Sorption of cadmium(II) and copper(II) by soil humic acids: temperature effects and sorption heterogeneity

Sorption by humic acids is known to modify the bioavailability and toxicity of metals in soils and aquatic systems. The sorption of cadmium(II) and copper(II) to two soil humic acids was measured at pH 6.0 using ion-selective electrode potentiometric titration at different temperatures. Sorption reactions were studied with all components in aqueous solution, or with the humates in suspension. Adsorption reactions were described using a multiple site-binding model, and a model assuming a continuous log-normal distribution of adsorption constants. Adsorption of Cu²⁺ was more favourable than adsorption of Cd²⁺. The log-normal distribution model provided the closest fit to observations and allowed parameterisation of adsorption data using a mean adsorption constant (log K _μ). Sorption of Cd²⁺ to dissolved humic acids increased slightly in extent and sorption affinity with increasing temperature, but the effect was small (log K _μ 2.96–3.15). A slightly greater temperature effect occurred for sorption of Cd²⁺ to solid-phase humic acids (log K _μ 1.30–2.08). Sorption of copper(II) to both aqueous- and colloidal-phase humates showed more pronounced temperature dependence, with extent of sorption, and sorption affinity, increasing with increasing temperature (log K _μ 3.4–4.9 in solution and 1.4–4.5 in suspension). The weaker adsorption of Cd²⁺ than Cu²⁺, and smaller temperature effects for dissolved humates than suspended humates, suggested that the observed temperature effects had a kinetic, rather than thermodynamic, origin. For any metal-to-ligand ratio, free metal ion concentration, and by inference metal bioavailability, decreased with increasing temperature. The consistency of the data with kinetic rather than thermodynamic control of metal bioavailability suggests that equilibrium modelling approaches to estimating bioavailability may be insufficient.     

Biosorption of chromium(VI), nickel(II) and copper(II) ions from aqueous solutions using Pithophora algae

The biosorption of heavy metals is considered to be one of the best alternatives for the treatment of wastewater. The metal binding capacity of algae and acid-treated algae is investigated to find out the removal characteristics of Cr(VI), Ni(II) and Cu(II) ions from single metal solutions. Batch experiments are conducted and the study is extended to investigate the effect of pH, amount of adsorbent and adsorbate concentration on the extent of biosorption. The results indicate that the adsorption capacity of algae depends strongly on pH. The maximum adsorption of Cr(VI), Ni(II) and Cu(II) occurs at pH values of 2, 7 and 4.3, respectively. The adsorption process follows first-order kinetic equation. The data obtained are correlated with Freundlich and Langmuir adsorption isotherms.     

Suitability of various chemically prepared activated carbons for the removal of copper(II) ions

Studies on the suitability of various chemically prepared activated carbons (CPACs) like straw carbon (SC), sawdust carbon (SDC), dates nut carbon (DNC) and commercial activated carbon (CAC) for the removal of copper(II) ions by adsorption from simulated wastewater have been carried out under batch mode at 30?±?1°C and the results are compared. The percentage removal of Cu(II) ions increased with a decrease in initial concentration, particle size and added electrolytes (ionic strength) and increased with an increase in contact time, dose of adsorbent and initial pH of the solution. The adsorption data were fitted with the Langmuir isotherm. The applicability of the first order kinetic equation viz. Lagergren equation was tested by correlation analysis. The adsorption process is concluded to be a spontaneous, first order reaction, occurring with increased randomness at the solid–liquid interface. Studies on the desorption of Cu²⁺-loaded activated carbons (ACs) were carried out with nitric acid (0.2–1?N). The possibility of reuse of the regenerated ACs in cycle (in cue-one after another) was tested. SC was found to be a suitable adsorbent alternative to CAC among CPACs for the removal of metal ions, in general, and Cu²⁺ ions, in particular.     

