Home About us Contact
|
Home About us Contact | ||
|
|
||
Mg L (mg + l)
Selected AbstractsBiological treatment of textile dye Acid violet-17 by bacterial consortium in an up-flow immobilized cell bioreactorLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2004D.K. Sharma Abstract Aims:, To develop a cost effective and efficient biological treatment process for small scale textile processing industries (TPI) releasing untreated effluents containing intense coloured Acid violet-17 (AV-17), a triphenyl methane (TPM) group textile dye. Methods and Results:, The samples collected from effluent disposal sites of TPI were used for selective enrichment of microbial populations capable of degrading/decolourizing AV-17. A consortium of five bacterial isolates was used to develop an up-flow immobilized cell bioreactor for treatment of feed containing AV-17. The bioreactor, operating at a flow rate of 6 ml h,1, resulted in 91% decolourization of 30 mg AV-17/l with 94·3 and 95·7% removal of biochemical oxygen demand and chemical oxygen demand of the feed. Comparison of the input and output of the bioreactor by UV-visible, thin layer chromatography and 1H-nuclear magnetic resonance spectroscopy indicates conversion of the parent dye into unrelated metabolic intermediates. Significance:, These results will form a basis for developing ,on-site' treatment system for TPI effluents to achieve decolourization and degradation of residual dyes. [source] Organic carbon and nitrogen removal in anoxic/oxic-membrane bioreactor treating high-strength wastewaterENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009Zhimin Fu Abstract The performance of an anoxic/oxic membrane bioreactor system for the simultaneous removal of nitrogen and chemical oxygen demand (COD) was investigated. This process removed up to 87% of total nitrogen (TN) and 94% of COD, with the influent concentrations of 200 mg NH4+ -N/L and 4000 mg COD/L and a recycle ratio (R) of 200%. Biological assimilation and simultaneous nitrification and denitrification (SND) were considered on nitrogen removal process. The TN removal efficiency was above 87.5%, while the nitrogen being removed through SND was above 75.5% and nitrogen assimilated into the biomass was below 24.5%, with influent concentration below 200 mg NH4+ -N/L. Increasing the influent concentration to 400 mg NH4+ -N/L, TN removal efficiency decreased significantly to 37.5%, of which 49.5% was provided by microorganism growth. Batch experiments provided evidence for the phenomena of SND. Furthermore, the SND removal efficiency increased gradually from 26.8 to 90.0%. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Phenotypical variation in a toxic strain of the phytoplankter, Cylindrospermopsis raciborskii (nostocales, cyanophyceae) during batch cultureENVIRONMENTAL TOXICOLOGY, Issue 6 2001Peter R. Hawkins Abstract A nonaxenic strain of Cylindrospermopsis raciborskii Woloszynska (AWT 205) was grown in batch culture, with and without nitrate as the primary N source. Rapid log-phase growth with nitrate was 1.0 doubling/day versus 0.3 doubling/day without nitrate. Cylindrospermopsin (CYN) production was measured by HPLC. The rate of intracellular CYN production matched cell division rate for both the diazotrophies at cell densities less than 107 cell/ml. At cell density >107 cell/ml, additional resource limitation in batch culture slowed log-phase growth to 0.04 division/day and cell division and CYN production decoupled. Intracellular CYN concentration increased at a rate of 0.08 doubling/day, twice the cell division rate. Extracellular CYN as a proportion of the total CYN increased from 20% during the rapid growth phase, to 50% during the slow growth phase. The total CYN yield from cultures grown out to stationary phase (55 days) exceeded 2 mg CYN/l. C. raciborskii cells in log-phase growth, exposed to 1 ppm copper (as copper sulphate), lysed within 24 hours. After copper treatment, all CYN was in the filterable fraction. These findings imply that in naturally occurring blooms of C. raciborskii, the movement of intracellular CYN into solution will be the greatest during stationary phase, when intracellular concentrations are highest and cell lysis is more frequent. The application of algicides that promote cell lysis will exacerbate this effect. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 460,467, 2001 [source] Influence of water chemistry on the acute toxicity of copper and zinc to the cladoceran Ceriodaphnia cf dubiaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005Ross V. Hyne Abstract This study determined the influence of key water chemistry parameters (pH, alkalinity, dissolved organic carbon [DOC], and hardness) on the aqueous speciation of copper and zinc and its relationship to the acute toxicity of these metals to the cladoceran Ceriodaphnia cf dubia. Immobilization tests were performed for 48-h in synthetic or natural waters buffered at various pH values from 5.5 to 8.4 (other chemical parameters held constant). The toxicity of copper to C. cf dubia decreased fivefold with increasing pH, whereas the toxicity of zinc increased fivefold with increasing pH. The effect of DOC on copper and zinc toxicity to C. cf dubia was determined using natural fulvic acid in the synthetic water. Increasing DOC was found to decrease linearly the toxicity of copper, with the mean effect concentration of copper that immobilized 50% of the cladocerans (EC50) value 45 times higher at 10 mg/L, relative to 0.1 mg/L DOC at pH 6.5. In contrast, the addition of 10 mg/L DOC only resulted in a very small (1.3-fold) reduction in the toxicity of zinc to C. cf dubia. Copper toxicity to C. cf dubia generally did not vary as a function of hardness, whereas zinc toxicity was reduced by a factor of only two, with an increase in water hardness from 44 to 374 mg CaCO3/L. Increasing bicarbonate alkalinity of synthetic waters (30,125 mg/L as CaCO3) decreased the toxicity of copper up to fivefold, which mainly could be attributed to the formation of copper-carbonate complexes, in addition to