Concentration Levels And Variation Characteristics Of Particulate Matter In Urban Air Of Changsha

With the rapid development of urban modernization,atmospheric pollution,especially suspended particulate matter,is very serious. Particulate matter can lead to decrease of visibility and adverse health effect.Many epidemiological studies show that there is strong correlation between the level of particle concentration and human health.The rise of particle concentration has lead to a significant increase of morbidity and mortality in respiratory and cardiovascular diseases.Therefore,it is very important to research the level of particle concentration.The mass concentrations and number concentrations of aerosol were measured continuously in urban air of Changsha from November 2007 to October 2008.The number concentrations and the mass concentrations of PM₁₀ and PM_2.5 were measured simultaneously in October 2008.Long periods monitoring was operated with TEOM,APS and DustTrak.All statistical analyses were conducted using a statistical analysis software package-SPSS 13.0.The research showed that the levels of PM₁₀ and PM_2.5 were high in Changsha and average diurnal concentrations were higher in autumn and winter.Average diurnal variations of PM₁₀ and PM_2.5 presented two peaks around 9:00 in the morning and 18:00 in the evening mainly attributed to traffic and meteorological conditions.The relationship between PM₁₀ and PM_2.5 suggested that PM_2.5 was main fractions in inhalable particles.Average diurnal number concentration of PM in range from 0.5 to 20μm was 517.0#/cm³.The median diameter of number concentrations was 0.635μm between 0.5 and 1μm.Average diurnal variations of particle number presented the same peak attributed to vehicle emission.The investigation the correlation between number concentrations and mass concentrations of particles indicated that the relationship between number concentration and PM₁₀ was better than PM_2.5 suggesting that fine particles mainly contributed number concentrations.When polluted sources were steady,the levels of particulate matter were influenced by meteorological parameters such as temperature, humid,wind speed,air pressure,rainfall and so on.Air temperature had effect on particle diffusion.An increase in relative humidity in the atmosphere led to growth of fine particles due to components of which absorbing water.Wind may play a role in transporting and diluting ambient particles and also lead to re-suspension of road dust.