Pollution characteristics of atmospheric fine particles and their secondary components in the atmosphere of Shenzhen in summer and in winter

Two field measurements for atmospheric fine particles were conducted in Baoan district of Shenzhen during the summer and winter in 2004. Totally 30 sets of 24 h samples were collected, and then the mass concentrations and chemical compositions were determined. The seasonal varia- tions and secondary pollution characteristics of fine particles during the sampling periods were dis-cussed with meteorological factors. The results show that seasonal variations of atmospheric particles are significant in Shenzhen. The average mass concentrations of PM2.5 and PM10 in summer were 35 μg·m-3 and 57 μg·m-3, respectively, and those in winter were 99 μg·m-3 and 135 μg·m-3, respec-tively. The concentrations of both PM2.5 and PM10 in winter increased 184% and 137%, respectively, compared to those in summer. PM2.5 accounted for 61% and 75% of PM10 in summer and in winter, respectively, indicating severe fine particle pollution in Shenzhen. During the summer and winter sampling periods, the mean OC/EC ratios were 3.4 and 1.6, respectively. The estimated secondary organic carbon (SOC) averagely accounted for 56% and 6% of the total OC in summer and in winter, respectively, which implies a major contribution of SOC to OC in summer. During the continuous high temperature period in summer, both the concentrations and fractions of secondary aerosol compo-nents in PM2.5 were highly elevated, suggesting severe secondary pollution again. The prevailing wind was from South China Sea in summer, and the air quality was good. The prevailing wind in winter was from Mainland China to the north, and the polluted air mass led to poor air quality.     

Ion chromatographic and spectrometric determination of water-soluble compounds in airborne particulates, and their correlations in an industrial area in Attica, Greece

In the time period from June 2005 to May 2006 in 42 sampling campaigns 84 filter samples of airborne particulate matter, coarse (PM_10–2.5) and fine (PM_2.5), were collected using a Gent stacked filter unit in the coastal industrial area of Aspropyrgos in Attica, Greece. The average PM₁₀ (PM_10–2.5 + PM_2.5) concentration was found to be 66 μg · m⁻³, exceeding more than 1.6 times the annual limit of 40 μg · m⁻³. The samples were analysed for Cl⁻, NO₃ ⁻, SO₄ ²⁻, Ca²⁺, Mg²⁺, Na⁺, K⁺ and NH₄ ⁺ using ion chromatography. The data were compared with results obtained with other spectrometric methods, such as inductively coupled plasma-atomic emission spectrometry, atomic absorption spectrometry, energy dispersive X-ray fluorescence and reflectometry. The determined average ionic content comprised about 44% of the PM₁₀ mass. The ionic composition, as well as the possible matrix compounds in both fractions were evaluated by dividing the sampling period into summer and winter season. In the PM_10–2.5/PM_2.5 fraction in summer time the concentrations of Ca²⁺, Mg₂₊ and NO₃ ⁻ were enriched in the coarse fraction. In winter time all species were enriched in the coarse fraction, especially Ca²⁺, Cl⁻ and NO₃ ⁻. NH₄ ⁺ was constantly higher in the fine fraction in summer as well as in winter time. Factor analysis was applied to obtain correlations between cations and anions leading to matrix compounds in both fractions. From the evaluation of the results obtained, some of the local air pollution sources could be identified. Correspondence: Klaus-Michael Ochsenkühn, Laboratory for Trace Element Studies, Institute of Physical Chemistry, NCSR “Demokritos”, Aghia Paraskevi 15310, Athens, Greece     

Size-fractionated airborne particulate matter characterization of a residential area near Islamabad airport by IBA methods

Size fractionated PM_2.5 and PM_2.5?C10 airborne particulates collected from the airport housing society site in Rawalpindi were characterized using the non destructive ion beam analysis method. Proton induced X-ray emission and Proton induced gamma ray emission were employed to quantify 28 trace elements in fine and coarse filter samples. The average PM_2.5 and PM_2.5?C10 masses were found to be 15.7 and 144???g/m³, respectively which, when combined exceed the Pakistani limit for PM₁₀ of 100???g/m³. The average black carbon (BC) content was found to be 3.49 and 5.95???g/m³ corresponding to 23.8 and 4.30% of the fine and coarse masses, respectively. The reconstructed mass (RCM) was calculated for both particle modes using 5 pseudo sources, namely soil, sulfate, smoke, sea salt and BC. It was found that 5 sources could account for 80.6 and 49.0% of the fine and coarse masses, respectively. The low value of RCM for the coarse mode may imply a much higher organic content. The major sources contributing to the fine mode were soil, sulfate and BC. Similarly for the coarse mass fraction it was found that soil was the major source whereas the sulfate and BC sources did not contribute as much.     

