浮游球衣菌对Pb2+、Cu2+、Zn2+、Cd2+的吸附性能研究

研究了浮游球衣菌（Sphaerotilus natans）在不同吸附条件下对溶液中Pb^2＋、Cu^2＋、Zn^2＋、Cd^2＋的吸附规律。结果表明,Sphaerotilus natans对这4种重金属离子均有一定的吸附作用,并在20min内达到吸附平衡,pH对吸附过程影响较大,pH为5.5时Sphaerotilus natans对这4种金属离子的吸附效果最好,Sphaerotilus natans对它们的吸附选择性为Pb^2＋〉Cu^2＋〉Zn^2＋〉Cd^2＋,Pb^2＋、Cu^2＋能部分置换出已被菌体吸附的Zn^2＋、Cd^2＋。HCI和EDTA溶液可有效地将金属离子从菌体上解吸下来,解吸后的菌体可重复使用。     

Modification of trace metal accumulation in the green mussel Perna viridis by exposure to Ag, Cu, and Zn

To examine the Cd, Hg, Ag, and Zn accumulation in the green mussel Perna viridis affected by previous exposure to Cu, Ag, or Zn, the dietary metal assimilation efficiency (AE) and the uptake rate from the dissolved phase were quantified. The mussel's filtration rate, metallothionein (MT) concentration, and metal tissue burden as well as the metal subcellular partitioning were also determined to illustrate the potential mechanisms underlying the influences caused by one metal pre-exposure on the bioaccumulation of the other metals. The green mussels were pre-exposed to Cu, Ag, or Zn for different periods (1-5 weeks) and the bioaccumulation of Cd, Hg, Ag, and Zn were concurrently determined. Pre-exposure to the three metals did not result in any significant increase in MT concentration in the green mussels. Ag concentration in the insoluble fraction increased with increasing Ag exposure period and Ag ambient concentration. Our data indicated that Cd assimilation were not influenced by the mussel's pre-exposure to the three metals (Cu, Ag, and Zn), but its dissolved uptake was depressed by Ag and Zn exposure. Although Hg assimilation from food was not affected by the metal pre-exposure, its influx rate from solution was generally inhibited by the exposure to Cu, Ag, and Zn. Ag bioaccumulation was affected the most obviously, in which its AE increased with increasing Ag tissue concentration, and its dissolved uptake decreased with increasing tissue concentrations of Ag and Cu. As an essential metal, Zn bioaccumulation remained relatively stable following the metal pre-exposure, suggesting the regulatory ability of Zn uptake in the mussels. Zn AE was not affected by metal pre-exposure, but its dissolved uptake was depressed by Ag and Zn pre-exposure. All these results indicated that the influences of one metal pre-exposure on the bioaccumulation of other metals were metal-specific due to the differential binding and toxicity of metals to the mussels. Such factors should be considered in using metal concentrations in mussel's soft tissues to evaluate the metal pollution in coastal waters.     

Accumulation of Al, Mn, Fe, Cu, Zn, Cd and Pb by the bryophyte Scapania undulata in three upland waters of different pH.

Measurements were made of the contents of Al, Mn, Fe, Cu, Zn, Cd and Pb in Scapania undulata in three streams (D2, D5, D11) in the English Lake District. The stream waters had average pH values of 5.35 (D2), 5.81 (D5) and 7.26 (D11), the main differences in other major chemical components being in Mg, Al, Ca and alkalinity. There was generally more metal accumulation in the older parts of the plants, but this was not significant in all cases. Extents of accumulation varied with stream pH and dissolved metal concentration. For Al, accumulation was greatest in streams D2 and D5. Mn accumulated most in D5 and Fe was without preference. Cu, Zn and Cd accumulated mostly in the plants in stream D11 and Pb accumulated more in D5 and D11. In terms of enrichment factors (amount of metal in the plants divided by stream water concentration) the sequence was Zn < Cd < Cu < Mn < Pb < Al < Fe. Laboratory experiments supported the findings of the field data, providing evidence that uptake increases with pH at constant total metal concentration. The results are interpreted qualitatively in terms of the chemical speciation of the metals in the stream water and competition between metal ions and protons at the plant-water interface. It is suggested that Al, Cu, Zn, Cd and Pb behave according to chemical complexation, whereas redox processes and/or colloidal interactions may be significant for Mn and Fe.     

