Heavy metal accumulation by the halophyte species Mediterranean saltbush

To identify Cd- and Zn-accumulating plants exhibiting a high growth rate, seeds from the halophyte species Mediterranean saltbush (Atriplex halimus L.) were collected on a heavy-metal-contaminated site in southeastern Spain (Llano del Beal, Cartagena). Seedlings from this ecotype were exposed for 3 wk to 0.1 mM Cd or Zn in a nutrient solution in a fully controlled environment. All plants remained alive and no significant growth inhibition was recorded until the end of the experiment. Mean Cd and Zn accumulation in aerial parts was 830 and 440 mg kg(-1), respectively, and the rate of metal translocation even increased with the duration of stress exposure. Resistance to heavy metals in this species may be partly linked to precipitation of Cd in oxalate crystals in the stems. A Cd-induced decrease in glutathione concentration also suggests that phytochelatins overproduction may occur in these conditions. We conclude that Mediterranean saltbush, which is able to produce up to 5 Mg dry matter ha(-1) yr(-1), may be an effective species for phytoextraction and should be tested for this purpose in field conditions.     

Assessment of heavy metal pollutants accumulation in the Tisza river sediments

In this study we have worked on the evaluation of heavy metal contamination in the sediments taken from the Tisza River and its tributaries, and thereby used the sequential extraction method, geochemical normalization, the calculation of the enrichment factor (EF), and the methods of statistical analysis. The chemical fractionation of Ni, Cu, Zn, Cr, Pb, Fe, and Mn, carried out by using the modified Tessier method, points to different substrates and binding mechanisms of Cu, Zn and Pb in sediments of the tributaries and sediments of the Tisza River. The similarities in the distributions of Fe and Ni in all types of sediments are the result of geochemical similarity as well as of the fact that natural sources mainly affect the concentration levels of these elements. The calculated enrichment factors (EF, measured metal vs. background concentrations) indicated that metal contamination (Cu, Pb, Zn and Cr) was recorded in the sediments of the Tisza River, while no indications of pollution were detected in the tributaries of the Tisza River and the surrounding pools. The maximum values of the EF were close to 6 for Cu and Pb (moderately severe enrichment) and close to 4.5 for Zn (indicating moderate enrichment). It can be said that the Tisza River is slightly to moderately severely polluted with Cu, Zn, and Pb, and minorly polluted with Cr. It is concluded that sediments of the Tisza serve as a repository for heavy metal accumulation from adjacent urban and industrial areas.     

pH,dissolved oxygen,and adsorption effects on metal removal in anaerobic bioreactors

Anaerobic bioreactors were used to test the effect of the pH of influent on the removal efficiency of heavy metals from acid-rock drainage. Two studies used a near-neutral-pH, metal-laden influent to examine the heavy metal removal efficiency and hydraulic residence time requirements of the reactors. Another study used the more typical low-pH mine drainage influent. Experiments also were done to (i) test the effects of oxygen content of feed water on metal removal and (ii) the adsorptive capacity of the reactor organic substrate. Analysis of the results indicates that bacterial sulfate reduction may be a zero-order kinetic reaction relative to sulfate concentrations used in the experiments, and may be the factor that controls the metal mass removal efficiency in the anaerobic treatment systems. The sorptive capacities of the organic substrate used in the experiments had not been exhausted during the experiments as indicated by the loading rates of removal of metals exceeding the mass production rates of sulfide. Microbial sulfate reduction was less in the reactors receiving low-pH influent during experiments with short residence times. Sulfate-reducing bacteria may have been inhibited by high flows of low-pH water. Dissolved oxygen content of the feed waters had little effect on sulfate reduction and metal removal capacity.     

Constitutive expression of a high-affinity sulfate transporter in Indian mustard affects metal tolerance and accumulation

The Stylosanthes hamata SHST1 gene encodes a high-affinity sulfate transporter located in the plasma membrane. In this study the S. hamata SHST1 gene was constitutively expressed in Indian mustard [Brassica juncea (L.) Czern.] to investigate its importance for tolerance and accumulation of various oxyanions that may be transported by SHST1 and for cadmium, which is detoxified by sulfur-rich compounds. The transgenic SHST1 lines SHST1-12C and SHST1-4C were compared with wild-type Indian mustard for tolerance and accumulation of arsenate, chromate, tungstate, vanadate, and cadmium. As seedlings the SHST1 plants accumulated significantly more Cd and W, and somewhat more Cr and V. The SHST1 seedlings were less tolerant to Cd, Mo, and V compared to wild-type plants. Mature SHST1 plants were less tolerant than wild-type plants to Cd and Cr. SHST1 plants accumulated significantly more Cd, Cr, and W in their roots than wild-type plants. In their shoots they accumulated significantly more Cr and somewhat more V and W. Shoot Cd accumulation was significantly lower than in wild-type, and As levels were somewhat reduced. Compared to wild-type plants, sulfur accumulation was enhanced in roots of SHST1 plants but not in shoots. Together these results suggest that SHST1 can facilitate uptake of other oxyanions in addition to sulfate and that SHST1 mediates uptake in roots rather than root-to-shoot translocation. Since SHST1 overexpression led to enhanced accumulation of Cr, Cd, V, and W, this approach shows some potential for phytoremediation, especially if it could be combined with the expression of a gene that confers enhanced metal translocation or tolerance.     

