ABSTRACT This paper discusses characteristics of the seasonal variation in phthalate acid esters (PAEs) in the PM2.5 in the city of Changji, which is located an arid area of Xinjiang Province, northwest China. Samples were collected using a Laoying 2030 median discharge intelligent total suspended particulate (TSP) sampler and analyzed by a Shimadzu GC-2010 gas chromatograph. The results showed that PAEs in PM2.5 were mainly composed of phthalic acid dibutyl phthalate (DBP) and phthalic acid (2-)ethyl hexyl ester (DEHP). DBP and DEHP are the most commonly used plasticizers, accounting for the majority of plasticizers used, and have large environmental emissions. Compared with the proportions of TSPs, proportions of DBP and DEHP in the PM2.5 were lower, while the proportions of DMP and DEP were higher. A correlation exists between the distribution of PAEs and the particle size and concentration of atmospheric particulates. Seasonal variations in DBP and DEHP were the same, with lowest concentrations in the summer. Although seasonal variation in DMP was not the same as those of DBP and DEHP, the general trend was similar. Seasonal variation in DEP was different from those of other PAEs. This pattern is related to PAE characteristics and seasonal variations in their sources. 相似文献
Journal of Geographical Sciences - Understanding biogeographic patterns and the mechanisms underlying them has been a main issue in macroecology and biogeography, and has implications for... 相似文献
We present optical luminosity functions(LFs) of galaxies in the~(0.1) g,~(0.1) r,~(0.1) i bands, calculated using data in~40 deg~2 sky area of the LAMOST Complete Spectroscopic Survey of Pointing Area(LaCoSSPAr) in the Southern Galactic Cap. Redshifts for galaxies brighter than r = 18.1 were obtained mainly with LAMOST. In each band, LFs derived using both parametric and non-parametric maximum likelihood methods agree well with each other. In the0.1 r band, our fitting parameters of the Schechter function are φ_*=(1.65 ± 0.36) × 10~(-2) h~3 Mpc~(-3), M_*=-20.69 ± 0.06 mag and α =-1.12 ± 0.08,which agree with previous studies. Separate LFs are also derived for emission line galaxies and absorption line galaxies. The LFs of absorption line galaxies show a dip at~(0.1) r ~18.5 and can be fitted well by a double-Gaussian function, suggesting a bimodality in passive galaxies. 相似文献
Maximum and minimum void ratios (emax and emin) of granular soils are commonly used as indicators of many engineering properties. However, few methods, apart from laboratory tests, are available to provide a rapid estimation of both emax and emin. In this study, we present a theoretical model to map the densest and the loosest packing configurations of granular soils onto the void space. A corresponding numerical procedure that can predict both emax and emin of granular soils with arbitrary grain size distributions is proposed. The capacity of the proposed method is evaluated by predicting the maximum and minimum void ratios of medium to fine mixed graded sands with different contents of fines. The influence of the grain size distribution, characterized quantitatively by uniformity parameter and the fractal dimension, on emax and emin is discussed using the proposed method. Moreover, application of this method in understanding the controlling mechanism for the void ratio change during grain crushing is presented.
At the beginning of the 21st century, a series of great earthquakes were recorded in northeastern Tibet, along the periphery of the Bayan Hara lithospheric block. An earthquake with MS = 8.1 occurred within the East Kunlun fault zone in the Kunlun Mountains, which caused an extended surface rupture with left-lateral strike slip. An earthquake with MS = 8 occurred in Wenchuan (China) on May 12, 2008, giving rise to an extended overthrust along the Lunmanshan fault zone. An earthquake with MS = 7.1 occurred in Yushu (China) on April 14, 2010; its epicenter was on the Grazze–Yushu–Funchuoshan fault; a left-lateral strikeslip offset was observed on the surface. An earthquake with MS = 7 occurred in the vicinity of Lushan on April 20, 2013; its epicenter was within the Lunmanshan fault zone, 103 km southwest of the zone of the catastrophic Wenchuan earthquake. An earthquake with MS = 8.2 occurred in Nepal on April 25, 2015. Based on the CSN seismic catalog, the energy of all earthquakes in eastern Tibet at the end of the 20th and beginning of the 21st centuries was estimated. It was found that Tibet was seismically quiet from 1980 to 2000. The beginning of the 21st century has been marked by seismic activation with earthquake sources migrating southward to surround the Bayan Hara lithospheric block from every quarter. Therefore, this block can be regarded as one of the most seismically active regions of China. 相似文献
The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at~10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar. 相似文献