Metal accumulation in the polychaete Hediste japonica with emphasis on interaction between heavy metals and petroleum hydrocarbons

The accumulation of cadmium (Cd) and copper (Cu) in the polychaete Hediste japonica exposed to the mixture of Cd (or Cu) and petroleum hydrocarbons (PHCs) was investigated and compared with that exposed to single Cd (or Cu). The increased bioavailability of Cd or Cu with exposure concentrations resulted in an increase in the accumulation and net accumulation rate of Cd or Cu during single metal exposure. The net accumulation rate of Cd increased, but the net accumulation rate of Cu decreased with exposure time during single metal exposure, suggesting that H. japonica could actively regulate Cu burden in their body by inhibition of absolute uptake or promotion of excretion. The interactions between Cd (or Cu) and PHCs had complicated influences on the net accumulation rate of Cd and Cu in H. japonica under the condition of the binary mixture, which are dependent on their concentration combinations and exposure time.     

The distribution and intracellular compartmentation of metals in the endogeic earthworm Aporrectodea caliginosa sampled from an unpolluted and a metal-contaminated site

The tissue distribution of Cd, Cu, Pb, Zn and Ca in the endogeic earthworm Aporrectodea caliginosa living in a non-polluted and a heavy metal polluted soil was investigated. The tissues of animals from the contaminated soil contained greater concentrations of Cd, Pb and Zn than the corresponding tissues of animals from the unpolluted soil. The greatest concentrations of Cd, Pb, Zn, and Ca were primarily accumulated within the posterior alimentary canal (PAC), a tissue fraction which contained the greatest proportion of the whole-worm burdens of the respective metals. Cu was distributed fairly evenly in the tissue fractions investigated. The pattern of accumulation for the 'heavy' metals is broadly similar to that for epigeic earthworms; in contrast, a different pattern of tissue accumulation was found for Ca. In animals from the uncontaminated site, the major elemental constituents of the chloragosomes were P, Ca, Zn and S. A significant positive correlation exists between P and Ca within the chloragosomal matrix. These intracellular vesicles are major foci for Pb and Zn accumulation within the PAC, with 'excess' metals associated with P ligands within the chloragosome matrix. The incorporation of Pb and Zn appears to involve the cationic displacement of Ca. Such compartmentation appears to prevent dissemination of large concentrations of these metals into other earthworm tissues, and may thus represent a detoxification strategy based on accumulative immobilization. No intracellular localization of Cd was identified in the study, although the Cd concentration in the metalliferous soils examined was not exceptionally high. The observations are discussed in the context of a contribution to enhanced understanding of metal ecotoxicology in earthworms by providing baseline data on a little investigated ecophysiological group of earthworms. Comparisons of metal distribution and mechanisms of metal sequestration are made with other ecophysiological groups of earthworms, and the significance of the findings to biomonitoring and toxicity-testing programmes is considered.     

Oxidative stress in Scenedesmus sp. during short- and long-term exposure to Cu2+ and Zn2+

Algae are exposed to elevated levels of heavy metals in water bodies generally for a long-term, and occasionally for a short-term duration. The present study deals with oxidative stress in Scenedesmus sp., commonly found in nutrient-rich freshwaters, during short- (6h) and long-term (7d) exposure to Cu(2+) and Zn(2+). The cells accumulated almost 2- and 4-times more Cu(2+) and Zn(2+) inside the cells during long-term than during short-term exposure to these metals. But the data on photosynthetic O(2) evolution and cell viability suggest that Scenedesmus sp. experienced lesser metal stress in long-term than in short-term experiment. Although malondialdehyde content was slightly higher in the long-term experiment, the amount produced by one unit intracellular metal was significantly lower than that in the short-term experiment. Superoxide dismutase activity of Scenedesmus sp. was >30% higher during long-term than during short-term exposure to Cu(2+) and Zn(2+). But, catalase and ascorbate peroxidase activities increased only at 2.5 microM Cu(2+) and 25 microM Zn(2+) when oxidative stress was mild, but were inhibited at 10 microM Cu(2+) under intense oxidative stress. Cu(2+) and Zn(2+) reduced glutathione reductase activity and total SH content of Scenedesmus sp. in both the experiments, with greater reduction occurring in the long-term experiment. The depletion of total thiol was positively related with the intracellular level of metals. Thiols might have helped Scenedesmus sp. in overcoming metal-induced oxidative stress, but depletion of thiol pool is known to make cells vulnerable to oxidative stress. The study suggests that antioxidant enzymes play a role only under mild oxidative stress. An increased accumulation of proline seems to be an important strategy for alleviating metal-induced oxidative stress in Scenedesmus sp. The study shows that Scenedesmus sp. could acclimatize during long-term exposure to toxic concentrations of the test metals.     