a pH effect. The toxicity of copper added to a range of natural waters with varying DOC content, pH, and hardness was consistent with the toxicity predicted using the data obtained from the synthetic waters. [source] Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryosENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001Christine M. Guadagnolo Abstract Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl,, 1.3 mg/L dissolved organic matter, 12.3 ± 0.1 °C) at nominal concentrations of 0.1, 1, and 10 ,g/L (measured = 0.117 ± 0.008, 1.22 ± 0.16, and 13.51 ± 1.58 ,g/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 ,g/L) were not significantly different from controls throughout embryonic development (days 1,32 postfertilization). Mortalities of embryos in the 13.5-,g/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-,g/L treatments reached the highest concentrations of 0.13 and 0.24 ,g/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-,g/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout. [source] Copper toxicity thresholds for important restoration grass species of the western United States,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2002Mark W. Abstract Copper toxicity thresholds for plant species that are used in restoration activities in western North America have not been established. As a result, ecological risk assessments must rely on toxicity thresholds established for agronomic species, which usually differ from those of species used in restoration. Thus, risk assessors have the potential for classifying sites as phytotoxic to perennial, nonagronomic species and calling for intensive remediation activities that may not be necessary. The objective of this study was to provide a better estimate of Cu toxicity thresholds for five grass species that are commonly used in restoration efforts in the western United States. We used a greenhouse screening study where seedlings of introduced redtop (Agrostis gigantea Roth.), the native species slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners var. Pryor), tufted hairgrass (Deschampsia caespitosa [L.] Beauvois), big bluegrass (Poa secunda J. Presl var. Sherman), and basin wildrye (Leymus cinereus [Scribner&Merrill] A. Löve var. Magnar) and the agricultural species common wheat (Triticum aestivum L.) were grown in sand culture and exposed to supplemental concentrations of soluble Cu of 0 (control), 50, 100, 150, 200, 250, and 300 mg/L. We determined six measures of toxicity: the 60-d mean lethal concentration (LC50), 60-d mean effective concentration (EC50)-plant, 60-d EC50-shoot, 60-d EC50-root, phytotoxicity threshold (PT50)-shoot, and the PT50-root. Results suggest that these restoration grass species generally have higher Cu tolerance than agronomic species reported in the past. Of the species tested, redtop appeared to be especially tolerant of high levels of substrate and tissue Cu. Values of EC50-plant for restoration grasses were between 283 and 710 mg Cu/L compared to 120 mg Cu/L for common wheat. Measured PT50-shoot values were between 737 and 10,792 mg Cu/ L. These reported thresholds should be more useful for risk assessors than those currently used, which are based largely on agronomic crops. [source] Copper Concentrations in Channel Catfish Ictalurus punctatus Ponds Treated with Copper SulfateJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2004Aaron A. McNevin Copper sulfate (CuSO45H2O) is used to reduce the abundance of blue-green algae and combat off-flavor in channel catfish culture. Copper sulfate usually is applied at a concentration of one-one hundredth of the total alkalinity. A study was performed at the Auburn University Fisheries Research Unit to determine the duration of elevated copper (Cu) concentration following copper sulfate applications. Two alkalinity treatments, 20-40 mg/L and 110-130 mg/L (as CaCO3), were examined. Copper sulfate was applied biweekly for 14 wk at 03 mg/L for the low alkalinity treatment and 1.2 mg/L for the high alkalinity treatment. Total copper concentrations in pond waters declined to the background level by 48-h post treatment. In addition, total copper concentrations were determined in waters of 38 catfish production ponds located in west central Alabama. The mean and standard deviation were 0.0092 ± 0.0087 mg Cu/L. Copper quickly precipitates from the water or is absorbed by sediments following copper sulfate treatment. Although concentrations of copper in pond waters increase immediately following copper sulfate treatment, they rapidly decrease and seldom exceed the United States Environmental Protection Agency's National Recommended Water Quality Criteria for Priority Toxic Pollutants of 0.013-mg Cu/L. Findings of this study suggest that copper sulfate treatment will not contaminate effluent from catfish ponds because of the short time that applied copper remains in the water column. Furthermore, the most frequent applications of copper sulfate occur in late summer months when rainfall is minimal and pond overflow is rare. [source] Assessment of tracheal temperature and humidity in laryngectomized individuals and the influence of a heat and moisture exchanger on tracheal climateHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 8 2008J. Karel Zuur MD Abstract Background The beneficial function of heat and moisture exchangers (HMEs) is undisputed, but knowledge of their effects on intra-airway temperature and humidity is scarce. The aim of this study was to evaluate the clinical applicability of a new airway climate explorer (ACE) and to assess the HME's influence on tracheal climate. Methods Intratracheal temperature and humidity were measured with and without HME in 10 laryngectomized patients. Results An HME causes the intratracheal mean humidity minima to increase with 3.2 mg H2O/L (95% CI: 1.5,4.8 mg H2O/L; p <.001), from 21.4 to 24.6 mg H2O/L, and the mean temperature minima to decrease with 1.6°C (95% CI: 0.9,2.4°C; p <.001) from 28.5°C to 26.9°C. Relative humidity values suggest that the tested HME keeps inspired air (nearly) fully saturated during the full course of inspiration. Conclusion Assessment of intratracheal temperature and humidity, and evaluation of HME effectiveness is feasible with the ACE. The tested HME significantly increases the intratracheal humidity, but decreases the intratracheal temperature. Relative humidity calculations suggest that increasing the thermal capacity of this rehabilitation device can further increase the heat and moisture exchange efficiency. © 2008 Wiley Periodicals, Inc. Head Neck, 2008 [source] Electroanalytical Determination of Cadmium(II) and Lead(II) Using an Antimony Nanoparticle Modified Boron-Doped Diamond ElectrodeELECTROANALYSIS, Issue 10 2009Kathryn Abstract We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by linear sweep anodic stripping voltammetry (LSASV) using an antimony nanoparticle modified boron doped diamond (Sb-BDD) electrode. Sb deposition was performed in situ with the analytes, from a solution of 1,mg L,1 SbCl3 in 0.1,M HCl (pH,1). Pb2+ inhibited the detection of Cd2+ during simultaneous additions at the bare BDD electrode, whereas in the presence of antimony, both peaks were readily discernable and quantifiable over the linear range 50,500,,g L,1. [source] Adsorptive Stripping Voltammetric Detection of Tea Polyphenols at Multiwalled Carbon Nanotubes-Chitosan Composite ElectrodeELECTROANALYSIS, Issue 6 2009Deyin Guo Abstract This study reports the catalytic oxidation and detection of tea polyphenols (TPs) at glassy-carbon electrode modified with multiwalled carbon nanotubes-chitosan (MWCNTs-CS) film. The adsorption of TPs at the surface of the MWCNTs through ,,, conjugation prevents the aggregation of nanotubes and induces a stable MWCNTs suspension in water over 30 days. Based on the adsorptive accumulation of polyphenols at MWCNTs, TPs is sensitively and selectively detected by adsorptive stripping voltammetry. The accumulation conditions and pH effect on the adsorptive stripping detection were examined. The linear range was found to be 100 to 1000,mg L,1 with a detection limit of 10,mg L,1 (S/N=3) for 2.5,min accumulation. Additionally, the MWCNTs-CS electrode is easily renewed by applying positive potential to remove the adsorbed TPs. This method was successfully applied to determine TPs in commercially available teas with satisfied result compared with that of conventional spectrometric analysis. [source] Simultaneous Determination of Quinoline and Pyridine Compounds in Gasoline and Diesel by Differential Pulse VoltammetryELECTROANALYSIS, Issue 6 2007Leonardo Abstract The presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion,exchange resin (Amberlyte IR,120,H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion-controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF4 0.1,mol L,1) for quinoline (,1.95,V) and pyridine (,2.52,V) vs. Ag|AgCl|KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300,mg L,1 and a limit of detection (LOD) of 5.05 and 0.25,,g L,1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0±0.3 and 33.0±0.7,mg L,1 and in diesel samples yielded 80.3±0.2 and 131±0.4,mg L,1, respectively. Spike recoveries were 94.4±0.3% and 101±0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV-vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests. [source] FIA Determination of Paracetamol in Pharmaceutical Drugs by Using Gold Electrodes Modified with a 3-Mercaptopropionic Acid MonolayerELECTROANALYSIS, Issue 9 2006Valber Abstract A flow injection analysis (FIA) method for the determination of paracetamol in pharmaceutical drugs using a gold electrode modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid is described. At optimized experimental conditions the dynamic concentration range was 0.15 to 15.0,mg L,1 with a detection limit of 0.2,,g mL,1 (S/N=3). The repeatability of current responses for injections of 10,,mol L,1 paracetamol was evaluated to be 3.2% (n=30) and the analytical frequency was 180,h,1. The lifetime of the modified electrode was found to be 15 days. The results obtained by using the proposed amperometric method for paracetamol determination in four different drug samples compared well with those found by spectrophotometry. [source] Voltammetric Determination of Phenylglyoxylic Acid in Urine Using Graphite Composite ElectrodeELECTROANALYSIS, Issue 2 2006Navrįtil Abstract A composite electrode prepared from graphite powder and epoxy resin was applied as a working electrode for the determination of phenylglyoxylic acid (one of the metabolites of styrene) in human urine. Cathodic differential pulse stripping voltammetry was used and optimum conditions have been found giving the limit of determination about 5,mg L,1. All results were compared with those obtained using hanging mercury drop electrode. For the confirmation of suggested mechanism of the electrochemical reaction the elimination voltammetry with linear scan was used. [source] Study of the Responses of a Sonogel-Carbon Electrode Towards Phenolic CompoundsELECTROANALYSIS, Issue 9 2005Cordero-Rando, Ma del Abstract The electrochemical behavior of a sonogel-carbon electrode towards nine phenolic compounds (chloro-, nitro- and alkyl-phenols) was studied; one of them (4-chloro-3-methylphenol) was used to evaluate characteristics of the electrode, such as accumulation and cleaning procedure of the electrode surface, reproducibility of the measurements, and influence of time from fabrication on electrochemical response. A polyethyleneglycol-modified sonogel-carbon electrode was found to improve the electrochemical response towards the analyte. A linear relationship between peak height and concentration in the range 0.005,0.5,mg L,1 was obtained, with a detection limit of 2.8,,g L,1. The studies of electrochemical parameters, as well as interferences, are also included. [source] A new morphospecies of Microcystis sp. forming bloom in the Cheffia dam (Algeria): Seasonal variation of microcystin concentrations in raw water and their removal in a full-scale treatment plantENVIRONMENTAL TOXICOLOGY, Issue 4 2007Hichčm Nasri Abstract Toxic