| With the unceasing development of industry and science and technology in Nanchang, and the influence of human activities, the current environment of Nanchang deteriorated, The concentration of sulfur dioxide, nitrogen dioxide, ammonia, total suspended particle(TSP) in the living environment, is more and more high, which do great harm to human body and environment. The human have done more and more study on these pollutants. How to reduce the concentration of several kinds of pollutants in the air to alleviate the problem of air pollution is a difficult task. By many scholars both at home and abroad long-term studies have found that rainfall is an important approach to reduce the pollutant in the air in order to explore the new city rainfall of gaseous pollutants removal efficiency and mechanism in new district in Nanchang. the lake before The project is taken on the roof of the environment building in the Lake compus of Nanchang university from September 2014 to January 2015 months rainfall, sulfur dioxide, nitrogen dioxide, ammonia, and a study on sampling the TSP. By comparing the concentration of sulfur dioxide, nitrogen dioxide in the air before and after the rain, total suspended particle(TSP), the removal efficiency of the rainfall on the several kinds of gaseous pollutants and the influence of various meteorological factors on the removal efficiency is learned.This research mainly got the following results:(1) The average concentration of so2 sample point during rainfall is 35.12μg/m3, the average concentration of nitrogen dioxide is 46.50μg/m3, the average concentration of ammonia is 58.48μg/m3,and the average concentration of TSP is 85.48μg/m3. The average pH of rainfall is 4.41,so it si strong acid rain, furthermore the frequency of acid rain is high, so the air pollution is more serious. Sulfur dioxide, nitrogen dioxide, ammonia, concentration of TSP four kinds of pollutants are characterized by high in autumn low in winter.(2) The concentration of sulfur dioxide, nitrogen dioxide, ammonia basically in the air of the sampling point after the rain fell. Three kinds of gaseous pollutants removal efficiency of rainfall with the seasons is not the same, but all show removal efficiency in the autumn is higher than theremoval efficiency in winter. In the same rainfall the three kinds of gaseous pollutants removal efficiency has the same change trend, the rainfall removal efficiency of ammonia is higher than the sulfur dioxide and nitrogen dioxide removal efficiency of rainfall. The rainfall of sulpHur dioxide, nitrogen dioxide removal efficiency and the rainfall is positively related to relationship of efficiency of ammonia gas.(3)Sulfur dioxide and nitrogen dioxide, ammonia, the three kinds of gaseous pollutants removal efficiency of rainfall and rainfall between the present main sex, when the rainfall is less than 1 mm of light rain, the concentration of pollutants is not increased rather than decreased.Three kinds of pollutants concentration during continuous rainfall are shown day by day to reduce the trend, in the first two daily rainfall of the three kinds of pollutant removal efficiency is higher, the latter two days even if there is rain the concentration of pollutants is basically the same, the rainfall for pollutant removal efficiency is very low. The correlation coefficient of removal efficiency of rainfall and temperature of the three kinds of gaseous pollutants is low, irrelevant of efficiency of precipitation and temperature. The relationship between the pressure is negative correlation, the less rainfall of the three kinds of pollutant removal efficiency is higher. Rainfall for three kinds of gaseous pollutants removal efficiency and air relative humidity were positively correlated, the relationship between the air relative humidity is greater, the more conducive to rainfall of the three kinds of gaseous pollutants removal effect.The lower the pH of the rainfall can be conductive to the removal of three kinds of gaseous pollutants, and it present negative correlation relationship between them. The sulfur dioxide, nitrogen dioxide, ammonia in air is clearedby rainfall absorption.Rainfall absorption of gaseous contaminants includ pHysical absorption and chemical absorption(4)the TSP of efficiency of rainfall factors: the influence of rainfall on TSP removal efficiency changes between- 0.6%- 46.07%, the average removal efficiency was 12.49%. In the same rainfall, the rainfall on TSP removal efficiency is greater than on the sulfur dioxide, nitrogen dioxide, ammonia. in general, the greater the rainfall,the more the particles will be flowed into the rain, it has positively correlated relationship between them. During continuous rainfall, two days before the rain cleared to TSP of high efficiency, two days after the removal efficiency is low. Because of the influence of other factors such as wind speed, the TSP of efficiency of precipitation and temperature is not relevant. The TSP of rainfall and the pressure of efficiency of negative correlation relationship. The TSP of efficiency of rainfall and atmospHeric relative humidity were positively correlated, the relationship between the correlation coefficient is 0.2993. TSP of efficiency of rainfall and the pH value of the rainwater is negatively related.(5)Such as the direction of diffusion, interception, brown inertia collision, cause the electropHoresis, diffusion electropHoresis and power mechanisms are the main clearing modes of aerosol particles in the air, through these roles’ touch to atmospHeric aerosol particles, so that the pollutants are rain cleared. During the previous stage of the continuous rainfall, the air in rainfall and large particles of high concentration, rainfall for the removal of the aerosol particles is given priority to with inertia collision, so the two at the start of the continuous rainfall weather sol particles rain to clear the efficiency is very high, the concentration of aerosol particles in the air will drop rapidly. In a few days after the rain, with declining aerosol particle concentration, and the size of the particle decreases. The main mechanism of rainfall of aerosol particle removal is diffusion and migration, the rainfall for its removal efficiency with the rainfall will reduce gradually, the basic of aerosol particles basically do not have clear effect in the last.(6) Heavy rain has obvious removal effect to SO2,PM10 and PM2.5 in atmospHeric.The rain that Is greater than 1mm also has evident to these pollutants,but its removal efficiency is less than heavy rainfall.Less than 1mm of rainfall has certain removal efficiency to PM10 and PM2.5,but for SO2, the removal efficiency of rainfall is not obvious,the concentration will rise.Rainfall has not obvious effect to the concentration of NO2.The substrate concentration of pollutants,rainfall time, rainfall frequency may also affect pollutant removal efficiency. |
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