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1.
The plant, Salvinia natans L., was found effective in the removal of Hg(H) from wastewater. Maximum accumulation was noted within a day and maximum removal (about 90%) was recorded below 5 ppm of Hg(II). Accumulation of the metal occurred mainly in the roots. The senescence of the plant started at and above 5 ppm of Hg(H). The biochemical constituents like chlorophyll, Hill-activity, Protein, RNA, dry weight, and activities of catalase and protease decreased while free amino acid content, peroxidase activity and the ratio of acid to alkaline pyrophosphatase activity increased over control values at and above 5 ppm of Hg(H).  相似文献   

2.
The uptake of Ni (II) and toxic effects of the metal on some biochemical parameters in Salvinia natans L. were studied. The uptake of Ni (II) by the plants gradually increased with increase in concentration of Ni (II) in the culture medium. Maximum accumulation of Ni (II) was noted within a day and maximum removal (about 90%) was recorded upto 20 Μg mL?1 of Ni (II). Accumulation of the metal in roots (14.75 Μg mL?1) is greater than that of shoots (5.25 Μg mL?1). Ni (II)>10 Μg mL?1 promoted senescence of Salvinia plants by decreasing chlorophylls, protein, amino acid, Hill activity, dry weight and by inducing necrosis. In the absence of other pollutants, Salvinia plants may be used for removal of Ni (II) from effluents and also as an indicator of Ni pollution.  相似文献   

3.
Plants expressing a modified bacterial mercury reductase, merA, are highly resistant to Hg(II) toxicity as a result of the enzymatically catalyzed electrochemical reduction of Hg(II) to the much less toxic and volatile Hg(0). merA expression may allow plants to manifest a suite of responses to mercury exposure, making them more capable than wild-type plants of interacting with and removing mercury from contaminated soil or water. We have engineered merA-expressing Nicotiana tabacum (tobacco) as a model plant for examining these responses. Mercury resistance was demonstrated by germinating and growing merA tobacco seeds on semi-solid medium spiked with a HgCl2 concentration acutely toxic to wild-type plants. On similar growth medium, merA plant roots penetrated a highly concentrated, localized Hg(II) zone of HgS (cinnibar) more readily than wild-type roots. In hydroponic medium spiked with HgCl2, merA plants maintained higher evapotranspiration activity than wild-type plants. The ability of merA Hg(II)-reductive activity to counter typical plant-catalyzed Hg(0) oxidation to Hg(II) was demonstrated by a lower net foliar absorption of atmospheric Hg(0) than wild-type plants. Mercury translocation through merA plants was examined through reciprocally grafted merA and wild-type tobacco grown on HgCl2-spiked hydroponic medium. Elevated mercury concentrations in wild-type shoots grafted to merA roots suggest the vertical movement of mercury within merA tissues or plants may be facilitated by dynamic balance between native Hg(0) oxidation and MerA-catalyzed Hg(II) reduction. These experiments demonstrate that merA-engineered tobacco plants display an array of tissue-level and whole-plant attributes which should allow for more efficient mercury extraction and processing compared to the wild-type.  相似文献   

4.
Total and elemental mercury (Hg) in simulated flue gas was measured on-line by a commercial Semtech® Hg analyzer. This instrument is based on Zeeman modulated Atomic Absorption Spectrometry. Both a wet chemical solution and a dry physical pyrolysis converter were applied to reduce the Hg(II) in the gas before leading it to the detector. Results show that the Semtech® analyzer is suitable for measuring elemental Hg even in the presence of 2500 ppm SO2 and 500 ppm HCl. For the measurement of Hg(II), the wet method is suitable only at SO2 concentrations <50 ppm. The dry thermal converter filled with crushed quartz chips together with a small amount of soda lime converts Hg(II) quantitatively at laboratory scale. This result is promising, since the trace gases delivered to the system, such as SO2, and HCl are similar to those produced in coal burning and waste incineration processes. The limiting factor for such a converter is its comparatively short life time of performance, about 20 hours.  相似文献   

