Effect of seasonal variation on dust samples of a winter fog affected urban environment of India,South East Asia

Physical and chemical characteristics of leaf dust (LD) samples, collected between 2011 and 2013, of a severely winter fog affected and polluted urban environment (Allahabad, India) of Indo-Gangetic plain are presented in this study. The weather changes in the study area are grouped into three effective annual seasonal periods – winter fog, pre-monsoon and post-monsoon. The pronounced impact of seasonal variations is observed in LD characteristics, as ~46% of the winter fog period samples ranges in size between 2.5 and 20 µm with high magnetic susceptibility (up to 938.22 × 10^?8 m³ kg^?1). In comparison, 35% of the LD from pre-monsoon period occurs in the size range of 100–300 µm with low magnetic susceptibility (up to 43.29 × 10^?8 m³ kg^?1). The fractal analysis involving submicroscopic clast dimension of LD also reveals a seasonal influence. The toxic metals (Pb, Zn, Cd, Cr and Ni) in LD belonging to winter fog and post-monsoon periods increase in comparison to samples from pre-monsoon time. Multivariate statistical analysis of trace element data suggests that the LD collected from winter fog and post-monsoon periods originate predominantly from anthropogenic source, whereas those collected during pre-monsoon owe their origin to crustal and anthropogenic sources, mainly. The present study has demonstrated the role of seasonal variation in controlling the physical and chemical properties of particulate matter based on multiple parameter analyses, and the derivation of the dust load from a mixed source (upper continental crust, anthropogenic and vehicular) for the study area for the first time.     

Switchable solvent based liquid phase microextraction of palladium coupled with determination by flame atomic absorption spectrometry

A switchable solvent-based micro-extraction method for pre-concentration and separation of ultratrace palladium was developed prior to its flame atomic absorption spectrometric detection. Reverse change of hydrophilicity of N,N-dimethylcyclohexylamine (DMA) was achieved by reaction with carbonated water. The hydrophilic bicarbonate salt of the protonated DMA was used as extractant for palladium complexed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Formation of the hydrophobic form of switchable solvent from hydrophilic form of switchable solvent phase was achieved by addition of sodium hydroxide into the extractant-sample solution. The effect of key parameters affected extraction recovery was studied and optimised by using Plackett–Burman design, central composite design and three dimension (3D) surfaces response. The calibration plot was linear in the range 0.015–1.6 mg L^?1 of palladium with a correlation coefficient of 0.999. The limit of detections values of palladium for liquid and solid samples were 4.28 μg L^?1 and 0.54 µg g^?1, respectively. The pre-concentration factor was 37.5. The accuracy was confirmed by determination of palladium in certified reference material. The procedure was also applied for determination of palladium content of real samples as automotive catalytic converter, roadside dust, sea water and river water.     

Light scattering by large Saharan dust particles: Comparison of modeling and experimental data for two samples

Light scattering by large mineral-dust particles with small-scale surface roughness is investigated by comparing model simulations with laboratory-measured scattering matrices of two distinct dust samples collected from the Sahara desert. The samples have been chosen on the basis of their large effective radii, and the simulations are based on their measured size distributions. Size parameters larger than about 30 are modeled using a modified ray-optics model RODS (Ray optics with diffuse and specular interactions), while smaller particles are simulated with a T-matrix model. RODS allows us to mimic the surface roughness of large dust particles by covering the particle surface by a thin layer of external scatterers with specific single-scattering properties. The Gaussian-random-sphere geometry is used for the shapes of large dust particles. Small particles are modeled as an axial-ratio distribution of spheroids with smooth surfaces. One of the samples consists wholly of large particles and its scattering matrix can be reproduced very well by the RODS model, except for the phase function. The incorporation of wavelength-scale roughness is, however, necessary for good fits. The other sample, consisting of both small and large particles, proves more challenging to match with simulations. The analysis indicates, however, that the difficulties arise at least partially from the small-particle contribution, while RODS results are consistent with the measurements. Further, the results imply that the agreement with measurements would improve if roughness could also be accounted for in the small-particle simulations. Overall, the RODS method seems promising for modeling the optical properties of mineral-dust particles much larger than the wavelength.     

Dust Self‐Organized Structures II. Solutions of Master Equations for Small Diffusion

Master equations for spherical dust structures are solved numerically using the asymptotic solutions at the center of the structures for the case of absence of external ionization and small diffusions. The structures are determined by a single parameter, the external plasma flux at the surface of the structure. The equilibrium states that are possible in a limited range of this parameter are investigated numerically. It is demonstrated that in the range of existence of equilibria the structures are changing their shapes and type of distributions inside the structures. For large external fluxes the ion and dust distributions can have peaks inside the structures while for low external fluxes the dust distribution has a single maximum at the structure center. The lower is the external flux supporting the structure the larger is its size. An increase of the external flux decreases the accumulation of dust and ions at the center. The total number of dust confined by the structure is larger for larger size structures. Estimates of dust crystallization inside structures are given. The role of diffusion is calculated by perturbations and is shown to be small in all structure regions except the structure edges. In the perturbation theory we use the exact expressions of the diffusion coefficients calculated previously numerically. The regions with dust density peaks inside the structures have been calculated with two order of magnitude larger precision that allows to resolve the structure parameter dependencies inside the peaks. It is shown that although in peaks the gradients of all parameters are increased the diffusion flux is still small and that the continuity and hydrodynamic approach are applicable within an accuracy about several %‐s (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic Tops in Dusty Plasmas