Deep-UV absorption and Rayleigh scattering of carbon dioxide

Cavity ring-down spectroscopy and pressure ramp measurements have been used to determine the extinction coefficients of CO₂ in the deep-ultraviolet wavelength region, between 198 and 270 nm. The observed optical extinction confirms that there is a clear absorption onset of CO₂ in the deep-UV wavelength region. This onset has been reported previously around 205 nm. The new set of measurements presented here shows that the onset actually starts at higher energy, around 202 nm. For longer wavelengths it is found that the optical extinction demonstrates a 1/λ⁴ like behavior, as typical for Rayleigh scattering.     

Synthesis and application of some novel fluorescent heterocyclic disperse dyestuffs based on phenothiazine on polyester

A series of novel heterocyclic disperse dyestuffs derived from phenothiazine were prepared by standard reactions from phenothiazine as the starting material. Phenothiazine was nitrated and oxidized then reduced to obtain synthesized disperse dyestuffs. The reaction conditions were varied in order to obtain optimal yields for each stage of the preparation to obtain the corresponding derivative and final disperse dyestuffs. All intermediates and disperse dyestuffs were purified and characterized by DSC, FTIR, ¹H NMR, ¹³C NMR, elemental analysis and UV–Visible spectroscopic techniques. The molar extinction coefficients (ε), wavelengths of maximum absorption (λ_max) and solvatochromism effects were studied in solvents as toluene, acetone and N,N-dimethylformamide (DMF). Results represented that the dyestuffs had extinction coefficients of 2011–28189 L mol⁻¹ cm⁻¹, wavelengths of maximum absorption of 448–475 nm in acetone and positive solvatochromism by changing solvent from toluene to DMF. The disperse dyestuffs were applied to locally manufactured polyester fibers and their dyeing properties were investigated. Results showed that the buildup of dyestuffs was acceptable and dyed fibers had very good heat and wash fastness and medium light fastness on polyester fibers.     

Molar extinction coefficient of the incompletely relaxed excess electron in liquid water

Values of the molar extinction coefficients ϵ^λ_ir of the incompletely relaxed (e^-_ir) excess electron in liquid water at room temperature are estimated from an analysis of the subpicosecond time-resolved absorption measurements of Gauduel et al. at λ = 720, 900 and 1250 nm.     

Diffusing probe measurements in Newtonian and elastic solutions

The diffusion coefficients of polystyrene latex spheres and hematite particles in both Newtonian and elastic liquids have been measured using dynamic light scattering. The diffusion coefficients of the latex particles measured in glycerol/water (Newtonian) solutions obey Stokes–Einstein behaviour over a range of solvent viscosities and temperatures. Two apparent diffusion coefficients for the particles are measured in visco-elastic polyacrylamide and polyacrylate solutions and are designated D_fast and D_slow. The apparent fast diffusion coefficients measured in the elastic solutions show an increase to a maximum, above that measured in the solvent water, with increasing polyelectrolyte concentration. At higher polyelectrolyte concentrations the observed D_fast values decrease below the value obtained in the solvent water. D_fast increases with the scattering vector squared (q²) while D_slow, is independent of q².     

Observation of hydrated electron, (SCN)2 .- and CO3 .- radical in high temperature and supercritical water

Transient radicals (hydrated electron, (SCN)₂ ^.- and CO₃ ^.-) formed in supercritical water have been observed by the pulse radiolysis technique. The change of spectra of these radicals with temperature has been measured. It was found that the spectra and absorption coefficients of the radicals, e^- _aq and (SCN)₂ ^.-, are strongly dependent on the temperature of the water. Since it was found that the absorption spectrum and molar absorption coefficient of CO₃ ^.- radical seem to be almost independent of temperature, G-values of OH and e^- _aq could be derived. Then, the absolute values of the absorption coefficients for the radicals could be calculated. The G-values of the radical products in water radiolysis tend to increase with increasing temperature up to 400°C. Based on the above observation, radiolysis of supercritical water is discussed.     

