Ppm Sulfur Dioxide Research Articles

Investigating the Impact of Air Pollutants on Fuel Cell Performance and Durability: Experimental and Modeling Approaches

Fuel cells hold immense promise as efficient and sustainable power sources for transportation and stationary applications. However, their operation can be severely impacted by air pollutants, particularly sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants can adsorb onto the platinum catalyst, leading to a decrease in fuel cell performance and durability.In this study, we investigate the impact of SO2 and NO2 on PEM fuel cell performance and durability. The contamination tests were carried out at a constant current density of 0.5 A.cm−2, and they consisted of four steps: a pre-poisoning step to evaluate initial performance (15-16 h), poisoning step (50 h), self-recovery in a pure air stream (20-21 h) and a driven CV-induced recovery. Electrochemical characterizations were carried out at the end of each step (Polarization curve, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and H2 Crossover). Our initial investigation involved contaminating a single fuel cell with a low concentration of 0.1 ppm of sulfur dioxide (SO2). Remarkably, this resulted in a 1.1% decrease in cell voltage. Building on this foundation, our ongoing research aims to delve deeper into the impact of individual pollutant concentrations (SO2 and NO2) and their combined effects, considering varying temperatures and current densities to simulate real-world conditions.Simultaneously, a comprehensive model is being developed using Simscape in Matlab. The model accounts for the pollutants either as single-component gases or as a mixture. For single-component gas adsorption, the Langmuir Isotherm model is employed. To capture the competitive adsorption of SO2 and NO2 on platinum in gas mixtures, we are testing the Modified Competitive Langmuir Isotherm Model. The model will further be calibrated and validated using the experimental results.This combined experimental and modeling approach will provide a comprehensive understanding of the impact of air pollutants on fuel cell performance and durability. The insights gained from this study can inform the development of mitigation strategies and enhance the robustness of fuel cells in real-world applications as well as the sizing of a filter. Figure 1

INFLAMMATORY RESPONSE IN RAT LUNG AFTER EXPOSURE TO SULPHUR DIOXIDE GAS

In the present study, albino rats, Rattus norvegicus (Berkenhout) were exposed to 40 ppm and 80 ppm sulphur dioxide gas for 30 days and 60 days for one hour per day, and inflammatory responses were studied in the lung by physical and biochemical parameters. Significant increases in lung weight, lung total protein and alkaline phosphatase have been observed.

Kükürtlenmiş Kayısıların Raf Ömrünü Uzatmada Kükürtün Etkisinin Kinetik İncelenmesi

In this study, sulphurized apricots with different sulfur values were obtained from the factory in Malatya province. These apricot samples were kept at market temperature values (4, 26 and 40°C) in the package offered for sale, and their sulfur dioxide values were determined daily. As a result of the experimental periods, reduction rate and other data were determined by calculating the sulfur dioxide in the sample. Also, loss rate and kinetics of sulfur dioxide were determined from its change over time at different temperatures. From the results obtained, important findings such as shelf life of sulphurous apricots at different temperatures in the package, deterioration and effect of the sulfur dioxide value on the shelf life were obtained. According to the analysis results of apricots containing different amounts of sulfur, when the moisture and SO2 loss in dried apricot samples during their stay on the shelf were examined in the kinetic study, it was determined that it was suitable for the first order kinetic model for 4°C and the second order kinetic model for 26 and 40°C. From the experimental results, quite low sulfur removal values were obtained for the samples offered for sale after 980 hours at 4°C and 525 hours at 26°C. Moisture and SO2 losses accelerated after approximately 740 hours at a temperature of 40°C. In the sample containing 3280 ppm sulfur dioxide during shelf storage at 4°C, there was an 11% loss of sulfur dioxide after 980 hours. A 46% sulfur dioxide loss was determined in the same samples after 740 hours at 40°C. It has been determined that sulfur dioxide loss is greater at higher temperatures. When the storage conditions of the samples were examined in terms of humidity, it was observed that apricots lost their moisture in the range of 52-85% after 29 days at temperatures of 4 and 40 °C. Based on the fact that the water activity of the packaged sulfurized dried apricots offered for sale is 25%, in this study, an average shelf life of approximately 25 days was determined according to this value.

