PM_2.5 particles, with a diameter of 2.5 μm or less, are the primary pollutant in the air. In this study, PM_2.5 particles were generated with an aerosol generator, and absorption of NH₄⁺ and NO₃^- in PM_2.5 and their distribution in Populus euramericana seedlings were studied using ¹⁵N tracing techniques. The results showed that water-soluble inorganic components (NH₄⁺ and NO₃^-) in PM_2.5 can be absorbed effectively by P. euramericana. Absorption rates of NH₄⁺ and NO₃^- by P. euramericana leaves peaked one day after treatment, in both low and severe pollution treatments. Subsequently, the absorption rates of NH₄⁺ and NO₃^- in the low pollution treatment decreased rapidly and then leveled off, while the absorption rates in the severe pollution treatment decreased slowly to a stable level. At the low pollution level, ¹⁵N content of P. euramericana leaves peaked one day after treatment, when ¹⁵N (NH₄⁺) content was 0.11 mg/g and that of ¹⁵N (NO₃^-) was 0.14 mg/g, DW. Following this peak, ¹⁵N content decreased rapidly and remained relatively steady. At the severe pollution level, ¹⁵N content of P. euramericana leaves increased quickly in the first day of treatment before increasing slowly to reach its maximum 7 days after treatment, when ¹⁵N (NH₄⁺) content was 0.11 mg/g and that of ¹⁵N (NO₃^-) was 0.13 mg/g, DW. ¹⁵N content differed among tissues and organs of P. euramericana 7 days after treatment. In the low pollution treatment, NH₄⁺ and NO₃^- content was highest in fine roots, followed by that in bark, petiole and leaf, with the lowest content in pith. However, in the severe pollution treatment, NH₄⁺ and NO₃^- content in various tissues and organs was ranked as leaf > fine root > petiole > bark > pith. The NH₄⁺ and NO₃^- content of all tissues and organs of P. euramericana in the severe pollution treatment were higher than those in the low pollution treatment. Moreover, more NO₃^- was absorbed by P. euramericana than NH₄⁺ in both low and severe pollution treatments, which correlated well with NH₄⁺ and NO₃^- absorption rates and contents in leaves two days after treatment. In the severe pollution treatment, the Ndff value was highest in xylem (stem), followed by that in pith, and the lowest value was in leaf. The ¹⁵N partition rate of different tissues and organs was leaf > fine root > petiole > bark > coarse root > xylem (stem) > pith. Our results provide a basis for further research to elucidate the mechanism of PM_2.5 absorption by plants and develop strategies to reduce particulate matter pollution using plants.