Determination of the taste threshold of copper in water

Copper effects on human health represent a relevant issue in modern nutrition. One of the difficulties in assessing the early, acute effects of copper ingested via drinking water is that the taste of copper may influence the response and the capacity to taste copper in different waters is unknown. The purpose of the study was to determine the taste threshold of copper in different types of water, using soluble and insoluble salts (copper sulfate and copper chloride). Copper-containing solutions (range 1.0-8.0 mg/l Cu) were prepared in tap water, distilled deionized water and uncarbonated mineral water. Sixty-one healthy volunteers (17-50 years of age), with no previous training for sensory evaluation, participated in the study. A modified triangle test was used to define the taste threshold value. The threshold was defined as the lowest copper concentration detected by 50% of the subjects assessed. To evaluate the olfactory input in the threshold value obtained, 15 of 61 subjects underwent a second set of triangle tests with the nose open and clamped, using distilled water with copper sulfate at a concentration corresponding to the individual's threshold. The taste threshold in tap water was 2.6 mg/l Cu for both copper sulfate and copper chloride. The corresponding values for distilled deionized water were 2.4 and 2.5 mg/l Cu for copper sulfate and copper chloride, respectively. In uncarbonated mineral water the threshold values were slightly higher, 3.5 and 3.8 mg/l Cu for copper sulfate and for copper chloride, respectively, which are significantly higher than those observed in tap and distilled waters (P < 0.01, Kruskal-Wallis test). The taste threshold did not change significantly when the nose was clamped. In conclusion, the median values for copper taste threshold were low, ranging between 2.4 and 3.8 mg/l Cu, depending on the type of water.     

Transport of copper and manganese to the xylem exudate of sunflower

Abstract Absorption of copper and manganese by sunflower roots from solution cultures of varying composition was followed by measuring the concentrations of the metals appearing in whole roots, root cell sap and xylem exudate. Total copper in the fibrous roots was linearly related to the concentration of copper in the external solution but the concentration of copper released to the xylem exudate was buffered somewhat against the changes made externally. No such buffering was observed for managenese. A copper-sensitive electrode, responsive only to free cupric ions was used in conjunction with total copper analysis by atomic absorption spectrophotometry to show that little of the copper (usually < 1%) existed as a free ion in any phase of the system. Copper in the xylem exudate may be strongly complexed. An electron paramagnetic resonance spectrum of the xylem exudate indicated that manganese probably was a free divalent ion. Calculation of the electrochemical potential gradient for free cupric ions showed that no special metabolically-linked mechanism need be postulated to account for absorption of copper (or manganese) other than that necessary to maintain the transmembrane potential.     

An in vitro approach for modelling branchial copper binding in rainbow trout

The main objective of this study was to characterize the individual effects of water chemistry (Ca(2+), Na(+), dissolved organic matter (DOM), pH, alkalinity) on the rapid binding of copper to the gill surface of rainbow trout using an in vitro gill binding assay. In this assay, individual gill arches were exposed for 5 min to (64)Cu labelled copper solutions ranging from 0.02 to 0.16 microM in water chemistries reflecting the full range of fresh water values for the Great Lakes. The gills displayed saturable Cu binding within this Cu range but gill-Cu binding was completely unaffected over the full range of calcium, sodium and alkalinity concentrations used. Only low pH (pH 4.0) and commercial DOM (Aldrich humic acid at > or =3 mgC/l) altered copper binding to rainbow trout gills in vitro. These findings were consistent with the results of geochemical modelling of our water chemistry (using MINEQL+, Version 4.5) which showed that H(+) and DOM affected the free cupric ion concentration. However, DOM (up to 80 mgC/l) was only able to reduce Cu on the gills by 50%. We hypothesize that in the range of 0.02-0.16 microM Cu there are two high affinity Cu binding sites on the gills, one having a substantially higher affinity for copper than DOM. The absence of a calcium effect on gill copper binding was in accord with in vivo evidence that calcium primarily acts to alter the physiology of the gill binding sites through acclimatory processes, rather than through competitive interactions. It was a surprise that water chemistry parameters influence rapid gill-metal binding in a manner different to their influence on acute toxicity and different from the effects on long-term binding reported in other studies. Currently, the biotic ligand model uses the rapid increase of gill copper (believed to reflect binding to the physiologically active receptor sites) to model gill binding characteristics. The distinction between rapid surface binding and metal uptake obviously plays an important role in determining the toxic effects of copper, especially when regulators need to predict the modifying effects of water chemistry.     

