Arsenic hyperaccumulation by brake ferns and their potential in phytoremediation

Municipal solid waste incinerator （MSWI） fly ash is world-widely defined as hazardous waste because of its high concentration of heavy metals and high toxic equivalents of dioxin-like compounds. Therefore, if not properly disposed, it would pose a risk of being released into the environment including soil and groundwater. Heavy metals in the MSWI fly ash are considered as the most dangerous component owing to their leaching characteristics and migration capability. To get a better knowledge of their releasing behavior, it is important to assess the potential environmental mobility of heavy metals in MSWI fly ash and to investigate the factors affecting their leaching characteristics. Fly ashes from four MSW incinerators were characterized and leaching of heavy metals according to both Chinese HVEP and USA TCLP were performed. A geochemical modeling computer program, PHREEQC （version 2） was used to calculate the equilibrium concentration, the speciation and possible precipitation of heavy metals in the leaching systems. In the modeling, the heavy metals, Cd, Cr, Cu, Ni, Pb, Zn, were input as master aqueous species in solutions, while the major and accessory components, Ca, Na, K, Cl, S, etc., were defined as finite solids. The agreement between the experimental results and the modeling ones varies for different metals as well as for different fly ashes. In general, the fitness of the modeling for different heavy metals is： Pb〉Zn〉Cd〉Cu. The modeling is excellent for fly ashes with low calcium but high chloride content, or with high concentration of heavy metals, which favor the implicit postulation of component input in the modeling, i.e., high availability of heavy metals.     

Accumulation of heavy metals in soil and uptake by plant species with phytoremediation potential

Contamination of heavy metals represents one of the most pressing threats to water and soil resources, as well as human health. Phytoremediation can be potentially used to remediate metal contaminated sites. In this study, concentrations of copper, zinc, iron, and magnesium accumulated by native plant species were determined in field conditions of Hame Kasi iron and copper mine in the central part of Iran in Hamadan province. The results showed that metal accumulation by plants differed among species and tissue bodies. Species grown in substrata with elevated metals contained significantly higher metals in plants. Metals accumulated by plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance exists widely amongst them. The mentioned species could accumulate relatively higher metal concentrations far above the toxic concentration in the plant shoots. With high translocation factor, metal concentration ratio of plant shoots to roots indicates internal detoxification metal tolerance mechanism; thus, they have potential for phytoextraction. The factors affecting metal accumulation by plant species including metal concentrations, pH, electrical conductivity, and nutrient status in substrata were measured. Mostly, concentrations of zinc and copper in both aboveground and underground tissues of the plants were significantly, positively related to their total in substrata, while iron, zinc, and copper were negatively correlated to soil phosphorus.     

Potential of plant species for phytoremediation of metformin from solutions

Phytoremediation has been applied for treating an extensive range of environmental contaminants such as anti-diabetic drug metformin which is increasingly found as environmental contaminant. These contaminants are released to the environment via human and veterinary medicine and pharmaceutical industries. In this study, native plant capabilities for uptake of metformin from wastewater were investigated. Moreover, uptake rate of metformin was studied in two different concentrations of 20 and 50 mg l^?1 metformin solution by Amaranthus retroflexus, Ricinus communis, Brassica napus, Celosia cristata, Helianthus annuus and Phragmites australis. The results showed that after exposing to 20 mg l^?1 metformin solution 69.53 ± 2.25% of metformin was remediated by H. annuus plants. Also in 50 mg l^?1 metformin solution, H. annuus plants showed the most remediation potential (65.7 ± 1%). Metformin uptake is raised by B. napus and C. cristata plants along with increasing metformin concentration. There was no evidence of the presence of metformin in the roots and shoots of R. communis and C. cristata. The results also indicated that plants such as H. annuus can be a potential candidate for uptake of metformin from wastewater.     

柴达木盆地周缘镍矿床(点)成矿特征及找矿潜力分析

近年来,在青海柴达木盆地周缘(简称柴周缘)地区陆续发现了一系列与超基性岩体有关的镍矿床(点)。为此,根据已有地质矿产资料,通过综合研究分析,总结了柴周缘地区镍铜硫化物矿床的成矿地质背景、空间分布及成矿特征; 在柴周缘地区划分出柴北缘高压混杂岩带、欧龙布鲁克陆块、柴南缘昆北裂陷槽及柴南缘昆中岩浆弧带等4个镍成矿区带,并重点分析了各成矿区带的镍矿床(点)成矿特征; 在此基础上,总结了柴周缘镍矿床的幔源岩浆深部熔离和上侵贯入的成矿模式及含矿岩石风化露头和物化探异常等找矿标志,圈定出柴北缘高压混杂岩带西段的阿尔金南缘茫崖镇—冷湖镇、欧龙布鲁克陆块东段的乌兰、柴南缘昆北裂陷槽西段的冰沟南和东段的夏日哈木西北,以及柴南缘昆中岩浆弧带中段的夏日哈木—托拉海南和白日其利—哈图6处镍矿找矿潜力区。所取得的地质找矿效果,对推动整个柴周缘地区与超基性岩体有关的镍矿的勘查工作具有重要意义。     

