Plants play a pivotal role in mitigating PM_2.5 pollution by efficiently absorbing particulate matter from the atmosphere, thereby contributing to the improvement of air quality. Understanding the mechanisms underlying PM_2.5 uptake and its subsequent distribution within plant tissues is crucial for enhancing the ecological functions of vegetation and fostering a healthier environment. This study employed a one-time fumigation approach, coupled with a ¹⁵N tracer method, to investigate the mechanisms of PM_2.5 uptake and distribution in several representative tree species across Beijing. The selected species included Manchurian red pine (Pinus tabuliformis), Bunge's pine (Pinus bungeana), Corkscrew willow (Salix matsudana), Ginkgo (Ginkgo biloba), Japanese pagoda tree (Styphnolobium japonicum), and Goldenrain tree (Koelreuteria paniculata). Our focus was on the uptake and distribution characteristics of the water-soluble inorganic constituents ammonium (NH⁺₄) and nitrate (NO^-₃). The findings revealed several key insights: (1) The examined plants exhibited effective uptake of NH⁺₄ (ranging from 0.03 to 0.80 μg/g) and NO^-₃ (ranging from 0.02 to 1.10 μg/g) from PM_2.5. Among the species, the Corkscrew willow and Manchurian red pine demonstrated the highest ammonium uptake ability, followed by Ginkgo and Goldenrain tree, while Bunge's pine and Japanese pagoda tree showed the lowest uptake ability. In terms of nitrate, Corkscrew willow and Manchurian red pine again led in uptake ability, with Bunge's pine and Japanese pagoda tree following, and Goldenrain tree and Ginkgo exhibiting the least uptake ability. (2) The ability for ¹⁵N uptake and the allocation of nitrogen within above-ground plant organs surpassed that of their underground counterparts. Notably, leaves possessed the highest uptake ability (NH⁺₄: 0.08-1.63 μg/g, NO^-₃: 0.01-1.18 μg/g) and partitioning rate (NH⁺₄: 18.95%-76.10%, NO^-₃: 6.86%-91.64%) for both ions. (3) Statistical analysis indicated that varying concentrations of PM_2.5, tree species, and their interactions significantly influenced the ¹⁵N uptake ability and distribution rates within different organs (P<0.01), with the uptake ability of above-ground organs increasing in response to higher concentrations. (4) Plants exhibiting a smaller root-crown ratio, increased root biomass ratio, and larger branch biomass ratio were found to be more conducive to NH⁺₄ uptake, while those characterized by a smaller root-crown ratio, thicker and finer root biomass, along with a larger stem biomass ratio, were more favorable for NO^-₃ uptake. This study elucidates the mechanisms by which plants uptake PM_2.5 and highlights the interplay between intrinsic (plant traits) and extrinsic factors (PM_2.5 concentration). The insights garnered provide a scientific foundation for leveraging plant-based strategies to mitigate PM_2.5 pollution across various environmental contexts.