Purification Effect of Vegetation Biofilters on Particulate Transition Metals in Multi-Use Facilities

Abstract

Background and objective: Among multi-use facilities, underground subway stations are vulnerable areas where total management of particulate matter (PM) has been implemented through the Seasonal PM Management System. Through the friction between train wheels and railsthat occurs subway stations, iron oxide particles are generated, which can cause various diseases in the human body. This study aims to explore the application of plants to biofilters as a sustainable method for reducing metallic particle pollution.Methods: The experimental group was designed based on the application of plants and waterings to biofilters. Experimental data were obtained through time-series monitoring of PM using Indoor Air Quality (IAQ) stations and SEM-EDS-based chemical species analysis of PM samples. The chemical species analysis was involved in determining the weight ratio of Fe in the particles through 15 repeated analyses of large-area samples at 100 × magnification.Results: The highest concentration of PM was found during the 4th period of the day (when days were divided into 4 periods of 6 hours each), with PM<sub>10</sub> at 46.3 ± 27 μg/m<sup>3</sup> and PM2.5 at 23.8 ± 14.1 μg/m<sup>3</sup>. For the average weight ratio (AWR) of Fe, the experimental group (R.A.: 3.28wt%, S.A.: 0.25wt%) showed a reduction rate of approximately 92%, while control group 1 (R.A.: 0.51wt%, S.A.: 0.28wt%) showed a reduction rate of approximately 45%; control group 2 (R.A: 1.37wt%, S.A: 0.55wt%) showed a reduction rate of approximately 60%.Conclusion: The highest rate of Fe reduction was found when both plants and waterings were applied to the biofilters. This finding is consistent with those of previous studies on the positive effects of iron oxidation associated with plant growth.