Uptake and excretion of total inorganic arsenic by the freshwater alga Chlorella vulgaris

Arsenic-tolerant freshwater alga Chlorella vulgaris which had been collected from an arsenicpolluted environment were tested for uptake and excretion of inorganic arsenic. Approximately half the quantity of arsenic taken up by C. vulgaris was estimated to be adhered to the extraneous coat (10 wt %) of the cell. The remainder was bioaccumulated by the cell. Both adhered and accumulated arsenic concentrations increased with an increase in arsenic(V) concentration of the aqueous phase. Arsenic(V) accumulation was affected by the growth phse: arsenic was most actively accumulated when the cell was exposed to arsenic during the early exponential phase and then accumulation decreased with an increase in culture time exposed to arsenic. The alga grew well in the modified Detmer (MD) medium containing 1 mg As(III) dm^?3 and the growth curve was approximated by a ‘logistic equation’. Arsenic(III) was accumulated up to the second day of the culture time and arsenic(III) accumulation decreased with an increase in the culture time after that. Arsenic accumulation was also largely affected by various nutrients, especially by managanese, iron and phosphorus compounds. A modified MD medium with the three nutrients was proposed for the purpose of effective removal of arsenic from the aqueous phase. Using radioactive arsenate (Na₂H⁷⁴AsO₄), the arsenic accumulated was found to be readily excreted under conditions which were unfavourable for the multiplication of C. vulgaris.     

Biomethylation of arsenic and its excretion by the alga Chlorella vulgaris

Experimental results in this paper lead to the following conclusions. (1) Cell homogenates of Chlorella vulgaris adsorbed the inorganic arsenic compound Na₂HAsO₄ but no methylation of the arsenic occurred in vitro. (2) A small part of the arsenic bioaccumulated by C. vulgaris was methylated in vivo. The quantity of arsenic methylated in the cell increased with an increase of arsenic concentration in the medium. (3) When the arsenic-accumulating cells were transferred into arsenic-free media, the arsenic was excreted and the relative quantity of the methylated arsenic in the excrement was larger than that in the cell. (4) In the growth phase of C. vulgaris, a small fraction of the arsenic accumulated in the cell was first transformed to monomethyl and dimethyl-arsenic compounds during the early exponential phase, and after a short time a fraction was transformed to trimethylarsenic species.     

Uptake of lead and arsenic in food plants grown in contaminated soil from Barber Orchard, NC

Elevated levels of heavy metals in soil may allow uptake of these toxic species in food plants. Barber Orchard, Haywood County, NC has been designated a U.S. EPA Superfund site, primarily because of elevated levels of lead and arsenic. In this work, carrots, lettuce, and tomatoes were cultivated in a greenhouse in control soil and soil obtained from Barber Orchard. The resulting samples were then analyzed for lead and arsenic using inductively coupled plasma optical emission spectrometry (ICP-OES). Except for carrot roots grown in the contaminated soil, the concentrations of lead and arsenic in the plants were below the ICP-OES detection limit. The concentration of lead in carrot roots was 20 ± 11 μg/g, which represents a bioconcentration factor (BCF) of 0.03.     

Potentiometric microdetermination of lead(II) with an ion-selective lead electrode and its application to the analysis of organic lead compounds

Summary A method for the microdetermination of lead(II) by direct potentiometric titration with 0.0025 M sodium molybdate is described. A lead-selective indicator electrode and a double-junction reference electrode are used in conjunction with an expanded-scale pH-meter to detect the end-point. If the titrant is standardized against 1.5 mg of lead(II), accurate results are obtained for 1–2 mg of lead: the absolute error does not exceed 3gmg of lead. The relative standard deviation is 0.05%. The optimum pH for the titration is 5–5.5. In water-organic solvent mixtures the potential break at the endpoint increases, but the electrode response becomes very slow. The titration of lead is also possible in sodium nitrate and/or perchlorate media, so this titration is applicable to the microdetermination of lead in organic lead compounds after wet mineralization with HNO₃ and/or HClO₄. Chloride (up to 1000 times the lead content) and bromide (100 times) do not interfere. Iodide and sulphate interfere. Five organic lead compounds have been analysed successfully: the standard deviation of the absolute error was 0.1%.