Reduction of marine phytoplankton reproduction rates by copper and cadmium

The reproduction rates of 38 clones of marine phytoplankton were measured in media in which free cupric ion activity was controlled at different levels using a NTA-cupric ion buffer system. The major trend among species in their resistance to copper toxicity was a phylogenetic one, with cyanobacteria being the most sensitive, diatoms the least sensitive, and coccolithophores and dinoflagellates intermediate in sensitivity. The reproduction rates of most of the cyanobacteria were reduced at cupric ion activities above 10⁻¹² M, while most eukaryotic algae still had maximum reproduction rates at 10⁻¹¹ M. Four species, Emiliana huxleyi (Lohm.) Hay & Mohler, Skeletonema costatum (Grev.) Cleve, Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and Thalassiosira oceanica (Hustedt) Hasle were particularly resistant to copper, being able to reproduce well at the highest cupric ion activities tested, 10^−9.5 M and 10^−9.2 M. There was no major difference, however, between neritic and oceanic species in their sensitivity to copper.The sensitivity of 20 species of marine phytoplankton to free cadmium ion activity was measured in a similar manner using an NTA-cadmium ion buffer system. As observed with copper, the prokaryotic cyanobacteria were the most sensitive to cadmium toxicity, diatoms were the least sensitive, and coccolithophores and dinoflagellates were intermediate. All cyanobacteria tested were dead at a cadmium ion activity of 10^−9.3 M whereas the reproduction rates of most of the eukaryotic algae were not reduced significantly until 10^−8.3 M.Comparison of these data with natural concentrations in sea water implies that cadmium is not an important ecological factor in unpolluted waters but natural copper concentrations may inhibit the reproduction of some phytoplankton species, especially cyanobacteria, in upwelled sea water. Copper may influence the seasonal succession of species.     

Intestinal absorption of copper from drinking water containing fulvic acids and an infant formula mixture studied in a suckling rat model

The purpose of this study was to investigate if the intestinal absorption of copper in drinking water is altered in the presence of complexing agents from a fulvic acid mixture and an infant formula powder. Ten to twelve day old rat pups were given a single oral dose of radio-labeled Cu in deionized water (0.93 mg Cu/l), in water containing fulvic acids (10 mg/l), in infant formula mixed with deionized water, or in infant formula mixed with water containing fulvic acids. Six hours after dosage, radioactive Cu was analyzed in the mucosa of the small intestine, the liver and the remaining carcass (excluding the liver and gastrointestinal tract) by gamma counting. Dialysis and centrifugation experiments showed that Cu was complexed by components in the fulvic acid and formula mixtures, although the presence of fulvic acids in the water did not alter the Cu fractionation in the formula. The fractional Cu uptake (% of dose) from the intestinal lumen to the mucosa was not markedly changed by the presence of the chelating agents. However, the retention of Cu in the intestinal mucosa was increased by both fulvic acids and formula. Concomitantly, the absorption rate of Cd to the circulatory system was decreased. No interactive effect between fulvic acids and formula was found on the Cu absorption. These findings indicate that the water quality may be an important determinant of the rate of intestinal Cu absorption from drinking water. Moreover, in the future risk assessment of copper in drinking water, the possibility of alterations in absorption of drinking-water Cu has to be considered when the drinking water is used for cooking.     

