悬浮颗粒物海水及其声吸收

通过对悬浮颗粒物粘滞性声吸收的分析,指出了在悬浮颗粒物海水声传播研究中所需要的悬浮颗粒物参数;经海水中声吸收计算分析,给出了能够对声传播产生影响的悬浮颗粒物参数的范围。为应用于声学研究的悬浮颗粒物海水海洋调查、数据积累及海区划分提供依据。     

Organochlorine pesticides in particulate matter of Beijing, China

Eighteen organochlorine pesticides (OCPs) in air particulate matter (PM) samples collected from 20 sites in Beijing, China in 2005 and 2006 were analyzed to determine the composition, spatial distribution and sources. Total OCPs of PM_2.5 and PM₁₀ ranged from 32.59 pg m⁻³ to 9232.31 pg m⁻³ and 80.96 pg m⁻³ to 9434.97 pg m⁻³, respectively, categorized as heavier pollution compared to other cities of China. Among six kinds of functional zones involved, commercial areas and industrial centers were heavily polluted. Distinct concentrations variations were detected in PM with different particle diameters. Pollution distribution was spatially heterogeneous inside the city. The most heavily polluted sites located in the southeast part of the city, where laid many chemical factories. Compositional analysis and principal component analysis (PCA) suggested that past usage of OCPs was the main source, though there were new inputs in some sites.     

室内颗粒物的健康效应及控制标准

为了深入了解室内颗粒物对人体的危害,分析影响颗粒物对人体危害的因素,讨论相关控制标准,指出我国相关控制标准存在的问题,并对相关标准的修订提出一些建议。     

Relative intensity correction of Raman spectrometers: NIST SRMs 2241 through 2243 for 785 nm, 532 nm, and 488 nm/514.5 nm excitation

Standard Reference Materials SRMs 2241 through 2243 are certified spectroscopic standards intended for the correction of the relative intensity of Raman spectra obtained with instruments employing laser excitation wavelengths of 785 nm, 532 nm, or 488 nm/514.5 nm. These SRMs each consist of an optical glass that emits a broadband luminescence spectrum when illuminated with the Raman excitation laser. The shape of the luminescence spectrum is described by a polynomial expression that relates the relative spectral intensity to the Raman shift with units in wavenumber (cm(-1)). This polynomial, together with a measurement of the luminescence spectrum of the standard, can be used to determine the spectral intensity-response correction, which is unique to each Raman system. The resulting instrument intensity-response correction may then be used to obtain Raman spectra that are corrected for a number of, but not all, instrument-dependent artifacts. Peak area ratios of the intensity-corrected Raman spectrum of cyclohexane are presented as an example of a methodology to validate the spectral intensity calibration process and to illustrate variations that can occur in this measurement.     

Continuous automated measurement of hexavalent chromium in airborne particulate matter

An automated continuous instrument for the collection and measurement of aerosol Cr(VI) is described. The system alternately collects the sample on one of two glass fiber filters. After 15-min sample collection on one filter, the sampling switches over to the second filter. The freshly sampled filter is washed for 8.5 min, and the washings are preconcentrated on a minicolumn packed with anion exchange resin. The washed filter is dried with filtered hot air for the next 6.5 min so that it is ready for sampling at the end of the 15-min cycle. The preconcentrated Cr(VI) on the column is eluted with 0.1 M sodium perchlorate and then reacted with sym-1,5-diphenylcarbazide prior to absorbance detection with a light emitting diode-based dedicated flow-through absorbance detector. The detection limit (S/N = 3) is 5 ng of Cr(VI)/m3, orders of magnitude lower than current regulatory requirements. The instrument operates unattended over long periods. In continuous round-the-clock operation, filter replacement frequency is every 24-72 h, depending on dust loading. The system is portable for facile field deployment and permits fully automated rapid determinations at a very low analysis cost per sample.     

