Concentrations and Size Distributions of Inhalable Particles in Summer and Winter in Shenyang

Inhalable particles which refer to particles with aerodynamic diameters less than 10μm are the main pollutants in many cities. They are crucial to human health, visibility of atmosphere and radiation balance, and are also the good bearer of atmospheric chemistry reaction.Some studies about inhalable particles are made in Shenyang, but the studies on the number concentration of the surface layer aerosols and the polluted characteristic are scarce, especially the synchronous observation and research about the number and mass concentration of PM₁₀ and PM_2.5 are not enough. Atmospheric component monitoring station of Shenyang has begun to continuously and synchronously monitor the PM₁₀ and PM_2.5 with ambient dust monitor (Grimm 180) since July 2006. Based on continuous observations of inhalable particles including number and mass concentration data in the atmosphere in August 2006 (summer), in December 2006, and in January 2007 (winter), data are processed by mathematical statistics to obtain the average hourly, daily and seasonal concentration. In order to reveal pollution characteristics of Inhalable Particles in Shenyang, particle spectrum distribution and variations of concentration are analyzed.In addition, the relations to meteorological factors are investigated. Results show that the diurnal and inter-daily variations of concentration are obvious, and diurnal variations of summer and winter both show the characteristics of single peak and single vale. Peak value in summer is earlier than that in winter, but vale value is later. Number and mass concentrations reach the highest point at about 10:00 in winter, and the lowest point is between 13:00 and 14:00. The spectrum distribution conforms to the Junge distribution well, and the average relative error is 9.4%. Number of days that PM₁₀ and PM_2.5 mass concentration is above air quality standards, and is 77% and 87% of total days in winter respectively, and number of days that exceeds third class standard is 43%.The mean number density is 6668.7cm^-3, and the mass concentration reaches 252.8μg/m³, 3.0 and 2.4 times of summer respectively. Average mass percentage about PM_2.5/PM₁₀ of winter and summer respectively are 0.647 and 0.603, PM_2.5 average quantity accounts for over 99%of PM₁₀.Concentration variation has a good connection with wind speed, temperature and relative humidity. The spectrum distribution is different as well as the conditions of the different weather, and the precipitation and snowfall could wipe off aerosol concentration obviously, especially of the high clear rate for the fine particles, and the near ground temperature inversion and fog are important for aerosol increase. The visibility in the city is affected evidently by pollution of the airborne particulate matters.