Absorption of NO and NO2 in caprolactam tetrabutyl ammonium halide ionic liquids

To explore environmentally benign solvents for the absorption of NO and NO2, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO2 was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO2 in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO2 decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO2 was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO2.     

Absorption cross-sections of atmospheric constituents: NO2, O2, and H2O

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO₂, O₂ and its collision-induced absorption spectrum, and H₂O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth’s atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.     

Lipophilicity and Metabolic Route Prediction of Imidazolium Ionic Liquids * (6 pp)

- Aims and Background. Ionic liquid application in industry will offer several excellent solutions, but it also means that they will enter the environment sooner or later. Responsible product design should always take into consideration not only technological demands, but also the risks arising out of possible toxicity and ecotoxicity. In our strategy we are aiming to understand the fate of these entities through their life cycle in the environment as a complimentary element of their design. This paper presents results on the lipophilicity of selected imidazolium ionic liquids, a parameter that plays a key role in environmental and biological distribution. Additionally, the prediction of the most stable metabolite of a 1-butyl-3-methylimidazolium (BMIM) cation – a congener representative of this group of compounds is presented. Materials and Methods Lipophilicity was evaluated by means of reversed phase and immobilized artificial membrane chromatography and further compared to calculated data. Theoretical prediction of lipophilicity was undertaken using fragmental methodology combined with manual calculations of the geometric bond factor for quaternary ammonium and the electronic bond factor due to the presence of a charge. Results and Discussion All the substances studied are characterized by very low partition coefficients, and lipophilicity varies linearly with elongation of the n-alkyl chain. Prediction of metabolic routes was based solely on thermodynamic data of the radical intermediates formed during the reaction with the cytochrome P450 system. The energetically most stable radical structure is generated by hydrogen abstraction from the gamma position of the BMIM cation. Conclusions and Recommendations. The experimentally measured and theoretically estimated lipophilicity coefficients obtained for all the compounds studied generally indicate a relatively low lipophilicity and thus preferable partition to the aqueous phase. By means of thermodynamic data, it was also confirmed that the energetically most stable radical structure is generated by hydrogen abstraction from the gamma position on the alkyl chain in the 1-alkyl-3-methylimidazolium cation, as a result of which the C1 atom is preferentially oxidized. - * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August to 1 September 2004, Bordeaux, France.     

Modeling and monitoring of CO,NO and NO2 in a modern townhouse

Mass-balance models for indoor concentrations of CO, NO and NO₂ were applied to an energy-efficient townhouse. Model parameters included source emission rates, infiltrating airflows, and, for NO₂, loss rate coefficients. Emission factors for CO, NO and NO₂ were estimated for each of the gas-fired appliances in the house. Airflows were estimated using sulfur hexafluoride (SF₆) decay techniques. Loss rates for NO₂ were calculated as the difference between NO₂ removal rates and estimated air exchange rates; CO and NO concentrations decayed at a rate not significantly different than that for SF₆. Comparing model predictions with measured concentrations yielded differences averaging 17% for CO and NO, and 28% for NO₂.     

Laboratory measurements of NO and NO2 depositions onto soil and cement surfaces

Laboratory measurements have been made of the deposition of NO and NO₂ onto selected soil and cement surfaces. Experimental results yielded deposition velocities of ~ 0.1–0.2 cm s⁻¹ for NO and ~ 0.3–0.8 cm s⁻¹ for NO₂ over freshly prepared surfaces. Deposition was largely irreversible and decreased with time (exposure to NO or NO₂). The latter observations indicate a finite capacity of these surfaces for removal of the gaseous species. However, additional experiments carried out in this study suggest that surface activity in the environment can be regenerated, in the case of NO₂, but not NO, by interaction with atmospheric ammonia. The results further suggest, that for both NO and NO₂, surfaces can be reactivated by precipitation washing away soluble surface reaction products. The lower deposition rates and capacities, and more limited regeneration of surface activity observed for NO, relative to NO₂, suggest that uptake of NO by ground level surfaces in the environment will be considerably less important than that of NO₂.     