Metal toxicity in a sediment-dwelling polychaete: Threshold body concentrations or overwhelming accumulation rates?

We followed the net accumulation of As, Cu and Zn in the deposit-feeding polychaete Arenicola marina exposed in the laboratory to natural metal-contaminated sediments, one exposure leading to mass mortality between day 10 and 20, and the other not causing lethality over a period of 60 days of exposure. The worms showed lower total accumulated metal concentrations just before mortality occurred (<20 days) at the lethal exposure, than after 30 days of exposure to sediments not causing mortality. Moreover rates of accumulation of As, Cu and Zn were significantly higher in the lethal exposure than in the sublethal exposure. Our results show that it is not possible to link mortality to a critical total body concentration, and we add to a growing body of literature indicating that metal toxicity occurs when organisms cannot cope with overwhelming influx and subsequent accumulation rates.     

Influences of salinity on the biokinetics of Cd, Se, and Zn in the intertidal mudskipper Periophthalmus cantonensis

The biokinetics (aqueous uptake, dietary assimilation, and elimination) of Cd, Se, and Zn in the intertidal mudskipper, Periophthalmus cantonensis, were examined at different acclimated salinities using the radiotracer technique. The dietary assimilation efficiency from ingested radiolabeled polychaetes was the highest for Se (32–40%), followed by Zn (5–7%) and Cd (2–3%), and was not influenced by salinity within a range of 10–30 psu. Uptake from the dissolved phase typically exhibited a linear pattern within the first 12 h of exposure, followed by a second slower uptake. The highest concentration factor (CF) was found for Zn, followed by Cd and Se. Differences in salinity did not significantly affect the CF of the three metals within the first 12 h, but the CFs were significantly higher at lower salinities (10–20 psu) than at the highest salinity (30 psu) by the end of 48 h exposure. Because the degrees to which the uptake of Se (a metalloid) and Cd/Zn were affected by salinity were comparable, we concluded that metal speciation as a result of salinity change was not important in leading to a change in metal CF. Physiological changes may be responsible for the increasing uptake at lowered salinity. The elimination rates of the three metals (0.01–0.06 d⁻¹) were not significantly affected by salinity, but Se was eliminated at a faster rate following aqueous uptake than following dietary ingestion. There was no consistent influence of exposure routes on Cd and Zn elimination. The accumulated Cd was mainly associated with the gut, whereas the muscle was the dominant target site for Se and Zn accumulation.     

Plant accumulation of potentially toxic elements in sewage sludge as affected by soil organic matter level and mycorrhizal fungi.

Leek (Allium ameloprasum) was grown in pot trials in two clay loams of contrasting organic contents, with and without indigenous mycorrhizal propagules. Sewage sludges containing varying levels of Cd, Cu and Zn were added. Extractable soil metals, plant growth, major nutrient content and accumulation of metals, and soil microbial indices were investigated. The aim was to establish whether soil organic content and mycorrhizal status affected plant and microbial exposure to these metals. Extractable metals were higher and responses to inputs more pronounced in the arable, lower organic matter soil, although only Cd showed a soil difference in the CaCl2 fraction. There were no metal toxic effects on plants and some evidence to suggest that they promoted growth. Uptake of each metal was higher in the larger plants of the grassland, higher organic matter soil. Inoculation with arbuscular mycorrhizal fungi increased root Cd and Zn concentrations. With the exception of Cd (roots) and Zn (shoots), higher inputs of sludge metals did not increase plant metals. Zn and Cu, but not Cd, concentrations were higher in roots than in shoots.     

Metal accumulation from contaminated food and its effect on growth of juvenile landsnails Helix engaddensis