The effects of copper on the microbial community of a coral reef sponge

Marine sponges often harbour communities of symbiotic microorganisms that fulfil necessary functions for the well-being of their hosts. Microbial communities associated with the sponge Rhopaloeides odorabile were used as bioindicators for sublethal cupric ion (Cu2+) stress. A combined strategy incorporating molecular, cultivation and electron microscopy techniques was adopted to monitor changes in microbial diversity. The total density of sponge-associated bacteria and counts of the predominant cultivated symbiont (alpha-proteobacterium strain NW001) were significantly reduced in response to Cu2+ concentrations of 1.7 microg l(-1) and above after 14 days of exposure. The number of operational taxonomic units (OTUs) detected by restriction fragment length polymorphism (RFLP) decreased by 64% in sponges exposed to 223 microg l(-1) Cu2+ for 48 h and by 46% in sponges exposed to 19.4 microg l(-1) Cu2+ for 14 days. Electron microscopy was used to identify 17 predominant bacterial morphotypes, composing 47% of the total observed cells in control sponges. A reduction in the proportion of these morphotypes to 25% of observed cells was evident in sponges exposed to a Cu2+ concentration of 19.4 microg l(-1). Although the abundance of most morphotypes decreased under Cu2+ stress, three morphotypes were not reduced in numbers and a single morpho-type actually increased in abundance. Bacterial numbers, as detected using fluorescence in situ hybridization (FISH), decreased significantly after 48 h exposure to 19.4 microg l(-1) Cu2+. Archaea, which are normally prolific in R. odorabile, were not detected after exposure to a Cu2+ concentration of 19.4 microg l(-1) for 14 days, indicating that many of the microorganisms associated with R. odorabile are sensitive to free copper. Sponges exposed to a Cu2+ concentration of 223 microg l(-1) became highly necrosed after 48 h and accumulated 142 +/- 18 mg kg(-1) copper, whereas sponges exposed to 19.4 microg l(-1) Cu2+ accumulated 306 +/- 15 mg kg(-1) copper after 14 days without apoptosis or mortality. Not only do sponges have potential for monitoring elevated concentrations of heavy metals but also examining changes in their microbial symbionts is a novel and sensitive bioindicator for the assessment of pollution on important microbial communities.     

Acclimation of Daphnia magna to environmentally realistic copper concentrations

It may be hypothesised that as the bioavailable background concentration of an essential metal increases (within natural limits), the natural tolerance (to the metal) of the acclimated/adapted organisms and communities will increase. In this study the influence of acclimation to different copper concentrations on the sensitivity of the freshwater cladoceran Daphnia magna Straus was investigated. D. magna was acclimated over three generations to environmentally relevant copper concentrations ranging from 0.5 to 100 microg Cu/l (copper activity: 7.18 x 10(-15) to 3700 x 10(-12) M Cu2+). A modified standard test medium was used as culture and test medium. Medium modifications were: reduced hardness (lowered to 180 mg CaCO3/l) and addition of Aldrich humic acid at a concentration of 5 mg DOC/l (instead of EDTA). The effects of acclimation on these organisms were monitored using acute mortality assays and long-term assays in which life table parameters, copper body concentrations and energy reserves were used as test endpoints. Our results showed a two-fold increase in acute copper tolerance with increasing acclimation concentration for second and third generation organisms. Copper acclimation concentrations up to 35 microg Cu/l (80 pM Cu2+) did not affect the net reproduction and the intrinsic growth rate. The energy reserves of the acclimated daphnids revealed an Optimal Concentration range (OCEE) and concentrations between 5 and 12 microg Cu/l (0.5-4.1 pM Cu2+) and 1 and 35 microg Cu/l (0.023-80 pM Cu2+) seemed to be optimal for first and third generation daphnids, respectively. Lower and higher copper concentrations resulted in deficiency and toxicity responses. It was also demonstrated that up to 35 microg Cu/l, third generation daphnids were able to regulate their total copper body concentration. These results clearly indicate that bioavailable background copper concentrations present in culture media have to be considered in the evaluation of toxicity test results, especially when the toxicity data are used for water quality guideline derivation and/or ecological risk assessment for metals.     

