Association mechanisms of Europium(III) and Curium(III) with Chlorella vulgaris

The association of Europium(III) (Eu[III]) and Curium(III) (Cm[III]) with Chlorella vulgaris and with cellulose was studied by a batch method and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The kinetics study performed by the batch method showed that maximum adsorption of Eu(III) and Cm(III) on C. vulgaris was attained within 3 min of contact; afterward, the percentage adsorption decreased with time due to chelation of the ions with exudates released from C. vulgaris with a strong affinity for Eu(III) and Cm(III). The TRLFS revealed that the short-term adsorption of Eu(III) on C. vulgaris was attributable to its coordination with cellulose on the algal cell wall. However, Eu(III) coordinated with the functional groups of cellulose very weakly despite the large distribution coefficients observed. These results indicate that the reactions, both at the cell's surfaces through adsorption and in solution phases through chelation with the exudates, are important in estimating the behavior of Eu(III) and Cm(III) in aqueous environments.     

Adsorption of Cr(VI) and speciation of Cr(VI) and Cr(III) in aqueous solutions using chemically modified chitosan

A new type of grafting chitosan (CTS) was synthesized using 2-hydroxyethyl-trimethyl ammonium chloride (HGCTS). The adsorption of Cr(VI) on HGCTS was studied. The effect factors on adsorption and the adsorption mechanism were considered. The results indicated that the HGCTS could concentrate and separate Cr(VI) at pH 4.0; the adsorption equilibrium time was 80 min; the maximum adsorption capacity was 205 mg/g. The adsorption isotherm and kinetics were investigated, equilibrium data agreed very well with the Langmuir model and the pseudo second-order model could describe the adsorption process better than the pseudo first-order model. A novel method for speciation of Cr(VI) and Cr(III) in environmental water samples has been developed using HGCTS as adsorbent and FAAS as determination means. The detection limit of this method was 20 ng/L, the relatively standard deviation was 1.2% and the recovery was 99%~105%.     

Synthesis and spectroscopic studies of biologically active compounds derived from oxalyldihydrazide and benzil, and their Cr(III), Fe(III) and Mn(III) complexes

A new series of complexes have been synthesized by template condensation of oxalyldihydrazide and benzil in methanolic medium in the presence of trivalent chromium, manganese and iron salts forming complexes of the type [M(C(32)H(24)N(8)O(4))X]X(2) where M = Cr(III), Mn(III), Fe(III) and X = Cl(-1), NO(3)(-1), CH(3)COO(-1). The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, NMR, infrared and far infrared spectral studies. On the basis of these studies, a five coordinate square pyramidal geometry has been proposed for all these complexes. The biological activities of the metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential. Some of these complexes have been found to exhibit remarkable antibacterial activities.     

Dietary fiber suppresses elevations of uric acid and allantoin in serum and urine induced by dietary RNA and increases its excretion to feces in rats

This study was performed to examine the effects of several kinds of dietary fibers (DF) with different physical properties on dietary RNA metabolism. Male Wistar strain rats, 4 wk old, were fed diets with or without a 3% yeast RNA and a 5% DF (cellulose, chitin, chitosan, inulin, and xanthan gum) for 20 d (Experiment 1) or 5 d (Experiment 2). Feeding DF tested lowered the serum uric acid and allantoin concentrations and the urinary excretions of their compounds and increased the amount of RNA excreted into the feces compared with fiber-free. The water-holding capacity and nucleotide adsorption of chitin and chitosan in acidic solutions were higher than those of cellulose. The digestion rate of RNA by RNase A in vitro was found to be lower in the DF tested than in fiber-free. The decrease was remarkable in chitosan and xanthan gum. The uptakes of 14C-labeled adenosine and adenosine 5'-monophosphate (5'-AMP) in the rat jejunum were markedly decreased in regard to chitosan and xanthan gum in comparison with the fiber-free. These phenomena suggest that DF with high viscosity is more strongly associated with the suppression of RNA digestion by RNase A and the depression of the uptake of purine compounds to jejunum. The present results reveal that the elevation of serum uric acid concentration induced by dietary RNA can be suppressed by DF in rats.     