Metal accumulation by juvenile landsnails, Helix engaddensis, and its effect on growth rate was studied over a 5-week period of exposure and 2 weeks of recovery. An artificial food contaminated with Cu (4-2500 microg x g(-1)), Cd (50-800 microg x g(-1)), Pb, and Zn (20-12500 microg x g(-1)) was used. During the 7 weeks of the experiment, mortality rates were 20, 27, 30, and 38% among snails fed Cu-, Pb-, Zn-, and Cd-contaminated food, respectively. According to the ability to inhibit growth, metals were found to have the following order: Cd > Zn > Cu = Pb. Inhibitory effects of dietary metals started to be significant from the third week of exposure on. Inhibition of growth by Pb and Cu was found to be reversible, and within the first week of recovery, snails erupted their aestivation and resumed feeding and growth to gain weights similar to those of the control groups. Snails fed Cd- or Zn-contaminated food failed to resume growth during the 2 weeks of recovery. This indicates that in the case of Cu and Pb, growth inhibition was mainly due to starvation due to food rejection and aestivation. On the other hand, growth inhibition caused by Cd and Zn may have been resulting from irreversible toxicity. Therefore, snails were assumed to be sensitive to Cd and Zn but tolerant to Cu and Pb. Accumulation of Cu and Pb was significant only at the highest concentrations. At low and medium concentrations, no signs of accumulation were observed, indicating regulation at these concentrations. Cd and Zn accumulation starts at low concentrations but became significant at medium and high levels indicating accumulation of these metals.     

Phytostabilization of a metal contaminated sandy soil. II: Influence of compost and/or inorganic metal immobilizing soil amendments on metal leaching

A lysimeter approach (under natural climatologic conditions) was used to evaluate the effect of four metal immobilizing soil treatments [compost (C), compost+cyclonic ashes (C+CA), compost+cyclonic ashes+steel shots (C+CA+SS)) and cyclonic ashes+steel shots (CA+SS)] on metal leaching through an industrially contaminated soil. All treatments decreased Zn and Cd leaching. Strongest reductions occurred after CA+SS and C+CA+SS treatments (Zn: -99.0% and -99.2% respectively; Cd: -97.2% and -98.3% respectively). Copper and Pb leaching increased after C (17 and >30 times for Cu and Pb respectively) and C+CA treatment (4.4 and >3.7 times for Cu and Pb respectively). C+CA+SS or CA+SS addition did not increase Cu leaching; the effect on Pb leaching was not completely clear. Our results demonstrate that attention should be paid to Cu and Pb leaching when organic matter additions are considered for phytostabilization of metal contaminated soils.     

Bioaccumulation of heavy metals in terrestrial invertebrates.

In this literature study, accumulation data of metals in terrestrial invertebrates were collected and compared (Arthropoda and Lumbricidae). Based on total soil concentrations and body concentrations, regression equations were calculated for each metal (Cd, Cu, Pb and Zn) and each taxonomic group. We also tried to find out whether or not accumulation levels of metals in Lumbricidae are representative for all of the studied terrestrial invertebrates. Taxonomic groups could be ordered according to the extent of metal accumulation. Significant differences in accumulation levels of a factor 2-12 were found between taxonomic groups. Overall, metal concentrations were high in Isopoda and low in Coleoptera. The concentrations in Lumbricidae were in between. It should be kept in mind that the data for Lumbricidae were mainly derived from laboratory experiments, while the data for other groups were derived from field studies. The internal Pb, Cd and Cu concentration increased with the soil concentration for most taxonomic groups in the order Pb > Cd > Cu. Body concentrations of Zn were quite constant over a range of soil concentrations. The differences in accumulation level between taxonomic groups show the relevance of including detailed information on feeding behaviour in risk assessment for invertebrate-eating animals.     

Competitive sorption of heavy metal by soils. Isotherms and fractional factorial experiments

Competing ions strongly affect heavy metal sorption onto the solid surfaces of soil. This study evaluated competitive sorption of Cd, Cu, Ni, Pb and Zn on three soils: Calcixerollic Xerochrept, Paralithic Xerorthent and Lithic Haplumbrept. Monometal and competitive sorption isotherms were obtained at 25 degrees C. The individual effect of ions on retention of the others was ascertained by a fractional factorial analysis design. Most of the sorption isotherms belonged to type L subtype 2 in the classification of Giles. In competitive sorption the initial linear part was shorter and the knee sharper when compared with monometal sorption isotherms. Parameters related to sorptive capacity, such as Point B, Langmuir monolayer and Freundlich distribution coefficient, were higher in monometal than in competitive sorption, and in basic soils than in acidic soil. Calcium desorbed at different points of the sorption isotherms indicated that cationic exchange with Ca was the main retention mechanism in calcareous soils. For Pb, the ratio Ca desorbed/Pb sorbed was close to one; for Cu, Ni and Zn the ratio ranged from 1.20 to 1.37, probably due to partial dissolution of calcium carbonates by hydrolytic processes during retention. On the other hand, Cd had a ratio around 0.6 reflecting another additional retention mechanism, probably surface complexation. Fractional factorial design confirmed that the presence of the cations investigated reduced the amount of the five metals retained, but the presence of Cu and Pb in the system depressed Ni, Cd and Zn sorption more than the inverse. Cation mobility was enhanced when equilibrium concentration increased and the effect was higher in Ca-saturated soils.     

