Key Laboratory of Poyang Lake Environment and Resource Utilization of Ministry of Education, School of Resource, Environmental and Chemical Engineering, Nanchang University, Nanchang, Jiangxi 330031, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, No. 99, Linchengxi Road, Guiyang 550081, China.
Environ Pollut. 2019 Jun;249:655-665. doi: 10.1016/j.envpol.2019.03.074. Epub 2019 Mar 25.
Ammonia (NH) emissions from traffic have received particular attention in recent years because of their important contributions to the growth of secondary aerosols and the negative effects on urban air quality. However, few studies have been performed on the impacts of traffic NH emissions on adjacent soil and plants. Moreover, doubt remains over whether dry nitrogen (N) deposition still contributes a minor proportion of plant N nutrition compared with wet N deposition in urban road environments. This study investigated the δN values of road dustfall, soil, moss, camphor leaf and camphor bark samples collected along a distance gradient from the road, suggesting that samples collected near the road have significantly more positive δN values than those of remote sites. According to the SIAR model (Stable Isotope Analysis in R) applied to dustfall and moss samples from the roadside, it was found that NH from traffic exhaust (8.8 ± 7.1%) contributed much less than traffic-derived NO (52.2 ± 10.0%) and soil N (39.0 ± 13.8%) to dustfall bulk N; additionally, 68.6% and 31.4% of N in mosses near the roadside could be explained by dry N deposition (only 20.4 ± 12.5% for traffic-derived NH) and wet N deposition, respectively. A two-member mixing model was used to analyse the δN in continuously collected mature camphor leaf and camphor bark samples, which revealed a similarity of the δN values of plant-available deposited N to N-enriched traffic-derived NO-N. We concluded that a relatively high proportion of N inputs in urban road environments was contributed by traffic-related dustfall and NO rather than NH. These information provide useful insights into reducing the impacts of traffic exhaust on adjacent ecosystems and can assist policy makers in determining the reconstruction of a monitoring network for N deposition that reaches the road level.
近年来，由于交通排放的氨（NH）对二次气溶胶的增长和城市空气质量的负面影响，其受到了特别关注。然而，关于交通 NH 排放对相邻土壤和植物的影响的研究很少。此外，在城市道路环境中，与湿氮沉积相比，干氮（N）沉积对植物 N 营养的贡献是否仍然较小，这一点仍存在疑问。本研究调查了沿道路距离梯度采集的道路扬尘、土壤、苔藓、樟树叶和樟树皮样本的 δN 值，表明靠近道路的样本的 δN 值明显比偏远地区的样本更为正值。根据应用于路边扬尘和苔藓样本的 SIAR 模型（R 中的稳定同位素分析），发现交通尾气中的 NH（8.8 ± 7.1%）对扬尘总 N 的贡献远小于交通衍生的 NO（52.2 ± 10.0%）和土壤 N（39.0 ± 13.8%）；此外，路边苔藓中 68.6%和 31.4%的 N 可以用干氮沉积（仅交通衍生的 NH 为 20.4 ± 12.5%）和湿氮沉积来解释。使用二成员混合模型分析连续采集的成熟樟树叶和樟树皮样本的 δN 值，结果表明，植物可利用沉积 N 的 δN 值与富含 N 的交通衍生的 NO-N 相似。我们得出结论，交通相关的扬尘和 NO 而不是 NH 对城市道路环境中 N 输入的比例相对较高。这些信息为减少交通废气对相邻生态系统的影响提供了有用的见解，并可以帮助决策者确定达到道路水平的 N 沉积监测网络的重建。
