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1.
Soil contaminated by chromium (Cr) is a major concern for sustainable agriculture. Considering this as a basis, the present study was designed to isolate Cr(VI)-reducing and plant growth-promoting bacterial strain from contaminated sampling sources. In this study, Rhizobium strain ND2 was isolated from the root nodules of Phaseolus vulgaris grown in leather industrial effluent contaminated soil. The strain ND2 exhibited strong resistance to different heavy metals and reduced 30 and 50 µg ml?1 concentrations of Cr(VI) completely after 80 and 120 h of incubation, respectively, as well as chromium adsorption and immobilization were confirmed by scanning electron microscopic equipped with energy X-ray spectroscopy. In addition, the strain produced 21.73 and 36.86 µg ml?1 of indole-3-acetic acid at 50 and 100 µg ml?1 of L-tryptophan supplimentations, respectively. Strain ND2 positively affected the exo-polysaccharide, ammonia, protease and catalase production and stimulated root length of various test crops under Cr(VI) stress. Moreover, Rhizobium strain ND2 has the potential to colonize the diverse agricultural crops. Thus, the present findings strongly suggested that the multipotential properties of ND2 could be exploited for bioremediation of contaminated sites with Cr(VI) as well as potential bio fertilizer for enhancing the agricultural productivity.  相似文献   

2.
This study has investigated how to simultaneously remove both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid) from river water using potassium ferrate (K2FeO4), a multipurpose chemical acting as oxidant, disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal efficiency ranged 28–99% for Cu, 22–73% for Mn, and 18–100% for Zn at the ferrate(VI) doses of 0.03–0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH, whereas an overall temperature did not make any special effect on the reaction between the heavy metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03–0.7 mM (as Fe): 87–100% (Cu), 31–81% (Mn), 11–100% (Zn), and 33–86% (NOM). In the single heavy metal solution, the optimum ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn, and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy metals and negatively charged functional groups of NOM, enhancing the removal of both heavy metals and NOM by ferrate(VI).  相似文献   

3.
In consideration of the hazards associated with the presence of the textile azo-dye and their biotransformation products in the environment, the goal of this work was to study bioremediation process by the yeast strain Pichia kudriavzevii CR-Y103 related to the ability to degrade and detoxify the sulfonated Reactive Orange 16 azo-dye. In experimental conditions, the optimal inoculum/dye concentration ratio required for complete decolorization (100%) of culture medium and biomass within 24 h has been 1 g L?1 yeast cell (dry weight)/50 mg L?1 Reactive Orange 16. In the presence of 400 mg L?1 of Reactive Orange 16 (RO16), 95% of the dye was removed after 72 h of incubation. Also, the yeast strain could decolorize other eight textile dyes (56.48–99.98% decolorization within 24 h). NADH-DCIP reductase and azo reductase activities were significantly increased (ca. 5.4 times and ca. 37 times, respectively) during the decolorization process. UV-VIS spectra, high-performance liquid chromatography (HPLC), and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of new biotransformation products in extracted metabolites, highlighting the partial biodegradation of the dye by the new yeast isolate. The phytotoxicity evaluation strongly supported the decreased toxicity of biodegraded products as minor inhibition on germination (%), root and shoots elongation of T. pratense L. and T. aestivum L. seedlings. Increasing of mitotic index value and decreasing the frequency of chromosomal aberrations in tested plant meristem cells treated with biodegraded products, compared with RO16 treatment (500 ppm), confirmed their slightly toxic nature. A cell viability assay also confirmed the reduced toxicity of biodegraded products on healthy monkey kidney cells (Vero cells).  相似文献   

