Characterization of Respirable Particulate Matter Collected With Cyclones in School Environments of the Metropolitan Region of Rio de Janeiro

ABSTRACT The relevance of investigating atmospheric particulate matter (PM) in the school environment is related to its significant impact on the health of school‐age children. In this context, the present study focuses on the characterization of suspended atmospheric PM in eight elementary schools located in the metropolitan region of Rio de Janeiro (Brazil). Samples were collected during the winter of 2022 and the summer of 2023. The sampling time was 24 h, with a flow rate of 2.5 L/min at a height of 1.5 m from the ground. Experimental measurements by X‐ray fluorescence were performed using the commercial EPSILON 1 system (Malvern Panalytical), with an Ag target and an SDD (Silicon Drift Detector) with an energy resolution of less than 135 eV for the Mn‐Kα line. The samples were analyzed in two distinct experimental configurations: In the first (low Z), the focus was on exciting elements with atomic number Z ≤ 20 in the K lines, using a voltage of 12 kV, a current of 416 μA, an acquisition time of 60 s, and an Al filter (50 μm) in the X‐ray beam. In the second configuration (high Z), the goal was to excite elements with 20 < Z < 42 in the K lines and 55 < Z < 92 in the L lines, employing a voltage of 50 kV, a current of 100 μA, and a Cu filter (500 μm), with an acquisition time of 600 s. The following elements were detected: Si, S, Cl, K, Ca, Fe, Cu, and Zn. The average concentrations, considering all samplings in the metropolitan region of Rio de Janeiro, were: Si (2609 ± 988 ng m −3 ), S (2106 ± 797 ng m −3 ), Cl (2164 ± 620 ng m −3 ), K (685 ± 194 ng m −3 ), Ca (652 ± 564 ng m −3 ), Fe (321 ± 172 ng m −3 ), Cu (14 ± 7 ng m −3 ), and Zn (29 ± 19 ng m −3 ). The Student's t ‐test was applied to evaluate possible statistical differences in the concentrations of the detected elements between the samples collected in the winter and the summer. No significant seasonal variations in the concentrations were identified (α = 0.05). The results highlight the urgency of public policies that implement measures to reduce PM levels in schools, thus minimizing their harmful effects on health.