An investigation into copper catalyzed D-penicillamine oxidation and subsequent hydrogen peroxide generation

D-Penicillamine is a potent copper (Cu) chelating agent. D-Pen reduces Cu(II) to Cu(I) in the process of chelation while at the same time being oxidized to D-penicillamine disulfide. It has been proposed that hydrogen peroxide is generated during this process. However, definitive experimental proof that hydrogen peroxide is generated remains lacking. Thus, the major aims of these studies were to confirm and quantitatively assess the in vitro production of hydrogen peroxide during copper catalyzed D-penicillamine oxidation. The potential cytotoxic effect of hydrogen peroxide generation was also investigated in vitro against MCF-7 human breast cancer cells. Cell cytotoxicity resulting from the incubation of D-penicillamine with copper was compared to that of D-penicillamine, copper and hydrogen peroxide. The mechanism of copper catalyzed D-penicillamine oxidation and simultaneous hydrogen peroxide production was investigated as a function of time, concentration of cupric sulfate or ferric chloride, temperature, pH, anaerobic condition and chelators such as ethylenediaminetetraacetic acid and bathocuproinedisulfonic acid. A simple, sensitive and rapid HPLC assay was developed to simultaneously detect D-penicillamine, its major oxidation product D-penicillamine disulfide, and hydrogen peroxide in a single run. Hydrogen peroxide was shown to be generated in a concentration dependent manner as a result of D-penicillamine oxidation in the presence of cupric sulfate. Chelators such as ethylenediaminetetraacetic acid and bathocuproinedisulfonic acid were able to inhibit D-penicillamine oxidation. The incubation of MCF-7 human breast cancer cells with D-penicillamine plus cupric sulfate resulted in the production of reactive oxygen species within the cell and cytotoxicity that was comparable to free hydrogen peroxide.     

Acute Copper and Cupric Ion Toxicity in an Estuarine Microbial Community

Copper was acutely toxic to the estuarine microbial community of Middle Marshes, N.C. Under ambient water quality conditions, 10 μg of added total copper [Cu(II)] liter⁻¹ reduced the CFU bacterial abundance by up to 60% and inhibited the amino acid turnover rate (AATR) by as much as 30%. Copper toxicity, however, was a quantitative function of free cupric ion (Cu²⁺) activity that was not directly related to Cu(II) or ligand-bound copper. By using a nitrilotriacetic acid-cupric ion buffer to control pCu (−log Cu²⁺ activity), it was found that an in situ pCu of 10.1 was bactericidal, reducing the CFU by 60%, but inhibited the AATR by only about 10%. A bacterial bioassay that was used to estimate the pCu in Cu(II)-treated Middle Marshes samples indicated that less than 0.5% of added Cu(II) was in the free cupric ion form. CFU was a more sensitive indicator of low-level copper stress than was AATR. When tested at different times, native microbial community responses to acute cupric ion stress were quantitatively quite similar even when there were large differences in bacterial abundances and in situ metabolic rates. Variations were observed in response to Cu(II) treatments at different times, but these were likely due to differences in water quality, which would quantitatively influence the distribution of copper complexes that were present. Asymptotic response curves suggest that some degree of copper resistance exists in this community. At a pCu of 8, more than 2 orders of magnitude above the minimum inhibitory level, the CFU was still 5 to 10% and the AATR was about 3% of the control values.     

Excess diet copper increases systolic blood pressure in rats

Twenty Wistar and 20 Spontaneously Hypertensive Rats were divided into two diet copper intake groups at 5 wk of age. One group was fed 18 mg Cu as cupric carbonate/kg feed and the other group 100 mg Cu/kg feed. The basal diet was formulated after the AIN-76 diet. Animals were fed their respective diets until 20 wk of age. At age 8, 14, and 20 wk rats were placed in metabolic cages and food and water consumption as well as urine output were quantitated. Systolic blood pressures were measured triweekly by the tail-cuff method. Rats fed 100 mg Cu/kg feed showed an increase in systolic pressure compared to rats fed 18 mg Cu/kg feed. The increase was more pronounced for the Wistar strain. Body weights, urine output, and feed and water consumption did not differ (p>0.05) by copper intake. Rats fed 100 mg Cu/kg feed did have greater hemoglobin levels. Heart: body and liver: body weight strain differences were apparent. This study demonstrated increased blood pressure in rats fed excess diet copper.     

