Lead, chromium and manganese removal by in vitro root cultures of two aquatic macrophytes species: Typha latifolia L. and Scirpus americanus pers

The ability of in vitro roots cultures of Typha latifolia and Scirpus americanus to remove metals was studied. Roots were cultivated on Murashige-Skoog medium with 15 microg L(-1) Cr 11, 60 microg L(-1) Pb II or 1.8 mg L(-1) Mn II. Adsorbed metal to root surface was removed by washing with 0.042% HNO3. T. latifolia roots were able to uptake 68.8 microg Pb g(-1), 22.1 microg Cr g(-1) and 1680 microg Mn g(-1), while the S. americanus roots removed 148.3 microg Pb g(-1), 40.7 microg Cr g(-1) and 4037 microg Mn g(-1). About 80-90% of Pb and Cr were absorbed in both cultures. On the contrary, the Mn removal was due mainly to an adsorption process (82-86%). In comparison to the T. latifolia cultures, S. americanus cultures were twofold more efficient to remove Pb and Cr, and threefold more efficient to remove Mn. Both plant species capture metals in the following order: Cr >Pb >Mn. This investigation confirms that in vitro roots cultures could be an alternative as a phytoremediation approach for contaminated water with heavy metals.     

Petiolar felt-sheath of palm: a new biosorbent for the removal of heavy metals from contaminated water.

Biosorption of heavy metals such as Pb2+, Ni2+, Cd2+, Cu2+, Cr3+ and Zn2+ by petiolar felt-sheath of palm (PFP) from contaminated water was examined. PFP was found to efficiently remove all the toxic metal ions with selectivity order of Pb2+ > Cd2+ > Cu2+ > Zn2+ > Ni2+ > Cr3+. The uptake was rapid, with more than 70% completed within 15 min. The bound metal ions were successfully desorbed and the PFP fibrous-biomass remained effective after several adsorption-desorption cycles.     

Impact of long-term application of industrial wastewater on the emergence of resistance traits in Azotobacter chroococcum isolated from rhizospheric soil

A total of 57 (36 and 21) Azotobacter chroococcum were isolated from wheat (Triticum aestivum) rhizospheric soil irrigated with industrial wastewater (about a decade) and ground water (uncontaminated) and characterized on the basis of morphological, cultural and biochemical characteristics. Rhizospheric soils were analyzed for metal concentrations by atomic absorption spectrophotometery and the test soil samples were contaminated with Fe, Zn, Cu, Cr, Ni and Pb. All the isolates of A. chroococcum were tested for their resistance against Hg2+, Cd2+, Cu2+, Cr3+, Cr6+, Zn2+, Ni2+ and Pb2+. Among 36 isolates of Azotobacter from soil irrigated with industrial wastewater, 94.4% were resistant to Pb2+ and Hg2+ and 86.1%, 77.5% and 63.8% were resistant to Zn2+, Cr6+ and Cr3+ respectively. The highest minimum inhibitory concentration of 200 microg/ml for Hg2+ and 1600 microg/ml for other metals were observed against these bacteria from soil. The incidences of metal resistance and MICs of metals for A. chroococcum from wastewater irrigated soil were significantly different to those of uncontaminated soil. All A. chroococcum isolates were tested for their resistance against 11 commonly used antibiotics/drugs. 91.6% were found to be resistant against nitrofurantoin while 86.4% and 80.5% were found to be resistant against polymyxin-B and co-trimoxazole respectively. Agarose gel electrophoresis using the miniprep method for plasmid isolation revealed that these isolates harboured plasmids of molecular weights 58.8 and 64.5 kb using EcoRI and HindIII digests of X DNA and undigested X DNA as standard markers.     

Effect of dichromate on population and growth of various protozoa isolated from industrial effluents

Three protozoa belonging to genera Euglena, Vorticella and Stylonychia collected from industrial wastes were cultured in a medium containing inorganic salts, basically meant for the growth of algae. Protozoa showed rapid growth in the medium. Hexavalent chromium (K2Cr2O7) at a concentration of 5 micrograms/L in the medium adversely affected the growth of protozoa. At the end of eight days of Cr administration, the population of Euglena, Vorticella and Stylonychia increased 8-, 4.5- and 10-fold, respectively, as against 30-, 6.75- and 50-fold increase in the control cultures. No apparent death phase and no change in activity or morphology of protozoa was observed at this Cr concentration. The protozoa were also exposed to different metal ions, viz. Pb (2.42 mmol/L), Cr (0.48 mmol/L), Cd (0.36 mmol/L), administered in the culture medium for a period of 2 years. The metal tolerance for S. mytilus and V. microstoma was Pb > Cr > Cd. E. proxima could not tolerate any of the long-term metal treatments. Because of the ability of these protozoa to tolerate high concentrations of heavy metals, their potential role in remediation of heavy metals from industrial wastewater is considered.     

