“…Each membrane was weighed before and after sampling using an ultra-microbalance (Mettler Toledo UMX2, readability 1 µg, Zurich, Switzerland) to determine the daily mass trapped by each membrane, allowing the calculation of the daily mean concentration of PM2.5 ( 13 ). The black carbon concentrations were measured using the reflectance method ( 14 ) using the same membranes, and 1/3 of the membranes were submitted to X-ray fluorescence spectrometry ( 15 ) and ion chromatography ( 16 ) analysis to determine the concentrations of the predominant chemical elements (Na, Al, Si, P, S, K, Ca, Ti, V, Fe, Ni, Cu, Zn, and Pb), nitrates and sulfates. The daily mean concentrations of PM2.5 were used to calculate the annual daily mean of PM2.5 as described by the WHO ( 30 ).…”