4.
Abstract

Phytotoxicity, due to chromium [Cr (VI)] additions from low to very high levels in a swell–shrink clayey soil (Haplustert), in maize and spinach was studied in a pot culture experiment. Six levels of Cr (VI) (0, 5, 10, 25, 50, and 75 mg kg?1 soil) for maize and five levels for spinach (0, 2, 5, 10, and 25 mg kg?1 soil) were applied singly and in combination with two doses (0 and 20 t ha?1) of city compost. At levels of more than 75 mg Cr (VI) kg?1 soil for maize there was virtually no growth after germination, whereas 25 mg Cr (VI) kg?1 soil hindered the germination of spinach crop. Initial symptoms of Cr (VI) toxicity appeared as severe wilting of the tops of treated plants. Maize plants suffering from severe Cr (VI) toxicity had smaller roots and narrow brownish red leaves covered with small necrotic spots. In spinach, severe chlorosis was observed in leaves. Higher levels of Cr (VI) inhibited the growth and dry‐matter yield of the crops. However, application of city compost alleviated the toxic effect of Cr (VI). The concentration of Cr (VI) in plant parts increased when Cr (VI) was applied singly but decreased considerably when used in combination with city compost. There was evidence of an antagonistic effect of Cr (VI) on other heavy‐metal (Mn, Cu, Zn, and Fe) concentrations in plant tops. Thus, when Cr (VI) concentration increases, the concentration of other beneficial metals decreases. Chromium (VI) concentration in maize roots ranged from traces (control) to 30 mg kg?1and were directly related to soil Cr (VI) concentration. At 25 mg Cr (VI) kg?1 soil, yield of maize was reduced to 41% of control plants, whereas in spinach, 10 mg Cr (VI) kg?1 soil caused a 33% yield reduction. Experimental results revealed that the maize top (cereal) is less effective in accumulating Cr (VI) than spinach (leafy vegetables). Laboratory studies were also conducted to know Cr (VI) sorption capacity of a swell–shrink clayey soil with and without city compost, and it was found that Cr (VI) sorption reaction was endothermic and spontaneous in nature.  相似文献   

5.
The purpose of this study is to evaluate the combined Cr(VI) removal capacities of nonliving (untreated rubber wood sawdust, URWS) and living biomass (URWS-immobilized Acinetobacter haemolyticus) in a continuous laboratory scale downward-flow two column system. Synthetic solutions of Cr(VI) between 237 and 320 mg L?1 were mixed with 1 g L?1 brown sugar in a nonsterile condition. Final Cr(VI) of between 0 and 1.6 mg L?1 indicate a Cr(VI) removal capacity of 99.8–100%. The bacterial Cr(VI) reduction capacity increased with column length. This study shows the feasibility of using the two column system consisting of living (bacteria) and nonliving biomass (URWS) as a useful alternative treatment for Cr(VI) contamination in the aqueous system.  相似文献   

6.
The removal efficiency and tolerance of Typha domingensis to Cr(VI) in treatments with and without organic matter (OM) addition were evaluated in microcosm-scale wetlands. Studied Cr(VI) concentrations were 15 mg L?1, 30 mg L?1, and 100 mg L?1, in treatments with and without OM addition, arranged in triplicate. Controls (without neither metal nor OM addition—without metal with OM addition) were disposed. Cr(VI) was removed efficiently from water in all treatments. OM addition enhanced significantly Cr(VI) and total Cr removals from water. In the treatments with OM addition, significantly higher Cr concentrations were found in sediment than the treatments without OM addition. Plants of the treatments without OM addition showed significantly higher Cr concentrations in tissues but lower biomass increase than the treatments with OM addition. The highest Cr concentrations in tissues were observed in submerged parts of leaves, followed by roots. According to SEM analysis, in the 100 mg L?1 treatments, the highest Cr accumulation was observed in the epidermis of old leaves. Although Cr(VI) produced changes in root morphology, the OM addition favored the plant growth. In T. domingensis, root morphological plasticity is an important mechanism to improve metal tolerance and Cr uptake in wetland systems minimizing the environmental impact.  相似文献   

