Biosorption and Desorption of Lead(II) by Hydrilla verticillata

The potential of nonliving biomass of Hydrilla verticillata to adsorb Pb(II) from an aqueous solution containing very low concentrations of Pb(II) was determined in this study. Effects of shaking time, contact time, biosorbent dosage, pH of the medium, and initial Pb(II) concentration on metal-biosorbent interactions were studied through batch adsorption experiments. Maximum Pb(II) removal was obtained after 2 h of shaking. Adsorption capacity at the equilibrium increased with increasing initial Pb(II) concentration, whereas it decreased with increasing biosorbent dosage. The optimum pH of the biosorption was 4.0. Surface titrations showed that the surface of the biosorbent was positively charged at low pH and negatively charged at pH higher than 3.6. Fourier transform infrared (FT-IR) spectra of the biosorbent confirmed the involvement of hydroxyl and C?O of acylamide functional groups on the biosorbent surface in the Pb(II) binding process. Kinetic and equilibrium data showed that the adsorption process followed the pseudo-second-order kinetic model and both Langmuir and Freundlich isothermal models. The mean adsorption energy showed that the adsorption of Pb(II) was physical in nature. The monolayer adsorption capacity of Pb(II) was 125 mg g^?1. The desorption of Pb(II) from the biosorbent by selected desorbing solutions were HNO₃ > Na₂CO₃ > NaOH > NaNO₃.     

A comparative study of isoenzyme patterns ofHydrilla verticillata (L.f.) Royle in Japan

Isoenzyme patterns of 226 accessions ofHydrilla verticillata collected in Japan were compared. 17 and 23 electrophoretic phenotypes were identifiable in diploid and triploid accessions, respectively, in dioecious ones. To the contrary, monoecious plants showed no variation of banding patterns and were assumed to be rametes of the same clone. The cytological change from diploid to triploid was suggested to occur many times in dioecious plants.     

Identification of C4 responsive genes in the facultative C4 plant Hydrilla verticillata

The aquatic monocot Hydrilla verticillata (L.f.) Royle is a well-documented facultative C₄ NADP-malic enzyme species in which the C₄ and Calvin cycles operate in the same cell with the specific carboxylases confined to the cytosol and chloroplast, respectively. Several key components had already been characterized at the molecular level, thus the purpose of this study was to begin to identify other, less obvious, elements that may be necessary for a functional single-cell C₄ system. Using differential display, mRNA populations from C₃ and C₄ H. verticillata leaves were screened and expression profiles compared. From this study, 65 clones were isolated and subjected to a customized macroarray analysis; 25 clones were found to be upregulated in C₄ leaves. Northern and semi-quantitative RT-PCR analyses were used for confirmation. From these screenings, 13 C₄ upregulated genes were identified. Among these one encoded a previously recognized C₄ phosphoenolpyruvate carboxylase, and two encoded distinct pyruvate orthophosphate dikinase isoforms, new findings for H. verticillata. Genes that encode a transporter, an aminotransferase and two chaperonins were also upregulated. Twelve false positives, mostly housekeeping genes, were determined from the Northern/semi-quantitative RT-PCR analyses. Sequence data obtained in this study are listed in the dbEST database (DV216698 to DV216767). As a single-cell C₄ system that lacks Kranz anatomy, a better understanding of how H. verticillata operates may facilitate the design of a transgenic C₄ system in a C₃ crop species.Srinath K. Rao and Hiroshi Fukayama contributed equally to this study.     

Real-time determination of kinetics of adsorption of lead(II) onto palm shell-based activated carbon using ion selective electrode

In this study, the kinetics of adsorption of Pb(II) from aqueous solution onto palm shell-based activated carbon (PSAC) were investigated by employing ion selective electrode (ISE) for real-time Pb(II) and pH monitoring. Usage of ISE was very appropriate for real-time adsorption kinetics data collection as it facilitated recording of adsorption data at very specific and short time intervals as well as provided consistent kinetics data. Parameters studied were initial Pb(II) concentration and agitation speed. It was found that increases in initial Pb(II) concentration and agitation speed resulted in higher initial rate of adsorption. Pseudo first-order, pseudo second-order, Elovich, intraparticle diffusion and liquid film diffusion models were used to fit the adsorption kinetics data. It was suggested that chemisorption was the rate-controlling step for adsorption of Pb(II) onto PSAC since the adsorption kinetics data fitted both the pseudo second-order and Elovich models well.     