Uptake of heavy metals by <Emphasis Type="Italic">Stylonychia mytilus</Emphasis> and its possible use in decontamination of industrial wastewater

The heavy metal resistant ciliate, Stylonychia mytilus, isolated from industrial wastewater has been shown to be potential bioremediator of contaminated wastewater. The ciliate showed tolerance against Zn²⁺ (30 μg/mL), Hg²⁺ (16 μg/mL) and Ni²⁺ (16 μg/mL). The metal ions slowed down the growth of the ciliate as compared with the culture grown without metal stress. The reduction in cell population was 46% for Cd²⁺, 38% for Hg²⁺, 23% for Zn²⁺, 39% for Cu²⁺ and 51% for Ni²⁺ after 8 days of metal stress. S. mytilus reduced 91% of Cd²⁺, 90% of Hg²⁺ and 98% of Zn²⁺ from the medium after 96 h of incubation in a culture medium containing 10 μg/mL of the respective metal ions. Besides this, the ciliate could also remove 88% of Cu²⁺ and 73% Ni²⁺ from the medium containing 5 μg/mL of each metal after 96 h. The ability of Stylonychia to take up variety of heavy metals from the medium could be exploited for metal detoxification and environmental clean-up operations.     

Biosorption of Chromium(VI) and Lead(II): Role of Spirulina platensis in the Treatment of Industrial Effluent

Biosorption is the process of removal of any chemical molecules by the treatment of biological material. Industrialization resulted in the discharge of various toxic heavy metals into water bodies, which poses serious health hazards to humans and animals. In the present study, live Spirulina platensis was used as a biosorbent for the removal of the heavy metals chromium (Cr(VI)) and lead (Pb(II)) from the aqueous samples. S. platensis were cultured in the presence of different concentrations of heavy metals. The growth of the algal cells was found to be decreased by 59% and 36% in media containing 50 ppm Cr(VI) and Pb(II), respectively. To assess the biosorption of heavy metals, at different time intervals, the spent culture media were used to detect Cr(VI) by atomic absorption spectroscopy method and Pb(II) by 4-(2-pyridylazo)resorcinol indicator method. Results suggested that there was a significant uptake of Cr(VI) and Pb(II) from the medium by S. platensis, with corresponding decrease of metals in the medium. When metal salt solutions or industrial effluent samples were passed through the column containing immobilized live S. platensis in calcium alginate beads, the concentration of Cr(VI) was found to be reduced drastically. The present study indicates the application of S. platensis for the bioremediation of heavy metals from the samples obtained from industrial effluents.     

Biosorption of Ni, Cr and Cd by metal tolerant Aspergillus niger and Penicillium sp. using single and multi-metal solution

Fungi including Aspergillus and Penicillium, resistant to Ni2+, Cd2+, and Cr6+ were isolated from soil receiving long-term application of municipal wastewater mix with untreated industrial effluents of Aligarh, India. Metal tolerance in term of minimum inhibitory concentration (MIC) was 125-550 microg/ml for Cd, 300-850 microg/ml for Ni and 300-600 microg/ml for Cr against test fungi. Two isolates, Aspergillus niger and Penicillium sp. were tested for their Cr, Ni and Cd biosorption potential using alkali treated, dried and powdered mycelium. Biosorption experiment was conducted in 100 ml of solution at three initial metal concentrations i.e., 2, 4 and 6 mM with contact time (18 hr) and pretreated fungal biomass (0.1g) at 25 degrees C. Biosorption of all metals was found higher at 4 mM initial metal concentration as compared to biosorption at 2 and 6 mM concentrations. At 4 mM initial metal concentration, chromium biosorption was 18.05 and 19.3 mg/g of Aspergillus and Penicillium biomasses, respectively. Similarly, biosorption of Cd and Ni ions was also maximum at 4 mM initial metal concentration by Aspergillus (19.4 mg/g for Cd and 25.05 mg/g of biomass for Ni) and Penicillium (18.6 mg/g for Cd and 17.9 mg/g of biomass for Ni). In general, biosorption of metal was influenced by initial metal concentration and type of the test fungi. The results indicated that fungi of metal contaminated soil have high level of metal tolerance and biosorption properties.     

