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Equilibration Time (equilibration + time)
Selected AbstractsThe Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm MotilityJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2003Shuyang He Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher (P 0.01) sperm motility after 10 min of exposure as well as greater (P < 0.01) post-thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest (P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest (P < 0.01) post-thaw motility (38 ± 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 ± 2.3% and 6 ± 1.0% post-thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post-thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant (P < 0.001) interaction effect between DMSO concentration and equilibration time. Post-thaw motility was significantly greater (P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post-thaw motility of 40 ± 2.9% was achieved after 10 min equilibration using 5% DMSO. [source] On the general dynamic model of oceanic island biogeographyJOURNAL OF BIOGEOGRAPHY, Issue 6 2009Simone Fattorini Abstract Aim, To investigate the biological meaning of equations used to apply the general dynamic model (GDM) of oceanic island biogeography proposed by R. J. Whittaker, K. A. Triantis and R. J. Ladle. Location, Analyses are presented for 17 animal groups living on the Aeolian Islands, a volcanic archipelago in the central Mediterranean, near Sicily. Methods, In addition to the mathematical implementation of the GDM proposed by Whittaker, Triantis and Ladle, and termed here logATT2 (, where S is species number or any other diversity metric, t is island age, A is island area, and a, b, c and d are fitted parameters), a new implementation based on the Arrhenius equation of the species,area relationship (SAR) is investigated. The new model (termed powerATT2) is: . For logATT2 and powerATT2 models, equations were developed to calculate (1) the expected number of species at equilibrium (i.e. when the island has reached maturity) per unit area (Seq), and (2) the time required to obtain this value (teq). Whereas the intercept in the Gleason model (S = C + z log A) or the coefficient of the Arrhenius power model (S = CAz) of the SAR can be considered measures of the expected number of species per unit area, this is not the case for the parameter a of the ATT2 models. However, values of Seq can be used for this purpose. The index of ,colonization ability' (CAB), calculated as the ratio , may provide a measure of the mean number of species added per unit area per unit time. Results, Both ATT2 models fitted most of the data well, but the powerATT2 model was in most cases superior. Equilibrial values of species richness (Seq) varied from c. 3 species km,2 (reptiles) to 100 species km,2 (mites). The fitted curves for the powerATT2 model showed large variations in d, from 0.03 to 3. However, most groups had values of d around 0.2,0.4, as commonly observed for the z -values of SARs modelled by a power function. Equilibration times ranged from about 170,000 years to 400,000 years. Mites and springtails had very high values of CAB, thus adding many more species per unit area per unit time than others. Reptiles and phytophagous scarabs showed very low values, being the groups that added fewest species per unit area per unit time. Main conclusions, Values of equilibrial species richness per unit area are influenced by species biology (e.g. body size and ecological specialization). Theoretical and empirical evidence suggests that higher immigration rates should increase the z -values of the Arrhenius model. Thus, in the same archipelago, groups with larger z -values should be characterized by higher dispersal ability. Results obtained here for the parameter d conform to this prediction. [source] Creating metal-spiked bed sediments: A case study from Orewa estuary, New Zealand,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Xueqiang Lu Abstract Spiking sediments to achieve target concentrations of heavy metal pollutants is a key step in sediment toxicity tests. It is difficult, however, to ensure that metals in an artificially spiked sediment will behave naturally. A method has been developed in the present study to create Cu-, Pb-, and Zn-spiked sediments in which naturally occurring adsorption onto sediment surfaces is the dominant process binding the metals and in which precipitation of readily redissolved minerals and other metal-bearing phases (artifacts of the spiking procedure) are avoided. Uncontaminated bed sediment from an intertidal mudflat in the Orewa estuary, New Zealand, was characterized in terms of existing metal content, optimal adsorption pH, and adsorption capacity. Competitive adsorption between Cu and Pb as well as complexation by seawater anions only slightly affected metal adsorption from seawater. Surface complexation modeling indicated that iron oxide surfaces in the sediment likely were dominating metal adsorption processes. Spiking experiments were designed using these established adsorption characteristics but with significantly higher (>100-fold) concentrations of sediments and dissolved metals and a liquid to solid (L:S) ratio of