest that arsenic was detected only in the root systems while cadmium and lead were detected both in the root and shoot systems. Significant differences in the uptake were observed for different concentrations. Accumulation of arsenic was detected only in the root systems of B. juncea (cvs. Rai and BARI-11) at lower concentrations. Hence, this can be used as an agriculturally viable and efficient phytoaccumulator in the arsenic affected areas where contamination level is low and the contamination occurs at the rooting level.展开更多
Autism is a neurodevelopmental disorder characterized by stereotypic/repetitive behavior, impaired communication, imagination and social interactions. Recently, studies have investigated the possible association betwe...Autism is a neurodevelopmental disorder characterized by stereotypic/repetitive behavior, impaired communication, imagination and social interactions. Recently, studies have investigated the possible association between the etiology of autism and potential roles of various environmental agents, especially heavy metals. The aim of the present study was to examine levels of toxic metals in hair and urine samples of an autistic child. The levels of lead, cadmium, arsenic and manganese in hair and urine of this child were determined by atomic absorption spectrometry and compared with those of healthy children who had bee n assessed in previous studies. The autistic child had higher hair levels of lead （0.80 μg/g vs. 0.01 μg/g）, cadmium （0.083 μg/g vs. 0.06 μg/g） and arsenic （0.09 μg/g vs. 0.06 μg/g）. Urine levels of lead （12.54 μg/L vs. 3.36 μg/L） and cadmium （3.24 μg/L vs. 0.53μg/L） were higher than those of controls; whereas arsenic levels in urine were lower （6.81 μg/L vs. 32.06 μg/L）. Hair and urine samples of this autistic child contained lower concentrations of manganese （0.12 μg/g and 0.028 μg/g） as compared to healthy children （0.41 μg/L and 4.81μg/L）. In conclusion, our study demonstrated elevation in the levels of lead, cadmium and arsenic in a child with autism.展开更多
This study was carried out to detect content of heavy metals( Pb,Cd,and As) in vegetables,understand the current situation of heavy metal contamination in vegetables,and to provide scientific reference for further res...This study was carried out to detect content of heavy metals( Pb,Cd,and As) in vegetables,understand the current situation of heavy metal contamination in vegetables,and to provide scientific reference for further researches. It randomly selected 6 large vegetable markets and 6 supermarkets in Changsha City,selected 8 types of typical vegetables,and detected 96 samples. In accordance with maximum level of contaminants in foods in existing GB2762- 2012 standard,Nemerow composite pollution index( Pt) and grading standards,it made evaluation: uncontaminated( Pt≤ 1),mildly contaminated( 1 < Pt≤2),moderately contaminated( 2 < Pt≤3),and highly contaminated( Pt>3). Among 96 samples,range of content of Pb,Cd and As is( 0. 06- 1. 41),( 0. 06- 1. 26) and( 0. 00- 0. 91) mg / kg respectively; the over- limit rate of these metals exceeding the safety level is 78. 13%,45. 83%,and 34. 38% separately; the composite pollution index is in( 0. 90-6. 05),the eggplant is 6. 05 and hot pepper is 3. 24; the content of Pb( F =23. 908,P =0. 001) and Cd( F =64. 908,P =0. 000)are significantly different between 8 types of vegetables and there is no significant difference between the content of As( F = 4. 634,P = 0. 705> 0. 05) in 8 types of vegetables. Study shows that common vegetables in Changsha City has problem of excess Pb,Cd and As,and the Pb over- limit rate is the highest. The composite pollution index indicates that most heavy metal contamination of vegetables is mild and moderate contamination,melon,fruit and vegetable contamination is high contamination,and Cd is the major factor leading to contamination of melons,fruits and vegetables.展开更多
It is important to reduce Cd and As content in brown rice in contaminated paddy soils.We conducted research on the effects of rice husk ash (RHA) on the Cd and As in the rhizosphere microenvironment (soil,porewater,an...It is important to reduce Cd and As content in brown rice in contaminated paddy soils.We conducted research on the effects of rice husk ash (RHA) on the Cd and As in the rhizosphere microenvironment (soil,porewater,and iron plaque) and measured the Cd,As,and Si content in rice plants.The main elements in RHA were Si (29.64%) and O (69.17%),which had the maximum adsorption capacity for Cd was 42.49 mg/kg and for As was 18.62 mg/kg.Soil pH and available Si content increased,while soil available Cd and As decreased following application of 0.5%–2%RHA.RHA promote the transformation of Cd to insoluble fraction,while As was transformed from a poorly soluble form to a more active one.RHA reduced Cd content and increased Si content in porewater,and reduced As only at the later rice growth stages.RHA increased the amount of iron plaque,thereby decreasing the Cd content in iron plaque,while increased the As content in it.Cd and inorganic As content in brown rice were decreased,to 0.31 mg/kg and 0.18 mg/kg,respectively.The decrease of Cd in brown rice was due to the decrease of Cd mobility in soil,thereby reducing root accumulation,while the decrease of As in brown rice was affected by the transport from roots to stems.Therefore,RHA can be considered as a safe and efficient in-situ remediation amendment for Cd and As co-contaminated paddy soil.展开更多