Glow discharge mass spectrometric analysis of atmospheric particulate matter

A direct current (dc) glow discharge mass spectrometer has been used to analyze atmospheric particulate matter. The sample preparation used is simple and time-saving. The air is sucked by a pump through a single-orifice impactor stage, in which the aerosols are impacted on a metal support, forming a central spot. This metal plate is directly used as a cathode in a dc glow discharge mass spectrometer. Evaluation of the sample loading and of the discharge parameters allowed us to optimize the signal intensity and to minimize its decrease, the latter being a consequence of its consumption by continuous sputtering in the discharge. The available aerosol analysis time could be prolonged to more than 3 h, a time span necessary to perform a multielement analysis using a magnetic sector instrument and long integration times. A NIST reference aerosol was measured to evaluate the quantitative analysis potential. The internal reproducibility was better than 10% RSD, and the limits of detection were estimated to be in the low ppm or sub ppm region. Even without the use of any standards or correction factors, glow discharge mass spectrometry could offer good semiquantitative results, based only on the use of an internal standard.     

CFD-DEM simulation and optimization of gas-cyclone performance with realistic macroscopic particulate matter

Most of research concerns have been focused on developing new methods and parameters to make the cyclone separator performance better. In this work, the inverse-flow cyclone type geometry was performed and optimized through the modulation of changing the position and dimensions of the involute inlet portion and cyclone barrel section length at a fixed inlet air velocity of 30 ms^?1. Cyclones of different inlet sizes and portions were computationally modeled which named as cyclones I, II, III, IV, and V. The study was successfully accomplished for two heterogeneous groups of particulate matter mixed with air flow for applications pertinent to agricultural engineering. To capture the phenomena of constitutive air-granular materials behavior in the optimized separator, numerical simulations were generated using one-way coupling of commercial ANSYS-Fluent® 18.0 (CFD) and Rocky® 4.13 (DEM) software, which is considered as the first head start research approach in the cyclonic separation and purification field. Discrete Element Method (DEM) which was represented by Rocky® package simulates the movement of each particle individually, taking into consideration the interaction and collision of the particles. Whereas, the highly curved streamlines and the chaotic turbulence of the continuum air flow in the cyclone separator were modeled through the Computational Fluid Dynamics (CFD-Fluent®) technique using advanced turbulence model RNG $k-\epsilon$. The numerical results successfully captured the effects of new geometrical modifications done on the original cyclone separator. Numerically, the cyclone inlet height significantly improved the cyclone performance by increasing the separation efficiency, cleaning efficiency, and cyclone effectiveness, while other parameters had a negative effect. These data were useful for considering cyclone (III) as the most suitable modification and optimization design geometry for harvesting jojoba seeds with the lowest operation cost and highest performance.     

Metallic species in atmospheric particulate matter in Las Palmas de Gran Canaria

In this work, we quantified the total, water-soluble and insoluble fractions of 12 metallic species (Na, Ca, K, Mg, Fe, Zn, Cr, Ni, Cu, Cd, Pb and Mn) present in total suspended particulates (TSP) in an urban area with heavy traffic (about 80 000 vehicles/day) of Las Palmas de Gran Canaria (Canary Islands). Experimental measurements were made from July to December 2003 on a total of 42 samples (7 per month). Particulate matter (TSP) was collected in fiber filters and high volume samplers. PM₁₀ levels were estimated assuming the PM₁₀ fraction is about 70% of all TSP. Total fractions was determined gravimetrically. Water-soluble fraction was extracted by sonication. Concentrations of metallic elements were analyzed by flame atomic absorption spectrophotometer. Temporal changes in the concentrations of the target elements were examined and a multivariate approach used to identify the primary sources for each species. Mean value for TSP is 71.92 μg/m³. The water-soluble fraction consisted mainly of Na, Ca, Mg, and K. The insoluble fraction contained higher concentrations of all elements than the soluble except Na. In the water-soluble fraction, Na, K, Ca and Mg were found to come mainly from natural sources; Cr, Pb, Cd, Ni, Zn and Cu from anthropogenic sources.     

