烟气中二氧化硫及三氧化硫测定方法的研究

本文采用过氧化氢-氯化钡-钍试剂法以及80%异丙醇-氯化钡-钍试剂法分别测定了烟气中的二氧化硫及三氧化硫质量浓度,并对该方法的灵敏度、准确度以及各种影响因素进行了研究分析.本方法简单、快速、准确、便于现场监测控制.     

Improvement of a monitoring tape for nitrogen dioxide in air

A porous cellulose tape containing a silica gel that was previously impregnated with a processing solution containing p-toluenesulfonic acid, sulfanilic acid, N-1-naphthyl ethylene diamine dihydrochloride, ethylene glycol and methanol has been developed to provide a highly sensitive detection of nitrogen dioxide in air. When the sample including nitrogen dioxide was passed through the tape, the color of tape changed to red, and the degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). The calibration graph was linear up to approximately 0.10 ppm. The detection limit was 0.5 ppb for nitrogen dioxide with a sampling time of 8 min and a flow rate of 60 ml min(-1). No interferences were observed from ammonia (40 ppm), sulfur dioxide (51 ppm), carbon dioxide (21%), ozone (0.75 ppm), hydrogen sulfide (27 ppm) or nitrogen monoxide (99 ppm).     

Adsorption and catalysis at the solid/sulfur dioxide interface in the atmosphere. An examination of statistical data

From the official analytical data for sulfur dioxide and smoke in air pollution for one winter and one summer month covering residential and industrial areas in Great Britain, regression lines are computed. These reveal a large deficiency which is of very high significance of sulfur dioxide relative to smoke in winter compared with summer; the data show clearly that the deficiency is not due to the increase in domestic smoke in winter. Several reasons for the deficiency are examined semiquantitatively, and it is suggested that adsorption of sulfur dioxide occurs on solid particles followed by its catalytic oxidation by oxygen to sulfur trioxide. The amount of sulfur dioxide to be accounted for is far too high to be explained by simple adsorption on smoke particles. The catalysis may be due to traces of metals.The data also reveal that whatever may be the mechanism by which the sulfur dioxide is removed, it becomes less effective as the amount of smoke present increases, in all situations. It is suggested that a cause of this change might be the progressive covering of the very active surface of natural inorganic dust, possibly including meteoric dust, in the atmosphere by the less catalytically active smoke particles as their concentration rises.     

Atmospheric concentrations of sulfur dioxide, nitrogen oxides, ammonia, hydrogen chloride, nitric acid, formic and acetic acids in the south of Vietnam measured by the passive sampling method.

A passive sampling method was applied to measure the concentrations of air pollutants, such as sulfur dioxide, nitrogen oxides, ammonia, hydrogen chloride, and nitric, formic and acetic acids, in the ambient air at four test sites in the southern region of Vietnam. The monthly averages and the average concentrations of air pollutants during the period from July 2001 to September 2002 are reported here. The concentrations of air pollutants varied widely, depending on the test sites and the sampling periods. The average concentrations of sulfur dioxide in the air during the period from July 2001 to September 2002 at the four test sites were 3.3-16.9 ppb, and those of nitrogen dioxide were 5.4-12.8 ppb. The concentrations of nitrogen monoxide and hydrogen chloride were very low at all of the test sites. The observed concentrations of all of the above-mentioned pollutants were lower than those of the Vietnamese standards of air pollutants.     

A specific spectrophotometric determination of ozone in air in the presence of sulfur dioxide and nitrogen oxides

A sensitive, specific spectrophotometric method for the determination of ozone in air by the ozonolysis of 1,1-di-phenylethylene (DPE) is described. The yield of formaldehyde from the ozonolysis of several terminal olefins was determined, and DPE was found to give the highest yield, 90%. The method was checked against the EPA iodimetric method, and gives a consistent yield of formaldehyde over the ozone range 0.05–5.00 μg g^-1 of air. As sulfur dioxide is used as a reagent, its presence in air does not interfere. Interference by nitrogen oxides and other free radical oxidants is prevented by the addition of mesitol (2,4,6-trimethylphenol). Formaldehyde in air interferes, but can be determined by using the method with DPE omitted from the sampling train, and so accounted for. In the procedure, formaldehyde is determined by the reverse of the West—Gaeke method for sulfur dioxide.     