Grapevine downy mildew control using reduced copper amounts in organic viticulture

Copper is an essential natural micronutrient. However, copper used as a plant protection product may have long-term consequences due to its accumulation in the soil. Limitations on copper use have therefore been defined in organic farming (Regulation EC 889/2008). In the light of new developments and evidence, the European Commission has planned to assess whether further restrictions are needed in the quantities of copper permitted. A two-year field trial was therefore set up with new copper formulations to evaluate the possibility of reducing the copper quantities applied with treatments and consequently to reduce copper soil residues. Plots were prepared, each containing 12 plants and repeated four times in randomized blocks. The test organism was Plasmopara viticola (Berk. and M.A. Curtis) Berl. and De Toni. Cupric formulations characterised by a low metallic content (Glutex CU 90 and Labicuper) were tested in comparison with a reference product (standard) and an untreated control. Evaluations of treatments were carried out periodically on 100 leaves and 100 bunches for each replicate. Data obtained were subjected to statistical analysis. Chemical analyses were performed to determine copper residues on leaves, grapes and soil. Samplings of leaves and grapes were carried out for each replicate. Soil samples were taken from 0-20 cm and 20-40 cm depth. Total copper was determined using spectrophotometry in atomic absorption by acetylene-air flame (FAAS at lambda = 324.8 microm). The results showed that the tested products were effective in controlling downy mildew with a lower copper dosage than with the cupric formulations used as a standard. Glutex CU 90 formulation led to an annual input of copper that was a little more than a third compared to the standard and Labicuper about a fifth or a sixth. At harvest, copper levels in grapes were much lower than RML (fixed at 50 mg/kg). With regard to the impact of cupric treatments on organic vineyard soil, no statistically significant differential increase in Cu residue was observed in soil between tested products versus untreated control. In conclusion, the environmental impact of copper in organic viticulture could be minimized through the new cupric formulations developed by agrochemical companies.     

Copper toxicity: evidence for the conversion of cupric to cuprous copper in vivo under anaerobic conditions.

We have determined the toxicity to cells of Escherichia coli B of cupric copper applied under aerobic and anaerobic conditions in two ways. The growth of cells in liquid medium incorporating cupric copper shows differential inhibition, comparing aerobic and anaerobic conditions--toxicity being greater under anoxia. The growth of colonies upon agar plates incorporating cupric copper does not show such a differential effect. We conclude that colonies on plates are largely anoxic even when incubated aerobically. EPR spectra of cells obtained at various times after application of cupric copper under anoxic conditions indicate the conversion of a considerable proportion of the Cu(II) to a non-paramagnetic species, probably Cu(I). We demonstrate that Cu(I) is more toxic than Cu(II) to cells when applied under anoxic conditions and conclude that the difference in toxicity of Cu(II) applied to cells under aerobic and anaerobic conditions results from the greater extent of reduction of Cu(II) to Cu(I) under anaerobic conditions.     

Carnosine and neocuproine as neutralizing agents for copper overload-induced damages in cultured human cells

Copper is dangerous when it is present in excess, mainly because it can participate in the Fenton reaction, which produces radical species. As a consequence of copper pollution, people are involuntarily exposed to a copper overload under sub-clinical and sub-symptomatological conditions, which may be very difficult to detect. Thus, we investigated (i) the possible use of the chelator molecules carnosine and neocuproine to prevent the Cu overload-induced damage on cellular lipids and proteins, as tested in human cell culture systems, and (ii) the differential response of these two chelating agents in relation to their protective action, and the type of copper ion involved in the process, by using two types of human cultured cells (HepG2 and A-549). Cu treatment clearly enhanced (p < 0.01) the formation of protein carbonyls, thiobarbituric acid-reactive substances (TBARS) and the concentration of nitrate plus nitrites, with a concomitant decrease in cell survival, as estimated by the trypan dye exclusion test and lactate dehydrogenase leakage. Simultaneous treatment with Cu and carnosine or neocuproine indicated that carnosine is more efficient than neocuproine in protecting both types of cells from the effect of cupric ions on both the cell-associated damages and the decrease in the cellular viability. This observation was supported by the fact that carnosine is not only a complexing agent for Cu(II), but also an effective antioxidant that can dismutate superoxide radicals, scavenge hydroxyl radicals and neutralize TBARS formation. Carnosine should be investigated in more detail in order to establish its putative utility as an agent to prevent copper-associated damages in biological systems.     

