| The high concentration of atmospheric particulate matter remains one of the atmospheric environmental problems facing major regions of China.Mineral particles are an important part of atmospheric particulate matter.The heterogeneous chemical reaction on the surface of mineral particles is one of the important mechanisms for the formation of atmospheric composite pollution.Calcium carbonate and sulfur dioxide are typical representatives of mineral particles and polluting gases,respectively,and are the research objects of this study.This study uses environmental monitoring data such as PM10 and PM2.5 mass concentration released by the Mianyang City National Control Station in Sichuan Province.Combined with the data obtained from the self-built monitoring site of Southwest University of Science and Technology,the average daily variation characteristics of PM10 and PM2.5in Mianyang City from September 2017 to September 2018 were analyzed and the difference in hourly variation in different seasons,comparing the different characteristics of PM10 and PM2.5 in the suburbs.The results show that the daily variation of PM2.5 and PM10 concentration in Mianyang City is“W”type,and nighttime pollution is higher than daytime.Seasonal variations vary widely,overally variations in winter is the biggest,while in summer is the least.And the variations in spring is bigger than autumn.The most severe haze days occur in winter,anthropogenic emissions,topography and weather are the main factors.The PM2.5 and PM10 concentrations have a good linear relationship with a correlation coefficient of0.8771.The mass concentration of particulate matter is lower than that of urban areas in the suburbs,and the urban suburbs change more smoothly.The PM10 and PM2.5 of Mianyang City were collected by atmospheric particulate sampler,and their main mineral components and surface morphology were analyzed.The study also established a simple smoke chamber device for studying the heterogeneous reaction of carbon dioxide on the surface of calcium carbonate particles,and quantitatively investigated the concentration change of sulfur dioxide in the smoke chamber.The reaction products were characterized by SEM-EDX and infrared.It was found that a small piece of sulfated product adhered to the surface of calcium carbonate particles,and the main component was CaSO4·2H2O.The formation route of CaSO4·2H2O was studied,which was a liquid phase free radical chain reaction,exploring the reaction mechanism of sulfur dioxide on the surface of calcium carbonate.The effects of particle size,reaction temperature and illumination of the calcium carbonate particles on the heterogeneous reaction were discussed.The smaller the particle size,the higher the light intensity.The higher the temperature,the faster the reaction rate of CaCO3 and SO2.The impact is even greater.The in-situ analysis of the heterogeneous reaction of CaCO3 and SO2 was carried out by diffuse reflectance Fourier transform infrared spectrometer.The in-situ infrared standard curve of sulfate in the system was determined,and the intermediate product in the in-situ reaction of CaCO3 and SO2 was characterized.Salt and sulfite.The reaction kinetic curves of CaCO3 and SO2 were analyzed,and the gas uptake coefficient in the in-situ reaction was determined.The atmospheric significance of CaCO3 and SO2 reactions was evaluated.This reaction may be one of the important formation mechanisms of atmospheric composite pollution,and may also be an important sink mechanism of SO2. |
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