The effect of five forage species on transport and transformation of atrazine and isoxaflutole (balance) in lysimeter leachate

A field lysimeter study with bare ground and five different ground covers was established to evaluate the effect of forage grasses on the fate and transport of two herbicides in leachate. The herbicides were atrazine (ATR; 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) and isoxaflutole [IXF; 5-cyclopropyl-4-(2-methylsulfonyl-4-trifluormethyl-benzoyl)isoxazole], which has the commercial name Balance (Aventis Crop Science, Strasbourg, France). The ground covers included orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), and switchgrass (Panicum virgatum L.). The results suggested that the total IXF (parent + metabolites) showed higher mobility than ATR and its metabolites. Differences in the timing of transport reflected the rapid degradation of IXF to the more soluble, stable, and biologically active diketonitrile (DKN) metabolite in the system. Although grass treatments did not promote the hydrolysis of DKN, they significantly reduced its transport in the leachate through enhanced evapotranspiration. Grass treatments significantly enhanced ATR degradation in the leachates and soils, especially through N dealkylation, but they did not reduce total ATR transported in the leachate. Leachate from the orchardgrass lysimeters contained the highest proportion of ATR metabolites (64.2%). Timothy and smooth bromegrass treatments also displayed a significant increase in ATR metabolites in leachate. Grass-treated lysimeters showed higher microbial biomass carbon than bare ground. For ATR treatments, the proportion of metabolites in the leachate strongly correlated with the elevated soil microbial biomass carbon in forage treatments. In contrast, DKN degradation was poorly correlated with soil microbial biomass carbon, suggesting that DKN degradation is an abiotic process.     

Zinc accumulation in plant species indigenous to a Portuguese polluted site: relation with soil contamination

The levels of zinc accumulated by roots, stems, and leaves of two plant species, Rubus ulmifolius and Phragmites australis, indigenous to the banks of a stream in a Portuguese contaminated site were investigated in field conditions. R. ulmifolius, a plant for which studies on phytoremediation potential are scarce, dominated on the right side of the stream, while P. australis proliferated on the other bank. Heterogeneous Zn concentrations were found along the banks of the stream. Zn accumulation in both species occurred mainly in the roots, with poor translocation to the aboveground sections. R. ulmifolius presented Zn levels in the roots ranging from 142 to 563 mg kg(-1), in the stems from 35 to 110 mg kg(-1), and in the leaves from 45 to 91 mg kg(-1), vs. average soil total Zn concentrations varying from 526 to 957 mg kg(-1). P. australis showed Zn concentrations in the roots from 39 to 130 mg kg(-1), in the stems from 31 to 63 mg kg(-1), and in the leaves from 37 to 83 mg kg(-1), for the lower average soil total Zn levels of 138 to 452 mg kg(-1) found on the banks where they proliferated. Positive correlations were found between the soil total, available and extractable Zn fractions, and metal accumulation in the roots and leaves of R. ulmifolius and in the roots and stems of P. australis. The use of R. ulmifolius and P. australis for phytoextraction purposes does not appear as an effective method of metal removing, but these native metal tolerant plant species may be used to reduce the effects of soil contamination, avoiding further Zn transfer to other environmental compartments.     

Seasonal variation of leaf dust accumulation and pigment content in plant species exposed to urban particulates pollution

To assess the dust interception efficiency of some selected tree species and impact of dust deposition on chlorophyll and ascorbic acid content of leaves the present study was undertaken. The plant species selected for the study were Ficus religiosa, Ficus benghalensis, Mangifera indica, Dalbergia sissoo, Psidium guajava, and Dendrocalamus strictus. It was found that all species have maximum dust deposition in the winter season followed by summer and rainy seasons. Chlorophyll content decreased and ascorbic acid content increased with the increase of dust deposition. There was significant negative and positive correlation between dust deposition and chlorophyll and ascorbic acid content, respectively. Maximum dust interception was done by Dalbergia sisso and least by Dendrocalamus strictus. Thus plants can be used to intercept dust particles which are of potential health hazards to humans.     

