Presence Of Aerosol Particles Research Articles

Air quality particulate-pollution prediction applying GAN network and the Neural Turing Machine

Urban areas in many countries face significant concerns over the presence of aerosol particles and their effects on human health. These particles, which range in size from 1 nanometer to 100 micrometers, can easily penetrate organic matter and transport toxic gas compounds and mineral substances such as carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide. High concentrations of airborne particles pose serious challenges to health, the economy, the environment, and society, and it is crucial to investigate ways to improve the quality of life for people. The main objective of this study is to develop a framework that accurately predicts aerosol and air quality index (AQI) values in advance by estimating missing data and predicting future data. To achieve this, we propose the DAerosol.GAN.NTM framework, which combines a neural Turing machine with a generative adversarial network (GAN) to address the limitations of previous studies. Our framework outperforms previous methods, including DAerosol.NTM (without GAN) and four baseline studies using Multilayer Perceptron (MLP), Deep Neural Networks (DNN), Long-short Term Memory (LSTM), and Deep LSTM (DLSTM) models, in terms of accuracy, precision, root mean square error (RMSE), mean absolute percentage error (MAPE), and the prediction of aerosol pollution surge hours in advance according to the Time Interval Before and After the Aerosol Event (TIBAAE) criterion.

Potential of future stratospheric ozone loss in the midlatitudes under global warming and sulfate geoengineering

Abstract. The potential of heterogeneous chlorine activation in the midlatitude lowermost stratosphere during summer is a matter of debate. The occurrence of heterogeneous chlorine activation through the presence of aerosol particles could cause ozone destruction. This chemical process requires low temperatures and is accelerated by an enhancement of the stratospheric water vapour and sulfate amount. In particular, the conditions present in the lowermost stratosphere during the North American Summer Monsoon season (NAM) are expected to be cold and moist enough to cause the occurrence of heterogeneous chlorine activation. Furthermore, the temperatures, the water vapour mixing ratio and the sulfate aerosol abundance are affected by future global warming and by the potential application of sulfate geoengineering. Hence, both future scenarios could promote this ozone destruction process. We investigate the likelihood of the occurrence of heterogeneous chlorine activation and its impact on ozone in the lowermost-stratospheric mixing layer between tropospheric and stratospheric air above central North America (30.6–49.6∘ N, 72.25–124.75∘ W) in summer for conditions today, at the middle and at the end of the 21st century. Therefore, the results of the Geoengineering Large Ensemble Simulations (GLENS) for the lowermost-stratospheric mixing layer between tropospheric and stratospheric air are considered together with 10-day box-model simulations performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In GLENS two future scenarios are simulated: the RCP8.5 global warming scenario and a geoengineering scenario, where sulfur is additionally injected into the stratosphere to keep the global mean surface temperature from changing. In the GLENS simulations, the mixing layer will warm and moisten in both future scenarios with a larger effect in the geoengineering scenario. The likelihood of chlorine activation occurring in the mixing layer is highest in the years 2040–2050 if geoengineering is applied, accounting for 3.3 %. In comparison, the likelihood of conditions today is 1.0 %. At the end of the 21st century, the likelihood of this ozone destruction process occurring decreases. We found that 0.1 % of the ozone mixing ratios in the mixing layer above central North America is destroyed for conditions today. A maximum ozone destruction of 0.3 % in the mixing layer occurs in the years 2040–2050 if geoengineering is applied. Comparing the southernmost latitude band (30–35∘ N) and the northernmost latitude band (44–49∘ N) of the considered region, we found a higher likelihood of the occurrence of heterogeneous chlorine activation in the southernmost latitude band, causing a higher impact on ozone as well. However, the ozone loss process is found to have a minor impact on the midlatitude ozone column.

Experimental Study of Diurnal and Seasonal Variations in the Atmospheric Electric Field

In order to separate global and local effects of atmospheric electricity, measurements of the fair-weather electric field were performed in Nizhny Novgorod in 2013-2018. As a result of processing 139 diurnal records from four observation points spaced 6–8 km apart, diurnal variations in the fair-weather atmospheric electric field for different seasons and weekdays (working days and weekends) were studied. The curve of the local diurnal variation is shown to always have two maxima. The evening maximum of the diurnal variation (19:00–20:00 UT) coincides in time with the maximum of the Carnegie curve, which is a characteristic of the global electrical circuit. The highest values of the field amplitude are reached in the winter period. The field-intensity maximum in the first half of the day (09:00–11:00 LT) is characteristic of the urban environment and shows that local effects associated with the presence of aerosol particles in the air significantly contribute to the formation of diurnal variation, especially in summer. According to the 2013–2018 measurements, the seasonal variation in the monthly-average values of the atmospheric electric field is revealed and analyzed compared with the results of measurements of seasonal variation in other regions of the globe. The obtained results allow one to reveal the role of local effects in the formation of diurnal variation in the mid-latitude areas with temperate continental climate and provide a basis for developing a theory which can explain the physical mechanisms of local effects and suggest appropriate parametrization for finding the surface electric field in the weather and climate models.

