Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou 511443, China.
Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou 511443, China.
Sci Total Environ. 2020 Nov 1;741:139763. doi: 10.1016/j.scitotenv.2020.139763. Epub 2020 Jun 8.
Accurate estimation of speciated emissions of volatile organic compounds (VOCs) is challenging due to the complexity of both species and sources. Evaluation of the bottom-up emission inventory (EI) by atmospheric observation is needed to better understand the VOC emissions and then to control air pollutions caused by VOCs. This study conducts vertical measurements of VOCs between November 3 and 11, 2018 at the Canton Tower in the urban core of Pearl River Delta (PRD), China. A mixed layer gradient (MLG) technique is applied to the tower observation data to derive emission fluxes for individual VOC. The results show that the measured VOCs concentrations at ground level were always higher than those at the heights of 118 m and 488 m. Obvious vertical gradients of concentrations were found for VOC species, such as benzene, toluene and isoprene. The emission flux was estimated to be largest for propane (3.29 mg m h), followed by toluene (2.55 mg m h), isoprene (2.24 mg m h), n-butane (2.10 mg m h) and iso-pentane (1.73 mg m h). The total VOC emission fluxes were around 3 times larger than those in the EI, suggesting 1.5-2 times underestimations of ozone formation potential (OFP) and secondary organic aerosol potential (SOAP) by current EI. Substantial underestimations (3-20 times) were found for C-C alkanes by current EI. Due to unmeasured input parameters, limited sample size and short sampling period, there are still large uncertainties (40%-117%) in the estimated emission fluxes for individual species. Whereas, this study shows that the tower observation and emission estimation using MLG method could provide useful information for better understanding vertical distributions and emission fluxes of VOCs, and pioneer in assessing the existing emission inventories at species-level and hour-level.
准确估算挥发性有机化合物（VOC）的特定排放物具有挑战性，因为物种和来源都很复杂。需要通过大气观测来评估自上而下的排放清单（EI），以便更好地了解 VOC 排放情况，然后控制由 VOC 引起的空气污染。本研究于 2018 年 11 月 3 日至 11 日在珠江三角洲（PRD）城市核心区的广州塔进行了 VOC 的垂直测量。应用混合层梯度（MLG）技术对塔观测数据进行处理，得出了单个 VOC 的排放通量。结果表明，地面测量的 VOC 浓度始终高于 118m 和 488m 高度的浓度。发现苯、甲苯和异戊二烯等 VOC 物种存在明显的浓度垂直梯度。丙烷（3.29mg m h）的排放通量估计最大，其次是甲苯（2.55mg m h）、异戊二烯（2.24mg m h）、正丁烷（2.10mg m h）和异戊烷（1.73mg m h）。总 VOC 排放通量比 EI 中的大 3 倍左右，表明当前 EI 对臭氧形成潜力（OFP）和二次有机气溶胶形成潜力（SOAP）的估算低 1.5-2 倍。当前 EI 对 C-C 烷烃的估算存在较大低估（3-20 倍）。由于未测量的输入参数、有限的样本量和较短的采样期，单个物种的估算排放通量仍存在较大不确定性（40%-117%）。然而，本研究表明，使用 MLG 方法的塔观测和排放估算可以提供有关 VOC 垂直分布和排放通量的有用信息，并开创了在物种水平和小时水平评估现有排放清单的先河。