Spectral Features Differentiate Aging-Induced Changes in Parchment-A Combined Approach of UV/VIS, µ-ATR/FTIR and µ-Raman Spectroscopy with Multivariate Data Analysis.

From the moment of production, artworks are constantly exposed to changing environmental factors potentially inducing degradation. Therefore, detailed knowledge of natural degradation phenomena is essential for proper damage assessment and preservation. With special focus on written cultural heritage, we present a study on the degradation of sheep parchment employing accelerated aging with light (295-3000 nm) for one month, 30/50/80% relative humidity (RH) and 50 ppm sulfur dioxide with 30/50/80%RH for one week. UV/VIS spectroscopy detected changes in the sample surface appearance, showing browning after light-aging and increased brightness after SO2-aging. Band deconvolution of ATR/FTIR and Raman spectra and factor analysis of mixed data (FAMD) revealed characteristic changes of the main parchment components. Spectral features for degradation-induced structural changes of collagen and lipids turned out to be different for the employed aging parameters. All aging conditions induced denaturation (of different degrees) indicated by changes in the secondary structure of collagen. Light treatment resulted in the most pronounced changes for collagen fibrils in addition to backbone cleavage and side chain oxidations. Additional increased disorder for lipids was observed. Despite shorter exposure times, SO2-aging led to a weakening of protein structures induced by transitions of stabilizing disulfide bonds and side chain oxidations.

ROAD TRAFFIC INDUCED ENVIRONMENTAL AIR CONDITIONS ON STREET-ENTREPRENEURS IN AKURE-SOUTH LGA. ONDO STATE, NIGERIA

Roadside corridor serves as a major hub for street entrepreneurs to display their items and carry out their business in most African city. The major objective of this research is to be carried out roadside analysis of the surrounding air along street corridor in other to determine the amount of Carbon monoxide (CO), Sulphur dioxide (SO2), Nitrogen dioxide (NO2) and Particulate Matter (PM10) which are by-product of automobile on the street entrepreneurs on the selected street in Akure, Ondo State, Nigeria. Likewise, both Survey and experiment analysis was deployed to obtain the real state of some of the common air pollutant in the corridor of study. Results shows that these informal entrepreneurs are greatly affected by road traffic air pollutant; as 12.45% of the respondents have high nasal discharge, 12.21% of the respondents reported high throat irritation, 12.21% of the respondents cough often, 4.72% reported high level of breathlessness and 4.11% reported high asthmatic condition. While it was observed that between 13.943ppm to 3.225ppm of carbon monoxide, 0.025 ppm to 0.007 ppm sulphur dioxide, 0.071 ppm to 0.016ppm of Nitrogen dioxide and 1156.000 µg/m3 to 328.260µg/m3 of Particulate matter 10 (PM10) is generated along the corridors of study. The study recommends that entrepreneurs in the informal sectors operating along road corridors should carry out their business at least 150m away from major road traffic path to avoid over exposure to automobile generated air pollutions as this will lead to a decrease in health hazard occasioned by over-exposure.

IMPACT OF SULPHUR DIOXIDE EXPOSURE ON PHOTOSYNTHETIC PIGMENTS IN VIGNA MUNGO

The present studies carried out on Vigna mungo regarding impacts of SO2 exposure on photosynthetic pigments clearly revealed that sulphur dioxide has deleterious effects on different photosynthetic pigments. These effects had become more significant when the plants were exposed to higher doses of sulphur dioxide. During the present investigation four concentrations, i.e. 0.1, 0.3, 0.5 and 0.7 ppm of sulphur dioxide were taken in consideration and their impact on biochemical contents i.e chlorophyll ‘a’, chlorophyll ‘b’, total chlorophyll and carotenoids in Vigna mungo was studied. The observations obtained clearly revealed that a significant reduction was observed in photosynthetic pigments of Vigna mungo. This impact was of great extent in such plants which were exposed to 0.7 ppm of sulphur dioxide as compared to those exposed to lower concentration of sulphur dioxide. It was also observed that the impact was not only dose dependent but also age dependent.

