Oxidative potential and source apportionment of size-resolved particles from indoor environments: Dithiothreitol (DTT) consumption and ROS production

Abstract

Oxidation potential (OP) is an emerging index to measure the toxicity of atmospheric particulate matter (PM), but little research data on indoor PM OP are available. This study focuses on the size-resolved particle OP and source apportionment of PM from indoor environments. Different-size PM samples were gathered from March 6, 2022, to April 18, 2022, from offices, canteens, dormitories, and laboratories using Anderson samplers. Particles from these indoor environments were separated into nine size fractions, and the chemical components (including transition metals, ions, and water-soluble organic carbon (WSOC)) were measured. The water-soluble OP (OPws) of the investigated PM was highest in the dormitory (61.02 nmol min−1 μg−1) and lowest in the canteen (25.58 nmol min−1 μg−1), varying by factors of up to 2.38. Additionally, the particulate Mn (r2 = 0.94), Fe (r2 = 0.93), and Zn (r2 = 0.92) concentrations were closely related to OPws. The OPws distribution in indoor PM samples featured a single peak from 0.7 to 3.2 μm. ROS (·OH) showed the same trend (1.1–3.2 μm) as PM OP, which shows that PM3.2 is the main contributor to adverse health effects among all size fractions of PM due to the strengthened oxidative ability of PM3.2 compared to PM > 3.2. The source apportionment results showed that secondary sources (52.3%), construction sources (28%), vehicle emissions (18.5%), and dust sources (1.2%) were the main sources of indoor PM OP. Multiple path particle dosimetry (MPPD) model tests evidenced that PM3.2 control the lung OPws and ROS (accounting for >71.49% and 68.07%, respectively) deposition because of the high deposition efficiency and metal concentration in the alveolar region. The experimental trend of OP was closely related to that of ROS. Overall, since OPws is directly associated with diverse health effects for PM OP, special attention to PM3.2 impact.