Voltammetric studies of damages in DNA by mutagenic and carcinogenic alkylating chemicals

Voltammetry provides new insights into the effects exerted in vitro by methylation of native DNA. Applying single sweep voltammetry at a stationary mercury electrode the successive steps of the destabilization of alkylated DNA are investigated. The methylation of the nucleic acids is manifested by a specific electrochemical response, due to the 7‐methylguanine, a major product of the methylation of DNA. Short time effects of the methylation include the labilization of 4 to 5 base pairs per methylated guanine base. Furthermore, uncommon protonation properties of the base 7‐methylguanine‐cytosine have been detected. Long term effects of the methylation are ultimately spontaneous hydrolytic strand breaks induced by the prior depurination connected with the release of the 7‐methylguanine from the methylated DNA. A half time t_1/2 of 102 h for the depurination at 37°C has been determined. The depurination and the subsequent strand breaks alter the hydrodynamic properties of the damaged DNA, an effect which can be sensitively followed with voltammetry via the resulting changes in the diffusion coefficient of the damaged biopolymer.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. II. Uptake and elimination from64Cu-labelled diatoms and water

The amount of copper taken up via algae and water byMacoma balthica from the Oosterschelde sea arm, S.W. Netherlands, was established using the radioisotope⁶⁴Cu. As far as we know, this isotope has never been used before in marine flod chain studies. As a model food source the marine diatomPhaeodactylum tricornutum was allowed to accumulate⁶⁴Cu for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27mM). EDTA was added to prevent uptake of dissolved⁶⁴Cu that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed toM. balthica in the presence of dissolved⁶⁴Cu (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake byM. balthica.     

Uptake of 137Cs in cultured fresh water fish (Cyprinus carpio): Physiological and histological effects

An experiment was conducted in fresh‐water fish (Cyprinus carpio) cultured, in small water tanks, artificially contaminated with radioactive ¹³⁷Cs (3000 Bq/1) to determine the uptake of ¹³⁷Cs and its physiological and histological effects in different fish organs.

It was found that ¹³⁷Cs was located in muscular tissues, gills, head muscles, liver and kidneys. Moderate amounts were found in spleen, eyes, gonads, intestine and urinary bladder. It seems that sorption was of much less importance than ingestion in the uptake of ¹³⁷Cs. The histological examination in musculature tissue, revealed an acute hyperemia with focal hemorrages which may be due to allergic effects of ¹³⁷Cs. Hyperemia and focal fatty degeneration of hepatic cells was also noted in the liver which may be due to toxic effects of ¹³⁷Cs diffused hyperemia has also occurred in the brain and focal degeneration of epithelial cells of renal tubules.     

Fecundity of the freshwater fish, Notopterus notopterus (Pallas) in natural and heavy metal contaminated water

The knowledge of fecundity of fish from a specific aquatic body is extremely important in the successful management and exploitation of its fishery. In the present investigation the fecundity of the freshwater fish, Notopterus notopterus was studied in fish collected from a natural aquatic body (Sirnoor nala) near Gulbarga and also in fish exposed to some heavy metal contamination (HgCl2, CdCl2 and their combination) at sublethal concentration for 15 days in the laboratory. The mathematical relationship between fecundity and total length, body weight, ovary length and ovary weight were determined in both unexposed and exposed fish. The fish, N. notopterus has bigger oocytes and are few in number. Studies in the fish exposed to heavy metals indicate that significant reduction in these parameters after exposure to heavy metals at sublethal concentration was noticed. The fecundity has straight line relationship with total length, body weight, ovary length and ovary weight in control fish which did not alter after heavy metal exposure. This study provides the viability of species in only specific environment.     

Copper (II) adsorption studies using models of synthetic humic acids

A polymer with characteristics similar to those of humic acids was obtained by synthesis reactions from oxidative polymerization in an alkaline medium using para-benzoquinone, hydroquinone and 4-aminobenzoic acid as precursors. Samples of natural and synthetic humic acid were used to examine the adsorption behavior of Cu²⁺ ions on these substrates. The mathematical models described by Langmuir and Freundlich equations were applied, yielding the maximum adsorption intensity values K′ (Langmuir), maximum adsorption capacity, b (Langmuir) and the adsorbent adsorption capacity, m (Freundlich). Based on solubility studies, pH 3 was selected for the development of the adsorption experiment. The Cu²⁺ ion presented a favorable adsorption, with RL (equilibrium parameter) responses in Langmuir isotherms falling within the desirable ranges.     