Dissolution of trace element contaminants from two coastal plain soils as affected by pH

Trace element mobility in soils depends on contaminant concentration, chemical speciation, water movement, and soil matrix properties such as mineralogy, pH, and redox potential. Our objective was to characterize trace element dissolution in response to acidification of soil samples from two abandoned incinerators in the North Carolina Coastal Plain. Trace element concentrations in 11 soil samples from both sites ranged from 2 to 46 mg Cu kg(-1), 3 to 105 mg Pb kg(-1), 1 to 102 mg Zn kg(-1), 3 to 11 mg Cr kg(-1), < 0.1 to 10 mg As kg(-1), and < 0.01 to 0.9 mg Cd kg(-1). Acidified CaCl2 solutions were passed through soil columns to bring the effluent solution to approximately pH 4 during a 280-h flow period. Maximum concentrations of dissolved Cu, Pb, and Zn at the lowest pH of an experiment (pH 3.8-4.1) were 0.32 mg Cu L(-1), 0.11 mg Pb L(-1), and 1.3 mg Zn L(-1) for samples from the site with well-drained soils, and 0.25 mg Cu L(-1), 1.2 mg Pb L(-1), and 1.4 mg Zn L(-1) for samples from the site with more poorly drained soils. Dissolved Cu concentration at pH 4 increased linearly with increasing soil Cu concentration, but no such relationship was found for Zn. Dissolved concentrations of other trace elements were below our analytical detection limits. Synchrotron X-ray absorption near edge structure (XANES) spectroscopy showed that Cr and As were in their less mobile Cr(III) and As(V) oxidation states. XANES analysis of Cu and Zn on selected samples indicated an association of Cu(II) with soil organic matter and Zn(II) with Al- and Fe-oxides or franklinite.     

pH值对废水中氨氮监测结果的影响

在相同水温条件下,采用中华人民共和国国家环境保护标准HJ537—2009（（水质氨氮的测定蒸馏一中和滴定法》测量水中氨浓度时,不同的pH值会对废水中氨氮浓度的监测结果造成影响。pH值对测定水样氨氮含量监测结果的影响呈先增大后下降的趋势,在pH值为6。0～7．4之间测定水样氨氮含量最大。     

Phytostabilization potential of quailbush for mine tailings: growth, metal accumulation, and microbial community changes

Abandoned mine tailings sites in semiarid regions remain unvegetated for extended periods of time and are subject to eolian dispersion and water erosion. This study examines the potential phytostabilization of a lead-zinc mine tailings site using a native, drought-tolerant halophyte, quailbush [Atriplex lentiformis (Torr.) S. Wats.]. In a greenhouse study germination, growth, and metal uptake was evaluated in two compost-amended mine tailings samples, K4 (pH 3) and K6 (pH 6) at 75, 85, 90, 95, and 100% mine tailings, and two controls, off-site and compost. Microbial community changes were monitored by performing MPN analysis of iron- and sulfur-oxidizing bacteria as well as heterotrophic plate counts. Results demonstrate that germination is not a good indicator for phytostabilization since it was only inhibited in the unamended K4 treatment. Plant growth was significantly reduced in 95 and 100% mine tailings, while growth in 75, 85, and 90% treatments was similar to the off-site control. Quailbush accumulated elevated levels of the nutrient metals Na, K, Mn, and Zn in the shoot tissues; however, metal accumulation was generally below the domestic animal toxicity limit. Initially, autotrophic population estimates were four to six logs higher than heterotrophic counts, indicating extremely stressed conditions. However, post-harvest, heterotrophic bacterial counts increased to normal levels (approximately 10(6) CFU g-1 dry tailings) and dominated the rhizosphere. Therefore, with compost amendment, quailbush has good potential as a native species candidate for phytostabilization of mine tailings in semiarid environments.     

The metal mining industry in Eastern Europe

The mining industry has been one of the backbones of the socialist countries of Eastern Europe, not only in economic, but also in political, terms. Three years after the beginning of economic reforms, the mining industry in all the Eastern European countries is facing dramatic changes. Most mines are mining ores below acceptable cut-off grades, and there is no hope of finding new, richer deposits. Downstream metallurgical industries will need to replace their former suppliers. In addition, the social contract that had been maintained under the socialist governments is about to be undone and a new form of internal organization must be found. The success of the economic reforms in Eastern Europe depends upon the capacity to develop new industrial relations: the large mining combinates will have to be transformed into competitive capitalist enterprises and the role of the state must be redefined. Prospects for this transformation vary greatly, from metal to metal and from country to country. Finally, restructuring in Eastern Europe will also affect European and world markets, both on the supply and demand sides. The integration of the Eastern European mining industries into the international mining community should be the medium-term goal of all the participants .     