Spatial distribution of heavy metals in sediments from the Gulf of Paria, Trinidad

The Gulf of Paria receives heavy metal input from urban runoff, industrial and agricultural activity, sewage and domestic wastes: both from the west coast and from inland areas of Trinidad. Non-residual concentrations of nine metals, as well as total mercury concentrations, were used to determine spatial distributions of heavy metals in sediments in the Gulf of Paria. Surficial sediment samples were collected at 37 stations, which included the mouths of 11 major rivers that flow into the Gulf of Paria. Stations were sampled twice during the wet season (July 1998 and November/ December 1998) and twice during the dry season (March 1999 and April 1999). Sediments were analyzed for aluminium (Al), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn) and mercury (Hg). Total Organic Carbon (TOC) and grain size analyses were also performed on the sediments. Principal component analysis showed that sediments from river mouths subject to greatest land use and anthropogenic input, were distinct from other sediments in the Gulf of Paria. This was due to higher Pb, Zn, Cu and Hg concentrations (3.53-73.30 microg g(-1), 45.8-313.9 microg g(-1), 8.43-39.71 microg g(-1) and 0.03-0.10 microg g(-1), respectively). Sediments further from the coast were also distinct due to their higher Al, Fe, Cr and Mn concentrations (1.37-3.16 mg g(-1), 9.51-18.91 mg g(-1) , 17.22-28.41 microg g(-1) and 323.6-1,564.2 microg g(-1), respectively). Cd and Pb were higher in the wet season while Ni was higher in the dry season. Pb, Zn, Cu and Hg were correlated with each other and with TOC. Correlation was also observed between Al, Fe, Cr, Mn and Ni. Al, Fe, Cr and Mn were correlated with percentage clay in sediments. The results suggest that Pb, Zn, Cu and Hg are preferentially removed by organic matter, which settles at the river-mouths, while Al, Fe, Cr, Mn, and Ni become associated with clay minerals and are transported away from the coast.     

Equilibrium isotherm studies for the uptake of cadmium and lead ions onto sugar beet pulp

The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70-75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g(-1) for Cd2+ and at pH 5.0 and gives 43.5 mg g(-1) for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 gL(-1) was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.     

Performance of rose scented geranium (Pelargonium graveolens) in heavy metal polluted soil vis-à-vis phytoaccumulation of metals

An investigation was carried out to evaluate the effect of heavy metal toxicity on growth, herb, oil yield and quality and metal accumulation in rose scented geranium (Pelargonium graveolens) grown in heavy metal enriched soils. Four heavy metals (Cd, Ni, Cr, and Pb) each at two levels (10 and 20 mg kg–1 soil) were tested on geranium. Results indicated that Cr concentration in soil at 20 mg kg–1 reduced leaves, stem and root yield by 70, 83, and 45%, respectively, over control. Root growth was significantly affected in Cr stressed soil. Nickel, Cr, and Cd concentration and accumulation in plant increased with higher application of these metals. Chromium, nickel and cadmium uptake was observed to be higher in leaves than in stem and roots. Essential oil constituents were generally not significantly affected by heavy metals except Pb at 10 and 20 ppm, which significantly increased the content of citronellol and Ni at 20 ppm increased the content of geraniol. Looking in to the higher accumulation of toxic metals by geranium and the minimal impact of heavy metals on quality of essential oil, geranium can be commercially cultivated in heavy metal polluted soil for production of high value essential oil.     

