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

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

Background and objective: Among multi-use facilities, underground subway stations are vulnerable areas where totalmanagement of particulate matter (PM) has been implemented through the Seasonal PM Management System. Throughthe friction between train wheels and railsthat occurs subway stations, iron oxide particles are generated, which can causevarious diseases in the human body. This study aims to explore the application of plants to biofilters as a sustainablemethod 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 andSEM-EDS-based chemical species analysis of PM samples. The chemical species analysis was involved in determining theweight 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 periodsof 6 hours each), with PM10 at 46.3 ± 27 μg/m3 and PM2.5 at 23.8 ± 14.1 μg/m3. 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 group1 (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. Thisfinding is consistent with those of previous studies on the positive effects of iron oxidation associated with plant growth.