School of Water and Environment, Chang'an University, Xi'an, 710064, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an, 710064, China.
School of Water and Environment, Chang'an University, Xi'an, 710064, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an, 710064, China.
Environ Res. 2022 Aug;211:113036. doi: 10.1016/j.envres.2022.113036. Epub 2022 Mar 10.
As critical precursors of tropospheric ozone (O) and secondary organic aerosol (SOA), volatile organic compounds (VOCs) largely influence air quality in urban environments. In this study, measurements of 102 VOCs at all five major cities in the Guanzhong Plain (GZP) were conducted during Sep.09-Oct. 13, 2017 (autumn) and Nov. 14, 2017-Jan. 19, 2018 (winter) to investigate the characteristics of VOCs and their roles in O and SOA formation. The average concentrations of total VOCs (TVOCs) at Xi'an (XA), Weinan (WN), Xianyang (XY), Tongchuan (TC), and Baoji (BJ) sites were in the range of 55.2-110.2 ppbv in autumn and 42.4-74.3 ppbv in winter. TVOCs concentrations were reduced by 22.4%-43.5% from autumn to winter at XA, WN and BJ. Comparatively low concentrations of TVOCs were observed in XY and TC, ranging from 53.5 to 62.7 ppbv across the sampling period. Alkanes were the major components at all sites, accounting for 26.4%-48.9% of the TVOCs during the sampling campaign, followed by aromatics (4.2%-26.4%). The average concentration of acetylene increased by a factor of up to 4.8 from autumn to winter, indicating the fuel combustion in winter heating period significantly impacted on VOCs composition in the GZP. The OH radical loss rate and maximum incremental reactivity method were employed to determine photochemical reactivities and ozone formation potentials (OFPs) of VOCs, respectively. The VOCs in XA and WN exhibited the highest reactivities in O formation, with the OFP of 168-273 ppbv and the OH loss rates of 19.3-40.8 s. Alkenes and aromatics primarily related to on-road and industrial emissions contributed 57.8%-76.3% to the total OFP. The contribution of aromatics to the SOA formation at all sites reached 94.1%-98.6%. Considering the potential source-area of VOCs, regional transport of VOCs occurred within the GZP cities.
作为对流层臭氧 (O) 和二次有机气溶胶 (SOA) 的关键前体物，挥发性有机化合物 (VOCs) 很大程度上影响了城市环境的空气质量。在这项研究中，于 2017 年 9 月 9 日至 10 月 13 日（秋季）和 2017 年 11 月 14 日至 2018 年 1 月 19 日（冬季）对关中平原（GZP）的五个主要城市进行了 102 种 VOCs 的测量，以研究 VOCs 的特征及其在 O 和 SOA 形成中的作用。在秋季，西安（XA）、渭南（WN）、咸阳（XY）、铜川（TC）和宝鸡（BJ）站点的总挥发性有机化合物（TVOCs）浓度范围为 55.2-110.2 ppbv，在冬季为 42.4-74.3 ppbv。秋季到冬季，XA、WN 和 BJ 的 TVOCs 浓度降低了 22.4%-43.5%。在 XY 和 TC，TVOCs 浓度相对较低，整个采样期间为 53.5-62.7 ppbv。在所有站点中，烷烃都是主要成分，占采样期间 TVOCs 的 26.4%-48.9%，其次是芳烃（4.2%-26.4%）。乙炔的平均浓度从秋季到冬季增加了 4.8 倍，表明冬季供暖期的燃料燃烧对 GZP 中 VOCs 的组成有显著影响。使用羟基自由基损失率和最大增量反应性方法分别确定 VOCs 的光化学反应活性和臭氧形成潜力 (OFP)。XA 和 WN 的 VOCs 在 O 形成中表现出最高的反应活性，OFP 为 168-273 ppbv，OH 损失率为 19.3-40.8 s。主要与道路和工业排放有关的烯烃和芳烃对总 OFP 的贡献率为 57.8%-76.3%。所有站点的芳香烃对 SOA 形成的贡献达到 94.1%-98.6%。考虑到 VOCs 的潜在源区，VOCs 在 GZP 城市内发生了区域传输。