High-Performance Sulfur Dioxide Gas Sensor Based on Graphite-Phase Carbon-Nitride-Functionalized Tin Diselenide Nanorods Composite

In this paper, a composite of tin diselenide (SnSe2) functionalized by graphite-phase carbon nitride (g-C3N4) was successfully prepared by a hydrothermal method, and was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). These microstructure characterization results verified the successful synthesis of a multilayer g-C3N4/rod-shaped SnSe2 composite. The gas sensitivity results showed that when the g-C3N4 ratio was 30%, the g-C3N4/SnSe2 composite sensor had the highest response (28.9%) at 200 °C to 20 ppm sulfur dioxide (SO2) gas, which was much higher than those of pristine g-C3N4 and SnSe2 sensors at the optimum temperature. A series of comparative experiments proved that the g-C3N4/SnSe2 composite sensor demonstrated an excellent response, strong reversibility and good selectivity for ppm-level SO2 gas detection. The possible SO2 sensing mechanism was ascribed to the heterostructure between the n-type SnSe2 and n-type g-C3N4 nanomaterials. Furthermore, we also proposed the influence of the special structure of the g-C3N4 functionalized SnSe2 composite on the gas-sensing characteristics.

Preparation and properties of an intelligent adjustable functional paper for organic cultural relics

Abstract Precious organic cultural relics are easily affected by temperature, humidity, and harmful gases in the environment, resulting in embrittlement, fading, mildew, moth damage and other aging forms. An energy-saving and environmentally friendly material is needed to stabilize humidity and adsorb harmful gases in the environment. In this paper, with an intelligent adjustment function, functional paper containing sepiolite and tourmaline natural minerals was successfully prepared. The component of 80 % of wingceltis and 20 % of straw in dry pulp as main raw material was conducive to the desorption of water molecules. As favorable structure inside functional paper, the adsorption point and the adsorption contact area increased by the rough surface of fiber bundles, the addition of sepiolite and the ordered molecular chains of copolymers destroyed. So, the relative humidity could be adjusted to 55 % ± 3 within 2 hours and was stable with functional paper. At the same time, 1.11 ppm sulfur dioxide and 2.98 ppm ammonia could be effectively adsorbed in 10 and 12 h, respectively, by 1 g of paper in a 5 L container. The pH of the paper was adjusted to neutral with tourmaline, even if the pH was changed by acidic or alkaline gas absorption. Therefore, for long-term organic cultural relic preservation, preparing a constant-humidity and clean environment is of great significance. This is possible through this paper.

Titanium dioxide (TiO2) nanoparticles reinforced polyvinyl formal (PVF) nanocomposites as chemiresistive gas sensor for sulfur dioxide (SO2) monitoring

The present work reports the preparation of polyvinyl formal (PVF)/Titanium dioxide (TiO2) nanocomposite films using a solution casting method followed by the characterization of the synthesized PVF/TiO2 nanocomposite films using various analytical techniques namely FTIR, XRD, UV–vis, SEM and TGA analysis. The results obtained from different analyses confirmed that the TiO2 NPs was fine dispersed within the PVF matrix and there exists well compatibility among the polymer matrix and the nanofiller. The pristine TiO2 NPs based fabricated chemiresistive sensor exhibits the maximum sensitivity of 50.25% at 370 °C where as PVF/TiO2 nanocomposite sensor showed the enhanced sensitivity of 83.75% at a relatively low operating temperature of 150 °C towards 600 ppm sulfur dioxide (SO2) gas. The 25 wt% PVF/TiO2 nanocomposite film sensor exhibited good sensitivity (∼83.75%), selectivity, rapid response time (66 s)/recovery time (107 s), and long-term stability of 60 days for SO2 gas detection. The fabricated PVF/TiO2 nanocomposite film sensors in our work possesses the advantages of low power consumption, cost-effective, and distinguished sensing abilities for SO2 detection makes it possible for potential applications. Thus, the fabricated chemiresistive sensors based on TiO2 NPs reinforced PVF nanocomposites films are evaluated and experimental results to show an excellent behavior towards SO2 gas detection for industrial processes control and environmental monitoring applications.