Determination of sulfur dioxide in air

The determination of sulfur dioxide in air is based on a preliminary purification with a cellulose filter and 80% isopropanol and absorption of sulfur dioxide by means of two midget impingers in 0.3 N hydrogen peroxide. The formed sulfate is titrated in an aliquot with 0.005 M barium perchlorate employing Chlorophosphonazo III (CPA) as an indicator. The method is suitable for 0.3–19.0 mg of sulfur dioxide per 50 liters of air. The standard deviation of the titration is ±0.02 ml per consumption of 5.00 ml and is four times smaller than that of the Thorin method.     

Pneumatoamperometric determination of sulfur dioxide in air on ppb level

A simple device for the determination of sulfur dioxide at ppb concentrations in air is described. The device is composed of an enrichment unit operating continuously on the basis of gas extraction into polydisperse aerosol of a liquid transferring sulfur dioxide from liter amount of air into microliter amount of liquid. The analyte is determined pneumatoamperically from the concentrate on a gold-plated porous Teflon electrode. The detection limit is 0.3 ppb (v), i.e. 0.87 microgram/m3 of sulfur dioxide, the linear range covers several orders of magnitude. The analytical response is obtained few tenths of seconds after the gas contaminated with sulfur dioxide has entered the enrichment unit.     

Infrared Detection of Criegee Intermediates Formed during the Ozonolysis of β‐Pinene and Their Reactivity towards Sulfur Dioxide

Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β‐pinene. Their transient absorption bands between 930 and 830 cm^?1 appear only in the initial phase of the ozonolysis reaction when the scavenging of stabilized CIs by the reaction products is slow. The large CIs react with sulfur dioxide to give sulfur trioxide and nopinone with a yield exceeding 80 %. Reactant consumption and product formation in time‐resolved β‐pinene ozonolysis experiments in the presence of sulfur dioxide have been kinetically modeled. The results suggest a fast reaction of sulfur dioxide with CIs arising from β‐pinene ozonolysis.     

Chromatographic determination of the rate and extent of absorption of air pollutants by sea water

Summary A simple chromatographic method is developed to determine the rate constant for expulsion of an air pollutant from water or its diffusion parameter in the liquid, the rate constant for chemical reaction of the pollutant with water, its mass transfer coefficient in the liquid, and the partition coefficient between liquid water and air. From these physicochemical parameters, the absorption rate by sea water and, therefore, the depletion rate of a polluting substance from the air can be calculated, together with the equilibrium state of this absorption. The method has been applied to nitrogen dioxide being absorbed by triple-distilled water and by sea water, at various temperatures. From the temperature variation of the reaction rate constant and of the partition coefficient, the activation energy for the reaction and the differential heat of solution were determined.     

A simple diffuse reflectance Fourier transform infrared spectroscopic determination of sulfur dioxide in ambient air using potassium tetrachloromercurate as the absorbing reagent

This paper presents development of a simple, rapid, and precise analytical method for determination of sulfur dioxide in ambient air by a gas to solid-phase conversion method. Sulfur dioxide is determined in the form of sulfite (SO3(2-)) because the absorbing reagent, potassium tetrachloromercurate (TCM), used in this method absorbs sulfur dioxide from the atmosphere in the form of sulfite. Determination of submicrogram levels of sulfur dioxide was based on the selection of a quantitative analytical peak at 495 cm(-1) among the 3 observed vibrational peaks for the dichlorosulfitomercurate complex formed after reaction of sulfur dioxide with TCM and measurement of absorbance using diffuse reflectance Fourier transform infrared spectroscopy. The limits of detection and quantification of the method were found to be 0.09 and 0.4 microg/g SO3(2-), respectively. The precision in terms of standard deviation and relative standard deviation (RSD) at a level of 2 microg SO3(2-)/10.1 g KBr for n = 10 was found to be 0.036 microg SO3(2-) and 1.8%, respectively. The RSD (n = 10) for determination of sulfur dioxide in ambient air was observed to be in the range of 2.7-4.2%. The method proposed is time saving and eliminates the slow and cumbersome steps of pH maintenance of the reaction mixture and color formation of the U.S. Environmental Protection Agency recommended West and Gaeke spectrophotometric method and other methods for quantitative determination of sulfur dioxide.     