Photochemical Conversion of NO to NO2 by Hydrocarbons in an Outdoor Chamber

Significant differences occur between results of chamber work conducted outdoors versus work conducted indoors under constant light intensity. Under outdoor conditions at constant [NO_X]_O, lower [HC]o resulted in lower [NO₂]_max and NO₂ dosage during the daylight hours. The percent reduction in [NO₂]_max was a function of the [HC]₀ reduction and the [NO_X]_O level. Under all experimental conditions the 10 hour N0₂ average to maximum N0₂ concentration ratio appeared to be constant at 0.73 during the daylight hours. A regression equation relating [NO_x]_max to [NO_X]_O, [HC]_O, and measures of solar radiation accounted for 92% of the variance in the data. Although there is unavoidable confoundment between [HC]₀ and solar radiation, the HC term in this regression equation can introduce ±20 % change in [N0₂]_max - This variation can be partially offset or enhanced by variations in solar radiation.     

Application of CALINE4 to roadside NO/NO2 transformations

The CALINE4 roadway dispersion model has been applied to concentrations of NO_x and NO₂ measured near Gandy Boulevard in Tampa, FL (USA) during May 2002. A NO_x emission factor of 0.86 gr mi⁻¹ was estimated by treating NO+NO₂ (NO_x) as a conserved species and minimizing the differences between measured and calculated NO_x concentrations. This emission factor was then used to calculate NO₂ concentrations using the NO/NO₂ transformation reactions built into CALINE4. A comparison of measured and calculated NO₂ concentrations indicates that for ambient O₃ concentrations less than 40 ppb the model under-predicts the chemical transformation of NO. The enhanced transformation of NO may be due to reactions of NO with oxidants such as peroxy radicals that are present either in the atmosphere or in vehicle exhaust.     

Prediction of NO and NO2 concentrations near a street with heavy traffic in Santiago,Chile

Based on NO concentrations and meteorological variables recorded hourly at a point close to an avenue with heavy traffic in the city of Santiago, we are able to build a simple model that allows prediction of NO concentrations several hours in advance. Predicted NO concentrations in conjunction with forecasted meteorological data may be used to predict NO₂ concentrations with reasonable accuracy. We compare predictions generated using persistence, linear regressions and multi layer neural networks.     

Trend analysis of urban NO2 concentrations and the importance of direct NO2 emissions versus ozone/NOx equilibrium

The annual air quality standard of NO₂ is often exceeded in urban areas near heavy traffic locations. Despite significant decrease of NO_x emissions in 1986–2005 in the industrial and harbour area near Rotterdam, NO₂ concentrations at the urban background remain at the same level since the end of the nineties. Trend analysis of monitoring data revealed that the ozone/NO_x equilibrium is a more important factor than increasing direct NO₂ emissions by traffic. The latter has recently been identified as an additional NO₂ source due to the introduction of oxy-catalytic converters in diesel vehicles and the growing number of diesel vehicles. However, in Rotterdam over the period 1986–2005 direct NO₂ emissions by road traffic only increased 3–4%. Due to the importance of the ozone/NO_x equilibrium, it is concluded that local NO_x emissions in Rotterdam need substantial reduction to achieve lower NO₂ urban background levels. This is a relatively costly abatement strategy and, therefore, a “hotspot” approach aiming at reducing NO_x emissions by local traffic measures is more effective to meet European air quality standards.     

Carbon catalysis in the aqueous oxidation of SO2 by NO2 and air

Sulfur Dioxide and an oxidant gas — air or NO₂ — were bubbled through aqueous suspensions of both washed and unwashed carbon black as well as through samples of wash water, which contained whatever soluble species were originally present on the carbon, and high-purity water. The sulfate yields obtained showed the washed and unwashed carbon to be equally catalytic for the oxidation of SO₂ to sulfate by both oxidants whereas little sulfate was generated in either the wash water or high-purity water in the absence of carbon. These results indicate that the sulfate yields produced in aqueous suspensions of the carbon studied are due to catalysis by the carbon particles rather than by soluble species dissolved from them.     