Phytoremediation of Cd, Cr, Cu, Mn, Fe, Ni, Pb and Zn from aqueous solution using Phragmites cummunis, Typha angustifolia and Cyperus esculentus

A comparative bioaccumulation pattern and ultra structural changes were studied in Phragmites cummunis, Typha angustifolia and Cyperus esculentus in mixed metals solution of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). P. cummunis was observed to be a shoot accumulator for Cr, Fe, Mn, Ni, Pb, and Zn. However, T. angustifolia was found to be a root accumulator for Cd, Cr, Cu, Fe, Ni and Pb. In addition, C. esculentus also accumulated most of the tested heavy metals in the roots, while Mn and Fe were translocated up to leaves. Further, the long term metal treatment showed maximum accumulation of all heavy metals in P. cummunis followed by T. angustifolia and C. esculentus. Among heavy metals, Fe was accumulated maximum, i.e., >1000 microg g(-1) by all three plants. Simultaneously, the adverse effects on biochemical parameters were noted earlier in C. esculentus than T. angustifolia and P. cummunis. Ultra structural observation showed the cellular changes in wetland plants after longer exposure. Results revealed that P. cummunis and T. angustifolia had more potential for tested metals than C. esculentus. This study established that these wetland plants could be used for heavy metals phytoremediation from metal containing industrial wastewater.     

小麦不同生育时期Cd、Cr、Pb污染监测指标体系

以小麦为供试材料,分别采用发芽试验、溶液培养、土柱栽培等毒理试验方法,研究了小麦萌芽期、幼苗期及成株期受重金属污染毒害的指标体系。结果表明,①小麦根伸长抑制率可作为萌芽期重金属污染评价的一项生物指标;Cd、Cr、Pb对小麦根生长的7d半效应浓度(EC50)值分别为1.39、0.20mmo.lL-1和2.75mmol.L-1,据此得到3种重金属对小麦同一性状的毒性次序为CrCdPb;此外各性状抑制率与胁迫浓度的关系可用双曲线模型y=x/(a+x/100)或指数曲线模型y=a(1-exp(-bx))较好模拟。②Cd、Cr、Pb单一污染胁迫对小麦幼苗性状的毒性次序均以影响叶面积和冠部干重为主,表明叶面积和冠部干重为幼苗期污染监测的敏感指标;重金属对除根干重外所有性状的毒性次序:CrCdPb,该毒性次序是根据引起50%抑制的临界浓度即EC50值确定的;各性状抑制率与胁迫浓度的关系可用直线模型、或双曲线模型、或指数曲线模型较好模拟。③重金属单一污染胁迫造成小麦籽粒产量下降幅度是CdCrPb;二元互作对产量影响的重要性次序为CdCrCdPbCrPb;在Cd、Cr、Pb复合污染胁迫条件下,穗数可以作为成株期重金属污染监测的首选指标。以上指标可为农田小麦重金属污染的监测和综合治理提供一些理论依据。     

A novel staining method for detecting phytase activity

The level of microbial resistance to heavy metals is an important issue for the microbial ecology of heavy metal-contaminated habitats. However, assays based upon growth in nutrient media will overestimate the resistance level due to metal ion interactions with inorganic and organic components. The analysis of Pb-resistant bacteria isolated from soils containing up to 38 mmol total Pb x kg(-1) indicated that PYT80B medium which did not contain inorganic salts, contained low amounts of organic matter, and was buffered with a molecule that did not interact with metal ions (2-N-morpholinoethanesulfonic acid (MES)) provided the lowest estimates of lead resistance. However, better results were obtained by assaying metabolic activity (aerobic respiration) of resting cells suspended in 10 mM MES. By this criterion, 50% inhibition of Arthrobacter JS7 was found at 37 microM Pb(NO3)2. The effects of Pb+2 concentrations upon respiration of resting cells and growth rate in PYT80B medium were similar. The activity assay also showed that metal resistance was induced to higher levels when Arthrobacter JS7 was grown in the presence of Pb.     

Use of oligotrophic bacteria for the biological monitoring of heavy metals

Oligotrophic bacteria exhibited active growth even in nutritionally deficient medium made with nutrient broth that had been diluted with distilled water, 1 : 10 000. The oligotrophic bacteria, Sphingomonas paucimobilis KPS01 and Burkholderia cepacia KPC01 and KPC02 were found to be highly susceptible to heavy metals and to be potentially useful as sensors for the assessment of toxicity. The susceptibility of the bacteria to metals was measured by incubating the bacteria with metals of varying concentrations in the nutritionally deficient medium at 30 degrees C for 24 h. Bacteria were considered susceptible when the growth inhibition rate (EC50 was more than 50% of the control. The EC50 value of Ag+, Pb2+ and Cd2+ was 10(5)mmol l(-1) and Zn2+, Cr3+, Cr6+, Cu2+ and Hg2+ was 10(-4) mmol l(-1) in S. paucimobilis KPS01. Other strains also showed similar results. No difference in the EC50 was found using either the chloride or sulphate forms of these metals. The optimum incubation time was 24 h and a longer incubation time did not necessarily lead to more inhibition. The EC50 value rose in proportion to the concentration of nutrition in media. Environmental samples were tested and 14 out of 88 samples inhibited the growth of S. paucimobilis KPS01.     