cyanobacterial blooms are an increasing problem in Algeria. The production of cyanotoxins (microcystins) and their presence in drinking water represent growing hazards to human health. In this study, seasonal variations in the concentrations of total microcystins and physicochemical parameters (pH, temperature, dissolved oxygen, nitrate, orthophosphate, and chlorophyll- a) were analyzed in the Cheffia dam (Algeria), mainly used to supply drinking water. The removal of cyanobacterial cells and microcystins was also evaluated in full-scale plant associated with the Cheffia reservoir. The levels of microcystins (MCYSTs) in both raw and drinking water were evaluated using the protein phosphatase type 2A (PP2A) inhibition test as MCYST-LR equivalents. Identification of microcystin variants was achieved by LC/MS/MS. During the period of study (March,December 2004), microscopic observation showed the dominance in the autumn months (September,November) of a new morphospecies of Microcystis sp. The MCYST-LR equivalent concentrations in raw water varied between 50.8 and 28,886 ng L,1. The highest level of toxins was observed in October 2004 and was significantly correlated with the chlorophyll- a. Three variants of microcystins assigned as microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR), and 6Z -Adda stereoisomer of MCYST-LR were observed in the crude extract of the Microcystis sp. bloom sample. During the bloom period, total elimination of Microcystis sp. and toxins were achieved through a classical treatment plant comprised of coagulation and flocculation, powdered activated carbon at 15 mg L,1, slow sand filtration and chlorination before storage. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 347,356, 2007. [source] Phosphate regulates uranium(VI) toxicity to Lemna gibba L. G3ENVIRONMENTAL TOXICOLOGY, Issue 1 2007Martin Mkandawire Abstract The influence of phosphate on the toxicity of uranium to Lemna gibba G3 was tested in semicontinuous culture with synthetic mine water developed as an analogue of surface water of two abandoned uranium mining and ore processing sites in Saxony, Germany. Six concentrations of uranium were investigated under five different supply regimes of PO43, at constant pH (7.0 ± 0.5) and alkalinity (7.0 ± 1.6 mg L,1 total CO32,). The results showed significant inhibition of specific growth rates in cultures exposed to the highest uranium concentrations (3500 and 7000 ,g U L,1) at lowest PO43, supply of 0.01 mg L,1. An increase of phosphate concentration from 0.01 to 8.0 mg L,1 resulted in an increase of EC50 from 0.9 ± 0.2 to 7.4 ± 1.9 mg L,1 (significant with Student's t test, P > 0.05). The accumulation of uranium in L. gibba increased exponentially with the increase in uranium concentration in cultures with 0.01 and 0.14 mg PO43, L,1. Accumulation also increased significantly when PO43, supply was increased from 0.14 to 1.36 mg PO43, L,1 for all uranium concentrations. However, as the supply of PO43, gradually increased from 1.36 to 8.0 mg PO43, L,1, uranium bioaccumulation increased slightly but insignificantly before leveling off. Uranium speciation modeling with PhreeqC geochemical code predicted increases in the proportions of uranyl phosphate species when PO43, concentrations increase in the media. Most of these uranyl phosphate species have a high probability of precipitation [saturation indices (SI) > 0.93]. Therefore, the alleviation of uranium toxicity to L. gibba with phosphates is due to interactions among components of the media, mainly uranyl and phosphate which results in precipitation. Consequently, bioavailable fractions of uranium to L. gibba are reduced. This might explain lack of consistent EC50 values for uranium to most aquatic organisms. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 9,16, 2007. [source] First report of saxitoxin in Finnish lakes and possible associated effects on human healthENVIRONMENTAL TOXICOLOGY, Issue 3 2005Jarkko Rapala Abstract This study is the first report of saxitoxin in cyanobacterial blooms in Finland. Bloom samples (n = 50) were collected from Finnish freshwater sites during summer months of 2002 and 2003. These samples were screened for the presence of paralytic shellfish toxins (PSTs) using the Jellett rapid PSP screening test. Samples testing positive for PSTs (n = 7) were further analyzed with saxiphilin- and voltage-gated sodium channel [3H]-STX,binding radioreceptor assays and liquid chromatography using fluorescence and mass spectrometric analysis. The results indicated that saxitoxin (STX) was the only PST analogue in the samples and that it was present in high concentrations, as much as 1 mg L,1. Microscopic analysis revealed that 95%,100% of the phytoplankton in the positive samples consisted of Anabaena lemmermannii. The trophic status of lakes in which STX-containing blooms were found varied from oligotrophic to hypertrophic. All the lakes had high nitrogen-to-phosphorus ratios. In some instances, samples had been collected from sites where swimmers had reported adverse health effects, and in three such cases, reported adverse health effects were associated with sites from which samples testing positive for STX had been received. Symptoms of fever, eye irritation, abdominal pains, and skin rash were reported in children aged 2,10 years after exposure to the water. These were not the adverse human symptoms typical of STX poisoning; rather, they represented acute effects often reported following recreational exposure to cyanobacterial blooms. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 331,340, 2005 [source] Characteristics of microcystin production in the cell cycle of Microcystis viridisENVIRONMENTAL TOXICOLOGY, Issue 1 2004Keishi Kameyama Abstract The correlation between the content of three microcystins (types LR, RR and YR) and the cell cycle of an axenic strain of Microcystis viridis, NIES-102, was investigated under conditions of high (16 mg L,1) and low (1.0 mg L,1) nitrate (NO3 -N) concentrations. Each phase of the cell cycle was identified using a flow cytometer equipped with a 488-nm argon laser using SYTOX Green dye, which binds specifically to nucleic acids and can be exited by the wavelength (Ex/Em: 504/523 nm on DNA). Microcystin concentration showed a positive linear correlation with DNA concentration. The microcystin content of the cells changed remarkably as the cell cycle process proceeded, with maximum content in the G2/M phase and minimum content in the G0/G1 phase. Under a condition of high NO3 -N concentration, the ratio of the total content in the G0/G1 phase to that in the G2/M phase was about 6:1. In contrast, for the two batch cultures the total content was 1.3-fold greater in the G2/M phase. The compositions of the three microcystins also changed along with the cell cycle process, although there was little difference in composition that was related to NO3 -N concentration. Therefore, there were distinctive compositions specific to each phase of the cycle, and the cell cycle of the M. viridis strain was more strongly responsible for both the quantity and the types of microcystin production than was the effect of NO3 -N concentration. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 20,25, 2004. [source] Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailabilityENVIRONMENTAL TOXICOLOGY, Issue 1 2004Martin Mkandawire Abstract The toxicity of arsenic (As) species to Lemna gibba L. and the influence of PO on As bioavailability and uptake were tested in batch culture. L. gibba were exposed to six test concentrations of NaHAsO4 · 7H2O and NaAsO3, with 0, 0.0136, 13.6, and 40 mg L,1 KH2PO4. In batch culture As toxicity to L. gibba did not relate linearly to As concentration. The growth rate, related to frond number as recommended by OECD and ISO/DIN, was significantly inhibited in fronds exposed to 20,50 ,g L,1 As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50,250 ,g L,1 of both As(III) and As(V). After exposure to 300,800 ,g L,1 growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 ,g L,1 As(V) was inhibited the most. The bioaccumulation of As(III) and As(V) was significantly higher for P-deficient cultures (0.98 ± 0.08 and 1.02 ± 0.19 g kg,1, respectively for 0.0136 mg L,1 PO) than for P-sufficient cultures (243 and 343 mg kg,1 for 40 mg L,1, respectively). Plants exposed to As(V) had uptake and accumulation values slightly higher than did plants exposed to As(III). No significant differences in bioaccumulation were found between plants exposed to a concentration of As(III) >1 mg L,1 and those exposed to As(V) at the same concentration. This indicates a direct relationship to P content in the culture. Toxicity may result from the uptake of As(V) instead of PO as a result of ion competition during uptake because of close thermodynamic properties, which may change the interaction among components in the media. The toxicity pattern is interpreted as a manifestation of changing speciation in the batch culture and of the oxidation of As(III) to As(V) in an oxygen-rich environment. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 26,34, 2004. [source] A model predicting waterborne cadmium bioaccumulation in Gammarus pulex: The effects of dissolved organic ligands, calcium, and temperatureENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Bastien Pellet Abstract Metal bioavailability depends on the presence of organic ligands in the water and on the concentrations of competitive cations. The present study aims at testing whether the diffusive gradient in thin films technique (DGT) could be used to take into account Cd speciation and its consequences on bioavailability in a bioaccumulation model and whether the influences of the Ca concentration and temperature also should be considered. Four kinetic experiments were conducted on Gammarus pulex: a calibration of Cd turnover rates and of the DGT lability in mineral water, a study of the influence of ethylenediaminetetraacetic acid (EDTA) and humic acids (HA) on uptake rates, and two experiments testing the influence of the Ca concentrations and temperature on Cd uptake clearance rates (ku). In mineral water, where Cd was considered fully labile, the ku was 0.46 L g,1 d,1, and the depuration rate was 0.032 d,1. The initial Cd influxes were lowered significantly by additions of 10 ,g L,1 of EDTA or 10 mg L,1 of HA in the water but not at 5 mg L,1 HA, even if DGT measurements proved that Cd formed Cd,HA complexes in that treatment. Increasing Ca concentrations lowered ku values, and a competitive inhibition model between Ca and Cd fitted the data. A 30% enhancement of ku values was observed when the temperature was increased by 8°C, which appeared comparatively as a weak effect. Thus, taking into account the metal speciation and the influence of the Ca concentration should improve Cd bioaccumulation modeling in amphipods. In freshwater, where metal bioavailability is reduced by the presence of dissolved organic matter, forecasting Cd waterborne uptake using the labile concentrations should allow robust comparisons between laboratory and field studies. [source] Acute and chronic toxicity of imidazolium-based ionic liquids on Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2005Randall J. Bernot Abstract Room-temperature ionic liquids (ILs) are considered to be green chemicals that may replace volatile organic solvents currently used by industry. However, IL effects on aquatic organisms and ecosystems are currently unknown. We studied the acute effects of imidazolium-based ILs on survival of the crustacean Daphnia magna and their chronic effects on number of first-brood neonates, total number of neonates, and average brood size. Lethal concentrations of imidazolium ILs with various anions (X,) ranged from a median lethal concentration (LC50) of 8.03 to 19.91 mg L,1, whereas salts with a sodium cation (Na+ X,) were more than an order of magnitude higher (NaPF6 LC50, 9,344.81 mg L,1; NaBF4 LC50, 4765.75 mg L,1). Thus, toxicity appeared to be related to the imidazolium cation and not to the various anions (e.g., CI,, Br,, PF,6, and BF,4). The toxicity of