approximately 5.5. An equilibration time of at least 36 h was required to achieve a reproducible target metal concentration, which could be reliably predicted from the L:S ratio and the initial metal concentration in the spiking solution. Adsorption equilibrium remained the process governing metal binding to the sediment, and no indication was observed that the adsorption capacity of the sediment had been exceeded or that additional metal-bearing phases had been formed. [source] Automated diffusion chambers to monitor diurnal and seasonal dynamics of the soil CO2 concentration profileEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2009F. Albanito Summary To better understand the factors controlling carbon dioxide (CO2) production and transport in soil, we developed a new method to continuously monitor soil CO2 concentration at multiple depths, by using diffusion chambers. The soil diffusion chambers are constructed from a high-density polyethylene cylindrical frame enclosed by a micro-polyvinylidene difluoride flat membrane (PVDF). All chambers are linked to an infrared gas analyser positioned above-ground through a multi-port valve system. We set up two experimental sites for long-term measurements of soil CO2 concentration, soil temperature and soil water content at depths of 0, 10, 20, 40 and 80 cm. The system provides the following advantages : (i) the use of the PVDF combined with the small dimensions of the diffusion chambers allows rapid diffusion of soil gas into the chambers and therefore a short equilibration time of the gas phase with the surrounding soil atmosphere, (ii) the equilibrating closed loop system allows the semi-continuous measurement of soil profile CO2 concentrations without creating a pressure differential within the chambers, thus reducing gas concentration distortions in the soil, (iii) the small size of the closed diffusion chambers reduces the initial soil disturbance during installation, (iv) it allows sampling in wet, humid soils, including ones that are waterlogged or temporarily saturated, and (v) the chambers do not require removal for maintenance purposes and are inexpensive. [source] The use of peepers to sample pore water in acid sulphate soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2008P. VanOploo Summary Serious environmental impacts of acidic drainage from acid sulphate soils in coastal areas are the result of the interactions between the hydrologic cycle, land use and drainage management, and pore water chemistry. In this study, in situ, diffusion-controlled dialysis profile samplers, or peepers, were used to examine pore water chemistry of acid sulphate soils in a coastal, sugarcane-producing area in Eastern Australia. The peepers sampled pore water at 20-mm intervals over a 1.0-m length, permitting excellent resolution of the sharp transitions in pore water chemistry that occur around a soil profile's iron sulphide oxidation front. Comparison of peeper profiles with soil water profiles extracted from soil samples by centrifuging, illustrated the advantages of peepers over conventional soil water sampling techniques in unconsolidated, sulphidic soils. For conventional sampling, the low permeability, gel-like, unoxidized soil samples had to be frozen then thawed before water could be extracted by centrifuging. Peeper profiles of species not involved in redox reactions agreed well with those from centrifuged soil extracts. Redox sensitive species, however, were in poorer agreement because of the lengthy soil sample preparation and extraction procedures required for extraction by centrifuging. The approximately 6-day equilibration time required for peeper sampling allows them to follow monthly or seasonal changes in pore water chemistry in acid sulphate soils due to variations in climate, and land use and management. [source] Self-Assembling Peptide as a Potential Carrier for Hydrophobic Anticancer Drug Ellipticine: Complexation, Release and In Vitro DeliveryADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Shan Yu Fung Abstract The self-assembling peptide EAK16-II is capable of stabilizing hydrophobic compounds to form microcrystal suspensions in aqueous solution. Here, the ability of this peptide to stabilize the hydrophobic anticancer agent ellipticine is investigated. The formation of peptide-ellipticine suspensions is monitored with time until equilibrium is reached. The equilibration time is found to be dependent on the peptide concentration. When the peptide concentration is close to its critical aggregation concentration, the equilibration time is minimal at 5,h. With different combinations of EAK16-II and ellipticine concentrations, two molecular states (protonated or cyrstalline) of ellipticine could be stabilized. These different states of ellipticine significantly affect the release kinetics of ellipticine from the peptide-ellipticine complex into the egg phosphatidylcholine vesicles, which are used to mimic cell membranes. The transfer rate of protonated ellipticine from the complex to the vesicles is much faster than that of crystalline ellipticine. This observation may also be related to the size of the resulting complexes as revealed from the scanning electron micrographs. In