COS 286-4 - Tracing the source of PM2.5 in urban forests using stable isotope analysis

Abstract: There is an increasing global awareness and worry regarding the effect of particulate matter (PM) on the environment. The detrimental effects of PM are particularly alarming in urban regions, where they pose a significant threat to human well-being. Urban forests are known to reduce PM and improve air quality. In order to quantify the PM reduction ability of urban forests, it is essential to identify the pollution sources of PM. In this study, the influence of pollution sources according to the surrounding environment (residential area, urban forest, industrial complex) were analyzed using the carbon and nitrogen stable isotope ratio (δ¹³C, δ¹⁵N) of fine particulate matter (PM_2.5). The carbon and nitrogen stable isotope ratios were shown in the residential area (-27.35±0.13‰, 10.69±0.79‰), urban forest (-27.52±0.13‰, 9.88±1.14‰), and industrial complex (-27.06±0.19‰, 9.66±1.11‰). After setting the range of stable isotope ratios from diverse sources such as C3 and C4 plants, coal and fossil fuels by referring to representative preceding studies, the contribution of PM_2.5 sources was calculated through a Bayesian mixture model. PM_2.5 in urban forests was affected similarly by anthropogenic sources (coal and fossil fuels; approximately 50.5%) and natural sources (C3 and C4 plants; approximately 49.6%). It was found that C3 plants, coal fuels, fossil fuels, and C4 plants had the greatest impact in the order. In urban forest, the composition of C3 plant was the highest (46.2%) and the effect of anthropogenic sources was the lowest (49.4%). On the other hand, the industrial complex had the highest impact from anthropogenic sources (52.5%), and the ratio of C3 plants was the smallest (42.4%). Since the concentration of PM_2.5 shows a significant difference when the pollution source is different even in adjacent areas, identifying the pollution source helps to understand the PM reduction function of urban forests. Furthermore, it can contribute to establishing criteria for the establishment of urban forests and their management plans.