5.
The gas phase oxidation of elemental mercury by ozone   总被引：2，自引：0，他引：2  
The gas phase reaction between elemental mercury (Hg0) and ozone (03) has been studied in sunlight, in darkness, at different temperatures, and different surface-to-volume (s/v) ratios. At 03 concentrations above 20 ppm, a loss of Hg0 and a simultaneous formation of oxidized mercury (Hg(II)) was observed. The results suggest a partly heterogeneous reaction, with a gas phase rate constant of 3±2×10?20 cm3 molec.?1 s?1 at 20 °C. This corresponds to an atmospheric Hg half-life of about one year at a mean global 03 concentration of 30 ppb.  相似文献   

6.
The plant, Salvinia natans L., was found to be very useful in the removal of Cu (II) from waste water. Maximum accumulation was noted within one day and maximum removal (about 90%) was recorded below 50 μg mL?1 of Cu (II). Copper was successfully removed from the waste water of Hindusthan Copper Limited (HCL), ICC, Ghatsila, Bihar, India.  相似文献   

7.
Effect of the heavy metals chromium, nickel, copper, zinc, cadmium, mercury and lead on uptake and translocation of K and P by young barley plants The uptake of potassium and phosphate into the roots and shoots of 7 days old barley plants from double-labelled (42K, 32P) nutrient solutions containing chromium, nickel, copper, zinc, cadmium, mercury or lead (10?6 - 10?4 moles/1) was measured in a constant environment after 5 hours, in order to compare early stages of toxicity. K and P uptake and translocation were inhibited by the 7 heavy metals to a different extent; K was more affected than P, and translocation of both nutrients into the shoots was more inhibited than uptake into the roots. Plants showed no visible injuries. Mercury had by far the greatest effect, zinc was almost ineffective: K uptake e.g. was reduced to 21% of the control by 10?4 moles Hg/l, but only to 97% by the same amount of Zn, and P translocation was reduced to 8% by Hg, but was not affected by Zn. The least significant effect of Hg was detectable at a concentration of 4.10?7 moles Hg/l ( = 0,08 ppm) in the nutrient solution, the effect of Zn only above 10?4 moles Zn/l ( = 6,5 ppm). Arranging the tested heavy metals according to their effects leads to the sequence Hg > Pb > Cu > Cd > Cr > Ni > Zn which corresponds – apart from two deviations – to the electrochemical series of the elements.  相似文献   

8.
Accumulation of Hg and Cr and subsequent changes in the physiological and biochemical parameters were studied in species of the aquatic genera, Eichhornia crassipes (Mart.) Solms., Hydrilla verticillata (L.f.) Royle and Oedogonium areolatum Lagarh. Accumulation of Cr was highest in Eichhornia [10.21 μmol (g dry tissue wt)?1], followed by Hydrilla (9.0) and Oedogonium (6.02); that of Hg was maximum in Hydrilla (4.21), followed by Oedogonium (3.35) and Eichhornia (2.79). Accumulation of Cr and Hg in roots of Eichhornia was about twelve and two times higher, respectively, than that in shoots of the genus. Higher accumulation of Cr than that of Hg in the aquatics was observed. In general, Cr (19.23 × 10?6 M) and Hg (4.98 × 10?6 M) did not show significant changes over control data in these parameters, Hill activity, chlorophyll, protein, free amino acid, inorganic phosphorus, RNA, DNA, dry wt, permeability, the activities of protease, RNase, catalase and peroxidase, and acid: alkaline pyrophosphatase activity in the three aquatic plants. The plant species have tolerance capacity to the heavy metals applied.  相似文献   