一株耐铅、锌、铬菌株的分离鉴定及其吸附能力

【背景】采矿带来的土壤重金属污染问题对生态环境和人类健康产生了极大的危害,因此矿区重金属污染问题亟待解决。生物修复法成本低、资源广、没有二次污染,是修复土壤重金属污染的有效途径。【目的】以山东省曲阜市某煤矸石山周围土壤为材料,采用平板划线法分离筛选一株同时对铅、锌、铬有高耐性且吸附能力强的菌株。【方法】通过形态学特征、生理生化鉴定、分子生物学方法鉴定菌种;采用原子吸收分光光度计测量各重金属的浓度。【结果】鉴定菌株为蜡状芽孢杆菌(Bacillus cereus),命名为Bacillus cereus MZ-11。菌株MZ-11在pH为5.5-8.5、温度为15-45°C、NaCl质量分数为2%-8%时可正常生长。菌株MZ-11最高耐铅、锌、铬浓度高达1 000、1 200、1 600 mg/L。在培养基中铅、锌、铬3种重金属浓度分别为初始浓度(含Pb2+、Zn2+、Cr6+浓度分别为50、60、80 mg/L)、初始浓度的5倍、10倍、20倍的条件下,MZ-11对Cr6+和Zn2+的吸附比例则随浓度的提高逐渐增大,吸附百分比均在98%-99%以上。对Pb2+的吸附比例有一个最高值,并且P...     

广西锰矿恢复区食用农作物重金属污染评价

对广西平乐、荔浦两锰矿恢复区种植的食用农作物进行了调查和重金属含量分析.结果表明:两锰矿区农作物Zn、Pb、Cr、Cu和Cd的含量范围分别在1.18~20.46、0.52~16.16、0.33~6.62、0.01~6.24和0.01~2.76mg.kg-1之间.其中,豆类作物中的重金属含量最高,其次是薯类.单因子污染指数评价表明,农作物基本未受Zn、Cu污染,但受Pb、Cd和Cr污染严重,以Pb污染最重,受污染率达100%,Cr和Cd受污染率分别为96.9%和75.0%;从综合污染指数来看,农作物受污染率达100%,其中,重、中、轻污染分别占87.5%、9.4%和3.1%.表明在锰矿废弃地直接种植食用农作物存在较大风险,应重新考虑其恢复利用模式.     

Synthesis of chitosan-based polymeric surfactants and their adsorption properties for heavy metals and fatty acids

Chitosan-based polymeric surfactants (CBPSs) were prepared by N-acylation of chitosans (chitosan 10 and 500) with several acid anhydrides such as hexanoic (C6), lauric (C12), and palmitic (C16) anhydrides. Among the CBPS samples, CBPSs having a good solubility at pH 4.0 were selected and observed for viscosity, surface tension, and adsorption of heavy metals (Cd2+, Co2+, Cr2O7(2-), and Pb2+) as well as the fatty acid (n-octanoic acid). The 1H NMR spectrum of chitosan 10 modified with C16 at the substitution ratio of 0.4 (CBPS10-C16,0.4) showed 85% of acylation in 1% DCl/D2O solutions. CBPS10 with the substitution ratio less than 0.4 showed a good solubility because of shorter repeating units and lesser amounts of hydrophobic substituents. The intrinsic viscosity of CBPS10 was slightly increased, while that of CBPS500 was decreased. As the substitution ratio and length of the carbon chain increased, the surface tension of CBPS10 tended to decrease. CBPS10-C16,0.2 had high adsorption ability for cationic metal ions such as Cd2+, Co2+, and Pb2+ comparable to chitosan. Interestingly, CBPS(10)-C(16,0.2) showed a unique pH optimum for the anionic metal ion such as Cr2O7(2-). In addition, CBPS10-C16,0.2 exhibited the highest adsorption ability for n-octanoic acid among the tested CBPS10 with different carbon chains.     