7.
Trypan Blue, an azo dye, was decolorized using the self-immobilizing fungal biomass of Pycnoporus sanguineus. The extent and the rate of dye decolorization were directly proportional to the initial dye concentration (20–60 mg L?1) and the reaction temperature (25–45°C). Mass transfer within and outside the pellets did not limit dye degradation. The apparent kinetics of the decolorization reaction followed a first-order behavior. Activation energy for the biological decolorization was calculated at 23 kJ mol?1. The decolorization process was endothermic with the enthalpy and entropy values calculated at 45.6 kJ mol?1 and 146 J mol?1 K?1, respectively. Based on the value of Gibbs free energy change, the decolorization reaction under the conditions studied was non-spontaneous below 39°C but was spontaneous at higher temperatures.  相似文献   

8.
The aim of this work was to study the degradation of three azo dyes, Orange II, Methyl red and Biebrich Scarlet by electro-Fenton and the effect of the electrochemical pretreatment on the biodegradability of the solutions. The electrochemical pretreatment showed that an electrochemical reduction on the carbon felt electrode was mainly responsible for the decolorization of the azo dyes. Indeed, the electrochemical behaviour of the azo dyes highlighted their electroactivity; electrolysis with and without ferric ions led to the same decolorization yield, namely 99 % at 15 min for Methyl red, and stable chemical oxygen demand (COD) values were recorded during decolorization. In a second step and owing to the absence of by-product electroactivity in reduction, the formation of hydroxyl radicals by the Fenton reaction led to the oxidation of by-products from the electrochemical reduction. It was illustrated by the decrease recorded for the COD values. The results also showed that the azo bond cleavage occurring during the electrochemical reduction was not sufficient to significantly reduce recalcitrance, as shown from biological oxygen demand (BOD)5/COD ratio examination below the limit of biodegradability (0.4). Contrarily, a positive trend was recorded for Orange II during the electro-Fenton reaction, with a BOD5/COD ratio of 0.81 after 28 h of pretreatment.  相似文献   

9.
Abstract

A rapid, sensitive, and accurate method for the separation and speciative determination of chromium (Cr)(VI) and Cr(III) in water samples has been developed using sorption as the separation technique in conjunction with final determination by electrothermal atomic absorption spectroscopy (ETAAS). The present method, where granular calcite is used as selective sorbent, separates Cr(III) with retention values up to 99%, resulting in high accuracy determination of Cr(VI). Total Cr was likewise determined by ETAAS after an efficient reduction of Cr(VI) to Cr(III) using ascorbic acid as reducing agent, deriving Cr(III) concentration from the difference between total Cr and Cr(VI). The parameters of the separation technique, solution pH (4.5–5.5), solution flow rate through the calcite column (0.14–0.42 mL min?1), and calcite column internal diameter (1.5–3.0 cm), were evaluated. Best results were achieved with pH of 5.5, flow rate of 0.42 mL min?1, and column internal diameter of 1.5 cm. Optimum determination conditions were found using magnesium nitrate [Mg(NO3)2] as chemical modifier, pyrolysis, and atomization temperatures of 1400 and 2200°C, respectively. In such conditions, the detection limits (n=10) were 1.5 and 0.8 µg L?1 for Cr(III) and Cr(VI), respectively.  相似文献   