imidazolium-based ILs is comparable to that of chemicals currently used in manufacturing and disinfection processes (e.g., ammonia and phenol), indicating that these green chemicals may be more harmful to aquatic organisms than current volatile organic solvents. We conducted 21-d chronic bioassays of individual D. magna exposed to nonlethal IL concentrations at constant food-resource levels. Daphnia magna produced significantly fewer total neonates, first-brood neonates, and average neonates when exposed to lower concentrations (0.3 mg L,1) of imidazolium-based ILs than in the presence of Na-based salts at higher concentrations (400 mg L,1). Such reductions in the reproductive output of Daphnia populations could cascade through natural freshwater ecosystems. The present study provides baseline information needed to assess the potential hazard that some ILs may pose should they be released into freshwater ecosystems. [source] Relevance of post-methionine homocysteine and lipoprotein (a) in evaluating the cardiovascular risk in young CAD patientsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2005R. Marcucci Abstract Background, Aims of our study were to evaluate the prevalence of high lipoprotein (a) [Lp(a)] and homocysteine levels , both in the fasting state (FHcy) and post-methionine (PMHcy) , in young coronary artery disease (CAD) patients, and to investigate the role of genetic and environmental factors for hyperhomocysteinaemia. Materials and methods, We studied 140 patients with angiographically documented CAD (24 women , 55 years and 116 men , 50 years) and 140 healthy subjects as controls. Results, Both FHcy [13·2 (5·4,45·8) vs. 9·0 (5·1,24) µmol L,1); P < 0·0001] and PMHcy [(39·4 (9·0,66·4) vs. 25·2 (16·4,33·9); P < 0·0001] were significantly higher in patients than in controls. Lp(a) levels were significantly higher in patients than in controls (200 (3,1486) mg L,1 vs. 97 (10,412) mg L,1; P < 0·0001). At the multivariate analysis, adjusted for the classical cardiovascular risk factors and creatinine levels, the OR (95% CI) for CAD at young age significantly increased in the fourth quartile of the distribution of FHcy, PMHcy and Lp(a) levels [FHcy: 14·9 (4·1,58), P < 0·0001; PMHcy: 19·2 (4·0,86·3); P < 0·0001; Lp(a): 19·6 (4·7,78·6): < 0·0001]. Vitamin deficiencies were detected in 28/140 (20%) patients. The prevalence of the homozygous C677T (+/+) methylenetetrahydrofolatereductase genotype was higher, but not significantly different, in patients (22·8%) than in controls (18·6%). The allele frequency of the 844ins68 insertion variant in the cystathionine beta-synthase gene was 0·08 in the control group and 0·06 in the patient group. Conclusions, Results of the present study indicate the usefulness of including fasting and post-methionine Hcy, and Lp(a) determination in the diagnostic panels of young CAD patients, in order to obtain a better assessment of their cardiovascular risk profile. [source] Heterogeneous aerobic benzene-degrading communities in oxygen-depleted groundwatersFEMS MICROBIOLOGY ECOLOGY, Issue 2 2006Anne Fahy Abstract A sandstone aquifer beneath a petrochemicals plant (SIReN site, UK) is heterogeneously contaminated with benzene and oxygen-depleted. Despite low redox potentials in three of the most contaminated groundwaters (benzene concentrations from 17.8 to 294 mg L,1), we observed aerobic benzene degradation in microcosms, indicating the presence in situ of a latent community of obligate aerobic microorganisms or an active community of facultative aerobes responding rapidly to oxygen ingress. Moreover, benzene degradation occurred at the ambient pH of 8.9 and 9.4, considerably more alkaline conditions than previously reported. 16S rRNA analyses showed that the groundwater microcosm communities were distinct from each other, despite sharing the function of aerobic benzene degradation. From DNA fingerprinting, one consortium was dominated by Acidovorax spp., another by Pseudomonas spp.; these benzene-degrading consortia were similar to the in situ communities, perhaps indicating that these organisms are active in situ and degrading benzene microaerophilically or by denitrification. Conversely, in the third sample, benzene degradation occurred only after the community changed from a Rhodoferax -dominated community to a mix of Rhodococcus and Hydrogenophaga spp. Four of the main benzene-degrading strains were brought into culture: Hydrogenophaga and Pseudomonas spp., and two strains of Rhodococcus erythropolis, a ubiquitous and metabolically versatile organism. [source] Physiological and oenological traits of different Dekkera/Brettanomyces bruxellensis strains under wine-model conditionsFEMS YEAST RESEARCH, Issue 7 2008Ileana Vigentini Abstract Contamination of wine by Dekkera/Brettanomyces bruxellensis is mostly due to the production of off-flavours identified as vinyl- and especially ethyl-phenols, but these yeasts can also produce several other spoiling metabolites, such as acetic acid and biogenic amines. Little information is available about the correlation between growth, viability and off-flavour and biogenic amine production. In the present work, five strains of Dekkera bruxellensis isolated from wine were analysed over 3 months in wine-like environment for growth, cell survival, carbon source utilization and production of volatile phenols and biogenic amines. Our data indicate that the wine spoilage potential of D. bruxellensis is strain dependent, being strictly associated with the ability to grow under oenological conditions. 