New approaches to virus removal: the way to produce virus-free drinking water

Virus control in drinking water is considered one of the serious problems to be encountered in the near future. Trials to remove viruses from drinking water were directed to enhance water treatment processes, use of different disinfectants or use of a good virus adsorbent material. In the present study, four materials were prepared, dimethylaniinoethyl chitin, chitosan and cellulose and starch acrylate and examined for adsorption of hepatitis A virus from drinking water. Also, three types of eluates (3% beef extract-glycine, 3% beef Virus control in drinking water is considered one of the serious problems to be encountered in the near future. Trials to remove viruses from drinking water were directed to enhance water treatment processes, use of different disinfectants or use of a good virus adsorbent material. In the present study, four materials were prepared, dimethylaniinoethyl chitin, chitosan and cellulose and starch acrylate and examined for adsorption of hepatitis A virus from drinking water. Also, three types of eluates (3% beef extract-glycine, 3% beef extract and glycine) were used for virus recovery from adsorbed materials. The results obtained showed that dimethylaminoethyl chitosan was a good adsorbent (99.16%) and the three eluents were poorly desorb viruses.     

Influence of oxidizing or reducing agents on gastrointestinal absorption of U, Pu, Am, Cm and Pm by rats

Absorption of 233U, 238Pu, 241Am, and 244Cm from the gastrointestinal (GI) tract was measured in rats, fed ad libitum or fasted, that were gavaged with solutions containing ferric iron, ferrous iron, iron powder, quinhydrone or ascorbic acid. Absorption and retention of all of these actinides was increased substantially by fasting and by the addition of mild oxidizing agents, ferric iron and quinhydrone. In contrast, absorption and retention were decreased to below the fasted level by all the reducing agents except ascorbic acid, which caused diarrhea and an increase in absorption. Absorption of the lanthanide element 147Pm from the intestine of fasted rats was also increased by ferric iron. Some of these actinide elements are polyvalent and are, in some cases, known to be absorbed from the GI tract more readily in their higher oxidation states. This suggested an oxidation-reduction mechanism for the effect of fasting and the action of the chemical agents used. However, the improbability that either 241Am(III) 244Cm(III) or 147Pm is converted to a different oxidation state under these conditions makes that mechanism unlikely. Other explanations are suggested.     

Synthesis, characterization, antioxidant activity and DNA-binding studies of two rare earth(III) complexes with naringenin-2-hydroxy benzoyl hydrazone ligand

Two novel rare earth complexes, Y(III) complex (1) and Eu(III) complex (2), with naringenin-2-hydroxy benzoyl hydrazone ligand were synthesized and characterized. The interaction of the two metal complexes and the free ligand with calf thymus DNA (CT DNA) was investigated by electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurement. All the experimental evidences indicate that these three compounds can strongly bind to CT DNA via an intercalation mechanism. The intrinsic binding constants of the Y(III) complex (1), Eu(III) complex (2) and the free ligand with CT DNA were 2.1x10(4), 8.5x10(4) and 1.6x10(4)M(-1), respectively. Furthermore, the antioxidant activity of the metal complexes was determined by hydroxyl radical scavenging method in vitro.     

Biochemical and spectroscopic studies of the response of Convolvulus arvensis L. to chromium(III) and chromium(VI) stress

The objective of the present study was to determine the oxidative stress caused by hexavalent chromium (Cr[VI]), the chromium (Cr) uptake, and the Cr speciation in Convolvulus arvensis L. plants grown in hydroponics media containing either Cr(VI) or Cr(III). The results demonstrated that C. arvensis plants exposed to Cr(VI) concentrations ranging from 0 to 40 mg/L expressed higher ascorbate peroxidase specific activity in roots than in shoots. On the other hand, catalase activity monitored in plants exposed to 2 mg/L of Cr(VI) for 24 h increased in roots after a few hours of exposure. However, catalase activity in shoots revealed a decrement almost immediately after treatment was initiated. The results from x-ray absorption spectroscopic studies indicated that the oxidation state of the supplied Cr(III) remained the same in plant tissues. The supplied Cr(VI), however, was reduced to the trivalent form in plant tissues. The results of inductively coupled plasma/optical emission spectroscopy demonstrated that after 5 d, the roots of plants exposed to 40 mg/L of Cr(III) or Cr(VI) accumulated approximately 25,000 and 3,500 mg/kg dry weight of Cr, respectively. Nevertheless, shoots concentrated 1,500 and 2,000 mg/kg dry weight of Cr from Cr(III) and Cr(VI), respectively, which indicated that Cr moved faster into C. arvensis plants when supplied as Cr(VI).     

