PM2.5particles, with a diameter of 2.5 μm or less, are the primary pollutant in the air. In this study, PM2.5 particles were generated with an aerosol generator, and absorption of NH+4 and NO-3 in PM2.5 and their distribution in Populus euramericana seedlings were studied using 15 N tracing techniques. The results showed that water-soluble inorganic components ( NH+4 and NO-3 ) in PM2.5 can be absorbed effectively by P. euramericana. Absorption rates of NH+4 and NO-3 by P. euramericana leaves peaked one day after treatment, in both low and severe pollution treatments. Subsequently, the absorption rates of NH+4 and NO-3 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, 15 N content of P. euramericana leaves peaked one day after treatment, when 15 N ( NH+4 ) content was 0.11 mg/g and that of 15 N ( NO-3 ) was 0.14 mg/g, DW. Following this peak, 15 N 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 15 N ( NH+4 ) content was 0.11 mg/g and that of 15 N ( NO-3 ) was 0.13 mg/g, DW. 15 N content differed among tissues and organs of P. euramericana 7 days after treatment. In the low pollution treatment, NH+4 and NO-3 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, NH+4 and NO-3 content in various tissues and organs was ranked as leaf > fine root > petiole > bark > pith. The NH+4 and NO-3 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 NO-3 was absorbed by P. euramericana than NH+4 in both low and severe pollution treatments, which correlated well with NH+4 and NO-3 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 15 N 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 PM2.5absorption by plants and develop strategies to reduce particulate matter pollution using plants.%通过气溶胶发生系统模拟PM2.5颗粒的发生,运用15 N示踪技术研究了欧美杨107( Populus euramericana Neva.)对PM2.5中水溶性无机成分NH+4和NO-3的吸收与分配规律。结果表明,欧美杨能够有效吸收PM2.5中的NH+4和NO-3。轻度和重度污染下,欧美杨叶片对NH+4和NO-3的吸收速率均于处理后第1天达到峰值,之后,轻度污染下对NH+4和NO-3的吸收速率迅速降低以后趋于稳定,而重度污染下对NH+4和NO-3的吸收速率缓慢下降至趋于稳定。轻度污染下的欧美杨叶片的15 N含量在处理后第1天达到峰值,15N(NH+4)的含量为0.11 mg/g,干重,15N(NO-3)的为0.14 mg/g,干重,之后15N含量迅速下降至趋于稳定。重度污染下的叶片15N含量在处理第1天迅速增长,之后缓慢增长至处理后第7天达到最高值,15N(NH+4)的含量为0.11 mg/g,干重,15 N( NO-3)的为0.13 mg/g,干重。处理7 d后,欧美杨不同组织器官吸收或通过再分配获取的15 N含量存在差异。轻度污染下,细根对NH+4和NO-3的吸收量最高,树皮、叶柄、叶片次之,髓最低。而重度污染下,叶片对NH+4和NO-3的吸收量最高,细根、叶柄、树皮次之,髓最低。欧美杨各组织器官中NH+4和NO-3的含量均表现为重度污染大于轻度污染,且两种污染程度下的欧美杨各组织器官对NO-3的吸收均大于对NH+4的吸收。重度污染下,欧美杨茎木质部对15 N( NH+4和NO-3)的吸收征调能力( Ndff, Nitrogen derived from fertilizer)最大,其次为髓,叶片最小；欧美杨各组织器官中的15 N分配率表现为叶片>细根>叶柄>树皮>粗根>茎木质部>髓。研究结果对进一步揭示植物吸收PM2.5的机制及有效利用植物降低颗粒物污染、净化环境提供了重要的科学理论依据。
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