Cytoprotective effect of copper(II) complexes against ethanol-induced damage to rat gastric mucosa.

The cytoprotective effect of various copper(II) complexes on the gastric mucosa damage induced by acute intragastric administration of ethanol was investigated. For in vitro experiments, the following copper(II) complexes were tested: Cu(II)(L-Trp)(L-Phe), Cu(II)(L-Leu)Cu(II)(L-Leu-Leu)(L-Leu), Cu(II)(L-Phe-L-Leu), Cu(II)(Gly-His-Lys), and Cu(II)(cyHis)2(ClO4)2. Inorganic copper such as CuSO4 was also tested. The free radical generating system, acting for 2 hr on cardial and fundic mucosa scrapings or mucosal microsomes, was Fe++ (20 microM)/ascorbate (0.25 mM). We found a marked inhibition to 75% of lipid peroxidation in the range 10-100 mM, regardless of whether copper was given in complexed or inorganic form. The results suggest that nontoxic copper(II)-amino acid complexes are able to neutralize oxygen-derived free radicals. In addition, copper(II) complexes suppressed membrane lipid peroxidation when mucosa homogenates were exposed to t-butyl hydroperoxide (1-20 microM) plus Fe++ (50 microM). In vivo experiments on rat stomachs, pretreated p.o. by gavage either with Cu(II)(L-Trp)(L-Phe) as paradigmatic agent or with copper sulphate at equivalent doses in the range 3-30 mg/kg body weight showed a significant decrease (30 min after 95% ethanol administration) in the number and severity of mucosal hemorrhagic lesions. In the gastric mucosa scrapings of copper-treated rats after ethanol exposure, we found that malondialdehyde and conjugated diene levels were unchanged compared to those of untreated controls; five enzyme activities released from lysosomes were near control values. In isolated mucosal cells, whether or not pretreated with 200 microM solution of either Cu(II)(L-Trp)(L-Phe) or CuSO4, the release of cathepsin D activity was also unmodified. The results suggest that the cytoprotective effect of Cu(II) complexes against ethanol-induced mucosal lesions was not associated in vivo to lipid peroxidation.     

Inhibition of Candida valida growth by copper ions]

The high toxicity of copper ions for Candida valida growth was established at pH-auxostat regime. The value of mu max decreased even at the residual Cu2+ concentration 1.0 mg/l. The inhibition constant (Ki) that characterized a copper ion concentration at which yeast specific growth rate was halved was equal to 7.7 mg/l. A linear dependence of 1/mu max on a residual concentration of copper ions indicates that yeast growth inhibition is due to inhibition of one enzymic reaction which is the most sensitive to copper. Yeast growth inhibition by copper was accompanied by accumulation of Cu2+ ions in biomass, a decrease in nucleic acid and true protein contents, and changes in amino acid composition of protein. The amounts of cystine and cysteine in protein increased and tryptophane content decreased with inhibition of yeast growth. Yeast growth inhibition by copper did not affect the lipid content but significantly reduced the degree of unsaturation due to a decrease in the amounts of polyunsaturated linoleic and alpha-linolenic acids.     

Active site-specific reconstituted copper(II) horse liver alcohol dehydrogenase: a biological model for type 1 Cu2+ and its changes upon ligand binding and conformational transitions

Insertion of Cu2+ ions into horse liver alcohol dehydrogenase depleted of its catalytic Zn2+ ions creates an artificial blue copper center similar to that of plastocyanin and similar copper proteins. The esr spectrum of a frozen solution and the optical spectra at 296 and 77 K are reported, together with the corresponding data for binary and ternary complexes with NAD+ and pyrazole. The binary complex of the cupric enzyme with pyrazole establishes a novel type of copper proteins having the optical characteristics of Type 1 and the esr parameters of Type 2 Cu2+. Ternary complex formation with NAD+ converts the Cu2+ ion to a Type 1 center. By an intramolecular redox reaction the cuprous enzyme is formed from the cupric enzyme. Whereas the activity of the cupric alcohol dehydrogenase is difficult to assess (0.5%-1% that of the native enzyme), the cuprous enzyme is distinctly active (8% of the native enzyme). The implications of these findings are discussed in view of the coordination of the metal in native copper proteins.     