Adsorption of metals to membrane filters in view of their speciation in nutrient solution

Filtration of a solution may lower metal concentrations through adsorption of metal species to the filter. Processes such as filter-sterilizing nutrient solution and filtration of field water are sensitive to these sorption artifacts, yet basic data on the affinity of different filters for metals are lacking. This article describes the adsorption of five metals to eight types of 0.2-microm membrane filters used for sterilizing a plant (Lemna minor L.) culture medium. Filters of cellulose acetate, cellulose nitrate, mixed cellulose ester, nylon, polyamide, polycarbonate, polyester, and polyvinylidene fluoride were tested for their affinity toward mono- (K), di-(Mn, Cu, Zn), and trivalent (lanthanum [La]) metals. Metal concentrations were quantified using radioisotopes and speciation was calculated. Results showed that metals had the lowest affinity for polycarbonate and nylon filters and the highest affinity for cellulose- and polyester-type filters. Furthermore, it was shown that the metal load on cellulose filters correlated best with free ion concentrations (indicating electrostatic attraction), while loads on other filters correlated better with total metal concentrations. Filtering a 5-ml solution of pH 5 did not affect its metal concentrations, ranging from 10 nM (La) to 49 microM (K). To minimize filtration artifacts, we propose using polycarbonate or nylon filters, especially when dealing with low volumes of high pH and low metal species concentrations.     

Absorption of 233U, 237Np, 238Pu, 241Am and 244Cm from the gastrointestinal tracts of rats fed an iron-deficient diet

Absorption of U, Np, Am and Cm was increased by factors of 3.4, 7.1, 2.7 and 1.7, respectively, when nitrate solutions of these actinides were gavaged to adult rats fed an iron-deficient diet. Retention increased proportionately in liver, kidney and carcass. The concentration of the actinides excreted also increased substantially (over that of controls) in the urine of iron-deficient rats gavaged with 233U and 237Np, but not in those with 241Am or 244Cm. Weanling rats on an iron-deficient diet, gavaged with ferric nitrate immediately before administration of 238Pu nitrate, retained between 4% and 12% of the 238Pu retained by litter mates that were not treated intragastrically with iron.     

Subcellular location of horseradish peroxidase in horseradish leaves treated with La(III), Ce(III) and Tb(III)

The agricultural application of rare-earth elements (REEs) would promote REEs inevitably to enter in the environment and then to threaten the environmental safety and human health. Therefore, the distribution of the REEs ion, ¹⁴¹Ce(III) and effects of La(III), Ce(III) and Tb(III) on the distribution of horseradish peroxidase (HRP) in horseradish mesophyll cells were investigated with electron microscopic radioautography and transmission electron microscopic cytochemistry. It was found for the first time that REEs ions can enter into the mesophyll cells, deposit in both extra and intra-cellular. Compared to the normal condition, after the horseradish leaves treated with La(III) or Tb(III), HRP located on the tonoplast is decreased and HRP is mainly located on the cell wall, while HRP is mainly located on the plasma membrane after the horseradish leaves were treated with Ce(III). This also indicated that REEs ions may regulate the plant growth through changing the distribution of enzymes.     