Chromaticity characteristics of chromium(VI) solutions

The light-absorption spectra of solutions of chromium(VI) in the form of dichromate (pH 1–5) and chromate (pH 7–9) have been studied. The solutions have maxima of light absorption at 360 and 380 nm and molar extinction coefficients of 155 ± 7 and 935 ± 27 for Cr₂O ₇ ^2? and Cr O ₄ ^2? respectively. The chromaticity functions of these chromium(VI) forms have been investigated and it has been shown that they are 1.0–1.5 orders of magnitude higher than the molar extinction coefficients. In all cases, the yellowness is maximal.     

Spectral and kinetic characteristics of cycloalkyl radicals in the liquid phase

The C₅–C₁₀ cyclolakyl radicals have a weak light absorption in the 240–300 nm wavelength range that is due to Rydberg transition to the 3s orbital. The extinction coefficients at 250 nm are in the range of 350–900 mol^–1 dm³ cm^–1. At this wavelength for the C₆–C₁₀ radicals a local maximum appears. The radical decay obeys second order kinetics. The kinetic characteristics of the cyclic and linear radicals are generally similar, indicating that the rings are flexible and can easily overcome steric constraints in the termination process. Both the light absorption and decay characteristics of the cyclopentyl radical are somewhat different from those of the other radicals that are attributed to the special co-planar arrangement.     

Total Internal Reflection‐Based Extinction Spectroscopy of Single Nanoparticles

Herein we report a reflection‐mode total internal reflection microscopy (TIRM) to measure the extinction spectrum of individual dielectric, plasmonic, or light‐absorbing nanoparticles, and to differentiate absorption and scattering components from the total optical output. These capabilities were enabled via illuminating the sample with evanescent wave of which the lightpath length was comparable with the size of single nanoparticles, leading to a dramatically improved reflectance change (ΔI/I₀) up to tens of percent. It was further found that scattering and absorption of light contributed to bright and dark centroids, respectively, in the optical patterns of single nanoparticles, allowing to distinguish scattering and absorption components from the extinction spectrum by the use of an appropriate image processing method. In addition, wide‐field feature of TIRM enabled the studies on tens of nanoparticles simultaneously with gentle illumination.     

Using light scattering to evaluate the separation of polydisperse nanoparticles

The analysis of natural and otherwise complex samples is challenging and yields uncertainty about the accuracy and precision of measurements. Here we present a practical tool to assess relative accuracy among separation protocols for techniques using light scattering detection. Due to the highly non-linear relationship between particle size and the intensity of scattered light, a few large particles may obfuscate greater numbers of small particles. Therefore, insufficiently separated mixtures may result in an overestimate of the average measured particle size. Complete separation of complex samples is needed to mitigate this challenge. A separation protocol can be considered improved if the average measured size is smaller than a previous separation protocol. Further, the protocol resulting in the smallest average measured particle size yields the best separation among those explored. If the differential in average measured size between protocols is less than the measurement uncertainty, then the selected protocols are of equivalent precision. As a demonstration, this assessment metric is applied to optimization of cross flow (V_x) protocols in asymmetric flow field flow fractionation (AF⁴) separation interfaced with online quasi-elastic light scattering (QELS) detection using mixtures of polystyrene beads spanning a large size range. Using this assessment metric, the V_x parameter was modulated to improve separation until the average measured size of the mixture was in statistical agreement with the calculated average size of particles in the mixture. While we demonstrate this metric by improving AF⁴V_x protocols, it can be applied to any given separation parameters for separation techniques that employ dynamic light scattering detectors.     