Source characterization of total suspended particulate matter near a riverbed in Central Taiwan

Samples of total suspended particulate (TSP) matter were collected by using TSP samplers from certain areas representing the estuary of the Jhuoshuei River, Taiwan during monsoon and non-monsoon seasons in 2005. A total of 12 elements and nine inorganic ions were identified by inductively coupled plasma atomic emission spectrometry (ICP-AES) and ion chromatography (IC), respectively. Enrichment factors explaining a preponderance of the variance in the data were applied to the data sets. The results show that wind direction significantly affected the concentration of TSP during the monsoon season; moreover, these concentrations were also markedly higher during the monsoon than during the non-monsoon season. Low enrichment factor (EF) values (1.18-2.88) were observed during the monsoon for Ca, Fe, Na, Ba, Cd, Co, Li, Mn, and Sr, reflecting the importance of dust contribution by natural processes. Conversely, the EF values calculated for Ca, K, Ba, Co, Li, and Zn were relatively high (7.03-20.26) when observed during non-monsoon season, a phenomenon suggesting that they are mainly contributed from non-crustal sources. The observations of relatively enhanced EF values during monsoon indicate that the changes in wind direction between monsoon and non-monsoon seasons are associated with the different contribution sources. The high concentration of TSPs observed in the ambient air is believed to be primarily due to surface soil particle emission from the riverbeds.     

衡阳市冬春季大气颗粒物中重金属的污染评价

采用潜在生态危害指数法和富集因子法,对衡阳市冬春季大气颗粒物中重金属污染进行评价。结果表明:重金属元素的潜在生态危害大小为CdCrPbCuNi,春季冬季,细颗粒物PM~2.5总悬浮颗粒物TSP,Pb、Cd、Cr的潜在生态危害程度均属于极强;重金属的富集程度为:CdCrPbCuNi,PM_2.5TSP;Pb、Cu、Cd冬季富集程度大于春季,Cr和Ni冬季富集程度小于春季;TSP和PM_2.5中重金属的富集系数EF值均大于1,说明重金属的相对富集受到人为活动的影响。     

Sampling and analysis of particulate matter by glow discharge atomic emission and mass spectrometries

The direct introduction of particulate matter into glow discharge atomic emission and mass spectrometry sources through a particle beam/momentum separator apparatus is described. Vacuum action through a narrow (0.0625 in. i.d.) stainless steel tube allows the introduction of discrete samples of NIST SRM 1648 urban particulate matter (UPM) and caffeine in powder form. Introduction of "ambient" airborne particulate matter is also possible. Particles passing through the aerodynamic momentum separator impinge on the heated (～200-250 °C) inner surface of the glow discharge plasma volume and are flash-vaporized. The resultant atoms/molecules are subjected to excitation/ionization collisions within the low-pressure (0.5-5 Torr of He or Ar) plasma, producing characteristic photon emission and/or signature ionic species. In this way, atomic emission and mass spectrometry identification of particle constituents is possible. Basic design aspects of the apparatus are presented, and demonstrations of atomic emission detection of the constituents in the NIST SRM illustrate the general characteristics of the approach. Transient atomic emission signals are captured for the introduction of preweighed, discrete samples, with the integrated areas used to construct analytical response curves. Limits of detection using this relatively simple atomic emission system are on the order of tens of nanograms for sample masses of ～50 μg. Mass spectrometric monitoring of introduced caffeine particles and a mixture of polycyclic aromatic hydrocarbons (PAHs) illustrates the ability of the glow discharge plasma to produce high-quality, library (electron impact) searchable mass spectra of molecular species while also yielding isotopic identification of elemental components of the UPM. Limits of detection for Fe in the NIST SRM are on the order of 175 ng of material, equivalent to ～7 ng of analyte Fe. It is believed that the small size, low power consumption, ease of operation, and multimode sampling capabilities (AES/MS) of the particle beam-glow discharge (PB-GD) apparatus hold promise for applications in continuous monitoring and discrete particle sampling.     