Dormancy and germination in axillary turions ofHydrilla verticillata

Effects of environmental conditions and growth regulators on release from dormoncy of axillary turions inHydrilla verticillata were investigated. Coll treatment at 2 C for 33 days produced the most complete release from dormancy. One week of 2 C treatment was sufficient for the germination; however, longer cold periods produced more rapid growth in shoot or root lengths as well as a shorter lag time for germination. Dormancy in turions could be broken by a photoperiod of 16 hr but not by on of 8 or 12 hr, nor by continuous lighting. When a cold treatment was applied turions grew out in response to all of the photoperiodic conditions. Red and far-red irradiation during the incubation after a cold treatment promoted gremination; blue and green light markedly inhibited the germination. At 10⁻⁴ and 10⁻⁵ M, gibberellic acid broke dormancy of non-cold treated turions, but was toxic at 10⁻⁴ M to the development after germination. Gibberellic acid promoted growth of cold treated turions even at 10⁻⁶ M. Indoleacetic acid at 10⁻⁴, 10⁻⁵ and 10⁻⁶ M induced outgrowth of both non-cold treated and cold treated turions. Apparently normal growth and development was observed in a high concentration of indoleacetic acid.     

Reproduction and Development of the Biocontrol AgentHydrellia pakistanae(Diptera: Ephydridae) on Monoecious Hydrilla

Previous investigations of the laboratory biology and host range ofHydrellia pakistanae,a biological control ofHydrilla verticillata(hydrilla), used the dioecious hydrilla biotype common to Florida, Texas, and California. A monoecious biotype that is now spreading throughout the mid-Atlantic states, California, and Washington was not investigated during these original studies. We therefore compared the dioecious and monoecious hydrilla biotypes as hosts forH. pakistanae.FemaleH. pakistanaeaccepted the two biotypes equally as ovipositional substrates. Overall developmental success differed little: 42% of eggs oviposited on monoecious hydrilla produced adults compared to 39% of eggs oviposited on dioecious hydrilla. Fly development required about 33 days on both biotypes (at 22 ± 2°C), but larvae that completed development mined 1.6 times as many leaves on monoecious hydrilla as on dioecious plants. These data suggest thatH. pakistanaewould be a useful biocontrol agent of monoecious hydrilla, should this plant invade areas where it can grow as a perennial.     

Hydrellia spp. [Diptera: Ephydridae] attackingHydrilla verticillata in south India

The leaf-mining fliesHydrellia sp. andH. pakistanae Deonier were observed attacking the aquatic weedHydrilla verticillata (L.f.) L.C. (Hydrocharitaceae) in south India. Their life histories were very similar. The duration of the immature stages ofH. pakistanae was 25 to 29 days. The number of leaves ofH. verticillata mined by a single larva varied from 8 to 12. In the laboratory, adults feeding on 50% aqueous solution of honey lived for 6 to 21 days and laid an average of 26 eggs. Several overlapping generations occurred in the field except during the period of drought. BothHydrellia sp. andH. pakistanae were heavily parasitized by the braconidsAdemon sp. nr.decrescens Nees andChaenusa sp.      

Mercury(II) complex formation with glutathione in alkaline aqueous solution

The structure and speciation of the complexes formed between mercury(II) ions and glutathione (GSH = L-glutamyl-L-cysteinyl-glycine) have been studied for a series of alkaline aqueous solutions (\( C_{{{\text{Hg}}^{{2 + }}}}\,{\sim18\,{\rm{mmol}}\,{\rm{{dm^{-3}}}}}\) and C _GSH = 40–200 mmol dm^?3 at pH ～10.5) by means of extended X-ray absorption fine structure (EXAFS) and ¹⁹⁹Hg NMR spectroscopy at ambient temperature. The dominant complexes are [Hg(GS)₂]^4? and [Hg(GS)₃]^7?, with mean Hg–S bond distances of 2.32(1) and 2.42(2) Å observed in digonal and trigonal Hg–S coordination, respectively. The proportions of the Hg²⁺–glutathione complexes were evaluated by fitting linear combinations of model EXAFS oscillations representing each species to the experimental EXAFS spectra. The [Hg(GS)₄]^10? complex, with four sulfur atoms coordinated at a mean Hg–S bond distance of 2.52(2) Å, is present in minor amounts (<30%) in solutions containing a large excess of glutathione (C _GSH ≥ 160 mmol dm^?3). Comparable alkaline mercury(II) cysteine (H₂Cys) solutions were also investigated and a reduced tendency to form higher complexes was observed, because the deprotonated amino group of Cys^2? allows the stable [Hg(S,N-Cys)₂]^2? chelate to form. The effect of temperature on the distribution of the Hg²⁺–glutathione complexes was studied by comparing the EXAFS spectra at ambient temperature and at 25 K of a series of glycerol/water (33/67, v/v) frozen glasses with \( C_{{{\text{Hg}}^{{2 + }} }} \,{\sim7\,{\rm{mmol}}\,{\rm{{dm^{-3}}}}} \) and C _GSH = 16–81 mmol dm^?3. Complexes with high Hg–S coordination numbers, [Hg(GS)₃]^7? and [Hg(GS)₄]^10?, became strongly favored when just a moderate excess of glutathione (C _GSH ≥28 mmol dm^?3) was used in the glassy samples, as expected for a stepwise exothermic bond formation. Addition of glycerol had no effect on the Hg(II)–glutathione speciation, as shown by the similarity of the EXAFS spectra obtained at room temperature for two parallel series of Hg(II)-glutathione solutions with \( C_{{{\text{Hg}}^{{2 + }} }} \,{\sim7\,{\rm{mmol}}\,{\rm{{dm^{-3}}}}},\) with and without 33% glycerol. Also, the ¹⁹⁹Hg NMR chemical shifts of a series of ～18 mmol dm^?3 mercury(II) glutathione solutions with 33% glycerol were not significantly different from those of the corresponding series in aqueous solution.     

