Processes controlling aqueous concentrations for riverine spills.

The aqueous concentrations of sparingly soluble compounds resulting from oil, fuel, or chemical spills onto rivers predicted by numerical spill models contain an inherent degree of uncertainty due to the inaccuracies, or bias, of the user supplied rate coefficients. Methods for estimating the values of spreading, evaporation, dissolution, volatilization, and longitudinal dispersion coefficients for a small sheltered river are reviewed, and the uncertainties associated with each coefficient are estimated. The uncertainties in the predicted aqueous concentrations are then computed using a concurrently developed riverine spill model for a simulated spill of 10,000 kg of jet fuel. The resulting aqueous concentrations were found to be most sensitive to the saturation concentrations and the dissolution rates, moderately sensitive to the evaporation rates and longitudinal dispersion coefficient, and nearly completely insensitive to the volatilization coefficient.     

Analysis and monitoring of volatile analytes from aqueous solutions by extractions into the gas phase using microdialysis membranes and coupling to fast GC

Microdialysis membranes (3 mm lengthx200 microm i.d.) have been used to extract volatile analytes from aqueous samples into the gas phase and interfaced with fast gas chromatography. Gas-phase extracts generated from aqueous samples reach steady-state concentrations and are transported to the detector in 5 s. The recovery of the system ranges from 1.28% for toluene to less than 0.1% for ethanol. The lowest detectable concentration without preconcentration was 5 mM for most compounds using a flame ionization detector, and as low as 0.01 mM for more volatile hydrophobic analytes. When interfaced with a fast GC system, changes in aqueous phase concentrations were monitored with a temporal resolution of 10 s.     

Preparation Methods of Biodegradable Microspheres on Bovine Serum Albumin Loading Efficiency and Release Profiles

The solvent evaporation and multiple phase methods for preparing poly-(d, l) lactide microspheres of bovine serum albumin (BSA) were compared. The effects of poly (vinyl alcohol) concentration and external aqueous phase temperature on the loading efficient of BSA microspheres prepared by multiple phase emulsion method were evaluated as well. The BSA loading efficient of microspheres by multiple phase emulsion method was much higher than that by solvent evaporation method. The high aqueous solubility of BSA contributes to the low loading efficieny in the solvent evaporation method, suggesting that this method is inappropriate for proteins with high water solubility. The loading efficieny of microspheres, whcih were prepared by multiple phase emulsion method, increased with PVA concentration but decreased with external aqueous phase temperature. The burst phenomenon of release profiles of microspheres was influenced by poly (vinyl alcohol) concentrations and the external aqueous phase temperature. Considering the duration sustained release, 0.5% w/v of poly (vinyl alcohol) is most appropriate among the concentrations tested for preparing BSA microspheres by multiple phase emulsion method.     

Preparation Methods of Biodegradable Microspheres on Bovine Serum Albumin Loading Efficiency and Release Profiles

The solvent evaporation and multiple phase methods for preparing poly-(d, l) lactide microspheres of bovine serum albumin (BSA) were compared. The effects of poly (vinyl alcohol) concentration and external aqueous phase temperature on the loading efficient of BSA microspheres prepared by multiple phase emulsion method were evaluated as well. The BSA loading efficient of microspheres by multiple phase emulsion method was much higher than that by solvent evaporation method. The high aqueous solubility of BSA contributes to the low loading efficieny in the solvent evaporation method, suggesting that this method is inappropriate for proteins with high water solubility. The loading efficieny of microspheres, whcih were prepared by multiple phase emulsion method, increased with PVA concentration but decreased with external aqueous phase temperature. The burst phenomenon of release profiles of microspheres was influenced by poly (vinyl alcohol) concentrations and the external aqueous phase temperature. Considering the duration sustained release, 0.5% w/v of poly (vinyl alcohol) is most appropriate among the concentrations tested for preparing BSA microspheres by multiple phase emulsion method.     

Mitigation of the vapor hazard from silicon tetrachloride using water-based foams

The list of volatile hazardous chemicals contains a significant number of inorganic chlorides. Most react exothermically with water releasing a toxic,In a co-operate program, MSA and Wah Chang have investigated the potential of aqueous foam to mitigate the vapor hazard of one water reactive chloride,The tests conducted were successful in markedly reducing the vapor hazard from the spill. Foam blankets reduced the chloride concentrations in the air     

Headspace solvent microextraction.