In situ remediation of soils contaminated with toxic metal ions using microwave energy

Following onto our work on the in situ remediation of soils contaminated with PAH's, PCB's and other polychlorinated organic compounds using microwave energy, we now report a preliminary investigation on the in situ remediation of soils contaminated with toxic metal ions: Cd(II), Mn(II), Th(IV), Cr(III) and mainly Cr(VI). The soil is partially vitrified in the process, and extraction with hot (70 degrees C) 35% nitric acid for 4.5 h leads to the recovery of very small amounts of the metals which had been spiked into the clean soil: Cd, Mn, and Cr(III) are completely immobilized (unextractable), Th is mostly unextractable, and Cr(VI) partially extractable at very high levels of spiking, but almost completely unextractable using the US EPA Toxicity Characteristic Leaching Procedure. This suggests that contaminated soils which are not going to be used for agricultural purposes can be remediated safely to preset depths without fear of the toxic metal ions leaching out for a long time.     

Earthworms as biological monitors of cadmium, copper, lead and zinc in metalliferous soils

Earthworms (Lumbricus rebellus and Dendrodrilus rubidus) were sampled from one uncontaminated and fifteen metal-contaminated sites. Significant positive correlations were found between the earthworm and 'total' (conc. nitric acid-extractable) soil Cd, Cu, Pb and Zn concentrations (data log1) transformed). The relationships were linear, and the accumulation patterns for both species were similar when a single metal was considered, even though there were species difference in mean metal concentrations. Generally, the earthworm Cd concentration exceeded that of the soil; by contrast, the worm Pb concentration was lower than the soil Pb concentration in all but one (acidic, low soil Ca) site. Our observations suggest that Cu and Zn accumulation may be physiologically regulated by both species. Total-soil Cd explained 82-86% of the variability (V2) in earthworm Cd concentration; 52-58% of worm Pb and worm Zn concentrations were explained by the total-soil concentrations of the respective metals. Total-soil Cu explained only 11-32% of the worm Cu concentration. The effect of soil pH, total Ca concentration, cation-exchange capacity (CEC) and organic carbon on metal accumulation by L. rubellus and D. rubidus was investigated by multiple regression analysis. Soil pH (coupled with CEC) and soil Ca had a major influence on Pb accumulation (V2 of worm Pb increased to 77-83%), and there was some evidence that Cd accumulation may be suppressed in extremely organic soils. The edaphic factors investigated had no effect on Cu or Zn accumulation by earthworms. In the context of biomonitoring, it is proposed that earthworms have a potential in a dual role: (1) as 'quantitative' monitors of total-soil metal concentrations (as shown for Cd); and (2) as estimators of 'ecologically significant' soil metal, integrating the effects of edaphic factors (as shown for Pb).     

Early-phase immunodetection of metallothionein and heat shock proteins in extruded earthworm coelomocytes after dermal exposure to metal ions

This paper provides direct evidence that earthworm immune cells, coelomocytes, are exposed to bio-reactive quantities of metals within 3 days after dermal exposure, and that they respond by upregulating metallothionein (MT) and heat shock protein (HSP70, HSP72) expression. Indirect support for the hypothesis that coelomocytes are capable of trafficking metals was also obtained. Coelomocytes were expelled from adult individuals of Eisenia fetida after 3-day exposure either to metal ions (Zn, Cu, Pb, Cd) or to distilled water (controls) via filter papers. The number of coelomocytes was significantly decreased after Cu, Pb, or Cd treatment. Cytospin preparations of coelomocytes were subjected to immunoperoxidase staining with monoclonal antibodies against human heat shock proteins (HSP70 or HSP72), or rabbit polyclonal antibodies raised against metallothionein 2 (w-MT2) of Lumbricus rubellus. Applied antibodies detected the respective proteins of E. fetida and revealed that the expression of HSP70, HSP72 and w-MT2 proteins was either induced or significantly enhanced in coelomocytes from metal-exposed animals. In conclusion, stress protein expression in earthworm coelomocytes may be used as sensitive biomarkers of metal contaminations. Further experimentation is needed for quantitative analysis of kinetics of metal-induced stress protein expression in earthworm coelomocytes.     