9.
Isotopically exchangeable P (IEP) is usually considered to be completely plant‐available and the major source of P for plant uptake. The aim of the present study is to test whether plants can, besides IEP, also use non‐IEP and if part of the IEP has an equilibrium concentration in soil solution which is below the minimum concentration, CLmin, and can therefore not be taken up by plants. A pot experiment was carried out with maize for two years on two soils, an acid sandy and a neutral loamy soil, either without P fertilizer or fertilized with ten P sources of different solubility. Throughout both years of the study, pots were kept moist either without plants or planted twice with maize (Zea mays L., cv. Athletico). At the end of the experiment, plant P uptake, P concentration in the soil solution (CL), and P accessible to isotopic exchange within 5 d (E5d) were measured. Plant growth decreased the E5d which was about equal to P uptake by maize for most treatments in the acid soil. But for some treatments, i.e., five in the acid and eight in the neutral soil, P uptake was up to 50% larger than the decrease of E5d, indicating that plants had, besides IEP, also used P from non‐IEP sources. At adequate P supply, both soils had an E5d of about 100 mg P (kg soil)–1, but about 30 to 40 mg kg–1 of this IEP had an equilibrium P concentration in the soil solution below CLmin of 0.1 μmol L–1 at which P would actually not be plant‐available. This study shows that plants take up P mainly from IEP, but not the whole IEP is plant‐available. Furthermore, plants may also use P from non‐IEP sources.  相似文献   

10.
A sensor responsive to Hg2+ (pDL20) was constructed by fusing part of a narrow spectrum mer operon, including its regulatory elements, to promoterless lux genes. This was compared with another mer::lux fusion (pRB28) in order to estimate the available Hg in moss, a conventional bioindicator used for surveying Hg pollution in terrestrial environments. Hg(II) was measured as the relative luminescence unit (RLU) emitted by E. coli cells carrying either pRB28 or pDL20. The linearity ranges of standard curves were measured by spiking HgCl2 at different nanomole levels in a phosphate buffered solution (PBS). The level of correlation between RLU and spiked HgCl2 depended on the incubation time of E. coli cells: the correlation factors (R 2) of the regression lines were highly significant only after 150 min of incubation. pDL20 detected Hg(II) concentrations in the linear range between 0.05 nM and 0.5 nM and was approximately 27 times more sensitive than pRB28. The latter was less sensitive and showed a different range of linearity, from 20 nM to 200 nM. Measurements of bioavailable Hg were performed in buffered solutions leached from moss. Concentrations of Hg(II) were determined by external standard addition of HgCl2. pDL20 was found to be more reliable than pRB28 in the estimation of very low concentrations of bioavailable Hg (II). Both sensors were unable to determine Hg(0) emitted by geothermal activities.  相似文献   

11.
Using the Arrhenius thermodynamic equation, which relates rates of processes to temperature through the quantity E a , the ‘Heat (or Energy) of Activation’, we have evaluated the thermal relationships for several parameters of Hg cycling. It is shown that release from isolated leaves (shoots) of Hg0 is a two-step process with a higher E a value below 21 °C than above (28 vs 14 kcal mol?1). Open field air Hg measurements over a mixed stand of grasses and other plants in volcanic soil show strikingly similar behavior to detached organs. Mercury release from volcanic soil was uniform over a wide temperature range, resembling plant and open field emissions above 18 to 21°C with anE a value of 13 kcal · mol?1. We conclude that Hg release below 18 to 21 °C is limited by a physiological process, whereas above that range, release is controlled by the physical process of vaporization itself. Plant concentration of total Hg from 5 to 33 °C (air temperature), is a more complex function involving direct accumulation and re-release of Hg0 from the atmosphere, release from tissue storage, and root uptake with reduction.  相似文献   

12.
Mercury(II) toxicity experiments with green algae are complicated by the fast reduction and evaporation of Hg. A Hg buffer system is described, which considerably stabilizes the Hg(II) concentration in test solutions. The Hg buffer consists of mercury(II) chloride and N-methyliminodiacetic acid (MIDA). Dissociation of Hg-MIDA complex compensates for loss of Hg. With this system experiments were performed with Hg(II) concentrations between 0.02 and 2.0 mg I?1 at temperatures between 15° and 30°C. No effect of MIDA on the growth of the green alga Scenedesmus acutus was detected.  相似文献   