Recent trends and projections of primary NO2 emissions in Europe

An assessment of recent trends in primary NO₂ emissions has been carried out for ten case study locations across the European Union. Estimates of the percentage of NO_x from road traffic emitted as primary NO₂ (f-NO₂) have been derived for 1995, 2000 and 2005 by combining the results of a literature survey of primary NO₂ emission factors for different vehicle types and technologies with an emission inventory. Estimates of f-NO₂ have also been derived from ambient monitoring data at roadside sites in each case study location using a model.The results of the analysis of trends show that f-NO₂ has increased in recent years and that the rate of increase has been greatest since 2000. f-NO₂ has increased from 8.6% in 2000 to 12.4% in 2004 as an average across the monitoring sites and from an average of 6.3% in 2000 to 10.6% in 2005 as an average of the emission inventory based calculations for the case study countries. f-NO₂ is predicted to increase further to an average of 19.6% in 2010 and 32.0% in 2020 as a result of the further penetration of exhaust after treatment technologies for diesel vehicles in the fleets. This increase is expected to be offset by the large reduction in NO_x emissions over this period, resulting in an increase in NO₂ emissions from road traffic to 2015, followed by a decline to close to 2004 levels by 2020. Estimates of future ambient NO₂ concentrations have also been calculated for the roadside monitoring sites included in the study. At 29 out of 45 of these sites the annual mean NO₂ limit value is predicted to be exceeded in 2010. At 22 of these sites, the annual mean concentration is expected to remain above the limit value until 2020 and beyond.     

Estimation of night-time N2O5 concentrations from ambient NO2 and NO3 radical concentrations and the role of N2O5 in night-time chemistry

Dinitrogen pentoxide (N₂O₅), which is present in equilibrium with NO₃ radicals and NO₂, has been recognized for some time as an intermediate in the NO_x chemistry of night-time atmospheres. However, until the advent of long pathlength spectroscopic techniques for the measurement of atmospheric NO₃ radical concentrations, no reliable method for estimating N₂O₅ concentrations has been available. We have calculated maximum night-time N₂O₅ concentrations from the available experimentally determined concentrations of the NO₃ radical and NO₂ in the U.S. and Germany, and find that N₂O₅ concentrations as high as ~ 15 ppb can occur. We have also estimated removal rates for N₂O₅ and for NO₃ radicals during these nights. From data obtained under conditions devoid of point sources of NO_x, upper limit estimates of the homogeneous rate constant for the reaction of N₂O₅ with water vapor are obtained, leading to the conclusion that the homogeneous gas phase rate constant for this reaction is ⩽ 1 × 10⁻²¹ cm³ molecule⁻¹ s⁻¹ at 298 K, consistent with recent environmental chamber data.     

The change in O3, SO2 and NO2 concentrations in Lithuania

Due to the dynamic nature of the atmosphere, substantial amounts of gaseous and particulate pollutants are transported to the areas distant from their sources. In order to determine the regional concentration levels of atmospheric pollutants in Lithuania, concentrations of gaseous O₃, SO₂, NO₂ and other pollutants have been measured at the Preila background station (55°20′ N and 21°00′ E, 5 m a.s.l.) since 1981. The long-term concentration data set enabled us to get temporal trends, both on a seasonal and longer time scale, to identify source areas of pollutants and to relate them to the emission data. Based on the data obtained, the different tendencies in the pollutant concentration changes were revealed. Positive trends for ozone (of 2.9% per year during 1983–2000) and a distinct negative trend for both sulphur dioxide (of 3.8% per year during 1981–2000) and nitrogen dioxide (of 3.8% per year during 1983–2000) were found. The air mass back-trajectory analysis was used to assess the source region of air pollutants transported to Lithuania. The pollutant concentration levels were compared with their emission changes in Europe and Lithuania. The general trends in SO₂ as well as in NO₂ concentrations observed are consistent with changes in SO₂ and NO₂ emissions in Europe and Lithuania.     

基于MAX-DOAS的乌鲁木齐市NO2时空变化

为研究乌鲁木齐市NO2污染状况,了解其时空分布特征及其影响因素,基于多轴差分吸收光谱技术（MAX-DOAS）,利用2014年4月—2015年12月3个监测点和多次车载移动观测的数据,反演了乌鲁木齐对流层NO2垂直柱浓度（VCD）,并且结合气象和地形等因素进行了分析。结果表明：NO2 VCD由高到低的季节依次是冬季、春季、秋季和夏季,均值为10.84、7.78、5.98和3.56×1015 molec·cm-2;由高到低的监测站依次是城区站、工业区站和郊区站,年均值为9.52、8.44和5.58×1015 molec·cm-2;日变化上春冬两季呈U型,夏秋两季呈双峰型;NO2空间分布由南到北呈明显的"两头低中间高",高值通常出现在市区高架桥附近;乌鲁木齐NO2 VCD与气象因子温度、风速、相对湿度、日照时数都有较好的相关性;乌鲁木齐夏季盛行西北风,顺势于地形利于市区污染物传输出去,冬季盛行东北风,而东面有博格达山阻挡致使风速较低,污染物滞留堆积浓度高。     