addition, the complexes with protonated ellipticine are found to have a better anticancer activity against two cancer cell lines, A549 and MCF-7. This work forms the basis for studies of the peptide-ellipticine suspensions in vitro and in vivo leading to future development of self-assembling peptide-based delivery of hydrophobic anticancer drugs. [source] Separation of cobalt and nickel from acidic sulfate solutions using mixtures of di(2-ethylhexyl)phosphoric acid (DP-8R) and hydroxyoxime (ACORGA M5640)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2004Arisbel Cerpa Abstract DP-8R and ACORGA M5640 extractants diluted in Exxsol D100 were used to co-extract cobalt and nickel from aqueous acidic sulfate media. The influences of equilibration time, temperature, equilibrium pH and reagent concentrations on the extraction of both metals have been studied. It was observed that both cobalt and nickel extraction are slightly sensitive to temperature but are pH dependent. Metal extraction equilibria are reached within about 5 min contact time. In addition, cobalt extraction depends on the extractant concentration in the organic phase. For a solution containing 0.5 g dm,3 each of cobalt and nickel and an initial pH of 4.1, conditions were established for the co-extraction of both metals and selective stripping (with H2SO4) of cobalt and nickel. Using the appropriate reagent concentrations the yield (extraction stage) for both metals exceeded 90%, and stripping of cobalt and nickel was almost quantitative. Copyright © 2004 Society of Chemical Industry [source] How to obtain statistically converged MM/GBSA resultsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2010Samuel Genheden Abstract The molecular mechanics/generalized Born surface area (MM/GBSA) method has been investigated with the aim of achieving a statistical precision of 1 kJ/mol for the results. We studied the binding of seven biotin analogues to avidin, taking advantage of the fact that the protein is a tetramer with four independent binding sites, which should give the same estimated binding affinities. We show that it is not enough to use a single long simulation (10 ns), because the standard error of such a calculation underestimates the difference between the four binding sites. Instead, it is better to run several independent simulations and average the results. With such an approach, we obtain the same results for the four binding sites, and any desired precision can be obtained by running a proper number of simulations. We discuss how the simulations should be performed to optimize the use of computer time. The correlation time between the MM/GBSA energies is ,5 ps and an equilibration time of 100 ps is needed. For MM/GBSA, we recommend a sampling time of 20,200 ps for each separate simulation, depending on the protein. With 200 ps production time, 5,50 separate simulations are required to reach a statistical precision of 1 kJ/mol (800,8000 energy calculations or 1.5,15 ns total simulation time per ligand) for the seven avidin ligands. This is an order of magnitude more than what is normally used, but such a number of simulations is needed to obtain statistically valid results for the MM/GBSA method. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 [source] Poster Sessions AP13: Novel Techniques and TechnologiesJOURNAL OF NEUROCHEMISTRY, Issue 2002J. K. Yao Studies of the antioxidant defense system and the monoamine metabolic pathways are often complicated by cumbersome analytical methods, which require separate and multistep extraction and chemical reaction procedures. Thus, measurements of multiple parameters are limited in relatively small biological samples. High performance liquid chromatography (HPLC) coupled with a Coulometric Multi-Electrode Array System (CMEAS) provides us a convenient and most sensitive tool to measure low molecular weight, redox-active compounds in biological sample. The deproteinized sample was analyzed on a HPLC coupled with a 16-channel CMEAS, which incremented from 60 to 960 mV in 60 mV steps. Each sample was run on a single column (Meta-250, 4.6 × 250 mm) under a 150-minute complex gradient that ranged from 0% B (A: 1.1% pentane sulfonic acid) to 20% B (B: 0.1 m lithium acetate in mixture of methanol, acetonenitrile and isopropanol), with a flow rate of 0.5 mL/min. We have developed an automated procedure to simultaneously measure various antioxidant, oxidative stress marker, and monoamine metabolites in a single column with binary gradient. No other chemical reactions are necessary. In order to reduce the running time and yet achieve a reproducible retention time by the autosampler injection, our gradient elution profile was modified to produce a shorter equilibration time and to compensate for the initial contamination of mobile phase B following the first injection. Without the use of two columns in series and peak suppresser/gradient mixer, we have simplified the previously published method to measure over 20 different antioxidants, oxidative stress markers and monoamine metabolites simultaneously in biological samples. [source] A comparison of pseudo-ternary diagrams of aqueous mixtures of Quil A, cholesterol and phospholipid prepared by lipid-film