One-pot hydrothermal synthesis of nano-sheet assembled NiO/ZnO microspheres for efficient sulfur dioxide detection

The nano-sheet assembled NiO/ZnO microspheres with a diameter of ca. 2 μm have been synthesized via facile hydrothermal method followed by a thermal treatment process. The gas-sensing measurement results show that the sensor using nano-sheet assembled NiO/ZnO microspheres exhibits improved response to sulfur dioxide gas compared with the pure ZnO microspheres sensor. In particular, the sensor with a Ni/Zn molar ratio of 0.5 (0.5 mol% NiO/ZnO) shows high response value (S = 107) and superior selectivity to 10 ppm sulfur dioxide at a low operating temperature of 160 °C and the detection limit of the NiO/ZnO sensor toward sulfur dioxide is down to 1 ppm (S = 6). The enhanced sensing performance is attributed to the formation of p-n heterojunctions on the interface, the catalytic function of NiO and the three-dimensional microspheres composed of the lamellar structure with a large specific surface area. The three-dimensional microspheres provide more active sites for gas adsorption, and the interlayer gap facilitates the diffusion of gas in three-dimensional structure, resulting in high sensitivity and superior selectivity. This work provides a simple method for the synthesis of NiO/ZnO heterojunction microspheres with superior gas-sensing performance, which can be used as a potential material for sulfur dioxide detection.

Sulfur trioxide removal performance of alkaline sorbents injection in the temperature range 400–705 °C: a pilot‐scale study

AbstractBACKGROUNDSulfur trioxide (SO3) in coal combustion flue gas can adversely affect power plant equipment and the environment. In this work, the removal of SO3 with typical sodium (Na), magnesium (Mg) and calcium (Ca)‐based sorbents was investigated at a pilot‐scale facility in the temperature range 400–705 °C.RESULTSThe injection of sodium bicarbonate (NaHCO3) showed the highest SO3 removal efficiency, which was ∼85% at the sorbent/SO3 molar ratio of 2 with the gas residence time of 1 s. This is much higher than that of calcium hydroxide (Ca(OH)2) (∼25%) and magnesium hydroxide (Mg(OH)2) (∼30%). The removal efficiency of Mg(OH)2 and Ca(OH)2 increased with increasing the reaction temperature from 400 to 705 °C. With the addition of 800 ppm sulfur dioxide (SO2), the adsorption of SO3 on alkaline sorbents was inhibited due to the competitive adsorption, which caused SO3 removal efficiency to decrease by 5–12.5%. When injecting the sorbents in slurry form, the removal efficiency was found to be two times higher than that in powder form.CONCLUSIONNaHCO3 is the most effective sorbent comparing to Mg(OH)2 and Ca(OH)2. To increase the SO3 removal efficiency, the alkaline sorbents should be injected in the high temperature zone in flue gas. It is recommended to inject the sorbents in slurry form instead of injecting powders directly to achieve high removal efficiency. © 2019 Society of Chemical Industry