The influence of pH on biological solubulization of oxidized, low-rank coal

Solubilization of nitric acid oxidized Texas lignite by either microorganisms or alkali were compared. Three fungi and three actinomycetes were able to solubilize small amounts of 3.2 N nitric acid-oxidized coal in liquid culture. A correlation was observed between increases in culture fluid pH and solubilization. Extraction of 8 N nitric acid-oxidized Texas lignite with alkaline buffers (pH 7, 8, 10, 11, and 12.3) resulted in extensive coal solubilization. UV-Vis spectra of most microbially solubilized samples were similar to those of alkali solubilized coal. Addition of alkali soluble Texas lignite to growing cultures resulted in no UV-Vis spectral changes with time for the majority of cultures tested. Taken together these data suggest that alkali production is a mechanism by which microorganisms solubilize oxidized coal.     

不同pH值、不同比例的添加剂对土壤吸附铯的影响

铯极易被粘土矿物和有机质吸附而且不易解吸,在示踪水土侵蚀、处置核废物方面有着积极的作用。不同的pH值、不同比例的添加剂都会影响土壤对核素铯的吸附,实验证明两种土壤对核素铯的吸附在pH=4～7时很大,pH=7时达到最大;四种添加剂粗沸石、人造沸石、Ca（OH）2、MnO2只有粗沸石的加入量与铯的吸附比成正相关关系,可以提高土壤对铯的吸附能力。     

Promotional effect of transition metal doping on the properties of KF/CaO catalyst for biodiesel synthesis

A series of heterogeneous KF/CaO catalysts modified with transition metals (lanthanum, cerium, and zirconium) were prepared via wet impregnation method and applied to the trsansesterification process of waste cooking oil (WCO) as feedstock with methanol to biodiesel production. The structure, performance of the solid catalysts was characterized by X-ray diffraction (XRD), temperature programmed desorption of CO₂ (CO₂-TPD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The effect of methanol/oil molar ratio, ¹reaction time, reaction temperature, catalyst amount, and stability was investigated. The results showed that 10 wt% of lanthanum, cerium, and zirconium improved the catalytic activity of KF/CaO catalyst. The maximum catalytic activity using the lanthanum doping of 10wt% on KF/CaO catalyst was reached 98.7% under the optimal reaction condition of methanol/oil molar ratio of 12:1, reaction for 1 h at reaction temperature of 65°C, and 4% (wt/wt oil) catalyst amount. In addition, the FAME yield of KF/CaO/La catalyst remained higher than 95% after 10 cycles. The promotional effect of lanthanum doping could be attributed to the enhancement of the basicity strength of KF/CaO catalyst and block the leach of Ca²⁺ in the transesterification reaction.     

Evaluation of heavy metals accumulation by two emergent macrophytes from the polluted soil: an experimental study

The concentrations of copper (Cu) and lead (Pb) in, and the biomass of, the different parts of Persicaria glabra (Willd.) Gamez and Juncellus alopecuroides (Rottb.) C.B.Cl. were evaluated while grown in pots under laboratory conditions. Cu and Pb were added as sulphates (50, 100, 200, 400 mg/kg) to the pots. Heavy metal concentrations in the plants were measured by atomic absorption spectrometry. Results reveal that the biomass of J. alopecuroides (particularly roots) was higher than P. glabra, and that the growth tendency of macrophytes decreased with increasing heavy metal concentration in the soil, while in P. glabra, biomass went on increasing with the increase in copper concentration. Heavy metal accumulation in the roots was more than in aerial parts, and, therefore, barring two exceptions, the transfer factor of heavy metals from roots to aerial parts showed as less than 1, suggesting less transfer of heavy metals from roots to aerial parts. Thus, these macrophytes are efficient accumulators of trace elements, particularly J. alopecuroides, which can be recommended for biofiltration of heavy metals from contaminated soils.     