hydration and dialysisJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2004P. H. Demana Pseudo-ternary diagrams for Quil A, phospholipid (phosphatidylcholine (PC) or phosphatidylethanolamine (PE)) and cholesterol were established in order to identify combinations that result in the formation of immune-stimulating complex (ISCOM) matrices and other colloidal structures produced by these three components in aqueous systems following lipid-film hydration or dialysis (methods that can be used to produce ISCOMs). In addition, the effect of equilibration time (1 month at 4°C) on the structures formed by the various combinations of the three components was investigated. Depending on the ratio of Quil A, cholesterol and phospholipid, different colloidal particles, including ISCOM matrices, liposomes and ring-like micelles, were found irrespective of the preparation method used. In contrast, worm-like micelles were only observed in systems prepared by lipid-film hydration. For samples prepared by dialysis, ISCOM matrices were predominantly found near the Quil A apex of the pseudo-ternary diagram (> 50% Quil A). On the other hand, for samples prepared by lipid-film hydration, ISCOM matrices were predominantly found near the phospholipid apex of the pseudo-ternary diagram (> 50% phospholipid). The regions in the pseudo-ternary diagrams in which ISCOM matrices were observed increased following an extended equilibration time, particularly for samples prepared by lipid-film hydration. Differences were also observed between pseudoternary diagrams prepared using either PE or PC as phospholipids. [source] The Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm MotilityJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2003Shuyang He Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher (P 0.01) sperm motility after 10 min of exposure as well as greater (P < 0.01) post-thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest (P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest (P < 0.01) post-thaw motility (38 ± 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 ± 2.3% and 6 ± 1.0% post-thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post-thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant (P < 0.001) interaction effect between DMSO concentration and equilibration time. Post-thaw motility was significantly greater (P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post-thaw motility of 40 ± 2.9% was achieved after 10 min equilibration using 5% DMSO. [source] Improved method for isotopic and quantitative analysis of dissolved inorganic carbon in natural water samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2006Nelly Assayag We present here an improved and reliable method for measuring the concentration of dissolved inorganic carbon (DIC) and its isotope composition (,13CDIC) in natural water samples. Our apparatus, a gas chromatograph coupled to an isotope ratio mass spectrometer (GCIRMS), runs in a quasi-automated mode and is able to analyze about 50 water samples per day. The whole procedure (sample preparation, CO2(g),CO2(aq) equilibration time and GCIRMS analysis) requires 2 days. It consists of injecting an aliquot of water into a H3PO4 -loaded and He-flushed 12,mL glass tube. The H3PO4 reacts with the water and converts the DIC into aqueous and gaseous CO2. After a CO2(g),CO2(aq) equilibration time of between 15 and 24,h, a portion of the headspace gas (mainly CO2+He) is introduced into the GCIRMS, to measure the carbon isotope ratio of the released CO2(g), from which the ,13CDIC is determined via a calibration procedure. For standard solutions with DIC concentrations ranging from 1 to 25,mmol,·,L,1 and solution volume of 1,mL (high DIC concentration samples) or 5,mL (low DIC concentration samples), ,13CDIC values are determined with a precision (1,) better than 0.1,. Compared with previously published headspace equilibration methods, the major improvement presented here is the development of a calibration procedure which takes the carbon isotope fractionation associated with the CO2(g),CO2(aq) partition into account: the set of standard solutions and samples has to be prepared and analyzed with the same ,gas/liquid' and ,H3PO4/water' volume ratios. A set of natural water samples (lake, river and hydrothermal springs) was analyzed to demonstrate the utility of this new method. Copyright © 2006 John Wiley & Sons, Ltd. [source] Isotopic metrology of carbon dioxide.