Characterization of diene polymers. I. Infrared and NMR studies: Nonadditive behavior of characteristic infrared bands

Extinction coefficients of the characteristic infrared bands due to isomeric structural units were measured for polybutadiene and polyisoprene in CS₂ or CCl₄ solutions and were compared with the isomer composition determined by NMR. The NMR signal assignments were made on the basis of the spectra of deutero derivatives of the polymers. In the case of polyisoprene, linear relations were obtained between the extinction coefficients and the isomer contents determined by NMR for the absorption bands at 1385 cm^?1 (characteristic of trans-1,4 units), 1376 cm^?1 (cis-1,4 units), and 889 cm^?1 (3,4 units). However, for the absorption bands at 840 cm^?1 (characteristic of cis-1,4 and trans-1,4 units), isomerized polyisoprenes did not give such a linear relationship. In polybutadiene, the extinction coefficient for the atactic 1,2 units was found to be lower than that of the syndiotactic 1,2 unit. These experimental facts lead to the conclusion that additivity of the extinction coefficients does not always hold for diene polymers. The deviation from the linear relation may be associated with regular sequences of one isomeric conformation in the chain.     

离子色谱-电感耦合等离子体质谱联用测定大气颗粒物PM2.5和PM10中的六价铬

建立了大气颗粒物PM_2.5、PM₁₀中六价铬（Cr（Ⅵ））的离子色谱-电感耦合等离子体质谱（IC-ICP-MS）检测方法。采用碳酸氢钠（NaHCO₃）溶液超声提取大气颗粒物样品中的Cr（Ⅵ）,并使用含有0.22 g/L 乙二胺四乙酸二钠盐（Na₂EDTA）的75 mmol/L硝酸铵溶液（pH 7.0）淋洗液通过离子色谱柱（AG7,50 mm×4 mm）分离出样品中的Cr（Ⅵ）,电感耦合等离子体质谱测定。标准溶液中Cr（Ⅵ）的质量浓度在0.05~5 μg/L范围内呈良好的线性关系,相关系数达0.9999,标准溶液测定的精密度为1.0%~4.0%,标准样品测定的相对误差为3.3%;纤维素滤膜适用于Cr（Ⅵ）的采样,将纤维素滤膜碱化后,Cr（Ⅵ）的回收率从75%增加到102%;样品在20 mmol/L碳酸氢钠溶液中超声30 min后上机测试,提取完全且回收率稳定;当采样体积为20 m³,方法的检出限为0.0004 ng/m³;采集并测定了PM_2.5及PM₁₀实际样品,样品的加标回收率为91.6%~102%,精密度为1.7%~7.6%。该方法高效、稳定、灵敏,适用于大气颗粒物中六价铬的测定。     

A comparison of light scattering and far infrared absorption spectra of simple liquids

Light scattering and far infrared absorption spectra of CCl₄, C₂Cl₄, C₆H₁₂, CHCl₃, and CH₂Cl₂ in the liquid phase have been obtained in the range of 2 – 200 and 20 – 200 cm^?1 respectively. The energy absorption spectra obtained by the two techniques and the corresponding relaxation times were compared for each liquid. We observe systematic differences between the energy absorption profiles obtained from the light scattering spectra and the far infrared absorption spectras. We also find generally shorter relaxation times from the infrared absorption spectra. Despite the similarity of the physical processes leading to light scattering and to far infrared absorption some significant differences are observed (ref. 1,2).     

The reduction process of phytic acid–silver ion system: A pulse radiolysis study

Reduction of silver ion in a silver–phytic acid (1:1 ratio) system has been studied using pulse radiolysis technique. Time-resolved transformation of the intermediates, Ag⁺→Ag⁰→Ag₂⁺→Ag₃²⁺, has been clearly observed in the reduction of silver–phytic acid (1:1) system. The effect of phytic acid on the formation and decay of initial silver clusters has been also studied. The surface plasmon absorption band of stable silver nanoparticle (410 nm) and dynamic light scattering technique has been used to characterize the nanoparticles and measure the average size (R_av=100 nm).     