10.
Abstract

Soils under the main mangrove (Rhizophora racemosa and Avicennia germinans) forest in the Niger Delta, Nigeria, were characterized, and their capacities to retain heavy metals were examined by using soil column leaching experiments, using 20 mg L?1 Cu, 50 mg L?1 Zn, 20 mg L?1 Cd, and 100 mg L?1 Mn solutions. At the end of the leaching experiments, soil samples from each column were divided into two layers (0–5 cm and 5–10 cm) and analyzed for total metal retained. The fractionation of heavy metals in the surface soil samples (0–5 cm) was investigated by the sequential extraction technique. The study showed that the soils were influenced by tidal flow and characterized by the presence of very fine textured, thin (0–5 cm) to moderately thick (10–15 cm) layer of alluvium (mud) on the surface. The fibric soil material beneath the surface mud varies in thickness from about 70 to 100 cm, and beyond the histic layer is the plastic, very sticky, massive clay. In situ, the soils were neutral in reaction (pH 7.0–7.2), but became strongly acid (pH 3.3–4.8) upon drying. They are saline, high in soluble salts, highly reduced, with CEC that is low in the fibric layer, but high in the mineral, clayey subsoil horizon. The soils are saturated with water for much more than 30 days in a year and have fiber content that is more than 40 cm thick, with the fibric sphagnum constituting more than three‐fourths by volume to a depth greater than 90 cm. The soils, classified as Typic Sphagnofibrists, sequestered considerable amounts of copper (Cu), zinc (Zn), cadmium (Cd), and manganese (Mn) with most of the metals retained in the surface soils. The anthropogenic heavy metals were mostly adsorbed probably to the negatively charged sites of organics and clay. These loosely bound metals may be desorbed and reenter the aqueous phase, thus becoming a secondary source of metal pollution.  相似文献   

11.
The main purpose of this work was to conduct a kinetic study on cell growth and hexavalent chromium [Cr(VI)] removal by Candida sp. FGSFEP in a concentric draft-tube airlift bioreactor. The yeast was batch-cultivated in a 5.2-l airlift bioreactor containing culture medium with an initial Cr(VI) concentration of 1.5 mM. The maximum specific growth rate of Candida sp. FGSFEP in the airlift bioreactor was 0.0244 h?1, which was 71.83% higher than that obtained in flasks. The yeast strain was capable of reducing 1.5 mM Cr(VI) completely and exhibited a high volumetric rate [1.64 mg Cr(VI) l?1 h?1], specific rate [0.95 mg Cr(VI) g?1 biomass h?1] and capacity [44.38 mg Cr(VI) g?1 biomass] of Cr(VI) reduction in the airlift bioreactor, with values higher than those obtained in flasks. Therefore, culture of Candida sp. FGSFEP in a concentric draft-tube airlift bioreactor could be a promising technological alternative for the aerobic treatment of Cr(VI)-contaminated industrial effluents.  相似文献   

12.
Chromium occurs naturally at trace levels in most soils and water, but disposal of industrial waste and sewage sludge containing chromium compounds has created a number of contaminated sites, which could pose a major environmental threat. This study was conducted to enumerate and isolate chromium-resistant microorganisms from sediments of evaporation ponds of a metal processing plant and determine their tolerance to other metals, metalloids and antibiotics. Enumeration of the microbiota of Cr-contaminated sediments and a clean background sample was conducted by means of the dilution-plate count method using media spiked with Cr(VI) at concentrations ranging from 10 to 1000 mg L?1. Twenty Cr(VI) tolerant bacterial isolates were selected and their resistance to other metals and metalloids, and to antibiotics was assessed using a plate diffusion technique. The number of colony-forming units (cfu) of the contaminated sediments declined with increasing concentrations from 10 to 100 mg L?1 Cr(VI), and more severely from 100 to 1000 mg L?1 Cr(VI). The background sample behaved similarly to 100 mg L?1 Cr(VI), but the cfu declined more rapidly thereafter, and no cfu were observed at 1000 mg L?1 Cr(VI). Metals and metalloids that inhibited growth (from the most to least inhibitory) were: Hg > Cd > Ag > Mo = As(III) at 50 μg mL?1. All 20 isolates were resistant to Co, Cu, Fe, Ni, Se(IV), Se(VI), Zn, Sn, As(V), Te and Sb at 50 μg mL?1 and Pb at 100 μg mL?1. Eighty-five percent of the isolates had multiple antibiotic resistance. In general, the more metal-tolerant bacteria were among the more resistant to antibiotics. It appears that the Cr-contaminated sediments may have enriched for bacterial strains with increased Cr(VI) tolerance.  相似文献   

13.

