School of Environment and Planning, Liaocheng University, Liaocheng 252000, China.
School of Environment and Planning, Liaocheng University, Liaocheng 252000, China.
Sci Total Environ. 2021 Apr 20;766:144187. doi: 10.1016/j.scitotenv.2020.144187. Epub 2020 Dec 25.
Although the chemical compositions and sources of organic aerosols (OAs) have been extensively investigated at the summit of Mt. Tai in the North China Plain (NCP), their vertical distributions and characterizations in the Mt. Tai region is not well known. To better understand the vertical variations of OAs in the urban and mountainous atmosphere, PM samples were collected simultaneously on a daytime/nighttime basis at two sites of different altitudes (Taian urban site: 20 m above ground; the summit of Mt. Tai: 1534 m a.s.l.) during the summer of 2016. The concentrations of all the determined chemical compounds (e.g., OC, EC, inorganic ions, saccharides, n-alkanes, PAHs and hopanes) except for biogenic secondary organic aerosol (BSOA) tracers decreased with the increase in sampling height, indicating the relatively larger contribution of anthropogenic pollutants to OAs at the lower heights. The relatively low concentration levels of biomass burning tracers (e.g., levoglucosan, galactosan and mannosan) and the insignificant correlations of levoglucosan with carbonaceous species demonstrated a negligible effect of biomass burning on the mountaintop atmosphere. The enhanced concentrations of BSOA tracers were observed with the increase of height, largely due to the more intensive secondary oxidation of volatile organic compounds (VOCs) under the stronger radiation conditions at the summit. The daytime concentrations of carbonaceous species, primary sugars, sugar alcohols, PAHs and low molecular weight n-alkanes were significantly higher than those in nighttime at Mt. Tai, suggesting that these chemical compounds at the summit of Mt.Tai aerosols were transported from the ground surface by valley breezes in daytime. There was no correlation between BSOA tracers and relative humidity (RH) or liquid water content (LWC) at both the sites, because both the high RH and LWC can suppress the acid-catalyzed formation of BSOA due to the dilution of the aerosol acidity.
尽管已经在华北平原泰山山顶对有机气溶胶 (OA) 的化学组成和来源进行了广泛的研究，但对泰山地区 OA 的垂直分布和特征仍知之甚少。为了更好地了解城市和山区大气中 OA 的垂直变化，在 2016 年夏季，在两个不同海拔高度的站点（泰山城区站点：地面以上 20 米；泰山山顶：海拔 1534 米）同时进行了昼/夜间 PM 采样。除了生物成因的二次有机气溶胶 (BSOA) 示踪剂外，所有测定化合物（如 OC、EC、无机离子、糖、正烷烃、PAHs 和藿烷）的浓度均随采样高度的增加而降低，表明在较低高度下，人为污染物对 OA 的贡献相对较大。生物量燃烧示踪剂（如左旋葡聚糖、半乳糖和甘露糖）的浓度较低，且左旋葡聚糖与碳质物质的相关性不显著，表明在山顶大气中生物质燃烧的影响可以忽略不计。BSOA 示踪剂的浓度随高度的增加而增加，这主要是由于在山顶辐射条件较强的情况下，挥发性有机化合物（VOCs）的二次氧化更为剧烈。在泰山，碳质物质、初级糖、糖醇、PAHs 和低分子量正烷烃的日浓度明显高于夜间浓度，表明这些化学物质是由山谷风在白天从地面输送到山顶气溶胶中的。在两个站点，BSOA 示踪剂与相对湿度 (RH) 或液态水含量 (LWC) 之间均无相关性，因为高 RH 和 LWC 都会因气溶胶酸度的稀释而抑制 BSOA 的酸催化形成。