污染土壤植物修复中螯合诱导和转基因技术的应用现状与前景

近年来,螯合诱导技术和转基因技术作为强化植物吸收重金属的两种技术备受关注。文中系统地介绍了植物对重金属的解毒机理、植物的基因改良以及螯合诱导技术和转基因技术在提高植物修复能力中的应用等有关内容,最后探讨了螯合诱导技术和转基因技术的发展方向,认为这两项技术不失为大有潜力的土壤重金属污染修复技术,具有着广阔的应用前景。     

环境硒污染的植物修复研究进展

硒污染已成为全球性的环境问题,严重威胁人类健康和环境安全。本文概述了环境硒污染植物修复技术的研究进展,包括硒富集植物的应用、富集硒的机理及生物技术对它们的改造。指出了当前研究在硒富集植物富集机理及田间应用时的不足;并展望了今后如何进一步寻找和使用生物技术培育硒超富集植物、探求富集机理和田间试验。     

The nickel content of deep-sea deposits

Determinations of the nickel, manganese and iron present in sediment cores from the Central Pacific Ocean have been made by microchemical methods. The results show (a) that the nickel content is high relative to that of continental rocks and sediments and, (b) that there are considerable variations in the nickel contents with depth below the sediment surface. No correlation with the manganese and iron contents is evident except in cases where a change in the rate of sedimentation appears to have affected all three elements in the same manner.     

甘肃北山二叠纪镁铁-超镁铁质岩体地质、地球化学特征及铜镍成矿潜力

北山造山带是中亚造山带南缘镁铁-超镁铁质岩体的集中分布区之一,因其赋含二叠纪铜镍硫化物矿床而受到广泛关注。以往的研究多集中在北山造山带西部的新疆坡北地区,近年来随着对甘肃北山地区二叠纪镁铁-超镁铁岩体认识逐渐深入,新发现的矿化岩体有逐渐向东延伸的趋势。本文选择北山造山带中东部柳园地区骆驼山和西南山两个典型含铜镍硫化物岩体进行地质年代学、岩相学和岩石地球化学及同位素地球化学研究。岩体主要岩相包括橄榄岩相、辉石岩相、橄榄辉长岩相、橄长岩相和辉长岩相,其中硫化物主要出现在橄榄岩相和辉石岩相中。骆驼山岩体辉长岩锆石的U-Pb年龄为282.6 Ma,与坡北地区矿化岩体的形成时代一致。骆驼山和西南山岩体母岩浆稀土元素配分模式为轻微右倾型,富集大离子亲石元素,强烈亏损高场强元素Nb-Ta,中等亏损Zr-Hf,与坡北和东天山地区同时代矿化岩体母岩浆特征相似。岩体具有较高的全岩ε_Nd(t)值(+0.42～+6.10)和锆石ε_Hf(t)值(+7.9～+14.1)的特征,与坡北地区矿化岩体类似,表明具有相似的亏损地幔源区。橄榄石Fo值与Ni含量的关系和母岩浆微量元...     

Evaluating heavy metal concentration of plants on a serpentine site for phytoremediation applications

The chemical analysis of plants and soils is a frequently used approach in understanding a serpentine ecosystem. Studies on vegetation growth in serpentine soils focused on various plant species for remediation purposes of soil contamination with heavy metals, emphasizing their role in the metal extraction or stabilization in the soil. The aims of this study were to measure the concentrations of Cr, Mn, and Ni in the soils and plants and to elucidate the phytoremediation potential of the studied plants. This study was performed at an abandoned site of serpentine mining in eastern Taiwan. Seven plant species were collected for analysis of Cr, Mn, and Ni, including Crotalaria micans, Miscanthus floridulus, Leucaena leucocephala, Bidens pilosa, Pueraria lobata, Melilotus indicus, and Conyza canadensis. The Cr and Ni concentrations in all studied plants were higher than those in general plants. In all species, the mean concentrations of Cr, Mn, and Ni in the shoots were lower than those in the root. None of the collected specimens exhibited hyperaccumulation of Cr, Mn, and Ni. All studied species may be used to remediate contaminated soils through phytostabilization of Cr and Mn, whereas M. floridulus and M. indicus are appropriate plants for phytostabilization of Ni. However, C. micans, L. leucocephala, B. pilosa, P. lobata, and C. canadensis have the potential to remove Ni from contaminated soils for the purpose of phytoextraction.     