13.
Abstract

Addition of paclobutrazol (PP333) at 0.2 ppm to a nutrient solution in which 11‐month‐old apple seedlings were growing reduced terminal growth, fresh weight increase (FWI), transpiration and Ca and K uptake per seedling. Total root surface area was not affected by PP333 treatment. Reduced Ca uptake preceded the reduction in transpiration and FWI. In the case of K these changes were parallel. This may indicate that different mechanisms were responsible for reduced Ca and K uptake in PP333‐treated plants. At the conclusion of the experiment control and treated plants were absorbing similar amounts of Ca per unit of FWI. At the same time the amount of K uptake per unit of FWI was significantly lower in treated than control plants.  相似文献   

14.
Uptake and translocation of sodium in two cultivars of Lolium perenne The uptake and translocation of Na was investigated in two Lolium perenne cultivars (Dolewi and NFG). With increasing Na+ concentration in the nutrient solution (0, 1, 2 and 4 mMNa) the Na+ uptake per pot increased from 1.4 to 11.9 me/1 Na+ for Dolewi and from 1.1 to 6.9 me/l Na+ for NFG. The higher Na uptake by Dolewi can only partly be explained by better growth, the higher Na+ selectivity playing also an important role. In another experiment plants of both types were grown in solution cultures for 41/2 weeks at 15°C and 25°C, respectively. Hereafter the plants were supplied with 1.25 mM 24NaCl for six hours under equal conditions. Again the higher Na uptake and also a higher Na translocation (of about 20%) was found in Dolewi, whereas only 10% of the 24Na uptake had been translocated by NFG. When plants were grown in a nutrient solution with a lower temperature (at 15°C) the root lipids showed a higher linolenic acid and oleic acid content than the plants grown in a medium at 25°C. At the same time the 24Na uptake was higher in the plants grown at the lower temperature, yet the relationship between root lipids and Na uptake still remains to be elucidated.  相似文献   

15.
Ipomoea aquatica is commonly used as a vegetable and pig food in Thailand. The present study shows that the leaves and floating stems of this plant collected near a caustic soda factory in Thailand had accumulated between 0.75 to 1.26 ppm (average 0.95 ppm) Hg in the leaves and 0.28 to 0.68 ppm (average 0.43 ppm) Hg in the floating stems. Leaves and floating stems from unpolluted areas had Hg contents between 0.01 to 0.17 ppm and 0.01 to 0.06 ppm, respectively. The contaminated I. aquatica in the study area represents an additional source of Hg, since fish from the same area are also polluted with Hg. This constitutes a serious risk to public health.  相似文献   

16.
The aim of this work was to investigate the possibility of using plants for mercury (Hg) removal from a contaminated industrial soil, increasing the metal's bioaccessibility by using mobilizing agents: ammonium thiosulphate [(NH4)2S2O3] and potassium iodide (KI). The selected plant species were Brassica juncea and Poa annua. The addition of the mobilizing agents promoted Hg uptake by plants, with respect to controls. Treatments promoted Hg translocation to aerial parts. In the case of Poa annua, greater Hg uptake was found in plants after the 100 mM KI treatment, reaching values that were nearly 400 mg kg?1 in the aerial part. In contrast, Brassica juncea plants accumulated in their aerial part the greatest Hg quantities, about 100 mg kg?1, after treatment with 0.27 M (NH4)2S2O3. The ratio between the concentration of Hg in the shoots and the initial concentration in the soil support the potential for successfully applying Hg phytoextraction on this soil.  相似文献   