Paper contains the results of investigation of separate dust granules mechanical state. Observations were performed in high optical resolution. Magnetic induction varied up to 400 G. Motion of particles of different shapes was studied separately. These shapes were: ideally spherical, spherical with defects and non‐spherical. The peculiar physical features of fast rotating dusty granules (tops) were observed. They are the emergence of magnetic moment of rotating charged granule and the orientation change of magnetic moment at magnetic field superimposition. The effects observed in magnetic field are supplied with qualitative interpretation (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

非球对称星风中尘埃的形成

通过建立非球对称星风模型,研究了恒星尘埃的生成,发现在非球对称模型中,恒星更早地生成尘埃.对于较低的质量损失率,由非球对称模型给出的尘埃凝结度远远高于由球对称模型给出的尘埃凝结度.因而,非球对称模型可能给出更高的尘埃产量.对于较高的质量损失率,由于尘埃的凝结度已达到饱和,非球对称模型和球对称模型下,尘埃的凝结度基本一致,对尘埃的产量不会产生大的影响.     

Antimony as a traffic-related element in size-fractionated road dust samples collected in Buenos Aires

The growing interest of public opinion in environmental problems conducted us to investigate the levels of a toxic traffic-related element such antimony in 19 size-fractionated street dust samples. Samples were collected in the megacity of Buenos Aires during two months at 19 sites with different urban characteristics and traffic profile. Samples were sieved in four fractions (F1 < 37 µm, F2: 37-55 µm, F3: 55-75 µm and F4: 55-100 µm) before elemental analysis. A mixture of aqua regia and hydrofluoric acid was used to digest all samples. Antimony concentrations were quantified by inductively coupled plasma optical emission spectrometry (ICP OES) or flow injection hydride generation-atomic absorption spectrometry (FI-HG-AAS).Twenty four out of 73 sub-samples analyzed showed Sb levels < 0.05 µg g^− 1; in the rest of the samples mean Sb concentrations varied from 1.4 to 20.4 µg g^− 1. Maximum and minimum concentrations (in µg g^− 1) found in individual samples in the four fractions were: Fraction 1, < 0.05-20.4; Fraction 2, < 0.05-18.4; Fraction 3, < 0.05-6.3; Fraction 4, < 0.05-7.7.Antimony was found to be enriched in the smallest size fraction of road dust, with mean enrichment factors varying between 27 (F3) and 272 (F1). Concentrations of Sb were correlated with those of other traffic-related elements such as Cu and Pb and higher levels were found in areas with medium and high traffic densities.     

一次强沙尘暴长距离输送的数值模拟研究

利用HYSPLIT-4传输,扩散模式对2003年4月9日发生在我国西北的强沙尘暴进行长距离输送的数值模拟研究,并进行轨迹和浓度分析.研究结果表明:(1)2003年4月9日强沙尘暴过程的沙尘来源并非某单一地区;(2)此次沙尘暴长距离输送过程中,主要有两个高浓度中心向东传输.一个在北纬35度附近,主要在1 500～3000m高空传输,另一个在北纬40度附近,且主要在1 500m以下传输.后期两者合二为一.     

Influence of the vertical profile of Saharan dust on the visible direct radiative forcing

The vertical profile of Saharan dust in the atmosphere is generally characterized by a large aerosol concentration in the mid troposphere, differently from the climatological distribution of other types of particles, that show a peak at the surface and a rapid decrease with height. Saharan dust is also characterized by particles of relatively large size of irregular shape, and variable values of the single scattering albedo (the ratio between radiation scattering and extinction). The dust's peculiar vertical distribution is expected to produce an effect on the calculation of the direct aerosol radiative forcing at the surface and at the top of the atmosphere. This effect is investigated by comparing estimates of aerosol direct visible radiative forcing at the surface and at the top of the atmosphere for dust vertical profiles measured in the Mediterranean, and for the climatological profile. The radiative forcing is estimated by means of an accurate radiative transfer model, and for the ocean surface. The sensitivity of the results on the solar zenith angle, aerosol optical depth, and aerosol absorption is also investigated. The aerosol radiative forcing at the surface shows a very small dependency on the aerosol vertical profile. At the top of the atmosphere, the radiative forcing is weakly dependent on the vertical profile (up to 10% variation on the daily average forcing) for low absorbing particles; conversely, it shows a strong dependency (the daily radiative forcing may vary up to 100%) for absorbing particles. The top of the atmosphere visible radiative forcing efficiency produced by dust having single scattering albedo <0.7 is higher by 4 W m⁻² when the observed vertical profile instead of the standard profile is used in the calculations (i.e. it produces a lower cooling). For values of the single scattering albedo around 0.67, the sign of the forcing depends on the vertical profile. The influence of the vertical distribution on the radiative forcing is largest at small values of the solar zenith angle, and at short wavelengths.     

Backscattering Mössbauer spectroscopy of Martian dust

We report on the determination of the mineralogy of the atmospherically suspended Martian dust particles using backscattering ⁵⁷Fe Mössbauer spectroscopy on dust accumulated onto the magnets onboard the Mars Exploration Rovers. The spectra can be interpreted in terms of minerals of igneous origin, and shows only limited, if any, amounts of secondary minerals that may have formed in the presence of liquid water. These findings suggest that the dust has formed in a dry environment over long time in the history of the planet.