Thermal treatment can effectively decontaminate soils but alter their properties.Previous research mainly focused on volatile organic compounds andmetals,i.e.Hg,neglecting nonvolatile metal(loid)s.This study aimed to ...Thermal treatment can effectively decontaminate soils but alter their properties.Previous research mainly focused on volatile organic compounds andmetals,i.e.Hg,neglecting nonvolatile metal(loid)s.This study aimed to investigate Cd and As transformation during aerobic and anaerobic calcination.The results showed that both aerobic and anaerobic calcination increased soil pH by reducing soil organic matter(SOM)content,which also influenced the cation exchange capacity(CEC)and the leaching behavior of Cd and As in the soil.The total concentrations of Cd and As in the calcined soils varied depending on the calcination temperature and atmosphere.When the aerobic calcination temperature exceeded 700℃,Cd volatilized as CdCl_(2),while anaerobic calcination at relatively low temperatures(600℃)involved reductive reactions,resulting in the formation of metallic Cd with a lower boiling point.Similarly,As volatilized at 800℃aerobically and 600℃anaerobically.The formation of As-based minerals,particularly Ca3(AsO4)2,hindered its gasification,whereas anaerobic calcination promoted volatilization efficiency through the generation of C-As(III)based gaseous components with lower boiling points.Contrasting trends were observed in the TCLP-extractable Cd and As contents of the calcined soils.Over 70%of TCLP-extractable Cd contents were suppressed after thermal treatment,attributed to the elevated pH and reduced CEC of the soil,as well as volatilization.However,TCLP-extractable As contents increased with elevated temperatures,likely due to the desorption of AsO43−and re-adsorption of gaseous As2O3 during cooling.These findings have implications for assessing the environmental impact of thermal treatment and provide insights for remediation strategies concerning Cd and As-contaminated soils.展开更多
Arsenic(As),fluoride(F^(−))are both ubiquitous in groundwater,and co-exposure to these elements through contaminated drinking water may cause detrimental effects on human health more in comparison with individual expo...Arsenic(As),fluoride(F^(−))are both ubiquitous in groundwater,and co-exposure to these elements through contaminated drinking water may cause detrimental effects on human health more in comparison with individual exposure.As,F^(−)co-occurrence in groundwater of the inland plain in Huaihe River Basin,China is a major concern,where inhabitants are rely on groundwater as the leading water source for drinking to date.This work employs an approach of hydrochemical analysis and modelling to identify the possible origin of As and F^(−),to analyze co-enrichment mechanism,and to estimate the associated exposure risk.The results shows presence of elevated As and F^(−)concentrations is an important factor affecting groundwater quality from 62 groundwater samples.The recorded As concentrations vary from 0.23 to 20.40μg/L,with a mean of 5.95μg/L,F^(−)concentrations vary from 0.54 to 2.60μg/L,with a mean of 1.29 mg/L,and 8%of samples are simultaneously above their permissible limits in drinking water by the WHO.Groundwater with As,F^(−)co-contamination is occurred within reducing and alkaline aquifers,and its chemical type is HCO_(3)–Na.The hydrochemical processes involved in the co-contamination are reductive desorption,evaporation,and ion exchange,which are controlled by local geology,geomorphology,and hydrochemistry.Groundwater As is derived and released by reductive desorption and F^(−)is mainly originated by fluorite dissolution.Groundwater As,F^(−)are geogenic sources,and the mechanisms for co-contamination are associated with high elemental abundance,flat terrain,alkaline and reductive groundwater conditions.The research provides a case study about groundwater As,F^(−)co-contamination,which may be enhance understanding the co-enrichment mechanism in semi-humid areas.展开更多
基金This work was supported by the National Science Foundation for the Distinguished Young Scholar of China(No.40325003).