Chemometrical classification of biomonitoring analytical data for heavy metals part I. trees (leaves) as bioindicators

The application of tree species (leaves) as biomonitoring devices is studies by the use of cluster analysis. It is shown that the chemical analysis of leaf samples should be accompanied by a careful chemometrical data treatment in order to obtain a reliable information on the behaviour of various tree species to heavy metal exposure (8 trees for three heavy metals in twelve different places) in fall and spring season. Additionally, the distribution of the sampling sites is studied by the same approach and a commentary on the urban aspects of sampling is given.     

Impact of Ni(II), Zn(II) and Cd(II) on biogassification of potato waste

A study was conducted on anaerobic digestion of potato waste and cattle manure mixture, inoculated with 12% inoculum and diluted to 1:1 substrate water ratio at 37 +/- 1 degrees C. Initially pH of substrate was found to be 4.5 to 5.0. Lime and sodium bicarbonate solutions were employed to adjust the pH to 7.5. Biogas production continued up to 10 and 7 days, when lime and sodium bicarbonate solutions were used to adjust the pH, respectively. Biogassification potential was studied in response to different ratio of waste and cattle manure. Biogas production rate was higher when potato waste and cattle manure were used in 50:50 ratio. Effect of two different concentrations (2.5 and 5.0 ppm) of three heavy metals viz. (Ni (II), Zn (II) and Cd (II)) on anaerobic digestion of substrate (potato waste--cattle manure, 50:50) was studied. At 2.5 ppm, all the three heavy metals increased biogas production rate over the control value. The percentage increase in biogas production over the control was highest by Cd, followed by Ni and Zn. In all the treatments, methane content of biogas increased with increase in time after feeding. Various physico-chemical parameters viz. total solids, total volatile solids, total organic carbon and chemical oxygen demand considerably declined after 7 days of digestion and decline was greater in presence of heavy metals as compared to control. The physico-chemical parameters revealed maximum decrease in the presence of 2.5-ppm concentrations of heavy metals with the substrate. Among all the three heavy metals employed in the study, Cd++ at 2.5 ppm was found to produce maximum biogas production rate. The use of three heavy metals to enhance biogas production from potato and other horticultural waste is discussed.     

The potential of spatial information in human biomonitoring by example of two German environmental epidemiology studies

This study aimed at statistically investigating the association between the internal exposure of children and young adults to uranium (U) and epidemiologically relevant external determinants of exposure. The investigation was performed with data from two studies within the framework of the German health-related environmental monitoring program: The German Environmental Survey for Children (GerES IV) conducted by the Federal Environment Agency (Umweltbundesamt) with data on 1,780 children 3–14 years of age and their home environment and the German Environmental Specimen Bank (ESB, section: human specimens) with data on 2,253 students 20–29 years of age. Both studies provided data on the U levels in human urine for all probands. GerES IV furthermore provided an extensive environmental and demographic database on, e.g., U levels in drinking water. The data from GerES IV and ESB were linked by GIS to spatially relevant exposure information, including background values of U in stream sediments and in upper and lower soils, U levels in mosses and particulate matter in the lower atmosphere, precipitation and elevation as well as forest density. Bivariate correlation analysis and two decision tree models showed moderate but significant associations between U in human urine and U levels in drinking water, stream sediments and upper and lower soils. Future investigations considering additional epidemiologically relevant data sets may differentiate the results. Furthermore, the sample design of future environmental epidemiology studies should take the spatial evaluation of the data into greater account.     

A preliminary report on effect of pulsed magnetic fields on fresh water fish (Labeo rohita) chromosomes

Marine-life scientists around the world are already carrying out investigative trials to obtain higher yields under in-captive breeding conditions, on both edible varieties and ornamental fishes with optimal inputs. However, for such trials to succeed there is a need for genetic improvement. The idea that fish production can be enhanced by genetic manipulation is gaining acceptance, as there is a strong possibility that qualitative improvement of economically important traits can be achieved by identifying and utilizing more effective genotypes. In the present communication a tentative plan for genetic manipulation of fresh water fish using controlled, pulsed magnetic fields, is being discussed. Chromosome preparations of Labeo rohita were made using Colchicine-Methanol-Acetic acid air drying technique, using tissue from gills. The fish were exposed to Pulsed Magnetic Field (PMF)with intensity 0.2 Gauss, pulsing at 50 Hz frequency (sine wave) for 6 hours / day for a total period of 30 days inside specially designed magnetic field enclosures. The karyological investigations revealed no distinct difference between "test" and "control" groups.     

