Recycling arsenic-containing bio-leaching residue after thermal treatment in cemented paste backfill:Structure modification,binder properties and environmental assessment

The substantial arsenic(As)content present in arsenic-containing bio-leaching residue(ABR)presents noteworthy environ-mental challenges attributable to its inherent instability and susceptibility to leaching.Given its elevated calcium sulfate content,ABR exhibits considerable promise for industrial applications.This study delved into the feasibility of utilizing ABR as a source of sulfates for producing super sulfated cement(SSC),offering an innovative binder for cemented paste backfill(CPB).Thermal treatment at varying temperatures of 150,350,600,and 800℃ was employed to modify ABR’s performance.The investigation encompassed the examination of phase transformations and alterations in the chemical composition of As within ABR.Subsequently,the hydration characteristics of SSC utilizing ABR,with or without thermal treatment,were studied,encompassing reaction kinetics,setting time,strength development,and microstructure.The findings revealed that thermal treatment changed the calcium sulfate structure in ABR,consequently impacting the resultant sample performance.Notably,calcination at 600℃ demonstrated optimal modification effects on both early and long-term strength attributes.This enhanced performance can be attributed to the augmented formation of reaction products and a densified micro-structure.Furthermore,the thermal treatment elicited modifications in the chemical As fractions within ABR,with limited impact on the As immobilization capacity of the prepared binders.

Distribution and Contamination of Arsenic in Fish, Gastropods and Bivalves in the Aby and Tendo Lagoons in East of Ivory Coast

Lagoons are ecosystems for biodiversity and the livelihoods of coastal communities. The main objective of the study was to analyze the variability of arsenic concentrations in gastropods and bivalves in the Aby and Tendo lagoons, taking into account spatial, seasonal and hydrological variations. The study was carried out in four stages spread over two successive hydroclimatic cycles, including two seasons during the rainy season and two more during the dry season. The samples were taken in two areas of the Aby and Tendo lagoons. Arsenic levels were measured by ICP-MS. The results showed that mean arsenic concentrations in the muscles of organisms in Aby Lagoon ranged from 0.01 to 1.26 μg As/g, with a mean and median of 0.17 and 0.06 μg As/g, respectively. Fish had the highest levels of arsenic, followed by crustaceans, while molluscs and plants had lower and comparable concentrations of As. Arsenic concentrations in tilapia and jawbones varied significantly between sites and seasons, with higher concentrations at Tendo and during the rainy season. Arsenic concentrations in gastropods and bivalves were significantly higher than those of other species, with averages of 0.74 and 1.03 mg As/kg, respectively.

Roles of Aqueous Extract of Marigold on Arsenic-Induced Oxidative Damage in Pancreatic Islet β-Cells

Roles of Marigold extracts (ME) on arsenic trioxide (ATO)-induced oxidative damage to pancreatic β-cells need to be further elucidated. In this study, NIT-1 cells were treated with different concentrations of and/or ATO, following by the cell viability was detected by CCK8 assay. Then, intracellular reactive oxygen species (ROS) levels, lipid peroxide (MDA) contents and superoxide dismutase (SOD) activity were measured with a fluorescence probe method and colorimetric assay, respectively. The apoptosis rate and morphology was detected and observed with hoechst 33,258 staining assay. The mRNA levels and protein expressions of nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were measured by real-time fluorescence quantitative polymerase chain reaction and protein immunoblotting assay, respectively. Our results indicated that Co-treatment with ME and ATO exacerbated the cell viability decreasing reduced by ATO, while the addition of ME after ATO treatment effectively promote the recovery of ATO reduced survival rates. The ATO group increased apoptosis (P P β-cells by modulating the activation of the Nrf2 signaling pathway.