真菌吸附铅锌的研究

正随着采矿业的迅速发展,越来越多的重金属通过多种途径进入土壤环境中,对生态环境造成了不可估量的破坏并严重威胁人类健康。铅锌在工业上具有非常重要的作用且其应用极为广泛,而他们具有的难去除、难迁移和生物累积等特性使得铅锌在环境中的污染尤为突出。通过微生物的生长代谢,有效降低土壤重金属毒性,是促进植物生长的重要步骤之一。同时也要求微生物自身具有抵抗重金属的功能,根际微生     

Effect of Hirschmanniella caudacrena on the Submersed Aquatic Plants Ceratophyllum demersum and Hydrilla verticillata

In vitro pathogenicity tests demonstrated that Hirschmanniella caudacrena is pathogenic to Ceratophyllum demersum (coontail). Symptoms were chlorotic tissue, deformed stems, and, finally, death of the plant. Inoculum densities of 500 nematodes per 5-cm-long cutting in a test tube containing 50 ml of water resulted in death and decay of some of the cuttings within 8 weeks; 100 nematodes killed the plants in 12 weeks, and 50 and 25 nematodes killed them in 16 weeks. The lowest inoculum level of 10 nematodes did not seriously affect the plants at 16 weeks when the experiment was terminated. A second test conducted outdoors in glass jars containing 3 liters of water and two cuttings weighing a total of 15 g fresh weight showed damage, but results were not statistically significant. Hydrilla verticillata inoculated with H. caudacrena was not affected seriously.     

The biosorption of heavy metals from aqueous solution by Spirogyra and Cladophora filamentous macroalgae

The aim of this research was to develop a low cost adsorbent for wastewater treatment. The prime objective of this study was to search for suitable freshwater filamentous algae that have a high heavy metal ion removal capability. This study evaluated the biosorption capacity from aqueous solutions of the green algae species, Spirogyra and Cladophora, for lead (Pb(II)) and copper (Cu(II)). In comparing the analysis of the Langmuir and Freundlich isotherm models, the adsorption of Pb(II) and Cu(II) by these two types of biosorbents showed a better fit with the Langmuir isotherm model. In the adsorption of heavy metal ions by these two types of biosorbents, chemical and physical adsorption of particle surfaces was perhaps more significant than diffusion and adsorption between particles. Continuous adsorption-desorption experiments discovered that both types of biomass were excellent biosorbents with potential for further development.     

Adsorptive removal of Pb(II) by activated carbon prepared from Spartina alterniflora: Equilibrium,kinetics and thermodynamics

Low-cost activated carbon was prepared from Spartina alterniflora by phosphoric acid activation for the removal of Pb(II) from dilute aqueous solution. The effect of experimental parameters such as pH, initial concentration, contact time and temperature on the adsorption was studied. The obtained data were fitted with the Langmuir and Freundlich equations to describe the equilibrium isotherms. The kinetic data were fitted with the Lagergren-first-order, pseudo-second-order and Elovich models. It was found that pH played a major role in the adsorption process. The maximum adsorption capacity for Pb(II) on S. alterniflora activated carbon (SAAC) calculated from Langmuir isotherm was more than 99 mg g⁻¹. The optimum pH range for the removal of Pb(II) was 4.8–5.6. The Freundlich isotherm model was found to best describe the experimental data. The kinetic rates were best fitted to the pseudo-second-order model. Thermodynamic study showed the adsorption was a spontaneous exothermic process.     

