Size fractionated analysis of PM in an urban environment and assessment of potential risk of alveolar penetration in Tehran city
摘要
To investigate the concentration and chemical characteristics of PM0.4 in Tehran in relation to atmospheric parameters, samples were taken from 10 points for a year. The results showed that the concentration of PM0.4 had a clear seasonal pattern. High-traffic and dense urban stations recorded higher concentrations, indicating the role of local sources, especially traffic and urban activities. Statistical analyses showed that PM0.4 is significantly affected by atmospheric parameters; it was positively correlated with relative humidity and negatively correlated with temperature and wind speed. SEM-EDX results also confirmed the heterogeneous composition of PM0.4. They showed the simultaneous presence of carbon components, crustal elements, and secondary compounds, indicating multiple origins including traffic emissions, urban dust, and secondary formation in the atmosphere. The average concentration of these particles showed an increasing trend from the beginning of the year, peaking during the warm months. The lowest value was recorded in January (0.311 µg/m3), and the highest in September (0.614 µg/m3). Specifically, from May to October, particle concentrations were higher than in other months, reaching maximum values in July, August, and September. Thereafter, from October to January, concentrations decreased again. The results of this study showed that the concentration of submicron particles (PM0.4) in Tehran exhibited a different temporal behavior than PM2.5 and PM10 and depended more on atmospheric thermodynamic conditions and secondary formation processes than on primary sources and mechanical resuspension. The widespread presence of Si and Al at all stations, along with morphological evidence of angular and broken particles, indicated the dominance of mineral dust and resuspension of soil/construction particles.