Feasibility Evaluation of Using Biochar-based Permeable Reactive Barrier for the Remediation of Mercury and Arsenic Composite Polluted Water Bodies

This study employed a modified biochar material to construct a permeable reactive barrier(PRB)for the treatment of water bodies polluted with mercury and arsenic.The experimental results demonstrated that the addition of goethite-modified biochar significantly enhanced the remediation efficiency of As(III),achieving a maximum removal rate of 100%.Conversely,pure biochar exhibited high efficiency in the removal of Hg(II),with a maximum removal rate approaching 100%.Furthermore,the pH level of the water significantly influenced the adsorption efficiency of heavy metal ions,with the optimal removal performance observed at a pH of 6.0.The PRB system demonstrated excellent removal rates under low concentrations of heavy metals.However,as the concentration increased,the remediation efficiency exhibited a slight decrease.In summary,the findings of this study provide compelling evidence for the use of modified biochar in the construction of PRBs for the remediation of mercury and arsenic-polluted water bodies.Furthermore,the study reveals the mechanism by which pH and heavy metal concentration influence remediation efficiency.

Removal and stabilization of arsenic from anode slime by forming crystal scorodite

A process was proposed for removing and stabilizing arsenic(As) from anode slime. The anode slime with high arsenic concentration was pretreated by circular alkaline leaching process. Then, the arsenic in the leaching solution can be further precipitated as a form of scorodite crystalline(FeAsO4·2H2O). In the precipitating arsenic reaction, in which ferrous ions were oxidized by air gas, the effects of acidity(p H), reaction temperature, air flow rate, initial concentration of arsenic and initial molar ratio of Fe(II) to As(V) on arsenic precipitation were investigated. The results showed that sufficiently stable crystal scorodite could be achieved under the condition of initial arsenic concentration of 10 g/L, pH 3.0-4.0, Fe/As molar ratio of 1.5, the temperature of 80-95 °C, and the air flow rate higher than 120 L/h. Under the optimal condition, more than 78% of arsenic could be precipitated as a form of scorodite crystalline. The As leaching concentration of the precipitates was less than 2.0 mg/L and the precipitates may be considered to be safe for disposal.

Leaching behavior of metals from high-arsenic dust by NaOH-Na_2S alkaline leaching

Arsenic is selectively extracted from high-arsenic dust by NaOH-Na2S alkaline leaching process. In the leaching arsenic process, the effects of alkali-to-dust ratio, sodium sulfide addition, leaching temperature, leaching time and liquid-to-solid ratio on metals leaching efficiencies were investigated. The results show that the arsenic can be effectively separated from other metals under the optimum conditions of alkali/dust mass ratio of 0.5, sodium sulfide addition of 0.25 g/g, leaching temperature of 90 ℃, leaching time of 2 h, and liquid-to-solid ratio of 5：1 （mL/g）. Under these conditions, the average leaching efficiencies of arsenic, antimony, lead, tin and zinc are 92.75%, 11.68%, 0.31%, 29.75% and 36.85%, respectively. The NaOH-Na2S alkaline leaching process provides a simple and highly efficient way to remove arsenic from high-arsenic dust, leaving residue as a suitable lead resource.

Determination of Arsenic and Mercury in Soil by Microwave Digestion and Hidride GenerationAtomic Fluorescence Spectrometry

[Objective] The aim was to develop a rapid, simple method for determina- tion of arsenic and mercury in soil samples by atomic fluorescence spectrometry. [Method] The method for determination of As and Hg in soil by combined atomic fluorescence spectrometry and microwave digestion was used. [Result] The concentration curve was linear within the range of 0-80.0μg/L of As and 0-8.0 μg/L of Hg, and the detection limits of As and Hg was 0.036 μg/L and 0.015 μg/L, respectively. The precision for elevenfold determination of As at 40.0 ug/L level and Hg at 4.0μg/L level were 1.1% and 2.2%（RSD）, respectively. Recoveries of 103.0%-106.6% for As and 90.0%-95.0% for Hg were obtained for there soil samples. [Conclusion] The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for determination of As and Hg in soil samples.