Determination of monomethylarsonous acid, a key arsenic methylation intermediate, in human urine

In this study we report on the finding of monomethylarsonous acid [MMA(III)] in human urine. This newly identified arsenic species is a key intermediate in the metabolic pathway of arsenic biomethylation, which involves stepwise reduction of pentavalent to trivalent arsenic species followed by oxidative addition of a methyl group. Arsenic speciation was carried out using ion-pair chromatographic separation of arsenic compounds with hydride generation atomic fluorescence spectrometry detection. Speciation of the inorganic arsenite [As(III)], inorganic arsenate [As(V)], monomethylarsonic acid [MMA(V)], dimethylarsinic acid [DMA(V)], and MMA(III) in a urine sample was complete in 5 min. Urine samples collected from humans before and after a single oral administration of 300 mg sodium 2,3-dimercapto-1-propane sulfonate (DMPS) were analyzed for arsenic species. MMA(III) was found in 51 out of 123 urine samples collected from 41 people in inner Mongolia 0-6 hr after the administration of DMPS. MMA(III )in urine samples did not arise from the reduction of MMA(V) by DMPS. DMPS probably assisted the release of MMA(III) that was formed in the body. Along with the presence of MMA(III), there was an increase in the relative concentration of MMA(V) and a decrease in DMA(V) in the urine samples collected after the DMPS ingestion.     

Further studies on the influence of chemical form and dose on absorptions of Np, Pu, Am and Cm from the gastrointestinal tracts of adult and neonatal rodents

Absorption of isotopes of the actinide elements Np, Pu, Am and Cm from various organic media and/or in combination with plant or animal ligands or tissue is compared with their absorption from an inorganic nitrate medium. Gastrointestinal (GI) transport of 238Pu, 239Pu, 241Am and 244Cm at high concentrations from citrate medium by adult rats and/or mice was higher than from nitric acid medium. Neptunium-237 absorption, however, was not increased by citrate; probably because its oxidation state was reduced from 237Np(V) to 237Np(IV) by the medium and by the GI content. Increasing the mass of the 237Np dose resulted in increased absorption. Neither incorporation of 238Pu in rat liver nor retention of 238Pu oxide in rat lungs enhanced absorption when those Pu-containing tissues were administered intragastrically to either adult or neonatal rats. Ranking of GI absorption of the various forms of Pu gavaged in these studies suggests that transport is in the order: Pu citrate greater than Pu phytate greater than biologically incorporated Pu greater than Pu nitrate.     

Biotransformation of 3,5-dibromo-4-hydroxybenzonitrile under denitrifying,Fe(III)-reducing,sulfidogenic, and methanogenic conditions

Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) is a halogenated aromatic nitrile herbicide used on a variety of crops for the postemergence control of annual broad-leaved weeds. The anaerobic biodegradability of bromoxynil and its aerobic transformation product, 3,5-dibromo-4-hydroxybenzoate, were examined in enrichment cultures established with anaerobic sediment under denitrifying, Fe(III)-reducing, sulfidogenic, and methanogenic conditions. Bromoxynil (100 microM) was depleted in 20 to 30 d in the methanogenic, sulfidogenic, and Fe(IIi)-reducing enrichments but was stable under denitrifying conditions. The 3,5-dibromo-4-hydroxybenzoate (100 microM) was depleted within 20 to 35 d under all four anaerobic conditions. Both compounds were stable in sterile controls. Bromoxynil and 3,5-dibromo-4-hydroxybenzoate were readily utilized upon respiking of the cultures. During utilization of bromoxynil, stoichiometric release of bromide was observed with transient accumulation of metabolites identified as bromocyanophenol, cyanophenol, and phenol. Bromoxynil heptanoate and octanoate were rapidly hydrolyzed to bromoxynil, which was further degraded. These results indicate that bromoxynil and 3,5-dibromo-4-hydroxybenzoate are degraded under different anaerobic conditions. Anaerobic degradation of bromoxynil proceeds via reductive debromination to 4-cyanophenol, which is further transformed to phenol and can ultimately be degraded to carbon dioxide.     