顶空-气相色谱法测定卷烟主流烟气粒相物中吡啶

为研究气相色谱测定卷烟主流烟气粒相物中吡啶含量,采用碳酸钠水溶液作基质校正剂,通过顶空进样、DB-WAXETR色谱柱分离、火焰离子化检测器检测。结果表明:吡啶在0.20~16.20μg/mL质量浓度范围内线性拟合度为0.9998,加标回收率在98.4%~104.7%之间,定量限为0.08μg/支,RSD小于5%,该方法可以快速、准确地测定卷烟主流烟气粒相物中吡啶。     

Development of surface functionalized activated carbon fiber for control of NO and particulate matter

This study investigates the development and potential application of activated carbon fibers (ACF) functionalized with ammonia for control of NO and particulate matter (PM) in diesel engine exhaust. A tubular reactor packed with ACF was used to experimentally study the oxidation of NO at room temperature. Tests were conducted at ACF functionalized with three aqueous ammonia concentrations (3, 5, 10 M), three basic reagents (ammonia, pyridine, amine) and three NO concentrations (100, 300, 500 ppm). After offline investigation, the ACF-packed tubular reactor was installed downstream of the engine's exhaust to ascertain the PM capturing efficiency of ACF. The experimental conditions for PM removal included three weights of ACF (2, 3.5, 4.5 g), three engine loads (0, 25, 50 Nm) and three temperatures (150, 300, 450 °C). The maximum 70% conversion for NO was obtained at NO concentration of 300 ppm for ACF functionalized with 5 M ammonia, whereas maximum 90% reduction in PM was observed at engine load of 25 Nm and 450 °C. The study shows significant potential for the ACF based filters in capturing both homogeneous and heterogeneous pollutants emitted from automobiles. Our previously developed transport model incorporating the mechanism for the oxidation of NO was also used to explain the experimental data.     

Carbon particulate matter incineration in diesel engine emissions using indirect nonthermal plasma processing

One of the promising applications of nonthermal plasma (NTP) for environmental cleanup technology is low-temperature oxidation or incineration of carbon particulate matter (PM) in diesel engine emissions. In this process, NO₂ and activated radical species induced by NTP can incinerate carbon PM trapped by a diesel particulate filter (DPF) at low temperature (< 300 °C). In the present study, an experiment was carried out on indirect NTP DPF regeneration for real diesel engine emissions comprising CO₂ of several per cent, hydrocarbons of several hundreds of ppm and moisture of several tens of percentages. It was confirmed that DPF regeneration is possible for a real diesel emission at a low temperature of 280 °C. The removal energy efficiency was estimated to be 0.82 g/kW h. This electric power range is sufficient to meet the recently proposed long-term national regulation for diesel automobiles in Japan.     

Assessment of impact distances for particulate matter dispersion: A stochastic approach

It is known that pollutants can be dispersed from the emission sources by the wind, or settled on the ground. Particle size, stack height, topography and meteorological conditions strongly affect particulate matter (PM) dispersion. In this work, an impact distance calculation methodology considering different particulate sizes is presented. A Gaussian-type dispersion model for PM that handles size particles larger than 0.1 μm is used. The model considers primary particles and continuous emissions. PM concentration distribution at every affected geographical point defined by a grid is computed. Stochastic uncertainty caused by the natural variability of atmospheric parameters is taken into consideration in the dispersion model by applying a Monte Carlo methodology. The prototype package (STRRAP) that takes into account the stochastic behaviour of atmospheric variables, developed for risk assessment and safe distances calculation [Godoy SM, Santa Cruz ASM, Scenna NJ. STRRAP SYSTEM - A software for hazardous materials risk assessment and safe distances calculation. Reliability Engineering and System Safety 2007;92(7):847-57] is enlarged for the analysis of the PM air dispersion. STRRAP computes distances from the source to every affected receptor in each trial and generates the impact distance distribution for each particulate size. In addition, a representative impact distance value to delimit the affected area can be obtained. Fuel oil stack effluents dispersion in Rosario city is simulated as a case study. Mass concentration distributions and impact distances are computed for the range of interest in environmental air quality evaluations (PM_2.5-PM₁₀).