Hit from both sides: tracking industrial and volcanic plumes in Mexico City with surface measurements and OMI SO2 retrievals during the MILAGRO field campaig. - de Foy, B.; Krotkov, N. A.; Bei, N.; Herndon, S. C.; Huey, L. G.; Martínez, A.-P.; Ruiz-Suárez, L. G.; Wood, E. C.; Zavala, M.; Molina, L. T. (Atmospheric Chemistry & Physics, 2009)