Cholesterol reduction by glucomannan and chitosan is mediated by changes in cholesterol absorption and bile acid and fat excretion in rats

Glucomannan, a viscous polysaccharide, and chitosan, a derivative of chitin, have both been demonstrated to lower cholesterol in animals. However, the mechanism of cholesterol lowering has not been established for either material. This study was conducted to determine the effect of glucomannan (G), chitosan (CH), or an equal mixture of the two (G + CH) on cholesterol absorption and fat and bile acid excretion. Rats were fed a modified AIN-93G diet for 18 d containing 0.125 g/100 g cholesterol and initially 10 g/100 g of the test materials or cellulose (C) as the control. However, the concentration of test materials and cellulose was reduced to 7.5 g/100 g after 1 wk due to lower weight gain compared with controls. Total liver cholesterol was significantly reduced in G, CH and G + CH groups compared with the C group. The intestinal contents supernatant viscosity of the C and the CH groups was negligible, whereas both G and G + CH produced high viscosities. Cholesterol absorption, measured by the fecal isotope ratio method, was significantly reduced from 37.5% in the C group to 20.2% in G, 18.2% in G + CH and 9.4% in CH. Daily fecal fat excretion did not differ between the C and G groups, but was significantly greater in G + CH and CH compared with the C and G groups. Daily fecal bile acid excretion was significantly greater in the CH and G + CH groups compared with the C and G groups. These results suggest that G lowered liver cholesterol by a viscosity-mediated interference of cholesterol absorption. In contrast, CH appears to lower cholesterol through a different mechanism.     

An assessment of soil-to-plant concentration ratios for some natural analogues of the transuranic elements

A field study was conducted in an area of enhanced, natural radioactivity to assess the soil to edible vegetable concentration ratios (CR = concentration in dry vegetable/concentration in dry soil) of 232Th, 230Th, 226Ra, 228Ra, and the light rare earth elements (REE's) La, Ce and Nd. Twenty-nine soil and 42 vegetable samples consisting of relatively equal numbers of seven varieties were obtained from 11 farms on the Pocos de Caldas Plateau in the state of Minas Gerais, Brazil. This region is the site of a major natural analogue study to assess the mobilization and retardation processes affecting Th and the REE's at the Morro do Ferro ore body and U series radionuclides at a nearby open pit U mine. Thorium (IV) serves as a chemical analogue for quadrivalent Pu and the light REE's (III) as chemical analogues for trivalent Am and Cm. The geometric mean CR's (all times 10(-4] decreased as 228Ra (148) greater than 226Ra (76) greater than La (5.4) greater than Nd (3.0) = Ce (2.6) greater than 232Th (0.6), or simply as M (II) greater than M (III) greater than M (IV). These differences may reflect the relative availability of these metals for plant uptake. Significant differences were found in the CR's (for any given analyte) among many of the vegetables sampled. The CR's for the different analytes were also highly correlated. The reasons for the correlations in CR's seen among elements with such diverse chemistries as Ra-REE or Ra-Th are not clear but are apparently related to the essential mineral requirements or mineral status of the different vegetables sampled. This conclusion is based on the significant correlations obtained between the Ca content of the dried vegetables and the CR's for all of the elements studied.     

Geosorption of As(III) from Aqueous Solution by Red Clays: Kinetic Studies

The geosorption of As(III) on red clays from aqueous solution under different environmental conditions (i.e. initial concentration, pH and temperature) was studied. This process reached its equilibrium quickly (<120 min). A decrease of the percentage of adsorption was caused when the initial concentration was increased (0.1–10 mg As(III) L^?1), in all the experimental pH levels (4–10). The optimal pH value for adsorption on red clays at 0.1 mg As(III) L^?1 was 10, while for 10 mg As(III) L^?1 was 4. There wasn’t a significant effect of temperature on the As(III) adsorption. The kinetic pseudo-second order and the isothermal Langmuir were the models that best described the experimental data, suggesting an adsorption process in multistep. Likewise, there are not interactions between neighbor active sites on the red clay surface.     