Plasma quenching by air during single-bubble sonoluminescence

We report the observation of sudden and dramatic changes in single-bubble sonoluminescence (SBSL) intensity (i.e., radiant power, phi(SL)) and spectral profiles at a critical acoustic pressure (P(c)) for solutions of sulfuric acid (H2SO4) containing mixtures of air and noble gas. Nitric oxide (NO), nitrogen (N2), and atomic oxygen emission lines are visible just below P(c). At P(c), very bright (factor of 7000 increase in phi(SL)) and featureless SBSL is observed when Ar is present. In addition, Ar lines are observed from a dimmed bubble that has been driven above P(c). These observations suggest that bright SBSL from H2SO4 is due to a plasma, and that molecular components of air suppress the onset of bright light emission through quenching mechanisms and endothermic processes. Determination of temperatures from simulations of the emission lines shows that air limits the heating during single-bubble cavitation. When He is present, phi(SL) increases by only a factor of 4 at P(c), and the SBSL spectrum is not featureless as for Ar, but instead arises from sulfur oxide (SO) and sulfur dioxide (SO2) bands. These differences are attributed to the high thermal conductivity and ionization potential of He compared to Ar.     

A Quantitative Method by Gas Chromatography for Dibenzothiophene and Its Degrading-Products after Biodesulfurition

The petroleum is one of the most important industrial materials which contains carbon, hydrogen, oxygen, sometimes nitrogen, sulfur and phosphor are also in it. When these oils that contain sulfur are refined or combusted, sulfur dioxide is produced, which is main air pollution today, the environmental conditions become worse and worse, it is significant to remove sulfur especially hetero-sulfur from petroleum.     

The sampling of sulfur dioxide in air with impregnated filter paper

A method is suggested for the sampling of sulfur dioxide in air with impregnated filter paper instead of bubblers. The best aqueous impregnating solution contained potassium hydroxide with glycerol or triethanolamine. The possibilities and limitations of the method are discussed. High collection efficiencies (over 95%) were obtained at relative humidities above 25%. Collected sulfur dioxide was stable for at least several weeks when the filters were kept dry after the sampling. The method is especially suited for short-time measurements and for automatic sampling with smoke samplers.     

Choice of a scheme for desulfurization of rich metallurgical gases

Known schemes for production of sulfur from an oxygen-containing sulfurous gas are critically considered with account of the presence of sulfur trioxide in real metallurgical gases. An efficient technology for deep processing of metallurgical gases rich in sulfur dioxide was developed on the basis of a thermodynamic analysis and industrial “methane” technology for reduction of gases formed in autogenous smelting.     

A new fluorescence method for determination of ozone in ambient air

A new simple method for determination of ozone in ambient air is presented. The reaction employed is based on the known ozonolysis of indigo dye. The indigotrisulfonate molecule contains one carbon–carbon double bond (C═C), which reacts with ozone and generates isatinsulfonates and sulfoanthranilate. The quantitatively formed sulfoanthranilate presents fluorescence (λ_ex 245 nm, λ_em 400 nm). Ozone was collected using two cellulose filters coated with 40 μL of 1.0 × 10^{− 3} mol L^{− 1} of indigotrisulfonate. The analytical response was linear in the range 0–150 ppbv ozone, and a detection limit of 7 ppbv was achieved using a sampling time of 15 min and an optimum sampling air flow rate of 0.4 L min^{− 1}. There was no interference from sulfur dioxide, formaldehyde or nitrogen dioxide. The ozonolysis mechanism and the reaction products are discussed.     

Development of a monitoring tape for phosgene in air

A porous cellulose tape impregnated with a processing solution that includes 4-p-nitroben-zylpyridine, N-benzylaniline and methanol is a highly sensitive means of detecting phosgene and maintains stable sensitivity for at least three months in air in a desiccator. When the sample including phosgene was passed through the tape, the color of tape changed to red. The degree of color change was proportional to the concentration of phosgene at a constant sampling time and flow rate. The degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). The detection limit was 6 ppb for phosgene with a sampling time of 60 sec and a flow rate of 400 ml/min. Reproducibility tests showed that the relative standard deviation of response (n = 10) was 2.6% for 0.2 ppm phosgene. No interference was observed from ethanol (1 vol.%), trichloroethylene (1 vol.%), acetone (1 vol.%), carbon dioxide (4.9 vol.%), carbon monoxide (100 ppm), nitrogen dioxide (100 ppm), sulfur dioxide (50 ppm), hydrogen chloride gas (5 ppm), chlorine (3 ppm), acetic acid gas (24 ppm), ammonia (40 ppm), or benzyl chloride (20 ppm).     