Responses of herbaceous mimosa (Mimosa strigillosa), a new reclamation species, to soil pH

Growth responses of herbaceous mimosa (Mimosa strigillosa Torr. and Gray), a potential new reclamation species in the SE USA and Mexico, to nine soil pH scales were studied under a controlled environment at Nacogdoches, TX, USA. Twenty seeds were planted in each of 40 (nine scales plus one control in four replicates) 20.3-cm pots filled with Tonkawa sandy soil. These pots were treated with H₂SO₄ or Ca(OH)₂ to adjust each pot to its designated pH level. After 15 days of seeding, the emergence rate was at best about 50–70% for pH 4.7–6.6. The plant can survive and grow at soil pH as low as 4.7, but the optimum growth seems to be on soils with pH ranging from 6.2 to 7.1. At this pH range, the plant exhibits higher values of green and dry biomass, longer shoot growth and lower root/shoot weight and length ratios. The survival rate was greater than 90% for all treatments, except for pH 4.1. There were no nutrient deficiencies in plant tissues on soil pH 4.7 or higher. The plant allocated more growth to the shoot under optimum conditions, but more growth to the roots under environmental stress. It is not suitable for herbaceous mimosa to grow on soils with pH 4.1 or less.     

The role of co-products in stabilizing the metal mining industry

The objective of this paper is to test the hypothesis that cyclical metal mining activity is more stable when multi-metal products are produced. A theoretical short-run supply curve for a metal is developed showing by-product, co-product, and main product behaviour. This curve is used to illustrate co-product pricing trends that are indicative of different cyclical behaviour patterns. The non-parametrical sign test is used to test co-product price trends for the US metal mining industry. The results indicate that multi-metal production stabilizes the mining industry in the short run but not in the long run.     

Enhancing phytoextraction: the effect of chemical soil manipulation on mobility, plant accumulation, and leaching of heavy metals

For heavy metal-contaminated agricultural land, low-cost, plant-based phytoextraction measures can be a key element for a new land management strategy. When agents are applied into the soil, the solubility of heavy metals and their subsequent accumulation by plants can be increased, and, therefore, phytoextraction enhanced. An overview is given of the state of the art of enhancing heavy metal solubility in soils, increasing the heavy metal accumulation of several high-biomass-yielding and metal-tolerant plants, and the effect of these measures on the risk of heavy metal leaching. Several organic as well as inorganic agents can effectively and specifically increase solubility and, therefore, accumulation of heavy metals by several plant species. Crops like willow (Salix viminalis L.), Indian mustard [Brassica juncea (L.) Czern.], corn (Zea mays L.), and sunflower (Helianthus annuus L.) show high tolerance to heavy metals and are, therefore, to a certain extent able to use the surpluses that originate from soil manipulation. More than 100-fold increases of lead concentrations in the biomass of crops were reported, when ethylenediaminetetraacetic acid (EDTA) was applied to contaminated soils. Uranium concentrations could be strongly increased when citric acid was applied. Cadmium and zinc concentrations could be enhanced by inorganic agents like elemental sulfur or ammonium sulfate. However, leaching of heavy metals due to increased mobility in soils cannot be excluded. Thus, implementation on the field scale must consider measures to minimize leaching. So, the application of more than 1 g EDTA kg(-1) becomes inefficient as lead concentration in crops is not enhanced and leaching rate increases. Moreover, for large-scale applications, agricultural measures as placement of agents, dosage splitting, the kind and amount of agents applied, and the soil properties are important factors governing plant growth, heavy metal concentrations, and leaching rates. Effective prevention of leaching, breeding of new plant material, and use of the contaminated biomass (e.g., as biofuels) will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction.     

环境监测中pH平均值的计算探讨

本文根据pH的定义和水溶液电离平衡理论,探讨了pH平均值的计算方法,通过理论分析和实验验证指出了pH值现行计算方法的不足,本法对环境监测中酸沉降和水质监测pH数据的正确处理及编报具有现实的意义。     

The effect of navigational expertise on wayfinding in new environments

Becoming proficient at navigation in urban environments is something that we all aspire to. Here we asked whether being an expert at wayfinding in one environment has any effect on learning new spatial layouts. Licensed London taxi drivers are among the most proficient urban navigators, training for many years to find their way around a complex and irregularly-laid out city. We first tested how well they could learn the layout of an unfamiliar town compared with a group of non-taxi drivers. Second, we investigated how effectively taxi drivers could integrate a new district into their existing spatial representation of London. We found that taxi drivers were significantly better than control participants at executing routes through the new town, and representing it at a map-like survey level. However, the benefits of navigational expertise were not universal. Compared with their performance in the new town, taxi drivers were significantly poorer at learning the layout of a new area that had to be integrated with their existing knowledge of London. We consider reasons for this picture of facilitation and limitation, in particular drawing parallels with how knowledge acquisition occurs in the context of expertise in general.