4-Ethyl-phenol and 4-ethyl-guaiacol production ranged between 0 and 2.7 and 2 mg L,1, respectively, depending on the growth conditions. Putrescine, cadaverine and spermidine were the biogenic amines found. [source] Assessing macroinvertebrate metrics for classifying acidified rivers across northern EuropeFRESHWATER BIOLOGY, Issue 7 2010S. JANNICKE MOE Summary 1. The effects of acidification on ecological status of rivers in Northern Europe must be assessed according to the EU Water Framework Directive (WFD). Several acidification metrics based on macroinvertebrates already exist in different countries, and the WFD requires that they be comparable across northern Europe. Thus, we compiled macroinvertebrate monitoring data from the U.K. (n = 191 samples), Norway (n = 740) and Sweden (n = 531) for analysis against pH. 2. We tested new and existing acidification metrics developed nationally and used within the Northern Geographical Intercalibration Group. The new metrics were based on the acidification sensitivity of selected species and are proposed as a first step towards a new common indicator for acidification for Northern Europe. 3. Metrics were assessed according to responsiveness to mean pH, degree of nonlinearity in response and consistency in responses across countries. We used flexible, nonparametric regression models to explore various properties of the pressure,response relationships. Metrics were also analysed with humic content (total organic carbon above/below 5 mg L,1) as a covariate. 4. Most metrics responded clearly to pH, with the following metrics explaining most of the variance: Acid Water Indicator Community, Number of ephemeropteran families, Medin's index, Multimetric Indicator of Stream Acidification and the new metric ,Proportion of sensitive Ephemeroptera'. 5. Most metrics were significantly higher in humic than in clear-water rivers, suggesting smaller acidification effects in humic rivers. This result supports the proposed use of humic level as a typological factor in the assessment of acidification. 6. Some potentially important effects could not be considered in this study, such as the additional effects of metals, episodic acidification and the contrasting effects of natural versus anthropogenic acidity. We advocate further data collection and testing of metrics to incorporate these factors. [source] Stream macroinvertebrate occurrence along gradients in organic pollution and eutrophicationFRESHWATER BIOLOGY, Issue 7 2010NIKOLAI FRIBERG Summary 1.,We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH4,N, biological oxygen demand (BOD5)] from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Danish monitoring programme on the aquatic environment. Macroinvertebrate communities were sampled in spring using a standardised kick-sampling procedure whereas chemical variables were sampled six to 24 times per year per site. Habitat variables were assessed once when macroinvertebrates were sampled. 2.,The plecopteran Leuctra showed a significant negative exponential relationship (r2 = 0.90) with BOD5 and occurred at only 16% of the sites with BOD5 above 1.6 mg L,1. Sharp declines with increasing BOD5 levels were found for the trichopteran families Sericostomatidae and Glossosomatidae although they appeared to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD5 up to 3,4 mg L,1. In contrast, the response curve of the isopod Asellus aquaticus followed a saturation function reaching a plateau above 3,4 mg L,1 BOD5 and the dipteran Chironomus showed an exponential increase in occurrence with increasing BOD5 concentration. 3.,Macroinvertebrate occurrence appeared to be related primarily to concentrations of BOD5, NH4,N and total-P whereas there were almost no relationships to total-N. Occurrence of a number of taxa showed a stronger relationship to habitat conditions (width and substrate) than chemical variables. 4.,Important macroinvertebrate taxa are reduced at concentrations of BOD5 that are normally perceived as indicating unimpacted stream site conditions. Our results confirmed sensitivity/tolerance patterns used by existing bioassessment systems only to some degree. [source] Temporal dynamics of dissolved oxygen in a floating,leaved macrophyte bedFRESHWATER BIOLOGY, Issue 8 2008KARA GOODWIN Summary 1. Oxygen concentrations in shallow vegetated areas of aquatic systems can be extremely dynamic. In these waters, characterizing the average oxygen content or frequency of low oxygen events (hypoxia) may require high frequency measurements that span seasons and even years. In this study, moored sondes were used to collect 15-min interval dissolved oxygen (DO) readings in an embayment of the tidal Hudson River with dense coverage by an invasive floating leaved plant (Trapa natans) and in adjacent open waters. Measurements were made from late spring to summer over a 2-year period (2005, 2006). 2. Oxygen concentrations were far more dynamic in the vegetated embayment than in the adjacent open waters and while hypoxic conditions never occurred in the open waters, they occurred frequently in the vegetated site. Overall the vegetated site was hypoxic (DO < 2.5 mg L,1) 30% of the time and had an average oxygen concentration of 5.1 mg L,1. Oxygen concentration was significantly (P < 0.0001, anova) related to season, year and tide. Low tide periods during summer of 2006 had the lowest average oxygen concentration and the highest frequency of hypoxia. 3. The greater hypoxia in summer than spring is related to changes in plant morphology. In the spring and early summer when plants are submersed hypoxia occurs at lower frequency and duration than in the summer when dense floating vegetation covers the water. The tidal pattern in oxygen is related to hydrologic exchange with the non-vegetated open waters. Year-to-year variation may be related to relatively small changes in plant biomass between years. 4. Oxygen concentrations in aquatic systems can be critical to habitat quality and can have cascading impacts on redox sensitive nutrient and metal cycling. For some systems with dynamic oxygen patterns neither weekly spot sampling nor short-duration, high-frequency measurements may be sufficient to characterize oxygen conditions of the system. [source] Abundance and microhabitats of freshwater sponges (Spongillidae) in a Danubean floodplain in AustriaFRESHWATER BIOLOGY, Issue 6 2007IRIS DRÖSCHER Summary 1. This study examined the abundance and distribution of freshwater sponges (Spongillidae) at 32 sites in a floodplain on the Danube within the ,Donau-Auen' National Park east of Vienna, Austria. Ranked from abundant to rare, the species inventory comprised Ephydatia fluviatilis, Spongilla lacustris, Ephydatia mülleri, Eunapius fragilis and Trochospongilla horrida. 