Studies upon the copper fungicides: VIII. The penetration of copper into germinating peas

Three varieties of pea seed showed less damage when treated with solutions of simple cupric salts than with solutions of equivalent strength in which the copper could occur in complex form. On adding supplementary pea exudate to copper sulphate solution, thereby converting some cupric to complex copper, greater damage was caused. In spite of the greater phytotoxicity of complex forms of copper, the copper intake by the seeds was less. Sealing of the micropyle had little effect on the water and copper intake of peas.
Colorimetric tissue tests on treated peas indicated a high concentration of copper in the testa and the embryonic radical with only small amounts in the cotyledonary tissues. These observations were largely confirmed by chemical analyses-on the test as, cotyledons and embryos of copper treated peas.
The results suggest that when copper dissolves from dressings on pea seeds much becomes fixed on the testa, so providing fungicidal protection. The soluble complex forms of copper produced by pea exudate are markedly phytotoxic and injury to the embryonic radical is regarded as the main cause of damage to peas.     

Biosorption of copper(II) ions onto powdered waste sludge in a completely mixed fed-batch reactor: estimation of design parameters

Biosorption of Cu(II) ions onto pre-treated powdered waste sludge (PWS) was investigated using a fed-batch operated completely mixed reactor. Fed-batch adsorption experiments were performed by varying the feed flow rate ( 0.075-0.325 l h(-1)), feed copper (II) ion concentrations (50-300 mg l(-1)) and the amount of adsorbent (1-6 g PWS) using fed-batch operation. Breakthrough curves describing the variations of effluent copper ion concentrations with time were determined for different operating conditions. Percent copper ion removals from the aqueous phase decreased, but the biosorbed (solid phase) copper ion concentrations increased with increasing the feed flow rate and Cu(II) concentration. A modified Bohart-Adams equation was used to determine the biosorption capacity of PWS and the rate constant for Cu(II) ion biosorption. Adsorption rate constant in fed-batch operation was an order of magnitude larger than those obtained in adsorption columns because of elimination of mass transfer limitations encountered in the column operations while the biosorption capacity of PWS was comparable with powdered activated (PAC) in column operations. Therefore, a completely mixed reactor operated in fed-batch mode was proven to be more advantageous as compared to adsorption columns due to better contact between the phases yielding faster adsorption rates.     

Polymerization of amino acid methyl esters via their copper complexes.

Polymerization of glycine methyl ester catalyzed by cupric ions in organic solvents yields oligoglycines with a degree of polymerization up to none. With a trifunctional amino acid, the yield and degree of polymerization were much lower. Extension of this reaction to an aqueous medium was not successful even when copper ions were complexed with substances like montmorillonite or fatty acids. The prebiotic significance of this reaction is discussed.     

The effect that nickel,copper, and zinc salts have on seed germination and initial ontogenesis of water parsnip (<Emphasis Type="Italic">Sium latifolium</Emphasis> L.) and wood club-rush (<Emphasis Type="Italic">Scirpus silvaticus</Emphasis> L.)

The effect that nickel, copper, and zinc sulfates have on seed germination and the initial stages of the ontogenesis of water parsnip and wood club-rush has been investigated. Nickel and copper in the concentration range of 250–500 mg/l and zinc at a concentration of 500 mg/l were the most toxic for water parsnip seeds, while, for the wood club-rush seeds, maximum toxicity was observed at Ni and Cu concentrations ranging from 50 to 500 mg/l and at Zn concentrations of 250–500 mg/l. The development of water parsnip seedlings was normal at Ni concentrations of 1–25 mg/l, Cu concentrations of 1–10 mg/l, and Zn concentrations up to 50 mg/l; the development of wood club-rush seedlings was normal at a Ni concentration of 1 mg/l, and Cu and Zn concentrations of 1–25 mg/l. A further increase in the concentration caused photosynthesis suppression, slower growth of the vegetation organs, and their subsequent necrosis. Water parsnip is more resistant to the toxicants.