Purpose

The effect of pollutants in soil microorganisms is an important issue in order to understand their toxic effects in the environment, as well as for developing adequate bioremediation strategies. In this sense, the main objective of this study was to assess the involvement of the indigenous microbiota of an acidic forest Mediterranean soil by artificial pollution with heavy metals, and to detect and isolate resistant microorganisms that could be useful for bioremediation.

Materials and methods

Samples from a previously unpolluted acidic forest soil were amended with Cr(VI), Cd(II) or Pb(II) at total amounts ranging from 0.1 to 5,000 mg?kg?1. These soil microcosms were incubated under controlled laboratory conditions for 28 days. Soluble fractions of metals were determined from aqueous extracts. Both activity and composition of the microbial community were assessed, respectively, by respirometric assays and molecular analysis (polymerase chain reaction denaturing gradient gel electrophoresis). The isolation of metal-resistant microorganisms was attempted by culture plating from microcosms incubated with high concentrations of metals. Isolated strains were tested in cultures with minimal medium to check for their metal resistance and their capacity to reduce the presence of toxic Cr(VI).

Results and discussion

A decrease in the soil respirometric activity and changes in the microbial community composition were detected from 10/100 mg?kg?1 Cr and 1,000 mg?kg?1 Cd and Pb. Presumably resistant bacterial and fungal populations developed in most of these polluted microcosms; however, the microbiota was severely impaired at the highest additions of Cr. Even though Cr was the most damaging metal in soil microcosms, if the soluble fractions of metals are considered instead of their total added amounts, the comparison among their toxic effects suggests a similar potential toxicity of Cr and Pb. Isolated multiresistant microorganisms were related mainly to Actinobacteria, Firmicutes and Ascomycota. Some of them showed the capacity to reduce Cr(VI) concentrations between 54 % and 70 % of the initial value. These strains were affiliated to several species of Streptomyces and Bacillus.

Conclusions

The combination of respirometric assays with molecular methods has been useful to assess the effect of metals on the soil microbial community, which can greatly be explained by their differential bioavailability. Cultivation-dependent and -independent approaches have proved the presence and development of multiresistant microorganisms in a previously unpolluted soil. Due to their properties, some of the isolated strains are potentially useful for soil bioremediation.  相似文献   

14.
The use of two new ligands, (1Z)-1-(4-aminophenyl) ethan-1-one semicarbazone (L1) and (1Z)-1-(4-nitrophenyl)ethan-1-one semicarbazone (L2), was evaluated for their potential use as chelators in increasing phytoremediation effectiveness. The uptake of heavy metals by Teddy Bear sunflowers increased when L1 added at 0.1 and 0.3 g/kg. Metal uptake selectivity was Cr > Ni ? Cd for each treatment. The 0.1-g/kg L1 ligands produced a significant uptake of metals in Sundance sunflowers. The 0.3-g/kg L1 level increased the metal uptake, but it was lower than 0.1-g/kg L1 treatment. The uptake selectivity with L2 ligand was Cr > Ni > Cd, with the majority of metals retained in the roots. L1 ligand was better compared in comparison to L2 ligand for enhancing uptake of metals.  相似文献   

15.
The release of heavy metals in aquatic systems due to the discharge of industrial wastewaters is a matter of environmental concern. Heat-inactivated cells of a flocculent strain of Saccharomyces cerevisiae were used in the bioremediation, in a batch mode, of a real electroplating effluent containing Cu, Ni, and Cr. In this approach, no previous reduction of Cr(VI) to Cr(III) was required. Cr(VI) was selectively removed (98%) by yeast biomass at pH 2.3. At this pH, Cr(VI) is mainly in the form of HCrO 4 ? and yeast surface is surrounded by H+ ions, which enhance the Cr(VI) interaction with biomass binding sites by electrostatic forces. Subsequently, pH of the effluent was raised up to 6.0; this pH maximizes the efficiency of cations removal since at this pH the main binding groups of yeast cells are totally or partially deprotonated. The passage of effluent through a series of sequential batches, at pH 6.0, allowed, after the third batch, the removal of Cu(II), Ni (II), Cr total, and Cr(VI) in the effluent to values below the legal limit of discharge. The strategy proposed in the present work can be used in plants for the treatment of heavy metals rich industrial effluents containing simultaneously Cr(VI) and Cr(III).  相似文献   

