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1.
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   

2.
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   

3.
The capacity of microalgae to accumulate heavy metals has been widely investigated for its potential applications in wastewater (bio)treatment. In this study, the ability of Desmodesmus pleiomorphus (strain L), a wild strain isolated from a polluted environment, to remove Cd from aqueous solutions was studied, by exposing its biomass to several Cd concentrations. Removal from solution reached a maximum of 61.2 mg Cd g?1 biomass by 1 day, at the highest initial supernatant concentration used (i.e., 5.0 mg Cd L?1), with most metal being adsorbed onto the cell surface. Metal removal by D. pleiomorphus (strain ACOI 561), a commercially available ecotype, was also assessed for comparative purposes; a removal of 76.4 mg Cd g?1 biomass was attained by 1 day for the same initial metal concentration. Assays for metal removal using thermally inactivated cells were also performed; the maximum removal extent observed was 47.1 mg Cd g?1 biomass, at the initial concentration of 5 mg Cd L?1. In experiments conducted at various pH values, the highest removal was achieved at pH 4.0. Both microalga strains proved their feasibility as biotechnological tools to remove Cd from aqueous solution.  相似文献   

4.
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   

5.
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   

6.
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   

7.
Continual discharge of textile wastewaters loaded with a variety of synthetic dyes and metals is considered as a huge threat to surrounding ecosystems. In order to treat these undesirable pollutants, microbial bioremediation is considered as an efficient and economical technique. This study was conducted to evaluate the use of bacterial strains for simultaneous removal of azo dyes and hexavalent chromium [Cr(VI)]. Fifty-eight bacterial strains were isolated from Paharang drain wastewater and tested for their potential to decolorize reactive red-120 (RR-120) in the presence of 25 mg L?1 of Cr(VI). Among the tested isolates, FA10 decolorized the RR-120 most efficiently and was identified as Acinetobacter junii strain FA10. Based on quadratic polynomial equation and response surfaces given by the response surface methodology (RSM), Cr concentration and pH were found to be the main factors governing the RR-120 decolorization by FA10. The strain FA10 also exhibited a substantial salt resistance since it showed a considerable decolorization of RR-120 even in the presence of 150 g L?1 of NaCl. Moreover, the strain FA10 also showed the potential to simultaneously remove the Cr(VI) and the selected azo dyes in the same medium. More than 80 % of the initially added Cr(VI) was removed over 72 h of incubation along with the appreciable decolorization efficiency. The strain FA10 also exhibited good tolerance to considerable levels of different heavy metals. The findings of this study suggest that the strain FA10 might serve as an efficient bioresource to develop the biotechnological approaches for simultaneous removal of different azo dyes and heavy metals including Cr(VI).  相似文献   

8.
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   

9.
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   

10.
The present study deals with the synthesis and subsequent application of Fe3O4@n-SiO2 nanoparticles for the removal of Cr(VI) from aqueous solutions. Rice husk, an agrowaste material, was used as a precursor for the synthesis of nanoparticles of silica. Synthesized nanoparticles were characterized by XRD and SEM to investigate their specific characteristics. Fe3O4@n-SiO2 nanoparticles were used as adsorbent for the removal of Cr(VI) from their aqueous solutions. The effects of various important parameters, such as initial Cr(VI) concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) were analyzed and studied. A pH of 2.0 was found to be optimum for the higher removal of Cr(VI) ions. It was observed that removal (%) decreased by increasing initial Cr(VI) concentration from 1.36?×?10-2 to 2.4?×?10-2 M. The process of removal was found to be endothermic, and the removal increased with the rise in temperature from 25 to 45 °C. The kinetic data was better fitted in pseudo-second-order model in comparison to pseudo-first-order model. Langmuir and Freundlich adsorption capacities were determined and found to be 3.78 and 1.89 mg/g, respectively, at optimum conditions. The values of ΔG 0 were found to be negative at all temperatures, which confirm the feasibility of the process, while a positive value of ΔH 0 indicates the endothermic nature of the adsorption process. The present study revealed that Fe3O4@n-SiO2 nanoparticles can be used as an alternate for the costly adsorbents, and the outcome of this study may be helpful in designing treatment plants for treatment of Cr(VI)-rich effluents.  相似文献   

