Size-differentiated Inorganic Chemical Composition of Atmospheric Particles at the T1 Supersite during the MILAGRO Field Campaign

Cascade impactors with eight cut stages were used to sample atmospheric particles at Tec�mac (T1 supersite), State of Mexico, during the MILAGRO field campaign in March 2006. The sampling site is located in the northeast (NE) edge of Mexico City; it experiences both fresh local emission and aged pollutants produced in Mexico City. Samples were analyzed to determine total mass, Ca²⁺, Na⁺, Mg²⁺, NH₄⁺, K⁺, Cl^-, SO₄^2-, and NO₃^- concentrations. Mexico City pollution plume contributes with particle mass in all aerodynamic diameter sizes, but local emissions are quite important. PM₁₀ average mass concentration was 30.3 �g m^-3; for coarse mode (3.2 � 10 �m) was 11.7 �g m^-3 and fine mode (0.18 � 1.8 �m) was 18.6 �g m^-3. The ions NO₃^-, SO₄^2-, Na⁺, and NH₄⁺ were found in high concentrations on fine mode, and high concentrations of Cl^-, K⁺, Ca²⁺, and Mg²⁺ were found on coarse mode.