16.
The influence of culture medium composition on chromium(VI) quantification according to diphenylcarbazide (DPC) colorimetric determination was evaluated. Considering the eventual biospeciation of Cr(VI) as a mechanism of microbial bioremediation, the possibility to quantify Cr(III) in culture medium was also explored. Yeast nitrogen base (YNB) was identified as the least interferent culture medium for Cr(VI) quantification by DPC and it was applied to compare different strategies for Cr(III) oxidation. The most appropriate oxidation protocol consisted in the reaction with 80 mM KIO4 at room temperature for 30 min prior to DPC. Parameters like basal culture medium (vitamins + salts + oligoelements), C and N source were systematically evaluated, either independently or in combination. Results demonstrated that C source was the most interferent culture medium component, being the use of sucrose preferable to glucose. A medium arbitrarily named as YNB′ (YNB without amino acids and ammonium sulfate plus 50 g L?1 sucrose and 0.6 g L?1 (NH4)2SO4) was defined for Cr(VI)-amended fungal cultures. Kinetics of growth, Cr(VI) removal, and nutrient consumption for isolates A. pullulans VR-8, filamentous fungus PMF-1, and Lecythophora sp. NGV-1 were obtained. The order of Cr(VI) removal efficiency was as follows: A. pullulans VR-8 > Lecythophora sp. NGV-1 > filamentous fungus PMF-1, and a similar trend was observed for biomass yield and nutrients consumption. Studies on biospeciation by means of the selected Cr(III) oxidation protocol were unsuccessful, leading to Cr(VI) values much lower than expected. It revealed that this kind of protocols should be cautiously evaluated when studying microbial Cr(VI) bioremediation.  相似文献   

17.
The goal of this study was to compare the performances of strong base anion (SBA) exchange and activated carbon adsorption in the removal of hexavalent chromium, Cr(VI), from a real groundwater matrix exploited for drinking purposes. Two SBA resins and three granular activated carbons (GAC) were tested by batch experiments for kinetics and equilibrium isotherm determination. SBA resins showed higher affinity toward Cr(VI) (present in raw water at about 20 μg L?1) with respect to the GACs, with faster kinetics and higher equilibrium adsorption capacities. Among GACs, vegetal-based carbons showed higher Cr(VI) removal efficiencies than the mineral-based carbon, which can be related to the more developed textural properties. SBA resins also displayed relevant removal capacities towards nitrate and sulfate (present at mg L?1 concentration levels), while boron (present at about 60 μg L?1) was effectively removed by GACs. Batch experiment results were elaborated to estimate the chromium throughputs for the studied materials, to preliminary compare their performances in a real-scale application. The monitoring of a real-scale GAC adsorption stage permitted to validate throughputs estimation and confirmed that, despite being effective toward synthetic organics, GAC adsorption is a not feasible solution for Cr(VI) removal, with extremely early breakthrough. SBA exchange process resulted to be the most suitable solution, providing the best sorbent usage rates. However, SBA resin usage rates can strongly increase when considering the removal of nitrate and sulfate ions, requiring much shorter cycle times.  相似文献   