11.
The phytoremediation potential for Pb of Buddleja asiatica (a wild species) and a closely related cultivated species, B. paniculata, was investigated by means of field survey, hydroponic and pot experiments, and field trial experiments. Field surveys showed that B. asiatica had an extraordinary accumulation capacity and tolerance for Pb. Plants grown in soil with 2,369.8–206,152 mg kg?1 total Pb accumulated 1,835.5–4,335.8 mg kg?1 Pb in their shoots. Under hydroponic conditions (10, 20 mg l?1 Pb), both B. asiatica and B. paniculata showed unusually high concentrations of Pb in their roots (12,133–21,667 mg kg?1) and increased biomass production. A pot experiment in a greenhouse without any soil amendments was conducted on three different soils with various Pb contents (10,652, 31,304, 89,083 mg kg?1) for 3 months. The results showed that both species of Buddleja had an increase in the biomass similar to the control plants. There was a slight decrease in survival rates of plants grown in soil with 89,083 mg kg?1 Pb content. A field trial experiment was conducted for 6 months at three sites around the Pb mine area in which plants were provided with Osmocote fertilizer. Both Buddleja species showed 100% survival, increased biomass production and phytoextraction capacity (TF 1.1–2.3) when grown in soil with Pb content of 94,584–101,405 mg kg?1. Plants accumulated 2,273–3,675 mg kg?1 Pb in their shoots. The results suggest these Buddleja plants are suitable for use in the phytoremediation of Pb-contaminated soil.  相似文献   

12.
The present study explained the effect of pretreatments on the biosorption of Cr (III) and Cr (VI) by Cassia fistula biomass from aqueous solutions. For this purpose Cassia fistula biomass was pretreated physically by heating, autoclaving, boiling and chemically with sodium hydroxide, formaldehyde, gluteraldehyde, acetic acid, hydrogen peroxide, commercial laundry detergent, orthophosphoric, sulphuric acid, nitric acid, and hydrochloric acid. The adsorption capacity of biomass for Cr (III) and Cr (VI) was found to be significantly improved by the treatments of gluteraldehyde (95.41 and 96.21 mg/g) and benzene (85.71 and 90.81 mg/g) respectively. The adsorption capacity was found to depend on pH, initial metal concentration, dose, size, kinetics, and temperature. Maximum adsorption of both the Cr (III) and Cr (VI) was observed at pH 5 and 2. When Freundlich and Langmuir isotherms were tested, the latter had a better fit with the experimental data. The kinetic studies showed that the sorption rates could be described better by a second order expression than by a more commonly applied Lagergren equation.  相似文献   

13.
Rates of biosorption of cadmium and copper ions by nonliving biomass of the brown macroalga Sargassum sinicola under saline conditions were studied. Batch experiments show that the ability to remove cadmium is significantly diminished (from 81.8% to 5.8%), while the ability to remove copper remains high (from 89% to 80%) at a range of salinity from 0 to 40 psu. Maximum capacity of biosorption at 35 psu was 3.44 mg g?1 for cadmium and 116 mg g?1 for copper. The presence of salt did not significantly affect the rate of biosorption, which was about 90% of saturation in 60 min for both metals. There is an antagonistic effect on biosorption when both metals are present in the solution.  相似文献   

14.

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   

15.
The objective of this research was to assess the hexavalent chromium (Cr(VI)) reducing efficiency of sulfur-based inorganic agents including calcium polysulfide (CPS), iron sulfide (FeS), pyrite (FeS2) and sodium sulfide (Na2S) in three soils. An alkaline soil (soil 1), a neutral soil (soil 2) and a slightly acid soil (soil 3) constituted the investigated soils. The soils were spiked with two levels of Cr(VI) (100 and 500 mg Cr(VI) kg?1 soil) and incubated at field capacity (FC) for one month. Then, CPS, FeS, FeS2 and Na2S were added at 0, 5 and 10 g kg?1 and the concentrations of exchangeable Cr(VI) were measured after 0.5, 4, 48 and 168 h in a batch experiment. The pH and organic carbon content of the soils played predominant role in Cr(VI) self-reduction by the soil itself. Complete self-reduction of Cr(VI) from soils 1, 2 and 3 was achieved at maximum Cr(VI) levels of 1, 50 and 500 mg kg?1, respectively. Therefore, the concentration of Cr(VI) should not exceed the given levels in order to ensure that Cr(VI) is not released into the environment from contaminated sites. Moreover, decreasing pH in the alkaline soil caused significant increase of Cr(VI) reducing efficiency. Na2S, CPS and FeS, in contrast to FeS2, were efficient Cr(VI) reducing agents in all three soils. For all added amendments the following order of Cr(VI) reducing capacity was observed: Na2S > CPS > FeS > FeS2 in soil 1, Na2S ? CPS ~ FeS > FeS2 in soil 2 and Na2S ? FeS > CPS ~ FeS2 in soil 3.  相似文献   