Effect of relative humidity and the presence of aerosol particles on the α-pinene ozonolysis

The α-pinene ozonolysis under the different environmental conditions were observed in a smog chamber. The second-order rate constant (k) was determined to be (7.25±0.06)×10–17cm3/(molecule·sec) under 20% of relative humidity (RH) and room temperature. RH showed a marked influence on the α-pinene ozonolysis. The value of k increased with RH increase, which was 1.6 times faster at RH=80% than that at RH=20%. Additionally, the value of k apparently changed in the presence of the aerosol particles. The diesel soot increased the k value. The fly ash prohibited the reaction, however, H2SO4-treated fly ash promoted the reaction. The information of products gained using FT-IR and SPAMS showed that pinonic acid, 10-hydroxy-pinonic acid and pinic acid could be generated during the α-pinene ozonolysis. Water molecules could take part in the formation of the products, and play a vital role in the degradation of α-pinene. The atmospheric residence time calculation showed that the ozonolysis in the atmosphere is an important way of the α-pinene consumption as compared to that reacted with OH during daytime. The results suggested that the degradation of α-pinene via the ozonization in the atmosphere may be affected greatly by RH, as well as the presence of aerosol particles. The ozonolysis reaction may be an important way of the α-pinene consumption during daytime.

A DNS study of aerosol and small-scale cloud turbulence interaction

Abstract. The purpose of this study is to investigate the interaction between small-scale turbulence and aerosol and cloud microphysical properties using direct numerical simulations (DNS). We consider the domain located at the height of about 2000 m from the sea level, experiencing transient high supersaturation due to atmospheric fluctuations of temperature and humidity. To study the effect of total number of particles (Ntot) on air temperature, activation and supersaturation, we vary Ntot. To investigate the effect of aerosol dynamics on small-scale turbulence and vertical air motion, we vary the intensity of turbulent fluctuations and the buoyant force. We find that even a small number of aerosol particles (55.5 cm−3), and therefore a small droplet number concentration, strongly affects the air temperature due to release of latent heat. The system comes to an equilibrium faster and the relative number of activated particles appears to be smaller for larger Ntot. We conclude that aerosol particles strongly affect the air motion. In a case of updraught coursed by buoyant force, the presence of aerosol particles results in acceleration of air motion in vertical direction and increase of turbulent fluctuations.

Charge generation associated with liquid spraying in tank cleaning and comparable processes - preliminary experiments

The BG RCI has initiated investigations in order to improve the data basis for assessing the ignition hazard by electrostatic charging processes associated with the spraying of liquids. On the base of preliminary experiments, we established procedures for measurements of electric field strength and charging current in the presence of aerosol particles. Results obtained with three different nozzle types, variation of pressure and with built-in deflecting plate are presented.

Improving the Removal Efficiency of Elemental Mercury by Pre-Existing Aerosol Particles in Double Dielectric Barrier Discharge Treatments

Plasma technology has been employed for the removal of gaseous elemental mercury (Hg0) from simulated flue gases without pre-existing airborne particles. This study developed a double dielectric barrier discharge (DDBD) treatment system, in which two coaxial electrodes were covered by quartz dielectrics, for removing mercury with the presence of aerosol particles. The increase in pre-existing aerosol surface concentration can improve Hg0 removal efficiency up to 160% in the DDBD device. Inorganic aerosol particles (sodium chloride) perform better than organic ones (sucrose) in improving Hg0 removal efficiency. These aerosol particles can be collected in the DDBD system. For sodium chloride particles, a collection efficiency of more than 90% was observed in the tested diameter range of 10–100 nm. The improvement in Hg0 removal with the presence of particles is possibly due to that (i) aerosol particles provide additional surface for surface-induced Hg0 oxidations, (ii) reactive species (such as Cl) generated by plasma etching particle surface rapidly react with Hg0, and (iii) charged particles can in-flight adsorb mercury species.