Dissolved Inorganic Arsenic in the Yellow Sea and the East China Sea—Distributions and Seasonal Variations

The distributions and seasonal variations of total dissolved inorganic arsenic （TDIAs, [TDIAs] = [As^5＋]＋[As^3＋]） and arsenite （As3.） in the Yellow Sea and East China Sea are presented hero based on the observations of 9 cruises carried out in 2000 - 2003. The study area covers a broad range of hydrographic and chemical properties. The emphasis is put on a southeast transect from Changjiang Estuary to the Ryukyu Islands （i.e. PN section） in the East China Sea to discuss the impact of terrestdal input on the marginal seas of China. Arsenic species （TDlAs and arsenite） are determined by selective hydride generation - atomic fluorescence spectrometry （HG-AFS）. TDIAs concentrations were high in the coastal area of Changjiang Estuary and decreased slightly towards the shelf region. High concentratiOns of TDIAs were also existed in the near bottom layer of shelf edge of the East China Sea which indicated another source of arsenic from the incursion of Kuroshio Waters. The seasonal variations of TDIAs in the study area depend on the hydrographic stages of Changjiang and the incursion intensity of Kuroshio Waters. Arsenite showed opposite distributions with TDIAs, with higher concentrations appeared at the surface layer of shelf region, which was positive correlated with the chlorophyll a. Biological conversion of arsenate into arsenite was hypothesized for the observed distribution pattern and its seasonal variations. The stoichoimetric ratios of As to P were estimated to be about 2×10^3 at PN Section in summer. The concentrations of dissolved arsenic in the Yellow Sea and East China Sea were comparable with other areas in the world.

Arsenic trioxide inhibites transgenic tumor necrosis factor-α promoter activity in vascular smooth muscle cells and THP-1 monocytes in vitro

Aim This study was to evaluate the effect of arsenic trioxide （As2O3） on the transgenic TNF-α promoter activity in cultured vascular smooth muscle cells （VSMCs） and THP-1 monocytes. Methods Human TNF-α promoter was constructed by reporter gene system and was transiently transfected into VSMCs and THP-1 in vitro. The promoter activity was tested by luciferase activity with or without LPS and Ang Ⅱ stimulation, before and after different dosage of As2O3 treatment. Results 1. TNF-α promoter effectively expressed in VSMCs and THP-1 compared with CMV promoter （58.3% and 80.9%, respectively）. Both LPS and Ang Ⅱ significantly up-regulated TNF-α promoter activity （P〈0.05）. 2. As2O3 significantly inhibited, both intact and LPS/Ang Ⅱ stimulated promoter activity, in a dose dependent manner （P〈0.05）, and in both cell type. Conclusion These results manifested that, the inhibition effect of As2O3 on the activity of human TNF-α promoter indicated its potential inhibition on pro-inflammatory cytokine genes expression at transcriptional level and its potential anti-inflammatory property in the cardiovascular system.

Induction of apoptosis by arsenic trioxide and hydroxycamptothecin in gastric cancer cells in vitro

