Size-segregated physicochemical properties of inhalable particulate matter in a tunnel-ventilated layer house in...

This study investigated the physicochemical properties of the particles in a typical commercial laying hen barn in Southeast China. Mass concentrations and size distributions of the particulate matter (PM) and the key components (incl. organic carbon (OC), element carbon (EC), and the water-soluble inorganic ions (WSIIs)) were analyzed. The result shows that the mass concentrations of PM accumulated along with the airflow inside the house, with the total mass of the sampling particles increasing from 843.66 ± 160.74 μg/m³ at the center of the house to 1264.93 ± 285.70 μg/m³ at the place close to exhaust fans. The particles with the aerodynamic equivalent diameter, Dp > 9 μm, coarse particles (2.1 μm < Dp ≤ 9 μm), fine particles (Dp ≤ 2.1 μm) accounted for around 50%, 40%, and 10% of the total mass of the sampling particles, respectively. Mass closure analysis shows secondary inorganic ions (NH₄⁺, SO₄^2- and NO₃^-) were abundant in the fine-mode fraction and OC accounted for more than 40% of the coarse particles. Size distribution analysis shows that the three secondary inorganic ions were bimodally distributed, and the rest tested components were unimodally distributed. The ratios of OC/EC in fine particles were smaller than those in the coarse particles. The equivalent concentration of WSIIs indicated that fine particles were slightly acidic, and the large size particles were slightly alkaline. Knowledge gained from this study will lead to a better understanding of physicochemical properties, sources, and formation of PM.