17.
Field grown rice (Oryza sativa L.) plants exposed separately to 0.25 or 0.5 ppm SO2 for 1.5 hr daily for 40 days, showed significant decrease of catalase (p < 0.001) and increase of peroxidase (p < 0.001) activities as well as decreases of protein (p < 0.001) and ascorbic acid (p < 0.001) contents associated with leaf lesions, which were proportional to SO2-dose. Catalase and peroxidase activity levels showed an inverse relationship. It is hypothesized from the molecular structure of both enzymes and from the in vitro relationship between catalase and peroxidase activity that the tetrameric molecules of catalase in vivo might disintegrate into monomeric units with peroxidase activity, which in turn oxidise ascorbic acid and may reduce tolerance of plants to SO2.  相似文献   

18.
This study evaluated the effect of lead (Pb(II)), zinc (Zn(II)) and copper (Cu(II)) on growth and sporulation of four Halophytophthora species (Halophytophthora vesicula, Halophytophthora elongata, Halophytophthora spinosa var. lobata, and an oogonia-producing Halophytophthora sp.) isolated from different mangrove sites in Taiwan. Results show that all isolates grew well or even better at 1 ppm concentration of the heavy metals tested. Growth of all test isolates was totally inhibited at 500 ppm, except for H. spinosa var. lobata exposed to Zn(II). For sporulation, all isolates produced moderate to abundant zoosporangia or oogonia at 1 ppm Pb(II) and Zn(II). Production of zoosporangia by H. vesicula, H. elongata and H. spinosa var. lobata was significantly affected or totally inhibited at 1 ppm Pb(II) and Zn(II) and all concentrations of Cu(II). Abnormal oogonia were produced by Halophytophthora sp. at 10 ppm Cu(II) and 100 ppm of the three heavy metals. In general, Cu(II) and Zn(II) were found to be the most toxic, and the least toxic was Pb(II). H. spinosa var. lobata was the most tolerant to all the heavy metals, while H. vesicula and H. elongata were the most sensitive. Results of this study shows that increased concentrations of Pb(II), Cu(II), and Zn(II) in the mangrove environment can significantly affect growth and impair normal reproduction of Halophytophthora species.  相似文献   

19.
Zinc (Zn) deficiency in rice has been widely reported in many rice-growing regions of the world. A greenhouse experiment was conducted with the objective of determining Zn requirements of lowland rice. Zinc rates used were 0, 5, 10 20, 40, 80, and 120 mg Zn kg?1 of soil applied to an Inceptisol. Zinc application significantly affected shoot dry weight and grain yield as well as concentrations and uptakes of Zn in soil and plant. Maximum yield of shoot dry weight and grain yield were achieved at 5 and 20 mg Zn kg?1 of soil, respectively. Zinc concentration and uptake in shoot as well as Zn uptake in grain had significant quadratic increases as Zn concentration increased in the soil solution. Zinc concentration as well as uptake was greater in the shoot as compared with concentration and uptake in the grain. Zinc-use efficiencies significantly decreased with increasing Zn rates in the soil except agrophysiological efficiency, which had significant quadratic increases with increasing Zn rates. On average, about 6% of the applied Zn was recovered by the lowland rice plants. Mehlich 1 extracting solution extracted much more Zn than diethylenetriaminepentaacetic acid (DTPA). However, Mehlich 1 as well as DTPA-extractable Zn had significant positive correlations with each other as well as with Zn uptake in grain and shoot.  相似文献   

20.
Varying amounts of humic acid (Na-salt; 0 to 10 ppm) were first equilibrated with a dilute suspension of H+ -Kaolin and then with spiked (high activity radioactive 64Cu) water. After filtration, through a 0.45 µm Millipore membrane, the amount of radioactivity on the filter and the filtrate was measured separately using a Gamma ray well counter. Adsorption of Cu (expressed as distribution coefficient — K d ) was plotted against humic acid concentration. K d values decreased sharply upto 1 ppm humic acid concentration and thereafter remained constant up to 10 ppm.  相似文献   

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