AIM To study the effects of arsenic trioxide andHCPT on different degrees of differentiated gastriccancer cells（SGC-7901,MKN-45,MKN-28）withrespect to both cytotoxicity and induction ofapoptosis in vitro.METHODS The cytotoxicity of As2O3 and HCPTon gastric cancer cells was determined by MTTassay.Morphologic changes of apoptosis ofgastric cancer cells were observed by lightmicroscopy and transmission electron microscopy.Apoptosis and cell cycle changes of gastric cancercells induced by HCPT and As2O3 were investigatedby TUNEL method and flow cytometry.RESULTS As2O3 and HCPT had remarkablecytotoxic effects on different degrees ofdifferentiated gastric cancer cells.The IC50ofAs2O3 on well differentiated gastric cancer cellMKN-28,moderately differentiated gastric cancercell SGC-7901,and poorly differentiated gastriccancer cell MKN-28 were 8.91 μmol/L,10.57μmol/L,and 11.65 μmol/L,respectively.The IC50of HCPT on MKN-28,SGC-7901,and MKN-45 were9.35 mg/L,10.21 mg/L,and 12.63 mg/Lrespectively after 48 h treatment.After 12 h ofexposure to both drugs,gastric cancer cellsexhibited morphologic features of apoptosis,including cell shrinkage,nuclear condensation, and formation of apoptotic bodies.A typicalsubdiploid peak before G0/G1 phase was observedby flow cytometry.The apoptotic rates of SGC-7901,MKN-45,and MKN-28 were 13.84%,22.52%,and 9.68%,respectively after 48 hexposure to 10 μmol/L As2O3.The apoptotic ratesof SGC-7901,MKN-45,and MKN-28 were 21.88%,12.35%,and 30.26%,respectively after 48 hexposure to 10 mg/L HCPT.The apoptotic indicewere 7%-15% as assessed by TUNEL method.The effect of As2O3 on SGC-7901 showedremarkable cell cycle specificity,which inducedcell death in G1 phase,and blocked G2/M phase.HCPT also showed a remarkable cell cyclespecificity,by inducing cell death and apoptosis inG1 phase and arrest of proliferation at S phase.CONCLUSION As2O3 and HCPT exhibitsignificant cytotoxicity on gastric cancer cells byinduction of apoptosis.As2O3 and HCPT mighthave a promising prospect in the treatment ofgastric cancer,which needs to be further studied.

Effects of arsenic on seed germination and physiological activities of wheat seedlings

The effects of arsenic （As） were investigated on seed germination, root and shoot length and their biomass and some other factors to elucidate the toxicity of As. The results showed low concentrations of As （0-1 mg/kg） stimulated seed germination and the growth of root and shoot, however, these factors all decreased gradually at high concentrations of As （5-20 mg/kg）. The contents of O2^-, MDA, soluble protein and peroxidase （POD） activity all increased with increasing As concentrations. Soluble sugar content, ascorbate peroxidase （APX）, and superoxide dismutase （SOD） activities decreased at low concentrations of As, and increased at high concentrations of As. While acetylsalicylic acid （ASA） and chlorophyll contents, catalase （CAT） activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg, and then decreasing trend. By polyacrylamide gel electrophoresis （PAGE）, As induced the expression of POD isozymes of wheat seedlings. As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg. However, As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg. The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.

Practical performance and its efficiency of arsenic removal from groundwater using Fe-Mn binary oxide

A treatment unit packed by granular adsorbent of Fe-Mn binary oxide incorporated into diatomite （FMBO（1：1）-diatomite） was studied to remove arsenic from anaerobic groundwater without any pre-treatment or post-treatment. The raw anaerobic groundwater containing 35-45 μg/L of arsenic was collected from suburb of Beijing. Arsenic（Ⅲ） constituted roughly 60%-80% of the total arsenic content. Approximately 7,000 bed volumes （ratio of effluent volume to adsorbent volume） treated water with arsenic concentration below 10 μg/L were produced in the operation period of four months. The regeneration of FMBO（1：1）-diatomite had been operated for 15 times. In the first stage, the regeneration process significantly improved the adsorption capacity of FMBO（1：1 ）-diatomite. With increased loading amount of Fe-Mn binary oxide, the adsorption capacity for arsenic decreased 20%-40%. Iron and manganese in anaerobic groundwater were oxidized and adsorptive filtrated by FMBO（1 ： 1）-diatomite efficiently. The final concentrations of iron and manganese in effluents were nearly zero. The continued safe performance of the treatment units proved that adsorbent FMBO（1：1）- diatomite had high oxidation ability and exhibited strong adsorptive filtration.

Arsenic uptake and transport of Pteris vittata L.as influenced by phosphate and inorganic arsenic species under sand culture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in Ashyperaccumulator, uptake and transport of arsenate （As（V）） and arsenite （As（Ⅲ）） were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As（Ⅲ） more than As（Ⅴ）, while the reverse was observed at high concentrations of phosphate （≥1.0 mmol/L）. Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As（Ⅴ）. It may in part be due to competition between phosphorus and As（Ⅴ） during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As（Ⅲ）. Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposed to As（Ⅴ）, but the suppression of phosphate to As transport may be insignificant when P. vittata exposed to As（Ⅲ） under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.