控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响

采用固定滴灌(根区一侧固定供水)、控制性分根区交替滴灌(根区两侧交替供水)和常规滴灌(紧贴幼树基部供水)3种灌水方式和3种灌水定额(固定滴灌和交替滴灌均为10、20和30 mm,常规滴灌为20、30和40 mm),对比研究了控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响.结果表明： 交替滴灌的根区两侧土壤出现反复干湿交替过程,常规滴灌的根区两侧土壤含水率差异不显著.在灌水定额相同时,灌水侧的土壤含水率在3种灌水方式间差异不显著.与常规滴灌和固定滴灌相比,交替滴灌显著增加了苹果幼树的根冠比、壮苗指数和根系水分传导,在30 mm灌水定额处理下,交替滴灌的根冠比分别增加31.6%和47.1%,壮苗指数增加34.2%和53.6%,根系水分传导增加9.0%和11.0%.3种灌水方式下,根干质量和叶面积均与根系水分传导呈显著线性正相关.控制性分根区交替滴灌增强了苹果幼树根系水分传导的补偿效应,促进了根系对水分的吸收利用,有利于干物质向各个器官均衡分配,显著提高了根冠比和壮苗指数.     

Calcium and magnesium effect on divalent cation deficientHydrilla verticillata thylakoid electron transport activity

The role of divalent cations like magnesium (Mg²⁺) and calcium (Ca²⁺) was irrvestigated on energy distribution process ofHydrilla verticillata thylakoids. Effect of these cations was tested on relative quantum yield of photosystem (PS) II catalyzed electron transport activity, room and liquid nitrogen temperature fluorescence emission properties and thylakoid light scattering characteristics. The electron transport activity was found to be stimulated in the presence of these cations in a light intensity independent manner. The concentration of cation required for maximum stimulation was nearly 10–12 mM. Comparatively, Ca²⁺ was more effective than Mg²⁺. Cation induced stimulation in electron transport activity was not accompanied by increase in chlorophylla fluorescence intensity either at room (25°C) or liquid nitrogen (77°K) temperatures. Furthermore, 540 nm absorption and 90° light scattering properties of thylakoids remained insensitive towards divalent cations. These facts together suggest that divalent cations inHydrilla thylakoids are not effective in supporting the excitation distribution between the interacting photosystem complexes.     

A new distribution record for Trigonobalanus verticillata (Fagaceae) from Hainan Island, South China

Summary   Trigonobalanus verticillata Forman was found in central Hainan Island, South China, during a survey in 2005. The taxon was previously only recorded from Malaysia and Indonesia. It is characterised by having leaves arranged in whorls of three and trigonous cupules that are opposite or in whorls. The importance of this discovery is briefly discussed.     

汞,镉污染对黑藻叶细胞伤害的超微结构研究

黑藻（Ｈｙｄｒｉｌｌａ ｖｅｒｔｉｅｉｌｌａｎ（Ｌ．ｆ．）Ｒｏｙｌｅ）植株分别在Ｈｇ＾２＋、Ｃｄ＾２＋梯度浓度的污染水中培养,在培养的时间段中（Ｈｇ＾２＋为３ｘｄ,Ｇｄ＾２＋为６ｄ）,随着浓度的递增,叶片逐渐出现均匀退绿症状。电镜观察发现,叶细胞遭受Ｈｇ＾２＋、Ｃｄ＾２＋毒害初期,高尔基体消失,内质网膨胀后解体,叶绿体中的类囊体和线粒体中的脊突胀成呈囊泡状,核中染色质涕 集。随着叶细胞遭受毒害程度     

Adsorption of copper and zinc by biochars produced from pyrolysis of hardwood and corn straw in aqueous solution

Biochars produced by pyrolysis of hardwood at 450 °C (HW450) and corn straw at 600 °C (CS600) were characterized and investigated as adsorbents for the removal of Cu(II) and Zn(II) from aqueous solution. The adsorption data were well described by a Langmuir isotherm, with maximum Cu(II) and Zn(II) adsorption capacities of 12.52 and 11.0 mg/g for CS600, 6.79 and 4.54 mg/g for HW450, respectively. Thermodynamic analysis suggested that the adsorption was an endothermic process and did not occur spontaneously. Although Cu(II) adsorption was only marginally affected by Zn(II), Cu(II) competed with Zn(II) for binding sites at Cu(II) and Zn(II) concentrations ?1.0 mM. Results from this study indicated that plant-residue or agricultural waste derived biochar can act as effective surface sorbent, but their ability to treat mixed waste streams needs to be carefully evaluated on an individual basis.     