---

Zusammenfassung Ein Verfahren zur Mikrobestimmung von Blei(II) durch direkte potentiometrische Titration mit 0,0025M Natriummolybdat wurde beschrieben. Eine bleiempfindliche Indikatorelektrode und eine Bezugselektrode mit KNO₃-Zwischenelektrolyt wurde in Kombination mit einem pH-Meter mit gedehnter Skala zur Erkennung des Titrationsendpunktes verwendet. Unter Standardisierung der Maßlösung gegen 1,5 mg Blei(II) werden genaue Resultate im Bereich von 1 bis 2 mg Blei erhalten: der absolute Fehler ist innerhalb ±3g Blei. Die relative Standardabweichung beträgt 0,05%. Das günstigste pH liegt im Bereich 5–5,5. In Wasser-Aceton oder -Methanol nimmt der Potentialsprung am Äquivalenzpunkt stark zu; gleichzeitig wird jedoch das Ansprechen der Elektroden sehr langsam. Die Titration von Blei ist möglich auch in Medien von Natriumnitrat oder/und Natriumperchlorat, was die Anwendung dieser Titration auf die Bleimikrobestimmung in bleihaltigen organischen Verbindungen nach Mineralisierung auf nassem Wege mit HNO₃ oder/und HClO₄ ermöglicht. Chlorid (bis zum 1000fachen Gehalt an Blei) und Bromid (100fache Menge) stören nicht. Iodid und Sulfat stören. Fünf bleihaltige organische Verbindungen wurden erfolgreich analysiert; die Standardabweichung des absoluten Fehlers betrug 0,1%.

     

The influence of interstitial water on electronic conduction in lead ferrocyanide

Water molecules present as an interstitial impurity in crystals of Pb₂Fe(CN)₆ · 2H₂O in excess of bonded water is found to activate electronic conduction with an activation energy of 0.32 eV. A quantitative explanation is given to show why lead and several other heavy metal ferrocyanides have approximately the same thermal activation energies.     

Synthesis and characterization of lead phthalocyanine and its derivatives

Lead (II) phthalocyanine (PbPc); lead (II) tetranitro phthalocyanine (PbTNP) and lead (II) tetraamino phthalocyanine (PbTAP) are synthesized in pure state. These complexes are characterized using elemental analysis, UV-visible, IR-spectroscopy, X-ray crystallography and thermogravimetry. Kinetic and thermodynamic parameters associated with the thermal decomposition were calculated using thermogravimetric data. Electrical conductivity studies are done for all the three complexes using two-probe technique in the temperature range from 30 to 200 °C. The electrical conductivity observed at 30 °C are in the order PbTAP > PbTNP > PbPc. The relevant electrical conductivity data observed are reported.     

Measurement of lead isotope ratios in wine by ICP-MS and its applications to the determination of lead concentration by isotope dilution

 Methods are described for the accurate and precise determination of lead concentrations and the isotopic composition of lead in wine samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method needs little sample preparation. A comparison with lead isotope ratios measured by Thermal Ionization Mass Spectrometry (TIMS) in three wine samples reveals a good agreement between the two techniques. The lead concentration in three certified wine samples were measured by isotope dilution (ID) and the results are compared with those obtained by external calibration ICP-MS. Received: 10 June 1996/Revised: 23 September 1996/Accepted: 30 September 1996     

Speciation of lead in soils and relation with its concentration in fruits

The lead concentrations of the fruit samples were determined by using slotted tube atom trap (STAT)-enrichment-flame and graphite furnace atomic absorption spectrometry (FAAS and GF-AAS). The soil samples related to these fruits were also analysed for Pb after extraction with various chemical reagents. The relation between the fruit-lead and soil-extractable lead concentrations was examined in order to explain the bioavailability of lead. A linear relation was observed between the hot Na₂EDTA extraction-soluble Pb contents in the soil and the Pb concentrations in the mulberry (R²=0.95), strawberry and apple grown on these soils. Probable chemical forms of lead in soil were evaluated. Acceptable agreement (at least 91%) was achieved between the results of STAT-enrichment-FAAS and GF-AAS.     

Surface tension of tin and its alloys with lead

The temperature and concentration dependencies of the surface tension of high-purity tin and its alloys with lead were investigated in an ultrahigh vacuum by the large-drop method. It was shown that the tin surface-tension polytherm obeyed the equation σ(T) = 570.0 ? 0.08(T ? T _m). Lead was found to possess high surface activity in the range of its low concentrations in tin. Estimate was made for the limiting lead surface activity in tin-based alloys. Our conclusions about lead surface activity in alloys with tin are consistent with the literature data obtained by the modern electron-spectrometric methods for the surface compositions of the alloys studied.     

Unusual transformation of 3-carbomethoxy-Δ2-pyrazoline under the influence of lead tetraacetate

3-Carbomethoxy-1-(1-carbomethoxy-1-cyclopropyl)pyrazole and 3-carbomethoxy-1-(3-carbomethoxy-1-pyrazolyl)-²-pyrazoline were obtained by the action of lead tetraacetate on 3-carbomethoxy-²-pyrazoline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1239–1242, September, 1976.     

Aggregation in colloidal suspensions and its influence on the suspension viscosity

Influence of aggregate formation on rheological properties of concentrated suspensions is discussed and reviewed. Methods of Stokesian and Brownian dynamic simulations of aggregation are discussed and the results of simulations for both Brownian and non-Brownian particles are presented.     