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2003We report a pilot study of high-precision differential isotope ratio measurements made on replicate samples of pure carbon dioxide using three instruments of identical manufacture. Measurement protocols were designed to explore the effects of sample size, ion source conductance, and inlet changeover equilibration time on the raw measurements. Our goal was better understanding of factors that influence these measurements in order to establish procedures for highly reproducible and accurate determinations of Reference Material (RM) isotopic compositions. Evaluation and modeling of reported data illuminated effects consistent with two instrumental memory sources,one short-lived (t½,,,10 s) and the other long-lived (t½,,,6,10,min), uncompensated by normal background measurements,that can significantly influence measurements made by the dual inlet method. These biases, proportional to the difference in isotopic compositions between the measured sample and reference gases, decrease in magnitude with increasing sample size, source conductance, and equilibration time. We observed biases as high as 0.1, per 10, difference between sample and reference gases. These memory sources may be responsible for measured ,13C values of RMs generally being highly reproducible within any single laboratory but less reproducible among independent laboratories. The magnitude of the bias is consistent with the ranges of ,13C values reported in prior laboratory intercomparisons. Uncertainties are most likely due to high and variable long-lived memory among the instruments tested. Published in 2003 by John Wiley & Sons, Ltd. [source] Isotopic metrology of carbon dioxide.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2003We report high-precision isotopic carbon dioxide measurements, made before and after ion source modification to gas isotope ratio mass spectrometry (IRMS) instruments. Measurement protocols were designed to explore the effects of ion source material substitution, source conductance, inlet pressure, electron emission, acceleration potential, and inlet changeover equilibration time. After modification of the IRMS instruments at the National Institute of Standards and Technology (NIST) and the Max-Planck-Institute for Chemistry (MPI-Mainz), immediate changes were observed. At NIST, measurements were no longer sensitive to inlet equilibration times greater than 15,s, and different settings of ion source conductance resulted in ,13C shifts of about 0.04, per 10, measurement difference between sample and reference, a five-fold improvement. No significant changes in machine performance were observed after a month of use. After a year, performance had degraded slightly, but was controlled by ion source cleaning and the use of low-energy ion acceleration to minimize sputtering. At MPI-Mainz, results were very similar. We report cross-contamination coefficients measured since 1996, and discuss the role of adsorption, ion implantation, and sputtering on cross contamination in mass spectrometry systems. We recommend that users of high-precision IRMS instruments test for and minimize the effects described. Published in 2003 by John Wiley & Sons, Ltd. [source] Adsorption Behavior of Potassium Ion on Planting MaterialsCHINESE JOURNAL OF CHEMISTRY, Issue 9 2007Dechprasitthichokea Paunpassanan Abstract Characterization of planting materials used as adsorbent has been studied in order to compare potassium ion adsorption on two types of planting materials, which are a fired planting material (FPM) made from a mixture of 4 kinds of wastes (bottom ash, flue gas desulfurization (FGD) gypsum, paddy soil and sawdust) formed and fired at 850 °C and the commercial planting material called "hydroball" (HDB) bought from Jatujak market, Bangkok. The physical characteristics of both types of planting materials indicate that the FPM has a larger specific surface area than the HDB. The factors affecting potassium adsorption on both the planting materials such as an equilibration time and some solid/solution ratios were investigated. The suitable equilibration time for the adsorption to reach an equilibrium on the FPM and HDB is one and two hours, respectively. The highest amounts of potassium ion adsorbed on both the planting materials were obtained when the solid/solution ratio was 1:15. The adsorption behavior on both the planting materials tends to correspond with the Freundlich isotherm. [source] Direct high-performance liquid chromatographic separation of the enantiomers of venlafaxine and 11 analogs using amylose-derived chiral stationary phasesCHIRALITY, Issue 6 2009Salvatore Caccamese Abstract A direct liquid chromatographic enantioselective separation of venlafaxine and 11 analogs was obtained in the normal phase mode using Chiralpak AD. For some compounds, a comparison between the enantioseparation using coated and immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phases (Chiralpak AD and Chiralpak IA, respectively) was made. The best separations were achieved on Chiralpak AD with ethanol as alcoholic modifier in a mobile phase made basic by DEA addition: separation factor ranges between 2.08 and 1.15 and resolution factor between 7.0 and 1.0. Using the same CSP and 2-propanol doped with TFA as acidic modifier, 10 compounds were enantioseparated with separation factor ranging between 1.40 and 1.04 and resolution factor between 3.1 and 0.3. The use of ethanol as alcoholic modifier also has the advantage of better solubility of the compounds in the mobile phase. The nature of the substituent (electron donating or withdrawing) affects in general the separation factor. A memory effect that involves a long equilibration time of the CSP is present when switching from an acidic mobile phase to a basic one. Chirality, 2008. © 2009 Wiley-Liss, Inc. [source] Assessing exposure of sediment biota to organic contaminants by thin-film solid phase extractionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009Lizanne