The importance of feldspar for ice nucleation by mineral dust in mixed-phase clouds

The amount of ice present in mixed-phase clouds, which contain both supercooled liquid water droplets and ice particles, affects cloud extent, lifetime, particle size and radiative properties. The freezing of cloud droplets can be catalysed by the presence of aerosol particles known as ice nuclei. One of the most important ice nuclei is thought to be mineral dust aerosol from arid regions. It is generally assumed that clay minerals, which contribute approximately two-thirds of the dust mass, dominate ice nucleation by mineral dust, and many experimental studies have therefore focused on these materials. Here we use an established droplet-freezing technique to show that feldspar minerals dominate ice nucleation by mineral dusts under mixed-phase cloud conditions, despite feldspar being a minor component of dust emitted from arid regions. We also find that clay minerals are relatively unimportant ice nuclei. Our results from a global aerosol model study suggest that feldspar ice nuclei are globally distributed and that feldspar particles may account for a large proportion of the ice nuclei in Earth's atmosphere that contribute to freezing at temperatures below about -15 °C.

Study of atmospheric electrical conductivity, SO2, NO2, aerosols SPM (>10 μ) and RSPM (

It is well known that atmospheric electrical conductivity is mainly due to the presence of small ions. Near the surface of the earth, radon and its daughter products predominantly produce small ions. In the presence of aerosol particles, the small ion concentration is reduced due to attachment of small ions to aerosol particles which decreases mobility and conductivity in the atmosphere. The ion pair production rate is estimated from the measured radon and its progeny concentrations and correlated with electrical conductivity of the atmosphere. Measurement of concentrations of suspended particulate matter (SPM), SO2, and NO2 of air was also carried out. Data showed that reduced electrical conductivity was related to concentration of airborne SPM.

A model for the performance of a vertical tube condenser in the presence of noncondensable gases

Some proposed vertical tube condensers are designed to operate at high noncondensable fractions, which warrants a simple model to predict their performance. Models developed thus far are usually not self-contained as they require the specification of the wall temperature to predict the local condensation rate. The present model attempts to fill this gap by addressing the secondary side heat transfer as well. Starting with a momentum balance which includes the effect of interfacial shear stress, a Nusselt-type algebraic equation is derived for the film thickness as a function of flow and geometry parameters. The heat and mass transfer analogy relations are then invoked to deduce the condensation rate of steam onto the tube wall. Lastly, the heat transfer to the secondary side is modelled to include cooling by forced, free or mixed convection flows. The model is used for parametric simulations to determine the impact on the condenser performance of important factors such as the inlet gas fraction, the mixture inlet flowrate, the total pressure, and the molecular weight of the noncondensable gas. The model performed simulations of some experiments with pure steam and air-steam mixtures flowing down a vertical tube. The model predicts the data quite well. The model described also provides a basis under which the presence of aerosol particles in the gas stream could be analyzed.

Surface Laser Plasma in Laser Treatment of Materials in High Pressure Gases

AbstractUsing holographic interferometry the surface laser plasma generation in high pressure gases has been investigated. Additional information about the generation of surface cover laser plasma, optical breakdown in the presence of aerosol particles and condensation front forming in high pressure gases is given.

Numerical simulation of the collective regime of the evolution of a low-threshold optical breakdown in an aerosol medium

Investigations of aerosol optical breakdown have recently been extensively developed, inasmuch as it is precisely the disperse fraction which determines the threshold of the onset of a plasma region and its main characteristics in the case of propagation of beams in the visible and infrared bands under real conditions. Defining breakdown as a plasma-formation effect in an optical field, it is necessary to separate two essentially different forms of this phenomenon. The first is characterized by relatively high threshold (in this case the aerosol particles assume only the role of a "primer") while the second, with lower threshold, calls for the presence of aerosol particles (or of their vapors) in the focal region of the laser during all the stages of its evolution. Naturally, the minimum breakdown threshold in an ensemble of aerosol particles would take place in the case when during the time not exceeding the duration of the laser pulse one can ensure effective interaction of the plasma formation processes between the individual aerosol particles. A similar collective regime of lowthreshold optical breakdown was first predicted in [i], and a number of its essential features were investigated in [2-4].

Combination coefficients of small positive ions with submicrometre aerosol particles

The work was concerned with the simultaneous measurement of the combination coefficients b and eta 0, between small ions and aerosol particles, and between small ions and uncharged aerosol particle respectively, for different particle radii. The ion-ion mutual repulsion coefficient gamma had a mean experimental value of 2.39 (+or-0.14)*10-6 cm3 s-1. The decay of ions in the presence of aerosol particles in a mylar vessel was recorded and compared with a family of computed theoretical ion-aerosol decay curves to determine b. eta 0 could then be determined from concentration of uncharged nuclei present. Satisfactory agreement was found between the b eta 0 versus radius results and various theoretically computed values. Possible reasons for discrepancies between theory and experiment are indicated.