16.
This study is aimed at assessing the ability of metal-resistant yeast, Candida tropicalis, to uptake cadmium from the liquid medium. The minimum inhibitory concentration of Cd2+ against C. tropicalis was 2,800 mg L?1. The yeast also showed tolerance towards Zn2+ (3,100 mg L?1), Ni2+ (3,000 mg L?1), Hg2+ (2,400 mg L?1), Cu2+ (2,300 mg L?1), Cr6+ (2,000 mg L?1), and Pb2+ (1,200 mg L?1). The yeast isolate showed typical growth curves, but low specific rate of growth was observed in the presence of cadmium. The yeast isolate showed optimum growth at 30°C and pH 7. The metal processing ability of the isolate was determined in a medium containing 100 mg L?1 of Cd2+. C. tropicalis could decline Cd2+ 57%, 69%, and 80% from the medium after 48, 96, and 144 h, respectively. C. tropicalis was also able to remove Cd2+ 56% and 73% from the wastewater after 6 and 12 days, respectively. Cd produced an increase in glutathione (GSH) and non-protein thiol levels by 146.15% and 59.67% at 100 mg L?1 concentration, respectively. Metal tolerance and accumulation together with changes in the GSH status and non-protein thiols under Cd exposure were studied in C. tropicalis.  相似文献   

17.
This study describes application of free liquid membrane (FLM) in micro-electromembrane extraction (μ-EME) of Cr(VI) from wastewater samples. Amount of Cr(VI) was quantified by electrothermal atomic absorption spectrometry. The transportation of Cr(VI) across the FLM was explored by electrokinetic migration and ion-exchange process. FLM and acceptor solution types, pH of donor and acceptor solutions, applied electrical potential, as well as FLM thickness were optimized. Presence of an anion exchange carrier (methyl trialkyl-ammonium chloride, Aliquat 336) in FLM facilitated Cr(VI) transportation. The best performance was observed for 1-octanol (containing 5% Aliquat 336) with thickness of 1 mm used as FLM, under applied electrical potential of 75 V, when 0.5 M NaClO4 and 0.1 M HCl were used as the acceptor and donor phases, respectively; and the extraction time was set to 5 min. Linearity was obtained in the working range of 0.5–14.0 ng mL?1 Cr(VI) (R2?>?0.98). The calculated limit of detection was below 0.06 ng mL?1. Application of this method to wastewater samples showed that relative recoveries of the spiked Cr(VI) in the samples were in the range of 73.8–85.1%, based on the standard addition method.  相似文献   

18.
This paper discusses the possibility of including the culturing of microalgae within a conventional wastewater treatment sequence by growing them on the blackwater (BW) from biosolid dewatering to produce biomass to feed the anaerobic digester. Two photobioreactors were used: a 12 L plexiglas column for indoor, lab-scale tests and a 85 L plexiglas column for outdoor culturing. Microalgae (Chlorella sp. and Scenedesmus sp.) could easily grow on the tested blackwater. The average specific growth rate in indoor and outdoor batch tests was satisfactory, ranging between 0.14 and 0.16 day?1. During a continuous test performed under outdoor conditions from May to November, in which the off-gas from the combined heat and power unit was used as the CO2 source, an average biomass production of 50 mgTSS L?1 day?1 was obtained. However, statistical analyses confirmed that microalgal growth was affected by environmental conditions (temperature and season) and that it was negatively correlated with the occurrence of nitrification. Finally, the biochemical methane potential of the algal biomass was slightly higher than that from waste sludge (208 mLCH4 gVS?1 vs. 190 mLCH4 gVS?1).  相似文献   

19.
The effects of selenium (Se) (VI) soil fertilization with 2 μg Se L?1 or foliar spraying twice with 20 mg Se L?1 in the form of sodium (Na) selenate on the physiological and biochemical characteristics of cabbage plants were studied. The ability of the plants to take up Se and translocate it to different parts of the plants was also studied. Despite the high concentration of Se in the foliar solution, there was no effect on photosynthesis, transpiration rate, photochemical efficiency of PSII, or electron transport system activity. The amount of chlorophyll and anthocyanins were unchanged. At harvest, the concentration of Se in control plants was lower than 100 ng Se g?1 dry weight (DW), while plants treated with 20 mg Se L?1 contained 5500 ng Se g?1. Selenium enriched cabbage could be used in human nutrition. The tolerance of cabbage to Se could be explained by the formation of insoluble compounds that are not available for the plant.  相似文献   

20.
Brown algae Sargassum sinicola and Sargassum lapazeanum were tested as cadmium biosorbents in coastal environments close to natural and enriched areas of phosphorite ore. Differences in the concentration of cadmium in these brown algae were found, reflecting the bioavailability of the metal ion in seawater at several sites. In the laboratory, maximum biosorption capacity (q max) of cadmium by these nonliving algae was determined according to the Langmuir adsorption isotherm as 62.42?±?0.44 mg g?1 with the affinity constant (b) of 0.09 and 71.20?±?0.80 with b of 0.03 for S. sinicola and S. lapazeanum, respectively. Alginate yield was 19.16?±?1.52% and 12.7?±?1.31%, respectively. Although S. sinicola had far lower biosorption capacity than S. lapazeanum, the affinity for cadmium for S. sinicola makes this alga more suitable as a biosorbent because of its high q max and large biomass on the eastern coast of the Baja California Peninsula. Sargassum biomass was estimated at 180,000 t, with S. sinicola contributing to over 70%.  相似文献   

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