Search

Sandstorm is a natural meteorological disaster that can appear suddenly and is often extremely destructive. In areas with small number of meteorological observation stations, it is difficult to effectively monitor sandstorm. Moderate Resolution Imaging Spectroradiometer (MODIS) data have the characteristics of high resolution and wide coverage, making it possible to monitor dynamic weather changes in a large area over time, and such data are widely used in sandstorm monitoring. The purpose of our research was to achieve a more accurate identification of sandstorm according to the differences in reflectance and brightness temperature between sandstorm and other phenomena, and to better understand the formation, movement track and driving cause of sandstorm extreme event. Taking the intense sandstorm event that occurred in the Yellow River Basin from March 13th to 18th, 2021 as an example, sandstorm process was analyzed based on MODIS data and meteorological monitoring data. The threshold of Normalized Difference Dust Index (NDDI) and Normalized Brightness Temperature Dust Index (NBTDI) realized accurate sandstorm monitoring and quantification of the sandstorm coverage areas. Sandstorm covered 32.89 % and 37.23 % of the total areas of the Yellow River Basin on March 15th and 16th, 2021, respectively. In addition, observation data from 22 meteorological stations also provided an important reference for further understanding of sandstorm weather. The intense sandstorm event in China on March 15th, 2021 originated from the dust in Mongolia. This sandstorm event caused great damage to the ecological environment and caused serious losses to people's lives and properties. This study improved the monitoring of sandstorm by remote sensing technology, and the results had importance for the long-term monitoring and prevention of sandstorm.

As one of the main components of combustion of tobacco products occurs (CARB), crotonaldehyde has an acute toxicity and widely exists in the atmosphere, which is harmful to human health. The removal efficiency of VOCs by ozonation can reach 80–90%. Based on the theory of quantum chemistry, the degradation mechanism, kinetics and toxicity of crotonaldehyde by ozonation in gas phase and heterogeneous phase were studied. Ozone was added to the olefins unsaturated double bond to form a five-membered ring primary ozonide, which was further fractured due to its unstable structure to form a Criegee intermediate and an aldehyde compound. The reaction rate constant of crotonaldehyde with ozone was 1.24 × 10−17 cm3 molecule−1 s−1 at 298 K and 1 atm, which was an order of magnitude higher than the experimental value. From toxicity assessment, it was found that the ozonation of crotonaldehyde is beneficial to the removal of toxicity. Mineral dust aerosol exists in the atmosphere in large quantities, and SiO2 is the most abundant component. VOCs are transformed into particle state on their surface through homogeneous nucleation and heterogeneous nucleation. Referring to the crystal structure of SiO2, five hydroxylated silica oligomer cluster structures were simulated and the adsorption configurations of crotonaldehyde on their surface were simulated. The adsorption of crotonaldehyde on the surface of the clusters was achieved by forming hydrogen bonds and had good adsorption effects. The adsorption of hydroxylated silica oligomer clusters didn't change the ozonation mechanism of crotonldehyde, but had a certain effect on the reaction rate.

Acrylonitrile (ACN) is a highly toxic substance that exists widely in the environment. It can pollute the environment and endanger human health. VOCs prone to nucleation and heterogeneous reaction on the mineral dust aerosols surface. Based on the DFT calculation, the ozonolysis processes of ACN in homogeneous reactions, heterogeneous reactions on SixOy(OH)z clusters surface and heterogeneous reactions on (Al2O3)n clusters surface were studied in this paper. Ozone addition was the rate-determining step for ozonolysis of ACN with the rate constant of 2.03 × 10−18 cm3 molecule−1 s−1 at 298 K and 1 atm. Toxicity assessment showed that ozonolysis degradation effectively reduced the ecotoxicity of ACN. In this study, six kinds of non-metallic oxides SixOy(OH)z clusters and thirteen kinds of metal oxides (Al2O3)n clusters were selected to simulate the adsorption behavior of ACN adsorbed on different mineral dust aerosols surface. ACN-SixOy(OH)z cluster polymers formed hydrogen bond interactions, while ACN-(Al2O3)n cluster polymers mainly formed metallic bonds (Al-N), and they also had hydrogen bond interactions. The adsorption of SixOy(OH)z clusters and (Al2O3)n clusters did not change the reaction mechanisms for ozonolysis of ACN, but affected the reaction rate constant to varying degrees. In addition, it was found that the adsorption modes of mineral dust aerosols surface had no correlation with the rate constants for ozonolysis of ACN.

In this paper, the gas-phase and heterogeneous reactions of acrolein with ozone were studied comprehensively and deeply. Acrolein is one of the simplest unsaturated aldehydes found widely in the fuel combustion and industrial emissions. Mineral particles produced by frequent sandstorms have important effects on the tropospheric chemistry and the climate change. The content of silica in clay minerals is rich, thus three kinds of clusters (the monomeric model Si(OH)4, the linear model Si3O2(OH)8 and the cyclic hexamer model Si6O6(OH)12) were selected for the heterogeneous study. The reaction rate constant of acrolein with ozone at 298 K and 1 atm was 7.46 × 10−18 cm3 molecule−1 s−1, which was in agreement with the experimental value. SiO2 clusters interacted with acrolein via the hydrogen bonds and had good adsorption properties. The hydrogen bond between the oxygen of aldehyde group on acrolein and the hydrogen of silica surface was stronger and the adsorption energy was greater. The adsorption of silanol groups did not change the ozonation mechanism of acrolein, but had effects on the reaction rate. Among them, three silanol groups acted as positive catalysts. The kinetic data within the temperature range of 216.65–288.15 K corresponding to the height of the troposphere at 0–11 km showed that the rate constant of O3-initiated reaction of acrolein is positively correlated with the temperature. In addition, we also studied the reaction mechanism and kinetic of the Criegee intermediates reacting with atmospheric small molecules and isomerization process in gas-phase and heterogeneous processes.