M. Meloche Abstract Differences in bioavailability among sediments are a source of variability and uncertainty in sediment quality assessment. We present three sets of studies designed to test a thin-film solid phase extraction technique for characterizing the bioavailability of organic chemicals in sediments. Laboratory studies with spiked natural sediments reveal highly reproducible thin-film extractions for chemicals with octanol,water partition coefficients between 104.5 and 108.5, with 95% equilibration times between 1 and 600 h. Studies with field-collected sediments illustrate that method detection limits are sufficiently low for field application at contaminated sites. Bioaccumulation studies with clams (Macoma balthica) show excellent correlations between thin-film and animal tissue concentrations. We conclude that thin-film extraction provides an ecologically relevant, fugacity-based measure of chemical exposure that can be expected to improve sediment quality assessments. [source] Mechanisms affecting the dissolution of nonaqueous phase liquids into the aqueous phase in slow-stirring batch systemsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001Mathias Schluep Abstract Understanding the kinetics of the exchange processes between nonaqueous phase liquids (NALs) and water is important in predicting the fate of anthropogenic compounds such as petroleum hydrocarbons, i.e., benzene, toluene, ethylbenzene, and xylene (BTEX) as well as polynuclear aromatic hydrocarbons (PAHs). Exchange processes occurring in the environment resemble the experimental setup of the slow-stirring method (SSM) designed to determine solubilities and octanol-water partition coefficients. Data obtained from SSM experiments for diesel fuel compounds are interpreted by a linear transfer model that is characterized by an aqueous molecular boundary layer and the water/NAPL equilibrium partition coefficient. For the chosen experimental setup, the boundary layer thickness is 2.42 × 10,2 cm. Typical equilibration times lie between 1 and 2 d. Due to the temperature dependence of the aqueous diffusivity, this time increases with decreasing temperature. Transport within the NAPL phase can slow down the exchange process for the more water-soluble compounds (e.g., benzene) provided that the stirring rate exceeds a critical value. [source] Methods for determining labile cadmium and zinc in soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2000S. D. Young Summary Isotopically exchangeable cadmium and zinc (,E values') were measured on soils historically contaminated by sewage sludge and ones on zinc-rich mine spoil. The E -value assay involves determining the distribution of an added metal isotope, e.g. 109Cd, between the solid and solution phases of a soil suspension. The E values for both metals were found to be robust to changes in the position of the metal solid,solution equilibrium, even though the concentration of dissolved metal varied substantially with electrolyte composition and soil:solution ratio. Concentration of labile metal was also invariant over isotope equilibration times of 2,6 days. The use of a submicron filtration procedure, in addition to centrifuging at 2200 g, proved unnecessary if 0.1 m Ca electrolyte was used to suspend the soils. The proportion of ,fixed' metal, in non-labile forms, apparently increased with increasing pH, although there was considerable variation in both sets of contaminated soil. Zinc and cadmium in the sludged soils were similarly labile. Several possible methods for the measurement of chemically reactive metal were explored for comparison with E values, including single extraction with 1 m CaCl2 and a ,pool depletion' (PD) method. The latter involves comparing solid,solution metal equilibria in two electrolytes with differing degrees of (solution) complex formation, 0.1 m Ca(NO3)2 and CaCl2. Both the single extraction and the PD method gave good estimates of E value for Cd, although the single extraction was more consistent. Neither technique was a useful substitute for determining labile Zn, because of weak chloro-complexation of Zn2+. We therefore suggest that 1 m CaCl2 extraction of Cd alone be used as an alternative to E values to avoid the inconvenience of isotopic dilution procedures. [source] The Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm MotilityJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2003Shuyang He Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher (P 0.01) sperm motility after 10 min of exposure as well as greater (P < 0.01) post-thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest (P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest (P < 0.01) post-thaw motility (38 ± 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 ± 2.3% and 6 ± 1.0% post-thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post-thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant (P < 0.001) interaction effect between DMSO concentration and equilibration time. Post-thaw motility was significantly greater (P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post-thaw motility of 40 ± 2.9% was achieved after 10 min equilibration using 5% DMSO. [source] | ||||||||||||||||