Dispersive liquid-liquid microextraction-gas chromatography-mass spectrometric determination of polycylic aromatic hydrocarbons in water

In this work, a sample preparation method based on dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was developed for the extraction of polycyclic aromatic hydrocarbons (PAHs), namely phenanthrene and fluoranthene from water sample. In this method, a mixture of carbon tetrachloride, CCl4 (extraction solvent) and acetone (disperser solvent) was injected using a syringe into 5 mL water sample to form emulsion where the PAHs were extracted into the fine droplets of extraction solvent. The solution was then centrifuged for 3 min at 3000 rpm and the fine droplets were sedimented at the bottom of centrifuge tube. Sedimented phase (1 ?L) was injected into the GC-MS for separation and determination of PAHs. The effects of various extraction parameters namely extraction solvent type, disperser solvent type, volume of extraction solvent, and volume of disperser solvent were investigated. The optimized conditions for DLLME of selected PAHs were carbon tetrachloride as extraction solvent, 60 ?L of extraction solvent (CCl4), acetone as disperser solvent and 1 mL of disperser solvent (acetone). The correlation coefficient (r2) of the calibration curve for phenanthrene and fluoranthene were 0.9993 and 0.9973, respectively. The limits of detection (LODs) obtained for phenanthrene and fluoranthene were 0.0008 ?g/mL and 0.0006 ?g/mL, respectively. The proposed method proved to be reproducible with relative standard deviations (RSDs) of 10.69 % and 9.72 % for phenanthrene and fluoranthene, respectively. The analyte recoveries were 100.5 – 107.8 %. The concentration of was 0.02-0.15 ?g/mL. It was found that phenanthrene and fluoranthene were present in lake water sample at concentrations of 3.47×10-3 and 2.69×10-3 ?g/mL. The DLLME method combined with GC-MS proved to be an efficient method and was applied successfully for the determination of PAHs from water sampl

On the numerical solution of chaotic dynamical systems using extend precision floating point arithmetic and very high order numerical methods

Multiple results in the literature exist that indicate that all computed solutions to chaotic dynamical systems are time-step dependent. That is, solutions with small but different time steps will decouple from each other after a certain (small) finite amount of simulation time. When using double precision floating point arithmetic time step independent solutions have been impossible to compute, no matter how accurate the numerical method. Taking the well-known Lorenz equations as an example, we examine the numerical solution of chaotic dynamical systems using very high order methods as well as extended precision floating point number systems. Time step independent solutions are obtained over a finite period of time. However even with a sixteenth order numerical method and with quad-double floating point numbers, there is a limit to this approach

Securities Class Actions Move North: A Doctrinal and Empirical Analysis of Securities Class Actions in Canada

The article explores securities class actions involving Canadian issuers since the provinces added secondary market class action provisions to their securities legislation. It examines the development of civil liability provisions, and class proceedings legislation and their effect on one another. Through analyses of the substance and framework of the statutory provisions, the article presents an empirical and comparative examination of cases involving Canadian issuers in both Canada and the United States. In addition, it explores how both the availability and pricing of director and officer insurance have been affected by the potential for secondary market class action liability. The article suggests that although overall litigation exposure for Canadian companies remains relatively low when compared to their U.S. counterparts, Canadian issuers that have listed their shares in the U.S. face considerable uncertainty as to the extent of their exposure to securities class actions. Through analysis of case law in both jurisdictions, the article highlights the crucial role of liability caps relating to costs in the decision of which jurisdiction to file suit

Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth

Abstract. Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi-periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer, as also confirmed by satellite images. The wave occurred during a Saharan dust event. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation of the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e., the radiative perturbation of the net surface irradiance produced by a unit of optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at about 60° solar zenith angle is −(181 ± 17) W m−2 in the shortwave, and −(83 ± 7) W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively

Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth

Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi-periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer, as also confirmed by satellite images. The wave occurred during a Saharan dust event. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation of the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e., the radiative perturbation of the net surface irradiance produced by a unit of optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at about 60° solar zenith angle is −(181 ± 17) W m−2 in the shortwave, and −(83 ± 7) W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively

QCALT: a tile calorimeter for KLOE-2 upgrade

The upgrade of the DA$\Phi$NE machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE-2 thus asking for the realization of two new calorimeters covering the quadrupoles area. To improve the reconstruction of $K_L\to 2\pi^0$ events with photons hitting the quadrupoles a calorimeter with high efficiency to low energy photons (20-300 MeV), time resolution of less than 1 ns and space resolution of few cm, is needed. To match these requirements, we are designing a tile calorimeter, QCALT, where each single tile is readout by mean of SiPM for a total granularity of 2400 channels. We show first tests of the different calorimeter components

Ultraviolet radiation and aerosol monitoring at Lampedusa, Italy

The measurements of UV spectral irradiance, ozone and aerosol load obtained with a double monochromator Brewer at the Station for Climate Observations of the National Agency for New Technology, Energy and Environment (ENEA) in Lampedusa, Italy, are presented. To derive the aerosol optical depth, the direct-sun measurements at the Brewer operational wavelengths (302.1, 306.3, 310.1, 313.5, 316.8 and 320.1 nm) were calibrated using the Langley method. A radiative transfer model was used to investigate the role of ozone and aerosols in modulating UV irradiance and to reproduce the measured UV spectra. The optical scattering and absorption properties of aerosols input to the model have been derived from measured size-distributions. The modelled and measured UV spectra are in agreement for different atmospheric conditions and allowed us to estimate the radiative impact of the aerosols for two case studies related to the PAUR II campaign held in 1999

Aerosol optical properties at Lampedusa (Central Mediterranean) ? 2. Determination of single scattering albedo at two wavelengths for different aerosol types

International audienceAerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001?September 2003. In a companion paper (Pace et al., 2005) the aerosol optical depth (AOD) and Ångström exponent were used together with airmass backward trajectories to identify and classify different aerosol types. The MFRSR diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for aerosol classified as biomass burning-urban/industrial, originating primarily from the European continent, and desert dust, originating from the Sahara, is used in this study to estimate the aerosol single scattering albedo (SSA). A detailed radiative transfer model is initialized with the measured aerosol optical depth; calculations are performed at the two wavelengths varying the SSA values until the modelled DDR matches the MFRSR observations. Sensitivity studies are performed to estimate how uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence the retrieved SSA values. The results show that a 3% variation of AOD or DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and 868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm; finally, an increase of the assumed surface albedo of 0.05 gives very small changes (0.01?0.02) in the retrieved SSA. The calculations show that the SSA of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of urban/industrial (UN) aerosols decreases from 0.96±0.02 at 415.6 nm to 0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is 0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN aerosols occur usually in June and July; BB aerosol episodes with large AOD and long duration are observed mainly in July and August, the driest months of the year, when the development of fires is favoured