18.
Immobilized microbial cells for the biological treatment have the potential to degrade toxic chemicals faster than conventional wastewater treatment systems. In the present study, suitability of immobilized Pseudomonas fluorescens SM1 strain in calcium alginate beads for remediation of the major toxicants in Indian water bodies was tested by means of GC/HPLC and AAS techniques. Roughly 80% reduction in the concentration of phenols was observed by immobilized SM1 cells compared with 60% by the free cells. Also, in the case of the bioremediation of heavy metals, immobilized SM1 cells were found to be more efficient compared with the free cells. Suspension of P. fluorescens SM1 cells in the test model water for 24 h brought down the concentrations of Cu++, Cd++, Ni++, and Pb++ by more than 75% under free cell state and 7?C9% better efficiency under the immobilized conditions. However, Cr(VI) could show only 44% removal by the cell immobilized system, whereas a mere 35% reduction in the Cr(VI) levels was shown in the test model water by the free SM1 cells under the same conditions. Moreover, a model water containing 2,000 ppb of BHC, 1,248 ppb mancozeb, and 312 ppb 2,4-D passed through the cell immobilized column resulted in the decline in their concentrations up to 362 ppb, 750 ppb, and 126 ppb, respectively. Generally, AAS, HPLC, and GC analyses of treated test model waters with the free and immobilized SM1 cells exhibited high potential of immobilized SM1 in detoxification of test water. From the results, we conclude that immobilized cells of P. fluorescens SM1 strain were quite effective in bioremediation of major toxicants present in Indian water bodies, and we also recommend the use of immobilized bacterial cells rather than the free cells for the bioremediation/detoxification process.  相似文献   

19.
The increasing number of cases of soil contamination by heavy metals has affected crop yields, and represents an imminent risk to food. Some of these contaminants, such as cadmium (Cd) and lead (Pb), are very similar to micronutrients, and thus can be absorbed by plants. This study evaluated the translocation of increasing amounts of cadmium and lead and the effects of these metals in the production of beans. Bean plants were grown in nutrient solution Clark and subjected to increasing levels of Cd (from 0 to 0.5 mg L?1) and Pb (from 0 to 10 mg L?1). Cadmium concentration of 0.1 mg L?1 translocated 39.8% to the shoot, and dry matter production was reduced by 45% in shoots and 80% in roots, compared to the control treatment. Lead showed impaired movement in the plant, however the concentration of 1.0 mg L?1 was observed in 5.7% of metal translocation to the leaves. The concentration of 10 mg L?1 Pb reduced dry matter production of roots and shoots in 83% and 76%, respectively, compared to the control treatment.  相似文献   

20.
Biomass-derived biochar is considered as a promising heavy metal adsorbent, due to its favorable physicochemical properties, from aqueous solution as compared with other adsorbents. However, there is a limited number of studies on the effects of biochar produced from different feedstocks and pyrolytic temperatures on metal removal from metal-contaminated water. So in this study, the removal of the most prevalent heavy metals [(lead (Pb(II)), cadmium (Cd), and chromium (Cr)] by green waste biochar (GWB) and popular twigs biochar (PTB), produced at different pyrolytic temperatures, i.e., low 350 and high 650 °C, has been investigated, following the determination of physical and chemical properties of biochar. The efficiency of heavy metals removal of biochar was studied at different concentrations of heavy metals (10 and 100 μg mL?1), biochar types and treatment duration (3, 6, 9, and 12 h) at isothermic condition of aqueous solution. Results revealed that both feedstock type and pyrolytic temperature to produce biochar significantly affected its metal sorption capacity. The maximum sorption capacities of all three metals, i.e., Pb (II), Cd, and Cr were determined in the GWB produced at low pyrolytic temperature 350 °C after 9 h of treatment duration at both high and low metal concentrations. This highest sorption capacity of all metals by low pyrolytic temperature produced GWB was due to its better physicochemical properties especially high surface area, cation exchange capacity, and oxygen-containing functional groups as compared with woody feedstock based high pyrolytic temperature produced PTB. Conclusively, low pyrolytic temperature produced GWB was evaluated as a potential adsorbent to efficiently reduced heavy metal concentration in metal-contaminated water.  相似文献   

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