The extraregional seismotectonic method for the assessment of seismic potential

The extraregional seismotectonic method for prognosis estimation of seismic potential (M _max) is presented. Information on the recent structure and state of the Earth's crust is used as the initial data for performing the seismotectonic analysis. The Earth's crust typification is performed applying computer procedures of cluster analysis for the territory of the major part of Europe of the adjacent aquatories and Central Asia. Application of the method results in an essential improvement of the prediction of the site and strength of expected earthquakes within seismically active territories and also makes possible the estimation of the seismic potential of weakly active regions from the same methodological standpoint.     

The formation and evolution of the Bitincke nickel laterite deposit, Albania

The Bitincke nickel laterite deposit, located in the south east of Albania, contains an estimated ore resource of 35.6?Mt of nickel ore with a grade of 1.2?% Ni. The deposit developed on peridotites within Late Jurassic ophiolites which were obducted in the Early Cretaceous and which form part of the Albanian Mirdita ophiolite zone. Limestones and conglomerates overlying the deposit delimit the minimum age of lateritization to the mid-Eocene. The laterite is composed of two distinct ore zones characterized by silicate nickel and iron oxide phases. Within the silicate zone, Ni concentrations reach a maximum of 1.5?wt% and although laterally and vertically variable this zone is typically characterized by olivine and serpentine at the base of the horizon which are gradually replaced by secondary silicates and iron oxides up section. The boundary between the silicate and the oxide zone above is normally sharp and characterized by an increase in Fe₂O₃ (from ~10 to 80?wt%), decreases in SiO₂ (from ~30 to 5?wt%) and a dramatic reduction in MgO content (from ~10 to 0.1?wt%). The oxide horizon is dominated by goethite and displays relatively little variation in textural morphology or geochemistry. Nickel concentrations are greatest near the base of this zone, reaching a maximum of 2.3?wt%. Weathering profile formation and variation in the thickness of the deposit was controlled by the interaction between topography, faulting and protolith fracture density. The oxide zone formed on topographic highs was subject to increased rates of erosion, whereas the laterite profile within topographic lows, and in areas of relatively high fracture density, tends to be thicker due to increased permeability. The most substantive sections of the Ni laterite weathering profile developed in small fault controlled basins and were preserved by the deposition of a sequence of limestones and mudstones.     

Lead tolerance and accumulation in three cultivars of Eucalyptus urophyllaXE.grandis: implication for phytoremediation

Eucalyptus urophyllaXE.grandis is a fast-growing economic tree species that contributes to habitat restoration of degraded or fragile environments. Hydrophonic experiments were performed to evaluate the extent of lead (Pb) tolerance and accumulation in three cultivars of this species, ST-2, ST-9 and ST-29, when exposed to nutrient solutions with different concentrations of Pb [7, 14, 28 or 56 mg Pb L^?1 as Pb(NO₃)₂]. Obtained results showed that, in the presence of Pb treatments, ST-9 grows well without any toxicity symptoms of leaf necrosis and reduced growth, indicating its feature of tolerance to Pb. Furthermore, marked variation in Pb accumulation was found among plant organs (roots, shoots and leaves), cultivars and Pb supply. In most cases, cultivar ST-9 was shown to accumulate more Pb than others. In conclusion, E. urophyllaXE.grandis ST-9 can be a good choice for remediating Pb-contaminated soils.     