Optimization on selenium and arsenic conversion from copper anode slime by low-temperature alkali fusion process

A process was proposed to convert and separate selenium and arsenic in copper anode slime(CAS) by low-temperature alkali fusion process.Central composite design was employed to optimize the effective parameters,in which Na OH/CAS mass ratio,fusion temperature and fusion time were selected as variables,and the conversion ratio of selenium and arsenic as responses.Second-order polynomial models of high significance and 3D response surface plots were constructed to show the relationship between the responses and the variables.Optimum area of >90% selenium conversion ratio and >90% arsenic conversion ratio was obtained by the overlaid contours at Na OH/CAS mass ratio of 0.65-0.75,fusion temperature of 803-823 K and fusion time of 20-30 min.The models are validated by experiments in the optimum area,and the results demonstrate that these models are reliable and accurate in predicting the fusion process.

Changes in hair arsenic concentration in a population exposed to heavy pollution:Follow-up investigation in Chenzhou City,Hunan Province,Southern China

Follow-up investigation on hair arsenic concentration was conducted in an arsenic heavily polluted area of southern China in 2002 and 2006. The results showed that the geometric mean of hair arsenic concentration decreased from 2.95 mg/kg in 2002 to 1.78 mg/kg in 2006, when the percentage of the population with levels over 1 mg/kg only decreased from 93.4% in 2002 to 80.5% in 2006. Over this four-year period, the population with high arsenic concentrations decreased significantly while there was no obvious change in hair arsenic concentration for people who had relatively low concentrations. In terms of age distribution, young and old people had higher hair arsenic concentrations than the middle-aged. All of these results showed that it is difficult to reverse the negative impact of arsenic pollution on human health. Arsenic pollution has a long-term continuous influence on the health of local residents.

Grape Seed Proanthocyanidin Extract Alleviates Arsenic-induced Oxidative Reproductive Toxicity in Male Mice

Objective To determine the ability of grape seed proanthocyanidin extract （GSPE） in alleviating arsenic-induced reproductive toxicity. Methods Sixty male Kunming mice received the following treatments by gavage： normal saline solution （control）; arsenic trioxide （ATO; 4 mg/kg）; GSPE （400 mg/kg）; ATO＋GSPE （100 mg/kg）; ATO＋GSPE （200 mg/kg） and ATO＋GSPE （400 mg/kg）. Thereafter, the mice were sacrificed and weighed, and the testis was examined for pathological changes. Nuclear factor （erythroid-derived 2）-like 2 （Nrf2）, heme oxygenase 1 （HO1）, glutathione S-transferase （GST）, NAD（P）H dehydrogenase, and quinone 1 [NQO1） expression in the testis was detected by real-time PCR. Superoxide dismutase （SOD）, glutathione （GSH）, total antioxidative capability （T-AOC）, malondialdehyde （MDA）, 8-hydroxydeoxyguanosine （8-OHdG）, and reproductive indexes were analyzed. Results ATO-treated mice showed a significantly decreased sperm count and testis somatic index and activity levels of SOD, GSH, and T-AOC than control group. Compared to the ATO-treated group, ATO ＋GSPE group showed recovery of the measured parameters. Mice treated with ATO＋high-dose GSPE showed the highest level of mRNA expression of Nrf2, HO, NO.O1, and GST. Conclusion GSPE alleviates oxidative stress damage in mouse testis by activating Nrf2 signaling, thus counteracting arsenic-induced reproductive toxicity.