Effect of high hydrostatic pressure on selected red wine quality parameters

The aim of this work was to examine the possible use of High Hydrostatic Pressure (HHP) as an alternative method for wine preservation, which could also lead to the production of wines with reduced amounts of SO2. For this purpose, red wine samples containing 0 ppm, 30 ppm, 60 ppm and 100 ppm of sulphur dioxide (SO2) were subjected to pressure of 350 MPa for 10 min at 8 ∘C. A second set of samples containing only SO2 was used as control. Colour parameters, acetic acid, total anthocyanin and phenolic contents and antioxidant activity were determined over a period of twelve months. During the first four months, most of the differences observed regarding the chemical composition of the pressurized and unpressurized wines were not statistically significant. However, after the period of six months, the pressurized samples in general were characterized by higher average values % yellow colour and acetic acid and lower of % red colour, total anthocyanin and phenolic content compared to the non-pressurized ones. The results obtained could be a possible indication that HHP could accelerate the polymerization reactions reducing the time needed for wine ageing. HHP combined with reduced SO2 contents might be a promising technology for wine industry.

Optimization of a Process for Preparation of Base Wine for Cider Vinegar Production

Apple juice is used to prepare cider vinegar a traditional fermented product consumed world over. An attempt has been made to optimize the alcoholic fermentation of apple juice by Saccharomyces cerevisiae var. ellipsoideus UCD 595 for subsequent acetic acid fermentation to prepare cider vinegar, with respect to initial concentration of TSS, DAHP and sulfur dioxide content, using RSM. It was found that the fermentability of the different runs varied according to the initial sugar and DAHP concentration. The optimum base wine quality characteristics: TSS (4.03 °B), rate of fermentation (0.42 °Brix/24 h), ethanol (6.05%), titratable acidity (0.43%), volatile acidity (0.021%), phenolics (149.76 mg/100 g), pH (3.43), reducing sugars (107.88 mg/100 gm), total sugars (0.377%) and residual sulfur dioxide (28.77 ppm) with 0.837 desirability, were obtained using 14 °B initial TSS, 0.1% DAHP and 50 ppm sulfur dioxide. Verification experiments were conducted to compare predicted and actual values, which revealed near concurrence among them; confirming that models used were capable of reasonably and accurately predicting the dependent variables. Hence, these conditions are considered optimum for the alcoholic fermentation to produce a desirable level of alcohol in the shortest time for subsequent conversion into cider vinegar by acetic acid fermentation.

Impact of SO2 on the Oxygen Exchange Kinetics of the Promising SOFC/SOEC Air Electrode Material La0.8Ca0.2FeO3-δ

The mass and charge transport properties of La0.8Ca0.2FeO3-δ (LCF82) were determined at 600–800°C and pO2 = 0.1 bar. The electronic conductivity is in the range of 112 S cm−1 at 700°C. The chemical surface exchange coefficient (kchem) and the chemical diffusion coefficient of oxygen (Dchem) were measured. LCF82 shows exceptionally fast oxygen exchange kinetics in pure O2-Ar at 700°C. Long-term measurements at 700°C in pure O2-Ar showed an excellent stability of the kinetic parameters during 1000 h. However, when 2 ppm of sulfur dioxide were added, kchem decreased by a factor of 40 within the first 24 h. After further 1000 h, the total decrease in kchem amounted to two orders of magnitude. Post-test analyses of LCF82 were performed by SEM-EDXS, XPS, and STEM. Ca-enrichment and La-/Fe-depletion of the LCF82 surface occurred during the first 1000 h without SO2. At the surface of the sample exposed to 2 ppm SO2 for additional 1000 h, CaSO4 crystals with diameters of 1–2 μm and an underlying layer of Fe2O3 (thickness approx. 300–450 nm) were found. Remarkably, LCF82 shows faster oxygen exchange kinetics than La0.6Sr0.4CoO3-δ even in the degraded state. Therefore, LCF82 is suggested as a promising material for SOFC and SOEC air electrodes.