不同超富集、富集植物-玉米间作模式对玉米中镉吸收、转运的影响研究

为了研究Cd污染条件下,玉米分别与苋菜、黑麦草、龙葵间作对重金属Cd吸收和转运的特点,从而选择适宜与玉米间作的富集植物,同时达到修复重金属Cd污染土壤的目的。该文以镉(Cd)污染的河南棕壤黏土为供试土壤,通过盆栽试验,基于玉米各器官中Cd含量、富集系数、转运系数、土壤有效态Cd含量的变化,研究了间作苋菜、黑麦草、龙葵对玉米各器官Cd的积累特性的影响及其迁移转运机制。结果表明：(1)龙葵、苋菜、黑麦草间作使得玉米地上部Cd含量显著性降低(P<0.05),其中以籽粒中Cd含量的下降最为显著。间作苋菜、黑麦草、龙葵,玉米籽粒中Cd含量分别下降了67.6%、75.7%和79.9%。(2)间作苋菜、黑麦草、龙葵使得玉米的富集系数较单作处理下玉米的富集系数分别下降了49.3%、39.7%和68.5%,且差异达到显著水平。(3)与苋菜、黑麦草间作相比,间作龙葵的玉米转运系数分别下降了27.5%、24.2%,且差异均达到显著水平。通过对人体每天摄入Cd量的安全值计算得出间作后土壤中Cd全量应低于2.26 mg·kg-1,土壤有效态Cd含量低于0.88 mg·kg-1。该污染农田在间作模式下,食用玉米Cd暴露对居民健康不存在风险。间作苋菜、黑麦草、龙葵能够抑制玉米对Cd的吸收,同时阻控玉米地上部Cd向地上部的转移,尤其是向籽粒转移。通过间作苋菜、黑麦草、龙葵,不仅降低了主栽作物玉米的Cd累积量,实现玉米安全、优质种植,同时也达到了修复污染土壤的目的。     

The use of vetiver grass (Vetiveria zizanioides) in the phytoremediation of soils contaminated with heavy metals

Recent research has shown that phytoextraction approaches often require soil amendments, such as the application of EDTA, to increase the bioavailability of heavy metals in soils. However, EDTA and EDTA–heavy metal complexes can be toxic to plants and soil microorganisms and may leach into groundwater, causing further environmental pollution. In the present study, vetiver grass (Vetiveria zizanioides) was studied for its potential use in the phytoremediation of soils contaminated with heavy metals. In the pot experiment, the uptake and transport of Pb by vetiver from Pb-contaminated soils under EDTA application was investigated. The results showed that vetiver had the capacity to tolerate high Pb concentrations in soils. With the application of EDTA, the translocation ratio of Pb from vetiver roots to shoots was significantly increased. On the 14th day after 5.0 mmol EDTA kg⁻¹ of soil application, the shoot Pb concentration reached 42, 160, 243 mg kg⁻¹ DW and the root Pb concentrations were 266, 951, and 2280 mg kg⁻¹ DW in the 500, 2500 and 5000 mg Pb kg⁻¹ soils, respectively. In the short soil leaching column (9.0-cm diameter, 20-cm height) experiment, about 3.7%, 15.6%, 14.3% and 22.2% of the soil Pb, Cu, Zn and Cd were leached from the artificially contaminated soil profile after 5.0 mmol EDTA kg⁻¹ of soil application and nearly 126 mm of rainfall irrigation. In the long soil leaching experiment, soil columns (9.0-cm diameter, 60-cm height) were packed with uncontaminated soils (mimicking the subsoil under contaminated upper layers) and planted with vetiver. Heavy metal leachate from the short column experiment was applied to the surface of the long soil column, the artificial rainwater was percolated, and the final leachate was collected at the bottom of the soil columns. The results showed that soil matrix with planted vetiver, could re-adsorb 98%, 54%, 41%, and 88% of the initially applied Pb, Cu, Zn, and Cd, respectively, which may reduce the risk of heavy metals flowing downwards and entering the groundwater.     

Bioaugmentation for the enhancement of hydrocarbon phytoremediation by rhizobacteria consortium in pilot horizontal subsurface flow constructed wetlands

The development of the bioaugmentation during the phytoremediation of contaminated water with diesel in pilot horizontal subsurface flow constructed wetlands was investigated for 63 days. The objective of this study was to examine the enrichment of rhizobacteria in a pilot-scale system for efficient treatment of total petroleum hydrocarbon (TPH) effluent. A consortium of three rhizobacteria strains (Bacillus aquimaris, Bacillus anthracis and Bacillus cereus), which were able to utilize hydrocarbon compounds as sole carbon sources, was injected into the constructed wetlands (batchwise operation) planted with Scirpus grossus. The TPH removals from water, without or with the addition of rhizobacteria, were found to be 72 and 84%, while from sand was found to be 59 and 77%, for each treatment, respectively. These results showed that the rhizobacteria strains could enhance S. grossus growth by decreasing diesel stress and protecting S. grossus against diesel, with 12 and 18% additional TPH removal from water and sand, respectively. Our results demonstrate that S. grossus is potential to improve the phytoremediation of hydrocarbon contaminants through inoculation with effective rhizobacterial strains.     

