Research On The Distributions Characteristics Of Atmospheric Particulate Matters And Particle Mercury Of Coal-fired Power Plants In Southeast Coastal Plains

Mercury is a kind of heavy metal pollutant with strong biotoxicity in the environment. The mercury exists mainly in the form of gaseous compounds in the atmosphere with minority in particle state; however, particle mercury plays a significant role during the circulation and evolution of mercury in the atmosphere Therefore, the study on transfer and transformation rules of inhalable particles and particle mercury from coal-fired power plant can not only provide theory foundations for mercury pollution studies but also be of great importance for mercury pollution control of coal-fired power plants in southeastern coastal areas.This thesis performed a sampling analysis of mercury in PM2.5 and PM10 of 9 sampling sites in different directions and distances in Jiaxing for a period of nine months. The experiment was divided into three parts:monitoring of PM2.5 and PM10 concentrations; monitoring of carbon components in PM2.5 and PM10 and monitoring of mercury concentrations in PM2.5 and PM10. The research results demonstrate:(1) Volume concentrations of PM2.5 and PM10in regional environment of the coal-fired power pant are respectively 37.52-181.67μg/m3 and 53.14-250.31μg/m3. and the proportion of PM25 in PM10accounts about 69.17±16.04%, and the proportion appears remarkable correlation. From the aspect of seasonal distribution. PM2.5 and PM10assume similar variation trend, namely winter> autumn>summer> spring. Viewed from space distribution, the concentrations of PM2.5 and PM10 in the atmosphere of the power plant increase with the distance of the coal-fired power plant, and so do the volμme concentrations Cv till the maximμm points of concentrations, and then Cv drops as the distance further increases and the falling points for maximμm concentrations of PM2.5 and PM10 are at locations of 1.3km-2.5km. Rules for concentration variation of pollutants conforming to elevated source emission of power plants under down wind illustrate that the coal-fired power plant leaves a significant influence on the inhalable particles within nearby regional environment.(2) The average contents of OC and EC in PM2.5 were 29.88μg·m3 and 7.99μg·m3 and those in PM10 were 40.68μg·m3 and 13.92μg·m3. As can be learned from results of contribution rate calculated by chemical mass balance (CMB) model and electron microscopy analysis, coal-fired dust was the main particulate pollutants of coal-fired power plants, followed by dining smoke, vehicle exhaust, biomass burning and dust.(3) The Cv average values of particle mercury in PM2.5 and PM10 are 294.88±94.94 pg·m-3 and 363.41±133.52 pgm-3. The Cm average values of particle mercury in PM25 and PM10 are 4.08±2.82μgg-1 and 3.34±2.29μg-g-1, which are both much higher than that in coal (37±/g) and flying ash (353±15ng/g) indicating that the inhalable particles possess the function of gaseous mercury enrichment. Cv of particle mercury in PM2.5 accounts for more than 81% in that of PM10, i.e. the particle mercury in atmosphere main concentrates on the particle matters with particle size of not greater than 2.5μm.(4) As can be seen from the seasonal distribution:particulate matter mercury Cv in PM2.5 and PM10 in the regional environment of the coal-fired power plant exhibitedsimilar variation trends:winter> spring> autumn> summer. The seasonal change of mercury Cm was spring> summer> autumn> winter. Seen from the spatial distribution, mercury in PM2.5 and PM10 increased with the increasing distance of the coal-fired power plant, which was similar to the distribution of particles. Cv also increased until the maximum point of concentration appeared. After that, Cv reduced with theincreasing distance of the coal-fired power plant. This change was in line with the downwind concentration variation rule of pollutants discharged by elevated source in power plants, indicating that distribution changes of mercury Cv in PM2.5 and PM10 were primarily affected by coal-fired power plants.(5) Particulates Cv(total-Hg), CV(HPM), CV(EPM) and CV(RPM) showed a significant negative correlation with temperature, relative humidity and light intensity and a significant positive correlation with Cv(OC) and Cv(EC). High temperatures andstrong light had inhibition on particulate matter mercury, while carbon components in particulate matters had a promoting effect on mercury.