A hanging microliter drop of 1-octanol is shown to be an excellent preconcentration medium for headspace analysis of volatile compounds in an aqueous matrix by gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). Model compounds benzene, toluene, ethylbenzene, and o-xylene (BTEX) are conveniently and rapidly preconcentrated in the microdrop. An internal standard, decane, is present in the organic extracting solvent, and linear calibration curves of relative peak area versus aqueous concentration are obtained for the four model compounds. Detailed kinetic studies reveal that the overall rate of mass transfer is limited by both the aqueous-phase stirring rate and the degree of convection within the organic phase. The very low vapor pressure of 1-octanol results in minimal evaporation of the microdrop during the extraction time. This system represents an inexpensive, convenient, and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at trace levels.     

中药水提取液冷冻浓缩的研究

文中介绍了冷冻浓缩在中药水提取液浓缩上的实验研究,从理论上和实践上说明,用冷冻浓缩代替三效真空蒸发浓缩法是可行的,并且可以免去醇沉工序,制品口感也得到改善.     

Estimation of potential impacts and natural resource damages of oil

Methods were developed to estimate the potential impacts and natural resource damages resulting from oil spills using probabilistic modeling techniques. The oil fates model uses wind data, current data, and transport and weathering algorithms to calculate mass balance of fuel components in various environmental compartments (water surface, shoreline, water column, atmosphere, sediments, etc.), oil pathway over time (trajectory), surface distribution, shoreline oiling, and concentrations of the fuel components in water and sediments. Exposure of aquatic habitats and organisms to whole oil and toxic components is estimated in the biological model, followed by estimation of resulting acute mortality and ecological losses. Natural resource damages are based on estimated costs to restore equivalent resources and/or ecological services, using Habitat Equivalency Analysis (HEA) and Resource Equivalency Analysis (REA) methods. Oil spill modeling was performed for two spill sites in central San Francisco Bay, three spill sizes (20th, 50th, and 95th percentile volumes from tankers and larger freight vessels, based on an analysis of likely spill volumes given a spill has occurred) and four oil types (gasoline, diesel, heavy fuel oil, and crude oil). The scenarios were run in stochastic mode to determine the frequency distribution, mean and standard deviation of fates, impacts, and damages. This work is significant as it demonstrates a statistically quantifiable method for estimating potential impacts and financial consequences that may be used in ecological risk assessment and cost-benefit analyses. The statistically-defined spill volumes and consequences provide an objective measure of the magnitude, range and variability of impacts to wildlife, aquatic organisms and shorelines for potential spills of four oil/fuel types, each having distinct environmental fates and effects.     

Evaporation kinetics of volatile liquids and release kinetics of water from a smectite clay: Comparison between experiments and finite element calculations

Numerical calculations of the evaporation kinetics of bulk volatile liquids and of water from smectite clay granules are compared with experimental results. The weight loss of the volatiles is analyzed by thermogravimetry and differential calorimetry. Under the thermodynamic conditions of the experiments, finite element calculations are in good agreement with the experimental data, and an approximate semi-analytical model is developed in order to explain the dependence of the rate of evaporation on the temperature, the chemical species and the carrier gas flow rate. The initial rate of evaporation of water from the clay granule is close to that for bulk water. Its decrease with time is determined mainly by changes in the gas/condensed phase partition given by the equilibrium desorption isotherm, with little limitations due to internal diffusion effects for the present experimental conditions. Its temperature dependence could also be approximately described by an Arrhenius-type equation derived from the semi-analytical model. Further analysis of the experimental measurements reveals steps in the heat of vaporization of water as a function of water concentration, that could be related to the equilibrium desorption isotherm.     

Streamlined system for purifying and quantifying a diverse library of compounds and the effect of compound concentration measurements on the accurate interpretation of biological assay results