Imprinted polymer particles for preconcentration of copper from water and biological samples

Imprinted polymer particles have been developed as a novel adsorbent for the adsorption of copper from aqueous solution. This method has received much attention in various fields because of their high selectivity for template molecules. In this work, separation of copper from water and biological samples by batch solid phase extraction based on molecular imprinting technique is presented. Copper-imprinted polymer was prepared by free radical solution polymerization in a glass tube containing CuSO₄, morin, 4-vinylpyridine as a functional monomer, ethyleneglycoldimethacrylate as a cross-linking monomer, 2,2′- azobisisobutyronitrile as an initiator. The polymer block obtained was ground and sieved, and the Cu-morin complex was removed from polymer particles. The synthesized polymer particles both prior to and after leaching have been characterized by IR and X-ray diffraction studies. The effect of different parameters, such as pH, adsorption and desorption time, type and least amount of the eluent for elution of the complex from polymer were evaluated. The limit of detection of the proposed method was 0.12 μg L⁻¹. The method was applied to the recovery and determination of copper in water and biological real samples.     

Manganese in natural waters II. Evidence for microbiological oxidation of Mn (II)

The oxidation of Mn(II) to Mn(IV) in natural waters has been investigated. Various hypotheses have been put forward for the mechanism of oxidation of Mn(II) of which only biological oxidation was found to occur in the aquatic system studied. The effect of adsorption, usually associated with the oxidation of Mn(II) was not observed in our study. The oxidation kinetics can be divided into three periods. The first period is the induction time corresponding to the growth of microorganisms that act as oxidising agents for Mn² _aq ⁺. During this stage Mn² _aq ⁺ remains constant. This period is followed by a decrease in Mn² _aq ⁺ concentration following zero order rate law. Finally in the third period the decrease in Mn² _aq ⁺ follows a first order rate law. The microorganisms acting as oxidising agents for Mn(II) have been identified to be filamentous Gallionella type bacteria and Leptothrix discophora.     

Deposition of copper nanoparticles on multiwalled carbon nanotubes modified with poly (acrylic acid) and their antimicrobial application in water treatment

A novel hybrid material, Cu-PAA/MWCNTs (copper nanoparticles deposited multiwalled carbon nanotubes with poly (acrylic acid) as dispersant, was prepared and expected to obtain a more effective and well-dispersed disinfection material for water treatment. X-ray energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), the X-ray fluorescence (XRF), X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FT-IR), Raman spectroscopy, and thermal gravimetric analyzer (TGA) were used to characterize the Cu-PAA/MWCNTs. Escherichia coli (E. coil) was employed as the target bacteria. The cell viability determination and fluorescence imaging results demonstrated that Cu-PAA/MWCNTs possessed strong antimicrobial ability on E. coil. The deposited Cu was suggested to play an important role in the antimicrobial action of Cu-PAA/MWCNTs.     

Comparative adsorption of Pb(II) and Cd(II) ions on chestnut shell in aqueous system

In this study, high capacity Chestnut shell, a waste product from the chestnut sugar production industry, was successfully applied to remove Pb (II) and Cd (II) ions from aqueous solutions. Maximum adsorption capacities were found as 541.25?mg/g and 75.86?mg/g for Pb(II), and Cd(II) respectively. Several important parameters influencing the adsorption of Pb(II) and Cd(II) ions such as contact time, pH, temperature and effect of metal concentration were investigated systematically by batch experiments. Langmuir and Freundlich adsorption models were used to describe adsorption isotherms and constants. The thermodynamic parameters, such as standard free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°), of the adsorption process were calculated. The adsorbents were characterised by scanning electron microscopy. It has been observed from the experimental results that in case of both Cd (II) and Pb (II), pseudo 2nd order kinetic model. From the results, Chestnut Shell are considered as an effective, low cost and environmental friendly adsorbent for the removal of Pb (II) and Cd (II) from wastewater.     