文摘Field investigation and greenhouse experiments were conducted to study the tolerance of Pteris vittata L. （Chinese brake） to cadmium （Cd） and its feasibility for remediating sites co-contaminated with Cd and arsenic （As）. The results showed that P. vittata could survive in pot soils spiked with 80 mg/kg of Cd and tolerated as great as 301 mg/kg of total Cd and 26.8 mg/kg of diethyltriaminepenta acetic acid （DTPA）-extractable Cd under field conditions. The highest concentration of Cd in fronds was 186 mg/kg under a total soil concentration of 920 mg As/kg and 98.6 mg Cd/kg in the field, whereas just 2.6 mg/kg under greenhouse conditions. Ecotypes of P. vittata were differentiated in tolerance and accumulation of Cd, and some of them could not only tolerate high concentrations of soil Cd, but also accumulated high concentrations of Cd in their fronds. Arsenic uptake and transportation by P. vittata was not inhibited at lower levels （〈20 mg/kg） of Cd addition. Compared to the treatment without addition of Cd, the frond As concentration was increased by 103.8% at 20 mg Cd/kg, with the highest level of 6434 mg/kg. The results suggested that the Cd-tolerant ecotype of P. vittata extracted effectively As and Cd from the site co-contaminated with Cd and As, and might be used to remediate and revegetate this type of site.
基金Project supported by the Fund Program Management in Conversionof Achievement of the Ministry Science and Technology of China (No.03EFN213300109)the Natural Science Foundation of ZhejiangProvince,China (No. Y304473)
文摘It is important to research the rules about accumulation and distribution of arsenic and cadmium by tea plants,which will give us some scientific ideas about how to control the contents of arsenic and cadmium in tea.In this study,by field investigation and pot trial,we found that mobility of arsenic and cadmium in tea plants was low.Most arsenic and cadmium absorbed were fixed in feeding roots and only small amount was transported to the above-ground parts.Distribution of arsenic and cadmium,based on their concentrations of unit dry matter,in tea plants grown on un-contaminated soil was in the order:feeding roots>stems≈main roots>old leaves>young leaves.When tea plants were grown on polluted soils simulated by adding salts of these two metals,feeding roots possibly acted as a buffer and defense,and arsenic and cadmium were transported less to the aboveground parts.The concentration of cadmium in soil significantly and negatively correlated with chlorophyll content,photosynthetic rate,transpiration rate and biomass production of tea plants.