Effects of Organic Acids and Sylvite on Phytoextraction of <Superscript>241</Superscript>Am Contaminated Soil

Contamination of soil with Americium (²⁴¹Am) at nuclear sites in China poses a serious problem. We screened six plants, from five families, for their ²⁴¹Am-enrichment potential. Europium (Eu), which is morphologically and chemically similar to the highly toxic ²⁴¹Am, was used in its place. Moreover, the effects of sylvite, citric acid (CA), malic acid (MA), and humic acid (HA) on the absorption of ²⁴¹Am by the plants, and its transport within them, were evaluated along with their effect on plant biomass and ²⁴¹Am extraction volume. Barley and cabbage showed relatively stronger Eu accumulation capacities. Citric acid promoted the absorption of ²⁴¹Am by barley roots and its transport within the plants. The effects of sylvite were not obvious and those of HA were the weakest in case of sunflower; HA, however, maximally increased the biomass of the plants. Our results could provide the basis for future radionuclide phytoremediation of contaminated soils.     

New cerium(III) complexes of coumarins - synthesis, characterization and cytotoxicity evaluation

Complexes of cerium(III) with bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-pyridin-2-yl-methane, bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-pyridin-3-yl-methane and bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-pyridin-4-yl-methane were synthesized by reaction of cerium(III) salt and the ligands, in amounts equal to metal-ligand molar ratio of 1:2. The cerium(III) complexes with bis-coumarins were characterized by different physicochemical methods - elemental analysis, IR-, Raman-, (1)H NMR- and (13)C NMR-spectroscopy and mass-spectral data. The spectral data of cerium(III) complexes were interpreted on the basis of comparison with the spectra of the free ligands. This analysis showed that in the Ce(III) complexes the ligands coordinated to the metal ion through both deprotonated hydroxyl groups. On the basis of the nu(CO) red shift observed, participation of the carbonyl groups in the coordination to the metal ion was also suggested. Cytotoxic screening by MTT assay was carried out. In the present study we performed comparative evaluation of the cytotoxic effects of the three newly synthesized cerium complexes against the acute myeloid leukemia derived HL-60 and the chronic myeloid leukemia (CML)-derived BV-173. In addition the cytotoxic effects of Ce(III) complex with bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-pyridin-2-yl-methane were evaluated on the SKW-3 cells. In order to elucidate some of the mechanistic aspects of the observed cytotoxic effects we evaluated the ability of this complex to trigger programmed cell death (apoptosis by means of agarose gel electrophoretic analysis of DNA, isolated from the cytosolic fraction of treated SKW-3 cells). In addition, microscopic morphological evaluation of the treated cells was carried out in order to establish morphological features indicative of programmed cell death.     

Marine microbial community response to inorganic and organic sediment amendments in laboratory mesocosms

Sediment amendments provide promising strategies of enhancing sequestration of heavy metals and degradation of organic contaminants. The impacts of sediment amendments for metal and organic remediation including apatite, organoclay (and apatite and organoclay in geotextile mats), acetate, and chitin on environmental microbial communities in overlying water and sediment profiles are reported here. These experiments were performed concurrent with an ecotoxicity evaluation (data submitted in companion paper) and X-ray absorption spectroscopy of zinc speciation post apatite amendments. X-ray absorption spectra showed that a modest modification of zinc speciation occurred in amended treatments. Significant changes in both bacterial cell densities and populations were observed in response to amendments of apatite+organoclay, chitin, and acetate. The enriched bacteria and breakdown of these amendments were likely attributed to water quality degradation (e.g. ammonia and dissolved oxygen). Molecular fingerprints of bacterial communities by denaturant gradient gel electrophoresis (DGGE) showed that distinct bacterial populations occurred in overlying waters from different amendments: apatite+organoclay led to the dominance of Gammaproteobacteria, acetate enriched Alphaproteobacteria, and chitin treatment led to a dominance of Bacteroidetes and Alphaproteobacteria. In amended sediments, Firmicutes, Bacteroidetes, and Deltaproteobacteria (Desulfovibrio) were commonly found with chitin and apatite+chitin treatments. Finally, sulfate-reducing bacteria (e.g. Desulfovibrio) and metal-reducing bacteria were also recovered with most probable number (MPN) analyses in treatments with acetate, chitin, and apatite+chitin. These geochemically important bacteria were stimulated by amendments and may play critical functional roles in the metal and organic contaminant remediation process for future investigations of contaminated sediments.