Effects of conjugated systems on UV-visible light-sensitive D-<Emphasis Type="Italic">π</Emphasis>-A type sulfonium salt photoacid generators

A series of D-π-A type sulfonium salt photoacid generators with different π-conjugated structures, such as triphenyl, phenylstilbene, styryl-biphenyl, and stilbene, were designed to determine the effect of molecular structures on the photochemical and photophysical properties. The mechanisms of photochemical generation of H⁺ were studied by UV-Vis spectroscopy, theoretical calculations, and fluorescence spectroscopy. It is found that the frontier orbits determine the absorption, the molar extinction coefficients, and the quantum yields of photoacid generation. Triphenyl systems connected with sulfonium are beneficial to increase the quantum yields of acid generation. The photoreactivity of four sulfonium salts was further evaluated through the polymerizations of various epoxide monomers at different irradiation wavelengths (365–425 nm) by using the real-time infrared spectroscopy with light-emitting diodes. The high quantum yields for acid generation (Φ _H ⁺ = ~0.32 to 0.58) and the high molar extinction coefficients (ε = ~23500 L?mol^?1?cm^?1 to 31000 L?mol^?1?cm^?1) of the sulfonium salts lead to high conversion rates (over 50%–80%). Hence, these photoinitiators exhibit potential for the photocuring applications.     

Portable,Ambient PM2.5 Sensor for Human and/or Animal Exposure Studies

A field-portable device for logging PM_2.5 mass concentration data has been developed. The device combines the Arduino microprocessor with an SD card, a Sharp DN7C3CA006 optical dust monitor, and 10,000-mAh battery. The dust sensor uses a virtual impactor to size select particles <2.5 microns prior to illuminating the selected fraction with an LED. The LED is triggered by a circuit controlled with the Arduino. Nephelometric detection at 120° referenced to incidence is used. The voltage signal reported by the dust sensor is converted to PM_2.5 mass through calibration onboard the Arduino. Data points can be saved to the SD card as rapidly as 0.3?s, although averaging signals over 60?s produced more optimal detection limits. For a 60?s average, the PM_2.5 mass limit of detection was 9?µg?m^?3, indicating that the sensor will be useful for monitoring human exposure to fine particles. Portable exposure monitoring has been demonstrated with the sensing platform as several individuals carried the device with them during daily activities in Lubbock, TX and Atlanta, GA. For this group of test subjects, values of PM_2.5 exposure varied from 0 to 1000?µg?m^?3 during the sampling periods. It was observed that, by far, the highest levels of PM_2.5 occur during periods of cooking, or being near cooking operations. Other periods of high PM_2.5 occurred during ground transportation, use of personal care products, vacuuming, and visiting restrooms. When hourly personal exposure data were correlated with hourly average PM_2.5 for outdoor air for the Atlanta data set, a very weak correlation was found (R²?=?0.026). Only two out of eight sampling periods did the personal monitoring estimate of exposure agree with that predicted by outdoor monitoring to within 15%. Personal exposure was often affected by circumstantial, short-term, high exposure events that are difficult to model or predict effectively. The short-term exposure events generally cause true exposure to be higher than that predicted by using outdoor ambient PM_2.5 to generate estimates. This finding complicates interpretation of epidemiological studies that find links between ambient outdoor PM_2.5 levels and human health, while it buttresses the case for using personal ambient monitors.     

The design,synthesis, and characterization of D-π-A-π-A type organic dyes as sensitizers for dye-sensitized solar cells (DSSCs)

New D-π-A-π-A type organic dyes were synthesized and characterized as sensitizers for dye-sensitized solar cells (DSSCs). These dyes showed wide absorption spectra (300–625 nm) and high molar extinction coefficients (ε_467 nm = 60,911 M⁻¹ cm⁻¹). As dye sensitizers in DSSC, the D-π-A-π-A dye having a cyanoacrylic acid as an acceptor gave the best cell performance with a short-circuit photocurrent density (J_sc) of 7.14 mA/cm², an open-circuit voltage (V_oc) of 0.62 V, and a fill factor (FF) of 0.72, corresponding to an overall conversion efficiency η of 3.19%.     

Light scattering from coloured systems: an example of polyaniline dispersions

Static light scattering of highly diluted dispersions in 0.005 M H₂SO₄ was used to determine particle parameters of polyaniline dispersions stabilized with colloidal silica. The refractive index of polyaniline n = 1.8 and the refractive index increment (dn/dc) = 0.22 cm³g⁻¹ at λ = 532 nm were determined. The light scattering data are affected by the absorption of the green polyaniline and by a small amount of aggregates. The absorption has a negligible effect on the results. The influence of the aggregates was corrected by using the intensity‐weighed size distributions determined by dynamic light scattering at different angles and by the two‐component separation in static light scattering. Both procedures yield the same result.