The Impact of Particle Size, Relative Humidity, and Sulfur Dioxide on Iron Solubility in Simulated Atmospheric Marine Aerosols

Iron is a limiting nutrient in about half of the world's oceans, and its most significant source is atmospheric deposition. To understand the pathways of iron solubilization during atmospheric transport, we exposed size segregated simulated marine aerosols to 5 ppm sulfur dioxide at arid (23 ± 1% relative humidity, RH) and marine (98 ± 1% RH) conditions. Relative iron solubility increased as the particle size decreased for goethite and hematite, while for magnetite, the relative solubility was similar for all of the fine size fractions (2.5-0.25 μm) investigated but higher than the coarse size fraction (10-2.5 μm). Goethite and hematite showed increased solubility at arid RH, but no difference (p > 0.05) was observed between the two humidity levels for magnetite. There was no correlation between iron solubility and exposure to SO2 in any mineral for any size fraction. X-ray absorption near edge structure (XANES) measurements showed no change in iron speciation [Fe(II) and Fe(III)] in any minerals following SO2 exposure. SEM-EDS measurements of SO2-exposed goethite revealed small amounts of sulfur uptake on the samples; however, the incorporated sulfur did not affect iron solubility. Our results show that although sulfur is incorporated into particles via gas-phase processes, changes in iron solubility also depend on other species in the aerosol.

Damage structures in leaf epidermis and cuticle as an indicator of elevated atmospheric sulphur dioxide in early Mesozoic floras

Volcanic episodes are considered to be potentially important drivers of many mass extinction events in Earth history, when a sharp decrease in the diversity and abundance of macroscopic organisms occurred. Such events are hypothesised to be associated with volcanic sulphur dioxide (SO2) release. The effect of volcanism on atmospheric composition varies widely and is related to the magnitude and duration of the volcanic episode. Currently, there are limited methods for detecting the timing of SO2 release in the geological past. In field conditions, the influence of SO2 on plants can be difficult to separate from the effects of other volcanic emissions, which enter via stomata and can affect plant physiology, anatomy and morphology. In order to assess the direct effects of SO2 associated with palaeo-volcanic episodes, we conducted a six month growth chamber experiment growing plants under control (zero parts per million (ppm)) and continuous elevated (0.2ppm) sulphur dioxide atmospheres. Leaf morphological responses of ten species representative of Mesozoic gymnosperm and fern fossil floras were examined using cryo-scanning electron microscopy. Here we show that expanded, fully mature leaves record unambiguous damage structures associated with injury from SO2 fumigation. In SO2 treated plants, leaves were smaller and did not persist; distinct raised areas of cuticle surrounding stomata appeared; surface waxes altered; blistering of the cuticle occurred; and the stomatal complex became distorted. These results have clear implications for application to the fossil record as many of the observed damage structures have the potential to be preserved in fossil plant cuticle and thus allow precise pinpointing of elevated SO2 episodes in the geological past.

Efficient fermentation of an improved synthetic grape must by enological and laboratory strains of Saccharomyces cerevisiae.

Grape must or freshly pressed grape juice is a complex chemical matrix that impacts the efficiency of yeast fermentation. The composition of natural grape must (NGM) can be variable; thus, to ensure reproducibility, a synthetic grape must (SGM) with defined composition is commonly used. The aim of this work was to create conditions to advance the use of Saccharomyces cerevisiae laboratory strains for wine fermentation studies, considering previous results obtained for enological strains fermenting NGM under simulated winery conditions. We designed a new SGM formulation, ISA-SGM, by introducing specific modifications to a commonly used formulation, putting together previous reports. We added glucose and fructose in equal amounts (125 g/l) and 50 parts per million (ppm) sulfur dioxide (SO2, corresponding to standard enological treatment), and we optimized the concentrations of malic acid (3 g/l), citric acid (0.3 g/l), and tartaric acid (3 g/l). Using ISA-SGM, we obtained similar fermentative profiles for the wine strain ISA1000, the prototrophic strain S288C, and its auxotrophic derivative BY4741. In this case, the concentrations of supplements were optimized to 120 mg/l L-uracil, 80 mg/l L-methionine, 400 mg/l L-leucine, and 100 mg/l L-histidine. All these strains tested in ISA-SGM presented a similar fermentative performance as ISA1000 in NGM. ISA-SGM formulation is a promising new tool to allow the use of the auxotrophic BY strains in the detailed assessment of the alcoholic fermentation process under simulated winery conditions, and it provides a foundation to extract relevant physiological conclusions in future research on enological yeast traits.