文摘Ferrihydrite, prepared in the presence of different amount of As and Cd in the solution, was used to study the combined effect of As and Cd coexisted in the same system on the transformation of ferrihydrite into crystalline products at pH & and pH 12. The data showed that there was apparent interaction between As and Cd in the transformation process. At pH 8, the transformation product was hematite with 1% As and different percent Cd (mole fraction, so as the follows), but the size of particles formed with different amount of Cd was different. At pH 12, the transformation products varied from sole hematite with 1% As and less than 2% Cd to a mixture of hematite and goethite with more than and equal to 2% Cd, and the percentage of goethite in the transformation products increased with the increasing level of Cd in the system. XRD (X-ray diffraction) and chemical analysis data showed that almost all As and part of Cd initially present in the system were retained in the crystalline products. The presence of As increased the amount of Cd retained in the structure of iron oxide. SEM (Scanning Electron Microscope) examination showed that the presence of As and Cd also altered the morphology of cry stalline products.
文摘Cadmium （Cd） concentrations in the water extracts of ten contaminated soils by arsenic （As） with various iron （Fe） contents were measured using inductively coupled plasma atomic emission spectrometry （ICP-AES） and electrothermal atomic absorption spectrometry （ETAAS）, Due to the potential spectral interferences of As and Fe in the quantification of Cd, two methods were used for the background compensation. The first method was based on the use of a deuterium lamp （BGCD2 mode）. The second one required a Cd hollow cathode lamp pulsated with a current for which the intensity varies in the course of time （BGCSR mode）. The results showed that the choices of the analytical technique and the method used for the background compensation depend on the Cd, As and Fe concentrations in the solution and the concentration ratios As/Cd or/and Fe/Cd. In comparison with the ICP-AES and the ETAAS in combination with the BGCD2 mode, it was shown that the high-speed self-reversal method （HSSR） was a more appropriate method to correct As and Fe spectral interferences during the Cd measurements. On the other hand, depending on the Cd concentration, it was established that no significant Fe interference occurred during the Cd determination even if Fe concentration was 50 mg/L, reflecting the efficiency of the HSSR method to overcome the Fe interferences in the determination of Cd concentration by ETAAS without any matrix modifier in water extracts.
文摘To investigate the effects of“Runbang”soil conditioner on simultaneously decreasing cadmium(Cd)and arsenic(As)in early-season paddy field,a typical red mud field in Hunan Province was selected for monitoring the dynamic changes of Cd and As contents in early-season rice plants and soils,plus the soil physical-chemical properties and rice yields.Results of the field experiments indicated that the soil conditioner could significantly reduce Cd and As contents in soil and rice grain,whereas it could increase rice yield.Applying Runbang soil conditioner(1500~2100 kg/hm^2)to paddies brought about a reduction of 23.7%~44.8% and 24.3%~40.5% in available Cd and As contents of the soil,an increase of 0.9~1.1 units in soil pH value,a decline of 35.6%~51.1% and 22.0%~40.6% in Cd and As contents of rice grains,and a rise of 2%~5% in rice yields,respectively.
文摘Although Brassica juncea (Indian mustard) is reported to be a good accumulator of metals, little is known of the selected varieties of B. juncea (cvs. Rai and BARI-11). This paper investigates the phytoaccumulation of arsenic, cadmium and lead by B. juncea (cvs. Rai and BARI-11) parents and F1 hybrids. The experiment was conducted in the hydroponic media in the greenhouse of University of Southampton under a Randomised Block Design. Sodium arsenite, cadmium sulphate and lead nitrate with 0 ppm, 0.5 ppm and 1 ppm were used. The cadmium treated plants were analysed by Varian Atomic absorption spectrophotometer-200. The samples of arsenic and lead were analysed by Inductively Coupled Plasma Atomic Emission Spectrophotometer. The results suggest that arsenic was detected only in the root systems while cadmium and lead were detected both in the root and shoot systems. Significant differences in the uptake were observed for different concentrations. Accumulation of arsenic was detected only in the root systems of B. juncea (cvs. Rai and BARI-11) at lower concentrations. Hence, this can be used as an agriculturally viable and efficient phytoaccumulator in the arsenic affected areas where contamination level is low and the contamination occurs at the rooting level.