The atmospheric transport potential for water vapour and dust in the Sahel region

The transport of water vapour and dust in the Sahel can be assigned to identical atmospheric flow systems, the African Easterly Jet, the Easterly Waves and the Squall Lines. The yield of the rainy season in the Sahel depends on the conditions in the preceding rains of the season and is closely coupled to the surface heat budget both in the monsoonal air in the S and the trades in the N. The heat budget, in particular the evaporation after the passage of a Squall Line, is influenced not only by the total amount of preceding rains but also by the plant cover pumping the water to the surface and smoothing the magnitude of the evaporation in time. This feed-back mechanism may be made responsible for the persistence of the Sahel drought as experienced in recent years. The dust export from the African continent towards the Atlantic can only be so effective, because the Squall Lines and the African Easterly Jet are meshed in a way that produces large amounts of suspended material and lifts it to great heights where the transport velocity is very fast.     

金川镍矿尾矿砂矿物组成特征与酸溶特性研究

金属矿山生产产生大量的尾矿,不但危害周围生态环境,而且对资源造成极大浪费。金川镍矿尾矿砂Ni、Cu和Co的平均含量分别达到0.21%、0.19%和0.01%,是够得上二次开发利用的宝贵资源。文中对金川镍矿尾矿砂矿物组成特征及酸溶特性进行了详细的研究,目的是为工业化高效回收尾矿砂中Ni、Cu和Co等有价金属提供科学依据与技术支撑。矿物学研究表明,金川镍矿尾矿砂主要由蛇纹石、绿泥石、橄榄石、辉石、透闪石、磁铁矿、白云石及少量磁黄铁矿、镍黄铁矿和黄铜矿等组成。经多年露天堆存,金川镍矿老尾矿库尾矿砂已发生不同程度的氧化作用。尾矿库3 m以上为强烈氧化带,金属硫化物矿物颗粒边缘、裂缝处基本都有强烈的氧化作用发生。碳酸盐等易溶矿物被大量消耗。硫酸溶解实验表明,金川镍矿老尾矿库尾矿砂中有价金属Cu、Ni和Co的平均浸出率分别可达88.6%、75.3% 和70.8%。尾矿砂中Cu、Ni和Co有价金属的浸出效果不但清楚直观地反映了尾矿库中尾矿砂的氧化程度,而且表明金属硫化物尾矿砂的风化作用,极大地促进了硫化物矿物中有价金属的酸溶浸出。     

The potential for free and mixed convection in sedimentary basins

 Free thermal convection and mixed convection are considered as potential mechanisms for mass and heat transport in sedimentary basins. Mixed convection occurs when horizontal flows (forced convection) are superimposed on thermally driven flows. In cross section, mixed convection is characterized by convection cells that migrate laterally in the direction of forced convective flow. Two-dimensional finite-element simulations of variable-density groundwater flow and heat transport in a horizontal porous layer were performed to determine critical mean Rayleigh numbers for the onset of free convection, using both isothermal and semi-conductive boundaries. Additional simulations imposed a varying lateral fluid flux on the free-convection pattern. Results from these experiments indicate that forced convection becomes dominant, completely eliminating buoyancy-driven circulation, when the total forced-convection fluid flux exceeds the total flux possible due to free convection. Calculations of the thermal rock alteration index (RAI=q·∇T) delineate the patterns of potential diagenesis produced by fluid movement through temperature gradients. Free convection produces a distinct pattern of alternating positive and negative RAIs, whereas mixed convection produces a simpler layering of positive and negative values and in general less diagenetic alteration. Received, January 1999/Revised, June 1999/Accepted, July 1999     

金川铜镍矿山尾矿砂酸溶性实验研究

为研究金川铜镍矿山酸性废水溶解尾矿砂实现综合治理废液与废固的可能性,进行了尾矿砂在硫酸中的溶解实验。结果表明,尾矿砂在硫酸浓度大于3mol/L、温度保持90℃以上并在液固比6.0下强力搅拌,能够较好地溶解于硫酸中,生成无定形二氧化硅;300℃的马弗炉焙烧4h有助于尾矿砂中绿泥石的溶解,对透闪石的溶解影响不大。尾矿砂中橄榄石、蛇纹石和透辉石较容易被硫酸溶解,透闪石、斜长石则比较难溶解,这与尾矿砂中矿物性质有密切关系。