Microbial associations in sponges. II. Numerical analysis of sponge and water bacterial populations

Three taxonomically distant sponges Pericharax heteroraphis, Jaspis stellifera and Neofibularia irata contain phenotypically similar bacterial symbionts which differ from bacteria in the ambient water. These symbionts are predominant in the sponges and were detected after computer analysis of 526 heterotrophic bacterial strains tested for 76 characters. These facultative anaerobic symbionts metabolize a wide range of compounds and may be important in removing waste products while the sponges are not circulating water. The bacteria produce sticky-mucoid colonies and thus would contribute to sponge structural rigidity. The fourth sponge Ircinia wistarii contains a mixed aerobic population similar to that in the ambient water. The majority of the bacteria are located around the inhalant canals, facilitating the uptake of dissolved organic matter and oxygen from the incoming water.     

Inbreeding avoidance in a poeciliid fish (Heterandria formosa)

Polyandry is hypothesized to give females an opportunity to avoid inbreeding through postcopulatory selection mechanisms if precopulatory inbreeding avoidance is not possible, for example, because of forced matings. Here, we report a postcopulatory, prefertilization, inbreeding avoidance mechanism in the least killifish, Heterandria formosa, a species in which males can force matings. Females had 50% less sperm in their oviducts and ovarian cavities after mating with a sibling compared to a mating with a nonsibling male. Neither sex showed inbreeding avoidance in a dichotomous precopulatory mate choice test or during mating trials. Females in this species invest substantially in each offspring after fertilization (matrotrophy), whereas males invest little more than sperm. Based on theory, females should therefore be more likely than males to avoid inbreeding in this species. We suggest that females do this by reducing the amount of sibling sperm in their reproductive system. However, the possibility that males invested more sperm to nonsiblings could not be ruled out. In a fertilization success experiment, the first male to mate with a female sired all the offspring in most cases, even if it was a sibling. However, large females were more likely to carry offspring of multiple males. Possibly female sperm storage sites were filled by the first male, and only large females had space for the second male's sperm.     

Solid phase extraction of Cu (II), Ni (II), Co (II), and Fe (III) ions in water samples using salicylaldehyde benzoylhydrazone on Amberlite XAD-4 and their determinations by flame atomic absorption spectrometry

A multi element preconcentration procedure for solid phase extraction on Amberlite XAD-4 as their salicylaldehyde benzoylhydrazone chelates and flame atomic absorption spectrometric determination of some trace metal ions in water samples are proposed in this work. The influences of some analytical parameters, including pH of aqueous solution, amounts of reagent, flow rates of sample and eluent solutions, and sample volume on the quantitative recoveries of copper, nickel, cobalt, and iron were investigated. The effects of concomitant ions on the retentions of the analytes were also examined. The developed method has been successfully applied to the determination of metal ions in some real samples, including, tap water, river water, spring water, and waste water.     

Imposex in Hexaplex trunculus (Gastropoda: Muricidae): first results from biomonitoring of tributyltin contamination in the Mediterranean

Imposex (the occurrence of penis and vas deferens in females) in Hexaplex trunculus collected from Malta (Central Mediterranean) in 1992 is reported. This phenomenon is related to the levels of tributyltin (TBT) in the organisms as well as in sediments. Imposex indices (relative penis size and vas deferens sequence) are used to biomonitor coastal contamination by TBT for the first time in the Mediterranean. In its response to TBT, H. trunculus is ranked as one of the most sensitive neogastropod species studied so far. Accumulation of TBT and its metabolites in the digestive glands, gonads and the rest of the body are described, and sex-related differences are shown. No preferential female mortalities are recorded in populations exposed to high levels of TBT. However, a reported shift in the size frequency distribution of H. trunculus in contaminated sites, towards bigger snails, may suggest reduced reproductive potential.