文摘Autism is a neurodevelopmental disorder characterized by stereotypic/repetitive behavior, impaired communication, imagination and social interactions. Recently, studies have investigated the possible association between the etiology of autism and potential roles of various environmental agents, especially heavy metals. The aim of the present study was to examine levels of toxic metals in hair and urine samples of an autistic child. The levels of lead, cadmium, arsenic and manganese in hair and urine of this child were determined by atomic absorption spectrometry and compared with those of healthy children who had bee n assessed in previous studies. The autistic child had higher hair levels of lead （0.80 μg/g vs. 0.01 μg/g）, cadmium （0.083 μg/g vs. 0.06 μg/g） and arsenic （0.09 μg/g vs. 0.06 μg/g）. Urine levels of lead （12.54 μg/L vs. 3.36 μg/L） and cadmium （3.24 μg/L vs. 0.53μg/L） were higher than those of controls; whereas arsenic levels in urine were lower （6.81 μg/L vs. 32.06 μg/L）. Hair and urine samples of this autistic child contained lower concentrations of manganese （0.12 μg/g and 0.028 μg/g） as compared to healthy children （0.41 μg/L and 4.81μg/L）. In conclusion, our study demonstrated elevation in the levels of lead, cadmium and arsenic in a child with autism.
基金Supported by Student Innovation Project of Central South University(YC12355)
文摘This study was carried out to detect content of heavy metals( Pb,Cd,and As) in vegetables,understand the current situation of heavy metal contamination in vegetables,and to provide scientific reference for further researches. It randomly selected 6 large vegetable markets and 6 supermarkets in Changsha City,selected 8 types of typical vegetables,and detected 96 samples. In accordance with maximum level of contaminants in foods in existing GB2762- 2012 standard,Nemerow composite pollution index( Pt) and grading standards,it made evaluation: uncontaminated( Pt≤ 1),mildly contaminated( 1 < Pt≤2),moderately contaminated( 2 < Pt≤3),and highly contaminated( Pt>3). Among 96 samples,range of content of Pb,Cd and As is( 0. 06- 1. 41),( 0. 06- 1. 26) and( 0. 00- 0. 91) mg / kg respectively; the over- limit rate of these metals exceeding the safety level is 78. 13%,45. 83%,and 34. 38% separately; the composite pollution index is in( 0. 90-6. 05),the eggplant is 6. 05 and hot pepper is 3. 24; the content of Pb( F =23. 908,P =0. 001) and Cd( F =64. 908,P =0. 000)are significantly different between 8 types of vegetables and there is no significant difference between the content of As( F = 4. 634,P = 0. 705> 0. 05) in 8 types of vegetables. Study shows that common vegetables in Changsha City has problem of excess Pb,Cd and As,and the Pb over- limit rate is the highest. The composite pollution index indicates that most heavy metal contamination of vegetables is mild and moderate contamination,melon,fruit and vegetable contamination is high contamination,and Cd is the major factor leading to contamination of melons,fruits and vegetables.
基金supported by the National Natural Science Foundation of China (No.41907126)the Key Research and Development Program of Hunan Province (No.2021NK2027)the Science and Technology Talent Lifting Project of Hunan Province (No.2019TJ-N05)。
文摘It is important to reduce Cd and As content in brown rice in contaminated paddy soils.We conducted research on the effects of rice husk ash (RHA) on the Cd and As in the rhizosphere microenvironment (soil,porewater,and iron plaque) and measured the Cd,As,and Si content in rice plants.The main elements in RHA were Si (29.64%) and O (69.17%),which had the maximum adsorption capacity for Cd was 42.49 mg/kg and for As was 18.62 mg/kg.Soil pH and available Si content increased,while soil available Cd and As decreased following application of 0.5%–2%RHA.RHA promote the transformation of Cd to insoluble fraction,while As was transformed from a poorly soluble form to a more active one.RHA reduced Cd content and increased Si content in porewater,and reduced As only at the later rice growth stages.RHA increased the amount of iron plaque,thereby decreasing the Cd content in iron plaque,while increased the As content in it.Cd and inorganic As content in brown rice were decreased,to 0.31 mg/kg and 0.18 mg/kg,respectively.The decrease of Cd in brown rice was due to the decrease of Cd mobility in soil,thereby reducing root accumulation,while the decrease of As in brown rice was affected by the transport from roots to stems.Therefore,RHA can be considered as a safe and efficient in-situ remediation amendment for Cd and As co-contaminated paddy soil.
