Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
J Environ Sci (China). 2019 Oct;84:155-165. doi: 10.1016/j.jes.2019.04.014. Epub 2019 Apr 25.
Nitrogen dioxide (NO) is an important substance in atmospheric photochemical processes and can also be absorbed by plants. NO fluxes between the atmosphere and P. nigra seedlings were investigated by a double dynamic chambers method in Beijing from June 15 to September 3, 2017. The range of NO exchange fluxes between P. nigra seedlings and the atmosphere was from -14.6 to 0.8 nmol/(m·sec) (the positive data represent NO emission from trees, while the negative values indicate absorption). Under ambient concentrations, the mean NO flux during the fast-growing stage (Jun. 15-Aug. 4) was -3.0 nmol/(m·sec), greater than the flux of -1.5 nmol/(m·sec) during the later growth stage (Aug. 8-Sept. 3). The daily exchange fluxes of NO obviously fluctuated. The fluxes were largest in the morning and decreased gradually over time. Additionally, the NO fluxes were larger under high light intensities than under low light intensities during the whole growth period. The effects of temperature on NO fluxes were different under two growth periods. The NO exchange fluxes were larger in a range of temperatures close to 44°C in the fast-growing stage, whereas there were no evident differences in NO exchange fluxes under widely differing temperatures in the later growth stage. Under polluted conditions, the uptake ability of NO was weakened. Additionally, the compensation point of NO was 5.6 ppb in the fast-growing stage, whereas it was 1.4 ppb in the later growth stage. The deposition velocities of NO were between 0.3 and 2.4 mm/sec.
二氧化氮（NO）是大气光化学反应过程中的一种重要物质，也能被植物吸收。本研究于 2017 年 6 月 15 日至 9 月 3 日在北京采用双动态箱法研究了大气与欧洲山杨幼苗之间的 NO 通量。欧洲山杨幼苗与大气之间的 NO 交换通量范围为-14.6 至 0.8 nmol/（m·s）（正值表示树木向大气排放 NO，负值表示吸收）。在环境浓度下，快速生长阶段（6 月 15 日至 8 月 4 日）的平均 NO 通量为-3.0 nmol/（m·s），大于生长后期（8 月 8 日至 9 月 3 日）的-1.5 nmol/（m·s）。NO 日交换通量明显波动。通量在清晨最大，随时间逐渐减小。此外，在整个生长期间，高光强下的 NO 通量大于低光强下的通量。温度对两个生长阶段的 NO 通量的影响不同。在快速生长阶段，接近 44°C 的温度范围内，NO 交换通量较大，而在生长后期，在广泛不同的温度下，NO 交换通量没有明显差异。在污染条件下，NO 的吸收能力减弱。此外，快速生长阶段的 NO 补偿点为 5.6 ppb，而生长后期的补偿点为 1.4 ppb。NO 的沉积速度在 0.3 至 2.4 mm/s 之间。