Multi-tolerance to heavy metals in Plantago arenaria Waldst. & Kit.: adaptative versus constitutive characters

Tolerance to Cu, Cd, Ni and Zn was investigated in a population of the pioneer species Plantago arenaria growing in a metallurgical landfill. Tolerance levels were compared with those of two other pioneer species (Coniza sumatrensis and Verbascum densiflorum) growing in the same location, and with a control population taken from an uncontaminated site. Results showed that the metalliferous population of P. arenaria was more tolerant to metal toxicity than C. sumatrensis and V. densiflorum. Comparisons with literature data confirmed that the metalliferous population of P. arenaria was highly tolerant to Cu, moderately tolerant to Cd and Ni, but not particularly tolerant to Zn. The control population of P. arenaria responded the same as the metalliferous one excepted for Cu, for which it was much more sensitive. This suggested that multi-metal tolerances in the metalliferous population of P. arenaria resulted both from constitutive and adaptative traits, depending on the metal. To check whether P. arenaria was able to cope with high internal metal levels, accumulation patterns were evaluated in pot experiments. Results showed that metals accumulated in roots and leaves, at levels proportional to soil content. Metal content was much higher in roots than in leaves and the leaf:root concentration ratio was kept constant over a wide range of soil metal contents. This suggested that metal tolerance was related to the ability to retain metal ions in roots and to tightly control their translocation to leaves. Finally metal tolerance in P. arenaria is discussed in relation to its pioneer and xerophytic characteristics.     

Metal accumulation in arthropods near a lead/zinc smelter in Arnoldstein, Austria. II. Formicidae

Ants are of considerable importance in the cycling of pollutant metals in contaminated terrestrial ecosystems. However, little is known about their ecophysiological response to chronic (and acute) metal stress, either at the individual or the population level. In the present study, the concentrations of Pb, Cd, Cu, and Zn were compared in 13 species of Formicidae from different sites in the vicinity of a lead/zinc smelter in Arnoldstein, Austria. Results indicate species- and metal-dependent differences in site-specific accumulation patterns. A generalized ranking of metal levels in higher taxa, in decreasing order, is: Formicinae-Dolichoderinae-Myrmicinae. Lead, Cd and Zn body burdens decreased with increasing distance from the emission source, at least in some species, whereas Cu levels appeared to be site-independent in most cases. In general, metal body burdens were higher in summer than in spring, irrespective of site, species or metal. Measured lead levels in Formicidae exceeded previously reported field data by 1 to 2 orders of magnitude, stressing the enormous impact of lead on the Arnoldstein area. A decrease of Cd, Cu and Zn concentrations was recorded in ants collected two years after closure of the smelting complex, but lead levels remained constant. The metal levels were lower in pupae than in workers. The present results indicate differentiated metal regulatory capabilities and strategies in the investigated species, but the inherent bionomics of ants render interpretations of field data difficult and more emphasis should be laid on the ecophysiology of metals in Formicidae.     

Detection and localization of aluminum and heavy metals in ectomycorrhizal Norway spruce seedlings

Norway spruce seedlings colonized with Hebeloma crustuliniforme were grown in growth pouches. After formation of ectomycorrhizas, the seedlings were exposed to Al or the heavy metals Cd, Cu, Ni, or Zn at various concentrations for 5 weeks to estimate the detection limits of metals with X-ray microanalysis in the cryo-scanning electron microscope. When the lowest metal concentrations (1 mM Al(3+), 0.1 mM Cd(2+), 0.2 mM Cu(2+), 0.5 mM Ni(2+), 2 mM Zn(2+)) were applied, only Al and Zn were detected at low X-ray counts in the ectomycorrhizas. After application of 10-fold higher metal concentrations, distinct metal accumulation patterns were observed. Cd was detected predominantly in the Hartig net, Al and Ni in the Hartig net and in the cell walls of the cortex, and Zn in the Hartig net, the cortical cell walls and the fungal mantle. Cu was not detected at all. By combining X-ray microanalysis with absolute metal concentrations found in the roots, the estimated detection limits of X-ray microanalysis were: Al> or =0.86 mg g(-1), Cd> or =0.26 mg g(-1), Ni> or =1.30 mg g(-1), and Zn> or =0.54 mg g(-1), whereas Cu was not detectable even at root concentrations of 0.47 mg g(-1). Treatments with the highest metal concentrations showed high X-ray counts of metals in cells of the stele but reduced concentrations of the macronutrients K, Mg, and P in roots, indicating a possible disturbance of root and ectomycorrhizal function.     

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.