Recent advances in arsenic trioxide encapsulated nanoparticles as drug delivery agents to solid cancers

Since arsenic trioxide was first approved as the front line therapy for acute promyelocytic leukemia 25 years ago,its anti-cancer properties for various malignancies have been under intense investigation.However,the clinical successes of arsenic trioxide in treating hematological cancers have not been translated to solid cancers.This is due to arsenic＇s rapid clearance by the body＇s immune system before reaching the tumor site.Several attempts have henceforth been made to increase its bioavailability toward solid cancers without increasing its dosage albeit without much success.This review summarizes the past and current utilization of arsenic trioxide in the medical field with primary focus on the implementation of nanotechnology for arsenic trioxide delivery to solid cancer cells.Different approaches that have been employed to increase arsenic＇s efficacy,specificity and bioavailability to solid cancer cells were evaluated and compared.The potential of combining different approaches or tailoring delivery vehicles to target specific types of solid cancers according to individual cancer characteristics and arsenic chemistry is proposed and discussed.

Evaluation of the adsorption potential of titanium dioxide nanoparticles for arsenic removal

The adsorption potential of titanium dioxide （TiO2） nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight （A-SL）, air-light （AL）, air-dark （AD） and nitrogen-dark （ND）. X-ray diffraction （XRD） analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystai sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As（V） was adsorbed more compared with As（Ⅲ）. The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.

Effect of arsenic trioxide on human hepatoma cell line BEL-7402 cultured in vitro

AIM To study the effect of a varyingconcentrations of arsenic trioxide on humanhepatoma cell line BEL-?402 cultured in vitro andits mechanism of action.METHODS The BEL-7402 cells were treatedwith arsenic trioxide（at the concentrations of0.5,1,2 μmol/L,respectively）for 4 successivedays.The cell growth and proliferation wereobserved by cell counting and cell-growth curve.Morphologic changes were studied withelectronmicroscopy.Flow cytometry was usedto assay celI-DNA distribution and the proteinexpression of Bcl-2 and Bax detected byimmunocytochemical method.RESULTS The cell growth was significantlyinhibited by varying concentrations of arsenictrioxide as revealed by cell counting and cell-growth curve,which was dose- and time-dependent.Arsenic trioxide treatment at 0.5,1and 2 μmol/L resulted in a sub-G1 cell peak,theapoptosis rate of the control group was 9.31%and that of 0.5 μmol/L arsenic trioxide 15.53%,no significant difference was seen between thetwo.The apoptosis rates of 1,2 μmol/L arsenictrioxide were 19.10% and 21.87% respectively,which were much higher（both P【0.05）.Decrease of G0/G1 phase cells and increase of Sphase cells were observed by flow cytometry,suggesting the inhibition effect of 0.5,1,2 μmol/L arsenic trioxide on BEL-7402 cell lay in the G0/G1 phase.Morphologic changes such asintact cell membrane,nucleic condensation,apoptotic body formation were seen undertransmission electronmicrescopy,whereas the0.5 mol/L arsenic trioxide-treated BEL-7402cells showed decrease of nucleocytoplasmicratio,round nucleus,well-differentiatedorganelles in the cytoplasm.The processes andmicrovilli on the cell surface of the experimentalgroups under scanning electron microscopy weresignificantly decreased.High expressions ofBcl-2 and Bax were detected in 1 and 2 μmol/Larsenic trioxide-treated cells,these were 46%,87.33% and 83.08%,95.83% respectively,among which that of Bax was more significant.Arsenic trioxide treatment at 0.5 μmol/Lresulted in a higher expression level of Bcl-2 andlower expression level of Bax,which were8.81% and 3.83% respectively,as comparedwith that of the control group（15.33%）（P1【0.01,P2【0.01）.CONCLUSION Arsenic trioxide not onlyinhibited proliferation but also induced apoptosisof human hepatoma cell line BEL-7402.Theinduced-apoptosis effect of 1,2 μmol/L arsenictrioxide was related to the expression level ofBcl-2 and Bax.

Potential of Pteris vittata L. for phytoremediation of sites co-contaminated with cadmium and arsenic: The tolerance and accumulation

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.