成都平原北部水稻土重金属含量状况及其潜在生态风险评价

为了解成都平原水稻土重金属含量状况和潜在的生态风险,选取成都平原北部水稻土典型区域为研究对象,采集了158个表层土壤样品,分析了土壤中pH值和Cd、Cu、As、Hg、Pb、Cr、Ni 7种重金属元素含量,以20世纪80年代测定的成都平原土壤重金属元素背景值为评价标准,采用Hakanson潜在生态危害指数法对研究区域的重金属潜在生态风险进行了评价。结果表明:研究区域水稻土Cd、Hg、Ni、Cu、Pb、Cr和As平均含量分别为0.709、0.187、32.08、34.12、31.52、82.13 mg/kg和7.25 mg/kg;Cd、Ni、Cu和Hg 4种重金属超过《土壤环境质量标准》(GB15618-1995) Ⅱ级标准值样本比例分别为87.34%、8.23%、3.80%和3.80%,Cd含量超标严重。7种重金属元素变异系数幅度为18.35%-49.03%,由大到小依次为Cd、Hg、Cu、As、Ni、Cr、Pb。75.32%的样本达到中度或较强重金属潜在生态风险,区域整体表现为中度潜在生态风险(RI平均值为198.65),Cd和Hg为高生态风险元素,对潜在生态风险贡献率分别为62.27%和20.78%,As、Pb、Cu、Ni、Cr为低生态风险元素;风险概率图显示城区周边和绵远河沿线的潜在生态风险等级较高。因此,成都平原水稻土农业生产中应采取一定的措施防控农产品Cd和Hg污染。     

胁迫时间与非毒性离子对重金属抑制拟南芥种子发芽及幼苗生长的影响

测定了Hg²⁺、Cd²⁺、Cu²⁺、Pb²⁺单一重金属胁迫对拟南芥种子发芽和幼苗生长的影响.结果表明,重金属对幼苗生长的毒性大于对种子发芽的毒性,以抑制种子发芽的IC₅₀为指标,4种重金属的毒性顺序为Hg²⁺＞Cd²⁺＞Pb²⁺/Cu²⁺,以幼苗生长为指标,则毒性顺序为:Cu²⁺＞Hg²⁺＞Cd²⁺/Pb²⁺,并随着胁迫时间延长,种子萌发率下降.此外,不同重金属在不同发芽时段对种子的毒性也不尽相同,Cd²⁺的毒性在种子吸水后的0～12 h大于12～24 h,而Hg²⁺毒性在12～24 h大于0～12 h,其中,种皮对减轻重金属毒性起着十分重要的作用.通过非毒性离子(Ca²⁺、Mg²⁺、K⁺、Na⁺)与重金属离子(Hg²⁺、Cd²⁺、Cu²⁺、Pb²⁺)交互作用对拟南芥种子发芽及幼苗生长效应的研究发现, mmol·L^-1的Ca²⁺、Mg²⁺、K⁺、Na⁺可以增强Hg²⁺对种子发芽的毒性,但对Cd²⁺的毒性却没有影响.对于幼苗来说,Ca²⁺、Mg²⁺、K⁺、Na⁺可以显著增强Hg²⁺的毒性,Ca²⁺可以缓解Cd²⁺的毒性,但却增加Cu²⁺的毒性,K⁺可以缓解Pb²⁺对幼苗的毒害作用.最后,本文对重金属的毒害机理进行了探讨.     

Metal uptake by mycelia during submerged growth and by sporocarps of an edible fungus Volvariella volvacea.

Uptake of a few metals by V. volvacea was determined during submerged growth of the organism in sublethal concentration of each metal salt. The uptake of Pb2+ and Hg2+ was 5 and 5.23 micrograms g-1 respectively while that of Cu2+ was 500 micrograms g-1 under experimental conditions. Treatment of spawned substrate separately with different metal salts showed maximum and minimum uptake of Pb2+ (100 micrograms g-1) and Cd2+ (2.93 micrograms g-1) respectively by sporocarps. All metal salts at test concentrations reduced biological efficiency of sporocarp production but markedly by Co2+. Cd2+ and Co2+ were highly toxic to mycelia and sporocarps respectively. The uptake of Cu2+ by mycelia and Pb2+ by sporocarps were highest among the five metals tested. Metal toxicity, tolerance and uptake capacity of V. volvacea differ considerably with concentration of metal ions.