Comparative Assessment of Elemental Concentrations in Urban Tree Species and PM2.5 Emitted from Their Combustion

This study examines the variations of elements in PM2.5 emitted from biomass burning in urban settings, which raises health concerns among urban dwellers. It specifically focused on how Sodium (Na), Calcium (Ca), Potassium (K), and Phosphorus (P) concentrations in tree combustibles affect their concentrations in PM2.5 emitted during combustion. Understanding these interactions is critical for evaluating air quality and its public health effects. Urban landscape coniferous and broad-leaf tree species combustibles (branches and leaves) were assessed, and the data were processed using Microsoft Excel, Origin Pro 2024, and R Studio. It was discovered that the species and organs had a common elemental concentration pattern (Ca > K > P > Na) in their combustibles but a different concentration pattern in the emitted PM2.5. Quantitatively, the concentrations in the combustibles varied, with Ca being the most abundant (69.85 mg/kg) and P the least (3.97 mg/kg). In PM2.5, the contrary was observed, i.e., Na (which was among the least concentrated elements in the combustibles) became prominent; the highest levels were recorded in PM2.5 from conifers (Na = 0.86 mg/kg). Among the assessed elements in PM2.5, P had the lowest concentration in all the tests, having the lowest values from broad-leaf species (P = 0.02 mg/kg). The SEM result further revealed that, quantitatively, the concentration of these elements in the combustibles does not necessarily mean that they will be in higher concentrations in the emitted PM2.5. These variations highlighted the importance of considering tree species, organ types, and elemental interactions when assessing the impacts of biomass combustion on urban air quality and human health.