基金supported by the National Key Research and Development Program of China(No.2019YFC1803900)the National Natural Science Foundation of China(No.42277486).
文摘Thermal treatment can effectively decontaminate soils but alter their properties.Previous research mainly focused on volatile organic compounds andmetals,i.e.Hg,neglecting nonvolatile metal(loid)s.This study aimed to investigate Cd and As transformation during aerobic and anaerobic calcination.The results showed that both aerobic and anaerobic calcination increased soil pH by reducing soil organic matter(SOM)content,which also influenced the cation exchange capacity(CEC)and the leaching behavior of Cd and As in the soil.The total concentrations of Cd and As in the calcined soils varied depending on the calcination temperature and atmosphere.When the aerobic calcination temperature exceeded 700℃,Cd volatilized as CdCl_(2),while anaerobic calcination at relatively low temperatures(600℃)involved reductive reactions,resulting in the formation of metallic Cd with a lower boiling point.Similarly,As volatilized at 800℃aerobically and 600℃anaerobically.The formation of As-based minerals,particularly Ca3(AsO4)2,hindered its gasification,whereas anaerobic calcination promoted volatilization efficiency through the generation of C-As(III)based gaseous components with lower boiling points.Contrasting trends were observed in the TCLP-extractable Cd and As contents of the calcined soils.Over 70%of TCLP-extractable Cd contents were suppressed after thermal treatment,attributed to the elevated pH and reduced CEC of the soil,as well as volatilization.However,TCLP-extractable As contents increased with elevated temperatures,likely due to the desorption of AsO43−and re-adsorption of gaseous As2O3 during cooling.These findings have implications for assessing the environmental impact of thermal treatment and provide insights for remediation strategies concerning Cd and As-contaminated soils.
基金The work was financially supported by China Geological Survey(Grant No.DD202201756,DD20230428).
文摘Arsenic(As),fluoride(F^(−))are both ubiquitous in groundwater,and co-exposure to these elements through contaminated drinking water may cause detrimental effects on human health more in comparison with individual exposure.As,F^(−)co-occurrence in groundwater of the inland plain in Huaihe River Basin,China is a major concern,where inhabitants are rely on groundwater as the leading water source for drinking to date.This work employs an approach of hydrochemical analysis and modelling to identify the possible origin of As and F^(−),to analyze co-enrichment mechanism,and to estimate the associated exposure risk.The results shows presence of elevated As and F^(−)concentrations is an important factor affecting groundwater quality from 62 groundwater samples.The recorded As concentrations vary from 0.23 to 20.40μg/L,with a mean of 5.95μg/L,F^(−)concentrations vary from 0.54 to 2.60μg/L,with a mean of 1.29 mg/L,and 8%of samples are simultaneously above their permissible limits in drinking water by the WHO.Groundwater with As,F^(−)co-contamination is occurred within reducing and alkaline aquifers,and its chemical type is HCO_(3)–Na.The hydrochemical processes involved in the co-contamination are reductive desorption,evaporation,and ion exchange,which are controlled by local geology,geomorphology,and hydrochemistry.Groundwater As is derived and released by reductive desorption and F^(−)is mainly originated by fluorite dissolution.Groundwater As,F^(−)are geogenic sources,and the mechanisms for co-contamination are associated with high elemental abundance,flat terrain,alkaline and reductive groundwater conditions.The research provides a case study about groundwater As,F^(−)co-contamination,which may be enhance understanding the co-enrichment mechanism in semi-humid areas.
