Outdoor PM₁₀ source apportionment in metropolitan cities--a case study

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Urban Air Quality

Background:

• Particulate Matter (PM10) poses significant health risks in urban environments.
• Identifying emission sources is crucial for effective air pollution control strategies.
• Tehran faces challenges with outdoor air pollution, necessitating source apportionment studies.

Purpose of the Study:

• To determine the contribution of various sources to PM10 emissions in Tehran.
• To apply the chemical mass balance (CMB) method for source apportionment in Iran for the first time.
• To assess the levels of specific metallic elements in PM10 and compare them with established standards.

Main Methods:

• Sampling of metallic elements (V, Ni, As, Pb, Cd, Hg, Mn, Al, Ca, K, Na, Fe, Zn, Sc, S) in PM10 using high-volume samplers at four Tehran stations.
• Quantification of elemental concentrations using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
• Application of the Chemical Mass Balance (CMB) model for source apportionment of PM10.

Main Results:

• Cadmium (Cd) concentrations exceeded permissible limits in specific areas (District 16).
• Anthropogenic elements (Zn, S, Ni, Hg) showed enrichment, indicating non-crustal origins.
• Road dust was identified as the dominant PM10 source (95.4%), followed by transportation (4.05%) and industries (0.4%).

Conclusions:

• Road dust, primarily from tire and asphalt wear, is the main contributor to Tehran's outdoor PM10.
• Road pavement quality significantly influences PM10 emissions in urban settings.
• The CMB method provides valuable insights for air quality management in Tehran and potentially other Iranian cities.