Vanadium doped tin dioxide as a novel sulfur dioxide sensor

Considering the short-term exposure limit of SO2 to be 5 ppm, we first time report that semiconductor sensors based on vanadium doped SnO2 can be used for SO2 leak detection because of their good sensitivity towards SO2 at concentrations down to 5 ppm. Such sensors are quite selective in presence of other gases like carbon monoxide, methane and butane. The high sensitivity of vanadium doped tin dioxide towards SO2 may be understood by considering the oxidation of sulfur dioxide to sulfur trioxide on SnO2 surface through redox cycles of vanadium-sulfur-oxygen adsorbed species.     

Analytical interference effects on laser-induced fluorescence of ethylene by selected molecular species

The interference of numerous compounds on the laser-induced fluorescence of ethylene at 10.6-mm was studied. The compounds studied were methane, propane, hexane, heptane, propylene, 1-butene, acetylene, benzene, cyclohexane, acetone, chloroform, carbon tetrachloride, methanol, ethanol, sulfur dioxide, nitrogen dioxide, nitric oxide, carbon dioxide, water, argon, helium, nitrogen, and air. Only some of these, in low concentrations, interfered at atmospheric pressure, but most interfered in evacuated systems. Compounds which absorbed the excitation 10.6μm radiation enhanced the fluorescence signals of ethylene, while non-absorbing compounds generally did not interfere. The quenching efficiencies of helium, argon, nitrogen, and methane on excited ethylene molecules were determined, and compared to values calculated from published data; good agreement was found except for methane. Quenching experiments with higher concentrations of added compounds were also performed.     

环保税制改革与雾霾协同治理

环保税是雾霾等污染治理中的一大利器,但2018年最新公布的环保税方案,能否有效促进当地的雾霾污染治理及区域间的协同治理等却受到一定质疑。为此,本文通过估算雾霾的主要污染源−二氧化硫、氮氧化合物和烟粉尘的影子价格来衡量雾霾治理的边际成本,以评估分析中国现有环保税的问题及改革方向。研究发现,中国雾霾污染排放的影子价格自2005年来已持续大幅增长,从而环保税额标准不能简单地“费税平移”,应建立阶段性的提升机制;其中,氮氧化合物的环保税额标准相对二氧化硫和烟粉尘而言严重偏低,作为未来减排重点,应有较大幅度调整。海南、广西等九个省市的当前环保税额标准相对远低于对应的以上三类污染物的影子价格,不利于对当地雾霾污染的有效治理。从污染程度和污染物影子价格的角度,石家庄、太原等多个区域城市群的环保税方案也不利于加强雾霾的区域协同治理。以长三角区域为例,建议环保税制改革优化的原则为：相对高影子价格的地区都应制定较高的环保税额标准,如合肥等;其中,相对高污染程度的地区应制定较高的环保税额标准,而影子价格较低的地区则应获得适度的经济补偿,如嘉兴等;而相对低污染程度低影子价格的地区则可保持相对较低的环保税额标准,如台州等。以上研究可为中国雾霾协同治理的环保税制改革提供重要参考。     

原煤低温氧化预脱硫的实验研究

采用三种高硫煤，在固定床反应器中考察了原煤在空气、空气水蒸气和空气氮气气氛下低温氧化预脱硫过程的影响因素，包括煤种（总硫含量、形态硫分布和挥发分含量）和化学反应条件（温度、停留时间）。脱硫前后的样品中硫及硫形态、热值、工业分析和元素分析依据国际进行测定。实验结果表明硫及碳质的氧化在开始阶段以不同的速率析出，随后反应中差别减小；黄铁矿硫可得到高的脱除率；水蒸气适当比例的加入可以增加黄铁矿的脱除，同时降低碳的转化和热量的损失；而氮气的加入在降低碳和热量的损失外，降低了硫的脱除。