The influence of chelating reagents on plumbane generation: Determination of lead in the presence of PAN-S

A series of 22 chelating reagents were tested for plumbane generation. Besides nitroso R salt, the reagents Bromo Pyrogallol Red, Pyrocatechol Violet, Alizarine Red-S, 5-Br-PADAP and PAN-S could significantly enhance the lead signal. The PAN-S system has been optimized. The characteristic concentration (5 ml sample) is 1.3 ng/ml, and the RSD at the 50 ng/ml level is 3.9%. Lead spiked into tap water and natural water was determined by HG-AAS in the presence of PAN-S. Recoveries of spiked lead were between 90 and 105 %. Study of the mechanism suggests that the lead hydride might be directly generated from the chelated Pb(II) instead of the metastable Pb(IV).     

Terpenoids of the red alga laurenciapinnatifida

The structures of three brominated terpenoids which are natural products from the red alga Laurencia pinnatifida (Gmal. Lamour) are described. The structures of the sesquiterpenes $\text{4}$ and $\text{5}$ were determined by spectral comparison and chemical interconversion. The structure of the squalene-derived terpenoid $\text{8}$ was secured by chemical transformation into thyrsiferol, a brominated triterpene previously isolated from the red alga Laurencia thyrsifera.     

Determination of lead oxide in and on the surface of high-purity lead metal

Summary A method has been developed for the determination of a minute amount of lead oxide in and on high-purity lead metal. The lead metal is shaken with 0.5% (w/v) ammonium acetate solution and sodium tetrahydroborate in nitrogen atmosphere. The metallic lead is unaffected while the lead oxide is dissolved in the aqueous solution and can be determined by atomic absorption spectrometry. The procedure is repeated in the presence of mercury. In this case lead is converted to amalgam and total lead oxide is dissolved and determined. The lead oxide contained in the interior of the sample is obtained by the difference. Lead oxide in commercial lead metals of various forms has been determined by this method. It is simple and fast, a minute amount of lead oxide can be determined precisely with high reproducibility (recovery is 98–100%).

---

Bestimmung von Bleioxid in und auf der Oberfläche von hochreinem Blei

Zusammenfassung Die Bleiprobe wird mit 0,5 %iger Ammoniumacetatlösung und NaBH₄ unter Stickstoff geschüttelt, wobei sich das an der Oberfläche befindliche Bleioxid löst und in der Lösung durch AHS bestimmt werden kann. Metallisches Blei wird durch diese Behandlung nicht angegriffen. Eine weitere Metallprobe wird dann in Gegenwart von Quecksilber ebenso behandelt, wobei Bleiamalgam gebildet wird und das gesamte Oxid in Lösung geht. Der Oxidgehalt in der Probe ergibt sich aus der Differenz der beiden Werte. Verschiedenartige Bleiproben wurden mit diesem Verfahren untersucht (Reproduzierbarkeit 98–100%).

     

Biosynthesis of triterpenoid hydrocarbons in the alga botryococcus braunii

¹⁴C-labelledtracers were incorporated into botryococcenes, triterpenoid hydrocarbons produced by a variety of the unicellular alga $\text{Botryococcus}$$\text{braunii}$. Data obtained with L-leucine might support for the biosynthesis the possibility of a non-mevalonoid pathway.     

铅离子印迹聚合物的制备表征及其吸附性能研究

以铅离子为模板,壳聚糖为功能单体,采用分子印迹技术,加入交联剂环氧氯丙烷,合成了铅离子印迹的交联壳聚糖。通过红外光谱对铅离子交联壳聚糖进行了结构表征,通过扫描电镜对其形态结构进行表征。研究了不同条件下交联壳聚糖对铅离子的吸附性能,结果表明,当溶液p H=4.5时,交联壳聚糖对溶液中铅离子的吸附效率较高。吸附在交联壳聚糖上的铅离子可用0.1mol·L的EDTA溶液洗脱,洗脱率达82.73%。利用原子吸收分光光度法对印迹聚合物的最大吸附量进行了研究,结果表明,所合成的模板交联壳聚糖分子印迹聚合物对铅离子具有良好的吸附性;对印迹聚合物的选择性吸收进行研究,研究表明,印迹聚合物对铅离子的选择性好,能用于水溶液中除去铅离子。     

The influence of the surfactant in a perfluorinated emulsion on the determination of thallium,lead and cadmium by anodic stripping voltammetry

The effects of the Pluronic F-68 surfactant in the emulsion are described. A study of the two electrode processes in the measuring cycle shows that the deposition stage is not affected provided that the deposition potential is negative enough. The peak potentials for Pb²⁺ and Cd²⁺ are slightly shifted and the stripping currents are seriously decreased when the differential pulse (d.p.) mode is used, but the inhibition is independent of metal ion concentration and deposition time, and the d.p. mode is suitable for quantitative work. The performance of hanging drop and film mercury electrodes is compared.