Observation of vertical profiles of NO, O<SUB>3</SUB>, and VOCs to estimate their sources and sinks by inverse modeling in a Japanese larch forest

Abstract

Trace atmospheric gases in the biosphere, such as ozone O 3 , nitrogen oxides NO x , and biogenic volatile organic compounds BVOCs , can affect the carbon cycle as well as the climate. Vertical profiles of nitric oxide NO , O 3 , and volatile organic compound VOC concentrations were measured at a Japanese larch Larix kaempferi forest in the foothills of Mt. Fuji in Japan over an 11-day period in July 2012. The concentrations of NO and O 3 during the day were highest above the canopy and decreased with proximity to the forest floor, but those of the VOCs had minimum and maximum points at different levels within the canopy depending on the species. Inverse multilayer models were applied to identify vertical sink and source distribution of these gases within the canopy. The model estimated that there was higher O 3 deposition and absorption at the forest floor than in the canopy layer; therefore, the understory was an important O 3 sink within the forest. A strong NO sink was simulated in the trunk space, where loss by reaction with O 3 is expected. The sinks and sources of BVOC as well as their oxidized products are simulated in the canopy layer and the forest floor. The sink and source distribution suggested that VOC transportation from the neighboring forest also affected the vertical sink and source distribution within the canopy.

Review: Exchanges of volatile organic compounds between terrestrial ecosystems and the atmosphere

“…Further reactions reduced MEK and 3-buten-2-ol to 2-butanol. A similar result has been reported by Tani et al 2020 , but they did not observe 3-buten-2-ol emission from non-isoprene-emitting species including three tree and one houseplant species. Cappellin et al 2019 determined the conversion ratio of MVK to MEK to be 73 , and that of MVK to all volatiles including MEK, 3-buten-2-ol, and 2-butanol to be 97.6 , suggesting that the absorbed MEK was mostly converted to volatiles and scarcely remained in leaves.…”

“…Cappellin et al 2019 determined the conversion ratio of MVK to MEK to be 73 , and that of MVK to all volatiles including MEK, 3-buten-2-ol, and 2-butanol to be 97.6 , suggesting that the absorbed MEK was mostly converted to volatiles and scarcely remained in leaves. On the contrary, MVK conversion ratios of the non-isoprene-emitting species determined by Tani et al 2020 were much lower than those reported by Cappellin et al 2019 ; i.e. 26 -39 for MEK and 33 -44 for all volatiles.…”

“…The compensation point of the compounds within leaves may vary, depending on their atmospheric concentration and production rate of these compounds within plants Fares et al, 2015 . Using an inverse model, a sink and source analysis of MACR and MVK was conducted by Wada et al 2020 , but their result suggests that larger amounts of data on spatial distribution of these compounds should be collected to provide a valid estimate.…”

Vigor and Health of Urban Green Resources under Elevated O3in Far East Asia

“…We employ O 3 -sensitive plants, such as morning glory (Ipomoea nil), as a biological indicator for avoiding O 3 stresses in a city [49]. As green area (trees and shrubs) has a high capacity for improvement of O 3 that is detected by flux monitoring [12,50,51], the green area has higher removal capacity (3.4 g m À2 yr. À1 on average) than green roofs (2.9 g m À2 yr. À1 as average removal rate), with lower installation and maintenance costs [13]. To overcome present gaps and uncertainties, they proposed a novel species air quality index (S-AQI) of suitability to air quality improvement for tree/shrub species.…”

Progress on the vertical observation methods of volatile organic compounds and their applications within the atmospheric boundary layer

“…法获取大气边界层内 VOCs 物种浓度的垂直分布数据 [39,40] 。随着民用无人机产业的快速发 展，许多性能优异(载荷大、续航时间长和操控稳定度高等)且价格低廉的中小型无人机被 广泛用于大气监测领域，获取边界层内各类大气参数的垂直分布数据 [41] 。无人机是近些年来 较为热门的大气垂直观测平台，基于无人机平台的各种优异性能，其在大气垂直观测领域有 广阔的应用前景。 无人机平台的优点在于其机动灵活性较高，能够在复杂环境中使用 [42] ，对后勤保障和观 测场地的要求较低，且其使用成本也相对低廉 [43] 。使用电池驱动的无人机可以有效避免燃油 废气排放对 VOCs 观测样本可能造成的污染，提高观测数据的可靠性 [44][45][46] 。虽然无人机平台 具有较好的操控性和灵活机动性，但也存在诸多因素限制。首先，受当前电池技术发展的限 制，无人机的续航时间仍然不足，有效载重较小，并且续航时间随附加设备重量的增加而急 剧下降 [47] ，严重限制了一个航次中能够有效获取的观测样本数量；其次，无人机平台主要使 用离线分析方法获取 VOCs 物种浓度的垂直分布数据，数据的时空分辨率通常较低 [48] [49][50][51] 。 比如， Zhou 等人研发的空气检测传感器 (Kolibri) 就是应用于无人机上的低成本检测传感器，它包括 VOCs 和颗粒物采集器以及黑炭分析仪 [49] 。Chen 等人设计用于无人机平台的苏玛罐采集系统，这种无人机有效载荷 1 kg，能满足 250 m 以下采样需求 [50] 。 1.5 遥感技术 遥感技术可以分为卫星遥感和地面遥感， 地面遥感技术主要使用激光雷达遥感 (Lidar) 和差分吸收光谱技术(DOAS) 。卫星遥感是借助传感器对远距离环境辐射和反射的电磁波 信号进行收集与处理 [52] ；激光雷达遥感是向目标发射激光束，将反射信号与发射信号比较并 适当处理，获取 VOCs 浓度的垂直分布数据 [53][54][55] 。 遥感技术作为长期稳定的监测手段，能及时反馈地球大气中关键 VOCs 组分浓度的时 空分布信息，例如卫星遥感能够能检测到乙二醛和甲醛的垂直柱浓度，并且能够监测全球范 围内 VOCs 浓度空间分布的实时变化 [56] 。但由于各类遥感技术的原理不同，空气中的颗粒 物和水蒸气等能对遥感信号造成干扰，因此遥感技术的准确性受到限制 [57] ；此外，使用遥感 技术测量的 VOCs 种类受到限制，目前遥感技术主要用于对流层大气中甲醛、乙二醛和一些 芳香烃的测量 [58,59] 。 卫星遥感能长期监测大范围空间内的 VOCs 变化特征 [60] ，常与模型计算结果进行对比 分析，以提高模拟结果的准确性 [61] 。比如，借助卫星平台的高空间分辨率遥感数据，研究人 员能够有效分析区域燃烧源相关 VOCs 的排放清单并加以验证 [62] ；DOAS 通常用于测量区 域甲醛和乙二醛的垂直柱浓度， 研究关于它们的大气化学过程 [63] [65] 和人为源(如工厂和机动车排放等) [66] 。源排放类型分为移动源 和固定源，移动源(如机动车)影响地面 VOCs 浓度 [67] ；固定源除了影响地面 VOCs 浓度 [68] 外，也影响 VOCs 垂直分布 [69][70][71] 。如 Wada 等人发现富士山上的 VOCs 垂直分布结构受到周 边森林排放 VOCs 影响 [69] ；Zhang 等人发现上海机动车排放高浓度的苯，导致地面 200 m 内 出现多个峰值 [71] 。当区域地面污染源排放结构存在显著差异时，关键 VOCs 物种和其他污 染物(如 NO X 和一氧化碳等)的垂直分布结构也出现显著的空间分布差异…”