As part of an overall systems approach to generating highly accurate screening data across large numbers of compounds and biological targets, we have developed and implemented streamlined methods for purifying and quantitating compounds at various stages of the screening process, coupled with automated "traditional" storage methods (DMSO, -20 degrees C). Specifically, all of the compounds in our druglike library are purified by LC/MS/UV and are then controlled for identity and concentration in their respective DMSO stock solutions by chemiluminescent nitrogen detection (CLND)/evaporative light scattering detection (ELSD) and MS/UV. In addition, the compound-buffer solutions used in the various biological assays are quantitated by LC/UV/CLND to determine the concentration of compound actually present during screening. Our results show that LC/UV/CLND/ELSD/MS is a widely applicable method that can be used to purify, quantitate, and identify most small organic molecules from compound libraries. The LC/UV/CLND technique is a simple and sensitive method that can be easily and cost-effectively employed to rapidly determine the concentrations of even small amounts of any N-containing compound in aqueous solution. We present data to establish error limits for concentration determination that are well within the overall variability of the screening process. This study demonstrates that there is a significant difference between the predicted amount of soluble compound from stock DMSO solutions following dilution into assay buffer and the actual amount present in assay buffer solutions, even at the low concentrations employed for the assays. We also demonstrate that knowledge of the concentrations of compounds to which the biological target is exposed is critical for accurate potency determinations. Accurate potency values are in turn particularly important for drug discovery, for understanding structure-activity relationships, and for building useful empirical models of protein-ligand interactions. Our new understanding of relative solubility demonstrates that most, if not all, decisions that are made in early discovery are based upon missing or inaccurate information. Finally, we demonstrate that careful control of compound handling and concentration, coupled with accurate assay methods, allows the use of both positive and negative data in analyzing screening data sets for structure-activity relationships that determine potency and selectivity.     

食品包装粘合剂中挥发性化合物的HS-SPME/GC-O-MS分析

目的研究食品包装材料常用的5种粘合剂样品中的挥发性成分。方法采用顶空固相微萃取法(HS-SPME)提取粘合剂中的挥发性化合物,再利用气相色谱质谱联用技术(GC-MS)结合气相色谱嗅觉测量法(GC-O),分析计算挥发性化合物的保留指数、量化强度值、气味和浓度,鉴定粘合剂中的主要挥发性化合物,并对挥发性组分及浓度进行定性、定量和对比分析。结果采用HS-SPME/GC-O-MS法能有效地鉴别和确认粘合剂中挥发性化合物的类别及浓度;各粘合剂的挥发性气味成分在组成和含量上存在差异,粘合剂中有33种嗅感物质,其中乙酸、丁酸、丁酸甲酯、1-丁醇和壬醛存在于大部分的粘合剂。结论粘合剂中含量最丰富的挥发性化合物是乙酸,其含量范围为22 900~8 930 000 ng/g,最佳的萃取纤维时间为15 min,最优萃取纤维是DVB/CAR/PDMS。     

Polymeric Membranes with Selective Solution-Diffusion for Intercepting Volatile Organic Compounds during Solar-Driven Water Remediation

Solar evaporation through a photothermal porous material provides a feasible and sustainable method for water remediation. Several photothermal materials have been developed to enhance solar evaporation efficiency. However, a critical limitation of current photothermal materials is their inability to separate water from the volatile organic compounds (VOCs) present in wastewater. Here, a microstructured ultrathin polymeric membrane that enables freshwater separation from VOC pollutants by solar evaporation with a VOC removal rate of 90%, is reported. The different solution-diffusion behaviors of water and VOCs with polymeric membranes facilitate their separation. Moreover, owing to increased light absorption, enlarged liquid–air interface, and shortened mass transfer distance, the microstructured and ultrathin configuration of the membrane helps to balance the tradeoff between permeation selectivity and water production capacity. The membrane is not only effective for evaporation of simulated volatile pollutants in a prototype, but can also intercept complex volatile organic contaminants in natural water sources and produce water that meets drinking-water standards. With practical demonstration and satisfactory purification performance, this work paves the way for practical application of solar evaporation for effective water remediation.     

A survey of modeling techniques for consequence analysis of accidental chemical releases to the atmosphere

This paper surveys techniques for estimating the consequences of accidental chemical releases to the atmosphere. The first section is devoted to a discussion of the characterization of gas, liquid and two-phase releases. In addition to the mass release rate, parameters such as phase composition, density and velocity are shown to be of critical importance in the subsequent dispersion of the release. Emissions due to boiling and evaporation from liquid spill pools are also treated. The second part of the paper describes the techniques for calculating the spatial and temporal variation of chemical concentrations due to jet and heavy gas dispersion. Methods are also presented for estimating the damage resulting from the ignition of a flammable plume or liquid spill pool. Finally, the paper deals with model prediction uncertainty and its impact upon the process of emergency response planning.     