Sensitivity of Native Desert Vegetation To SO2 and to SO2 and NO2 Combined

Interest in air pollution injury to native vegetation has been generated with the construction and planned construction of large coal-fired power plants near the coal reserves in the southwest desert areas of the United States. Since information on the effects of SO₂ on these native species was not available in the literature, fumigation studies were conducted with portable chambers placed over native species in the field with SO₂ and SO₂ + NO₂. Pollutant concentrations were measured and controlled with instruments located in a mobile laboratory. Each fumigation was of two hours duration and the concentration ranged from 0.5 to 11 ppm SO₂ and from 0.1 to 5 ppm NO₂. Concentrations of SO₂ above 2 ppm were required to cause injury to all but a few of the 87 species studied. Many of the native desert species proved to be highly resistant to injury from these gases.     

钒硅催化脱硫脱硝的研究

考察了经10% H2-90% Ar(体积分数)还原的钒硅催化剂在固定床石英玻璃反应器中的脱硫脱硝活性,研究了反应温度、SO2/NO摩尔比及O2浓度对SO2和NO脱除率的影响.结果表明,还原后的钒硅催化剂的平均NO脱除率提高了15%左右;反应温度对脱硫脱硝影响较大,当温度为400℃以上时SO2和NO脱除率基本保持稳定;SO2/NO摩尔比为2和5时,钒硅催化剂的NO脱除率较高;模拟烟气中有O2条件下的脱硫脱硝活性明显高于无O2条件,O2体积分数为6.00%时SO2和NO脱除率达到最大.     

Ammonium and nitrate tolerance in lichens

Since lichens lack roots and take up water, solutes and gases over the entire thallus surface, these organisms respond more sensitively to changes in atmospheric purity than vascular plants. After centuries where effects of sulphur dioxide and acidity were in the focus of research on atmospheric chemistry and lichens, recently the globally increased levels of ammonia and nitrate increasingly affect lichen vegetation and gave rise to intense research on the tolerance of lichens to nitrogen pollution. The present paper discusses the main findings on the uptake of ammonia and nitrate in the lichen symbiosis and to the tolerance of lichens to eutrophication. Ammonia and nitrate are both efficiently taken up under ambient conditions. The tolerance to high nitrogen levels depends, among others, on the capability of the photobiont to provide sufficient amounts of carbon skeletons for ammonia assimilation. Lowly productive lichens are apparently predisposed to be sensitive to excess nitrogen.     

2015年南京市SO2、NO2、CO和O3的污染特征分析

分析了2015年南京市二氧化硫（SO2）、二氧化氮（NO2）、一氧化碳（CO）和臭氧（O3）的污染特征。南京市SO2、NO2、CO和O3的年均浓度分别为19.3 μg·m-3、50.2 μg·m-3、0.972 mg·m-3和114 μg·m-3;SO2和CO污染相对较轻,NO2和O3污染相对严重。SO2、CO和O3的日变化呈"单峰型",而NO2的呈"双峰型";SO2、NO2和CO浓度在冬季最高,夏季最低,而O3相反。秸秆焚烧产物的区域输送在夏收（6月）和秋收（11月）时节对南京市CO的贡献显著。各监测点及全市的气态污染物普遍表现出"反周末效应",指示外来污染源。     

Mathematical Modeling of SO2 Absorption in a Venturi Scrubber

Abstract

A three-dimensional mathematical model was used to predict the removal efficiency of a venturi scrubber for SO₂ absorption into a water and alkaline solution. In order to obtain better results, nonuniform droplet concentration distribution was considered. The results of the model with nonuniform droplet concentration distribution are compared with several sets of experimental data, as well as with prediction data of a mathematical model with uniform droplet concentration distribution. Without exception, all comparisons indicated that including nonuniformity of droplet concentration distribution in the model will significantly improve the agreement between the experimental data and predicted values.