Indoor PM_2.5 and PM₁₀ pollution and their relationship with outdoor pollution in Liuzhou City

Objective To investigate the pollution status of indoor PM_2.5 and PM₁₀ at public places in Liuzhou, China and to analyze their relationship with outdoor pollution.

Methods In the summer and winter of 2020, the stratified random sampling method were performed to select 18 accommodation places, 8 bathing places, 6 swimming places, 16 beauty salons, and 2 waiting places for monitoring. Indoor and outdoor PM_2.5 and PM₁₀ mass concentration were simultaneously measured by light scattering method. The ventilation status and special conditions of the monitoring points during the on-site sampling were recorded at the same time.

Results The median mass concentration M(P₂₅, P₇₅) of indoor PM_2.5 in liuzhou public places was 25 (18-37) μg/m³, with a range of (5-168) μg/m³, and the qualified rate was 92.9%. The median mass concentration M(P₂₅, P₇₅) of PM₁₀ was 51 (36-79) μg/m³, with a range of (10-374) μg/m³, and the qualified rate was 92.9%. The indoor PM_2.5and PM₁₀ mass concentrations in public places in winter were significantly higher than those in summer, with a statistically significant difference. The mass concentrations of indoor PM_2.5and PM₁₀ varied in different types of public places. There was a linear relationship between the mass concentration of indoor PM_2.5 and PM₁₀, with a regression equation of y=2.083x-0.985, R=0.997;The mass concentration of indoor PM_2.5 was lower than that of outdoor PM_2.5, and existed a highly positive correlation between them(R=0.821). There was a positive correlation of PM₁₀ mass concentration between indoor and outdoor (R=0.790). The indoor and outdoor I/O ratios of PM_2.5 and PM₁₀ were 1.02 and 1.01 respectively.

Conclusion There are good conditions of indoor air PM_2.5 and PM₁₀ in public places in Liuzhou. Public places have good indoor ventilation, and indoor PM_2.5 and PM₁₀ pollution is mainly affected by outdoor pollution.