Effect of hydroxypropyl beta-cyclodextrin on drug solubility in water-propylene glycol mixtures

Combined effects of cosolvency and inclusion complexation on drug solubility were studied using a model hydrophobic compound (carbamazepine) and a model hydrophilic compound (Compound S). Propylene glycol (PG) was used as the nonaqueous solvent, and deionized water was employed for the aqueous systems. Hydroxypropyl β-cyclodextrin (HPβCD) was chosen as the complexing agent and studied at concentrations up to 28% (w/v). Complex formation constants (K_c) and solubility enhancement ratios were determined for the respective compounds in various water/PG vehicles. The data suggested that the inclusion of the compounds was most favorable when water alone was used as the vehicle. However, the combined approach of cosolvency and complexation resulted in a significant increase in the total apparent solubility of carbamazepine (the hydrophobic compound). The same was not observed with Compound S (the hydrophilic model), since PG weakened the interactions between the molecule and HPβCD, and thus, no synergistic or additive effects were observed with the combined approach of complexation and cosolvency.     

Determination of perfluorinated surfactants in surface water samples by two independent analytical techniques: liquid chromatography/tandem mass spectrometry and 19F NMR

Perfluorinated surfactants are an important class of specialty chemicals that have received recent attention as a result of their persistence in the environment. Two analytical methods for the determination of perfluorinated surfactants in aqueous samples were developed in order to investigate a spill of 22000 L of fire retardant foam containing perfluorinated surfactants into Etobicoke Creek (Toronto, Ontario). With the first method, aliquots of surface water (0.2-200 mL) were preconcentrated using solid-phase extraction. Liquid chromatography/tandem mass spectrometry was employed for identification and quantification of each perfluorinated surfactant. Total perfluorinated surfactant concentrations in surface water samples ranged from 0.011 to 2270 microg/L, and perfluorooctanesulfonate was the predominant surfactant observed. Interestingly, perfluorooctanoate was detected in surface water sampled upstream of the spill. A second method employing 19F NMR was developed for the determination of total perfluorinated surfactant concentrations in aqueous samples (2-100 mL). By 19F NMR, the surface water concentrations ranged from nondetect (method detection limit, 10 microg/L for a 100-mL sample) to 17000 microg/L. These methods permit comprehensive evaluation of aqueous samples for the presence of perfluorinated surfactants and have applicability to other sample matrixes.     

Keys to modeling LNG spills on water

Although no LNG ship has experienced a loss of containment in over 40 years of shipping, it is important for risk management planning to understand the predicted consequences of a spill. A key parameter in assessing the impact of an LNG spill is the pool size. LNG spills onto water generally result in larger pools than land spills because they are unconfined. Modeling of LNG spills onto water is much more difficult than for land spills because the phenomena are more complex and the experimental basis is more limited.

The most prevalent practice in predicting pool sizes is to treat the release as instantaneous or constant-rate, and to calculate the pool size using an empirical evaporation or burn rate. The evaporation or burn rate is particularly difficult to estimate for LNG spills on water, because the available data are so limited, scattered, and difficult to extrapolate to the large releases of interest.

A more effective modeling of possible spills of LNG onto water calculates, rather than estimating, the evaporation or burn rate. The keys to this approach are to:

• Use rigorous multicomponent physical properties.

• Use a time-varying analysis of spill and evaporation.

• Use a material and energy balance approach.

• Estimate the heat transfer from water to LNG in a way that reflects the turbulence.

These keys are explained and demonstrated by predictions of a model that incorporates these features. The major challenges are describing the effects of the LNG–water turbulence and the heat transfer from the pool fire to the underlying LNG pool. The model includes a fundamentally based framework for these terms, and the current formulation is based on some of the largest tests to-date. The heat transfer coefficient between the water and LNG is obtained by applying a “turbulence factor” to the value from correlations for quiescent film and transition boiling. The turbulence factor is based on two of the largest unignited tests on water to-date. The heat transfer from the fire to the pool is based on the burning rate for the largest pool fire test on land to-date.     