Collagen/cellulose hydrogel beads reconstituted from ionic liquid solution for Cu(II) adsorption

A novel adsorbent, biodegradable collagen/cellulose hydrogel beads (CCHBs), was prepared by reconstitution from a 1-butyl, 3-methylimidazolium chloride ([C₄mim]Cl) solution. The adsorption properties of the CCHBs for Cu(II) ion removal from aqueous solutions were investigated and compared with those of cellulose hydrogel beads (CHBs). The CCHBs have a three-dimensional macroporous structure whose amino groups are believed to be the main active binding sites of Cu(II) ions. The equilibrium adsorption capacity (q_e) of the CCHBs is greatly influenced by the collagen/cellulose mass ratio, and steeply increases until the collagen/cellulose mass ratio exceeds 2/1. The maximum adsorption is obtained at pH 6. The q_e of Cu(II) ions increases with increased initial concentration of the solution. Based on Langmuir isotherms, the maximum adsorption capacity (q_m) of CCHB3 (collagen/cellulose mass ratio of 3/1) is 1.06 mmol/g. The CCHBs maintain good adsorption properties after the fourth cycle of adsorption–desorption.     

Cobalt(II) and cadmium(II) chelates with nitrogen donors and O2 bonding to Co(II) derivatives

The formation of Cd(II) and Co(II) complexes with N-methylethylenediamine (men) has been studied at 298 K in dimethylsulfoxide (dmso) in an ionic medium set to 0.1 mol dm⁻³ with Et₄NClO₄ in anaerobic conditions by means of potentiometric, UV-Vis, calorimetric and FT-IR technique. Mononuclear ML_j (M=Cd, Co; j=1-3) complexes are formed in exothermic reactions, whereas the entropy changes oppose the complexes formation. The results are discussed in terms of different basicities and steric requirements and the whole of the thermodynamic data reported till now for the two ions with a number of diamines are summarized to visualize the selectivity of the ligands. The dioxygen uptake of Co(men)₂ species has also been studied by means of UV-Vis and EPR techniques. The kinetic parameters and stability constants obtained for the formation of the superoxo and μ-peroxo species are discussed in terms of solvent effect and steric hindrance due to methyl group.Cyclic voltammetry was used to confirm the stability constant for the Co(dmen)₂ (dmen=N,N^′-dimethylethylenediamine) superoxo adduct formation but was not successful to investigate this Co(men)₂-O₂ system.     

耐性真菌HA吸附铅、锌的影响因素及吸附机理研

【目的】从铅锌矿区分离筛选出耐铅锌性菌株,并研究其吸附铅、锌的影响因素及吸附机理,为重金属污染微生物修复提供参考。【方法】以从铅锌矿区筛选出的耐铅锌真菌HA作为试验菌株,考察影响其对铅、锌去除能力的主要因素(初始浓度、pH、接种量),同时通过等温吸附模型、动力学分析及红外光谱分析探讨其相关的吸附机理。【结果】经鉴定,从矿区筛选的对Pb2+、Zn2+有较强耐性的菌株HA为米曲霉(Aspergillus oryzae);在初始铅、锌浓度的实验范围内(100-800mg/L),HA对铅、锌离子的去除率随着其初始浓度增加而减小,25h后HA的生长进入平稳期,且对铅、锌离子的去除率趋于稳定。当铅、锌初始浓度为100mg/L、pH为5.0时,HA对铅、锌离子的去除率均达到最高,分别为97.8%、54.1%;当HA接种量为1mL时,其对铅、锌去除率的增长率达到最大。HA对铅、锌的吸附过程满足Langmuir吸附模型,其吸附以单层吸附为主。在动态吸附过程中,HA对Pb2+、Zn2+离子吸附性能与准二级动力学吸附方程的拟合程度更高,且对Pb2+的吸附效果明显高于Zn2+。红外光谱分析表明,HA细胞中羟基、烷基、酰胺基、羰基、磷酸基等参与了Pb2+、Zn2+的吸附过程。【结论】HA是一株对铅、锌有较强吸附能力的真菌,其吸附铅、锌影响因素及吸附机理研究结果将为重金属污染微生物修复提供指导。