Steeping preservation of cauliflower with hurdle concept.

Cauliflower is a rich source of proteins, carbohydrates, vitamins and minerals and also a very important vegetable having maximum availability in tropical climate from November to February which causes glut in the market and consequently producers do not get remunerative prices. The partially blanched cauliflower pieces of 3-4cm long having stalk upto 2cm in length are steeped in different levels of sodium chloride (NaCl, 2-6%) and acetic acid (1-2%) along with 350ppm sulphur dioxide (SO2) using modified response surface methodology (RSM). The cauliflower samples steeped in 4% NaCl, 1% acetic acid and 350ppm SO2 were rated best with maximum mean overall acceptability (OAA) score (6.90) and minimum mean preference (6.25) to the experimental run consisting of 6% NaCl, 2% acetic acid and 350ppm SO2 was noted after 120days of storage. There has been sharp decrease in pH values after 15days of storage in all the experimental run of preserved cauliflower samples. The maximum mean decrease in hardness values (15.20-0.55g.cm) was obtained in steeped cauliflower samples consisting of 6% NaCl, 2% acetic acid and 350ppm SO2 during storage for 120days at room temperature. The decrease in extent of browning, ascorbic acid and total carotenoids content in cauliflower samples was reported in all the experimental runs during 120days of storage at room temperature. The optimum concentration for maximum desirability in the preservation of cauliflower consisted of 3.5% sodium chloride and 1.1% acetic acid and 350ppm SO2.

Sulfur dioxide measurements using an ultraviolet light-emitting diode in combination with gas correlation techniques

The important air pollutant sulfur dioxide has a strong structured absorption band in the ultraviolet (UV) region around 300 nm. Recently, light-emitting diodes (LEDs) with structureless emission in a band about 15-nm wide in the UV region have become available. We demonstrate that they can be ideal sources for gas absorption measurements combined with the gas correlation technique, where an absorption cell with an optically thick column of the gas under investigation is used for analysing the target gas contents in a path between the LED and the measurement device. A sensitivity of 0.4 ppm sulfur dioxide was obtained with a 19-cm optical path length and 60-s integration time. Particularly compact and cost-effective monitors especially for industrial emissions can be envisaged.

Laboratory study of heterogeneous ice nucleation in deposition mode of montmorillonite mineral dust particles aged with ammonia, sulfur dioxide, and ozone at polluted atmospheric concentrations

Heterogeneous ice nucleation in deposition mode of montmorillonite mineral dust aerosol particles exposed to atmospheric trace gases (ammonia, sulfur dioxide, and ozone) was studied at temperatures warmer than −40°C with a continuous flow diffusion chamber. Pure and typical polluted atmospheric concentrations of ammonia, sulfur dioxide, and ozone gases were used to age montmorillonite mineral dust aerosol particles at room temperature and atmospheric pressure in a stainless steel chamber. Ammonia-, sulfur dioxide-, and ozone-exposed montmorillonite mineral dust aerosols act as ice nuclei in heterogeneous deposition freezing at warmer temperatures than required for homogeneous freezing. The ice nucleation efficiency of montmorillonite mineral dust aerosols increased about two times due to exposure to ammonia at a typical atmospheric concentration of about 100 ppt. This is the first experimental evidence for the enhancement of the ice nucleation efficiency of montmorillonite mineral dust aerosols by ammonia gas at typical atmospheric concentrations. Montmorillonite exposure to either pure (100%) or 45 ppm sulfur dioxide or to ozone at 200 ppb shows no clear evidence for changing the ice nucleation efficiency of montmorillonite mineral dust particles. Thus, we conclude that enhancements atmospheric trace gases (e.g., sulfur dioxide and ozone) due to anthropogenic activities have no significant impact on the heterogeneous ice nucleation of montmorillonite mineral dust particles.