Operating cost study through a Pareto-optimal fuzzy analysis using commercial ferrate (VI) in an ultrasound-assisted oxidative desulfurization of model sulfur compounds

There is a need for transportation fuel such as diesel oil to undergo a desulfurization process prior to its usage in order to comply with stringent environmental regulations. Predominant organic sulfur compounds present in fuel oils comprise benzothiophene (BT) and dibenzothiophene (DBT). High sulfur compound reduction is attainable through a desulfurization process but this often leads to risking higher operating cost due to longer reaction time and the use of large amounts of oxidizing agent and phase transfer agent. Fuzzy logic, which is often used in multi-objective decision-making models, is able to meet the desired objective and satisfy the given constraints at the same time. In this study, a pareto-optimal fuzzy analysis is used in order to determine the best conditions in the ultrasound-assisted oxidative desulfurization process and at the same time achieving the lowest possible operating cost for reducing BT and DBT. Process parameters investigated include ultrasonication time (10–30 min), phase transfer agent (100–300 mg), organic to aqueous phase ratio (10:30–30:10), and ferrate concentration (100–300 ppm) for the reduction of model sulfur compounds. Results through fuzzy optimization indicated optimum results of 93.79 % BT conversion with operating cost of US$ 0.830 and 88.36 % DBT conversion with operating cost of US$ 0.769.     

A method for measuring vapor pressures of low-volatility organic aerosol compounds using a thermal desorption particle beam mass spectrometer

A temperature-programmed thermal desorption method for measuring vapor pressures of low-volatility organic aerosol compounds has been developed. The technique employs a thermal desorption particle beam mass spectrometer we have recently developed for real-time composition analysis of organic aerosols. Particles are size selected using a differential mobility analyzer, sampled into a high-vacuum chamber as an aerodynamically focused beam, collected by impaction on a cryogenically cooled surface, slowly vaporized by resistive heating, and analyzed in a quadrupole mass spectrometer. A simple evaporation model developed from the kinetic theory of gases is used to calculate compound vapor pressures over the temperature range of evaporation. The data are fit to a Clausius-Clapeyron equation to obtain a relationship between vapor pressure and temperature and to determine the heat of vaporization. The technique has been evaluated using C13-C18 monocarboxylic and C6-C8 dicarboxylic acids, which have vapor pressures at 25 degrees C of approximately 10(-4) - 10(-6) Pa, but less volatile compounds can also be analyzed. The method is relatively simple and rapid and yields vapor pressures and heats of vaporization that are in good agreement with literature values. The technique will be used to generate a new database of vapor pressures for low-volatility atmospheric organic compounds.     

1,3-Dicyclohexyl urea nanosuspension for intravenous steady-state delivery in rats

Aqueous insolubility is recognized throughout the pharmaceutical industry as a major hurdle for pre-clinical and clinical drug delivery. Pre-clinical, early efficacy, and proof of concept studies oftentimes rely on model compounds that have less than ideal physiochemical properties, and the in vivo results from these studies often have critical impact on the future of the project. As such, effective delivery of prototype compounds with sub-optimal properties is important in target validation. 1,3-Dicyclohexyl urea (DCU), a potent inhibitor of soluble epoxide hydrolase (sEH) has been shown to lower systemic blood pressure in spontaneously hypertensive rats. This compound has limited aqueous solubility that makes in vivo delivery difficult. In such situations, co-solvents, complexation reagents, and emulsions are commonly used to increase the bioavailability of a prototype compound. However, these approaches are often limited by their capacity to get and keep a compound in solution and can have unwanted placebo effects, which can confound the interpretation of animal efficacy results. Nanosuspension formulations of DCU have been utilized for both intravenous injection and infusion to reach steady-state (Css) plasma concentrations in rat enabling the investigation of the target, chemistry space, and PK/PD in a timely manner without encountering confounding efficacy results.     

Distribution of heavy metals in Lakes Doirani and Kerkini, Northern Greece

The distribution of heavy metals in two lakes of high ecological significance, Doirani and Kerkini, located in Northern Greece was studied. Eight metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in water, total suspended solids, fine and coarse sediments. Moreover, the modified BCR fractionation scheme was employed in sediments and suspended solids to determine soluble, oxidisable, reducible and residual fractions of metals. The Lake Doirani presents higher metal concentrations in aqueous phase than Lake Kerkini; Cd, Cu, Ni, Pb and Zn are above the chronic freshwater quality criteria for aquatic life. In both lakes, Fe and Mn are the most abundant elements in total suspended solids whereas Cd the less abundant. The Lake Kerkini exhibits higher concentrations of all the examined metals in sediments comparing to the Lake Doirani, however the concentrations are lower than the sediment quality guidelines. Cd in sediments is mainly in soluble fraction, Pb and Cu exhibit significant oxidisable fractions whereas, Cr and Fe associated mainly with residual fraction.