Abstract:

In recent years, atmospheric pollution, particularly nitrogen oxides (mainly NO₂), has seriously increased, posing significant risks to both environmental safety and human health. In addition to controlling pollution sources, using green plants to absorb and purify pollutants has been an effective and sustainable treatment measure. Six representative greening tree species, incluing Pinus tabuliformis, Pinus bungeana, Ginkgo biloba, Styphnolobium japonicum, Koelreuteria paniculata, and Salix matsudana, were selected as research objects to explore the purification effect of typical greening tree species on nitrogen oxides and provide a basis for the selection of urban greening tree species. To achieve this objective, a comprehensive study employing artificially controlled experiments and field measurements was conducted. The monthly variations in NO₂ purification efficiency effect of six representative greening tree species throughout the growing season (June-October) were investigated in Beijing. Additionally, the common characteristics of purification capacities between the two methods were compared and analyzed to ensure the scientific integrity of the artificially controlled experiments. The findings of this study reveal the following key insights: 1) In the artificially controlled experiments, the NO₂ purification capacity per unit leaf area ranged from 2.04-7.85 μg∙dm⁻² for broadleaf species and 0.96-1.97 μg∙dm⁻² for conifers. Furthermore, the purification durations ranged from 48-127 minutes for broadleaf species and 41-107 minutes for conifers. 2) The field experiment showcased daily fluctuations in NO₂ concentrations within the forests of each tree species, following a “single peak and single valley” pattern, with the highest concentrations at 10:00 am (81.3-139 μg∙m⁻³), whereas the lowest at 14:00 (25.3-70.3 μg∙m⁻³). 3) The purification abilities of tree species, under both artificially controlled and natural conditions, exhibited a seasonal trend, with stronger performances in July and August, and weaker performances in June and October. Notably, the purification capacities were significantly higher in broadleaf forests compared to coniferous forests (P<0.05). 4) A comparative analysis between the monthly NO₂ purification capacities under artificial control conditions and the corresponding NO₂ concentrations in natural forest environments revealed a clear negative relationship. Greater NO₂ purification capacities under artificial control conditions corresponded to lower NO₂ concentrations in the forests of respective species under natural field conditions. Consequently, these monthly variations in NO₂ purification capacities align with the observed patterns in natural field conditions, thus confirming the scientific and rational nature of the results obtained from the controlled experiments.

Key words: greening tree species, NO₂, purifying effect, artificial control and field experiments, monthly change characteristics

摘要：

近年来，大气污染日益严峻，氮氧化物（主要为NO₂）是危害环境安全和人体健康的主要大气污染物之一，除控制污染源外，利用绿色植物吸收净化污染物为有效且可持续的治理措施。为探究典型绿化树种对氮氧化物的净化作用，以及为城市绿化树种选择提供依据，以油松（Pinus tabuliformis）、白皮松（Pinus bungeana）、银杏（Ginkgo biloba）、国槐（Sophura japanica）、栾树（Koelreuteria paniculata）、旱柳（Salix matsudana）为研究对象，采用人工控制试验结合野外测量试验研究6个北京典型绿化树种在植物生长季（6－10月）对NO₂净化作用月变化特征，并对比分析两种方法下树木净化能力的共同特征，验证人工控制试验的科学合理性。结果表明，1）人工控制试验中阔叶树种单位叶面积NO₂净化量为2.04－7.85 μg∙dm⁻²，针叶为0.96－1.97 μg∙dm⁻²；阔叶净化时间为48－127 min，针叶为41－107 min。2）野外试验中各树种林内NO₂质量浓度日变化均呈现“单峰单谷”特征，以10:00最高（81.3－139 μg∙m⁻³），14:00最低（25.3－70.3 μg∙m⁻³）。3）人工控制条件与自然条件下各树种净化能力均表现植物生长旺盛季（7、8月）最强，6、10月最弱，阔叶林的净化能力显著高于针叶林（P<0.05）。4）通过将人工控制条件下植物净化NO₂能力的月变化数据与自然条件下林内NO₂浓度进行对比，发现二者动态趋势具有明显相反规律，即人工控制条件下植物净化NO₂能力越大，野外自然条件下相对应树种林内NO₂浓度越低。人工控制条件下树种净化NO₂能力的月变化特征与野外自然条件下规律一致，证明人工控制试验结果科学合理。

关键词: 绿化树种, NO₂, 净化作用, 人工控制和野外试验, 月变化特征