2. The presence of hard substratum was essential for the growth of sponges. Timber stands near the water and drifting dead wood increased the abundance of E. fragilis, E. fluviatilis and E. mülleri, whereas stony substrata were important for S. lacustris. A small fraction of E. fluviatilis was collected from macrophytes (Phragmites). 3. Based on the area colonised, the abundance of S. lacustris, E. fragilis and E. fluviatilis was highest (94.2,100% of the total) in floodplain waters where hydrological connectivity with the Danube was low (0,6 days year,1), whereas E. mülleri and T. horrida made up 20.3,35.9% of the total at sites connected for up to 179 days year,1. Moreover, the area colonised by T. horrida at a current velocity >0.20 m s,1 was larger than in the remaining species. Sites with E. mülleri and T. horrida had a higher silicon concentration (0.9 mg L,1) than sites where the remaining three species were collected (0.4,0.6 mg L,1). 4. In most species, the length of macroscleres (the larger spicules) was positively correlated with conductivity and negatively with pH. With respect to aberrant macroscleres, hooks were observed most frequently, whereas the proportion of centrotylotes (ie with the one on more globular swellings along the spicule) was lowest. 5. Freshwater sponges have a great deal of potential as bioindicators and restoration measures that improve floodplain connectivity will favour rare species, such as E. mülleri and T. horrida, while impairing others (e.g. E. fragilis, S. lacustris and E. fluviatilis). [source] The impact of salinity pulses on the emergence of plant and zooplankton from wetland seed and egg banksFRESHWATER BIOLOGY, Issue 5 2007DARYL L. NIELSEN Summary 1. In this study we compared the emergence of aquatic biota from sediments under 14-day pulses of high (5000 mg L,1) and low (1000 mg L,1) salinity with emergence under freshwater and equivalent constant salinity levels. We tested the hypothesis that pulses of high salinity and short duration have no impact on the emergence of aquatic plants and zooplankton from wetland sediment. 2. The way salt is moved through the landscape may alter the response of biota to increases in salinity. Under natural hydrological regimes in rivers and floodplains salinity pulses occur often at concentrations that exceed predicted tolerance levels for aquatic biota. The impacts of natural pulses of high salinity followed by rapid return to fresh conditions may be used to inform management guidelines for the potential release of non-natural saline water into river systems with minimal impact. 3. For both aquatic plants and zooplankton the abundance and richness of the emerging taxa decreased at higher salinities kept at constant levels. In contrast, pulses of salinity followed by return to freshwater conditions did not have a negative impact on the emergence of aquatic plants or zooplankton. For many taxa of zooplankton a positive impact was demonstrated with higher emergence following the salinity pulse. 4. The responses of aquatic plant and zooplankton taxa are grouped into five response types. Type 1: negatively impacted by all salt regimes. Type 2: preference for constant salinities. Type 3: no difference between fresh and either pulse regime. Type 4: preference for high concentration pulses. Type 5: emergence higher under a low concentration pulse. 5. Although previous studies indicate that constant high-level salinity in rivers and wetlands can decrease the species richness of aquatic communities, this current study shows pulses may not have the same impact. Our results support the hypothesis that pulses of high salinity and short duration do not impact on the emergence of aquatic plants and zooplankton from wetland sediments. For zooplankton, pulses of salt may trigger emergence. 6. These trends may be used to explore the potential to use managed water releases to move salt through the landscape with minimal impact of salinity on aquatic biota. However, before such preliminary results are applied in management of saline water releases we need to determine the implications for interacting processes in natural ecosystems. [source] Interaction of an insecticide with larval density in pond-breeding salamanders (Ambystoma)FRESHWATER BIOLOGY, Issue 4 2005BRIAN S. METTS Summary 1. Amphibian populations residing in or near agricultural areas are often susceptible to pesticide contamination. Recent evidence suggests that the effects of pesticides on amphibians often exceed those estimated in laboratory toxicity tests because other environmental factors (e.g. predators, resource abundance) can influence pesticide toxicity. 2. To examine the effects of an insecticide (carbaryl) on two species of Ambystoma salamanders experiencing the natural stress of competition, we manipulated chemical concentration (control, 3.5 and 7.0 mg L,1) and larval density (low and high). We determined the effect of treatments on snout-vent length (SVL), growth rate, lipid reserves, time to metamorphosis, per cent survival and per cent metamorphosis. 3. Carbaryl negatively affected all response variables of Ambystoma maculatum significantly, and significantly reduced survival and metamorphosis of A. opacum. Increased density significantly influenced SVL, lipid reserves, growth rate and metamorphosis of A. maculatum. 4. The effects of carbaryl and increased density on per cent metamorphosis were nearly additive, but were generally less than additive on other variables. 5. The negative effects of chemical contamination on salamanders were likely because of pesticide-induced reductions of food resources, as zooplankton abundance decreased by as much as 97% following carbaryl application. 6. Our study demonstrates the importance of the interactive effects that chemical contamination and natural environmental factors have on salamanders. [source] | |||||||||||||||||||||||||||||||||||||