State Environmental Protection Key Lab of Environmental Risk Assessment and control on Chemical Processes, School of Resources & Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China.
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
Sci Total Environ. 2016 Nov 15;571:18-26. doi: 10.1016/j.scitotenv.2016.07.127. Epub 2016 Jul 22.
Humic-like substances (Hulis), the hydrophobic part of water-soluble organic compounds, have been recognized to play important roles in environmental behavior of PM2.5 in atmosphere. In this study, Hulis and other components of PM2.5, collected in urban Shanghai from September 2013 to August 2014 were analyzed. The annual average concentration of Hulis carbon (Hulis-C) was (2.61±2.58) μg/m(3), accounting for about 50% of water-soluble organic carbon (WSOC). The monthly average Hulis-C concentration peaked in December while the lowest was in summer, coinciding with the high and low of levoglucosan and secondary inorganic aerosol (SIA). Biomass burning and secondary formation were both important sources of Hulis-C, and their contributions showed obvious seasonality. In late autumn and winter, the strong inter-correlations among Hulis-C concentrations, NO3(-)/SO4(2-) mass ratios and nitrogen oxidation ratios (NOR) were found, suggesting the atmospheric oxidation of NOx to nitrate and related gas-phase reactions may be inter-linked with Hulis-C formation. In summer, photochemical reaction was clearly the major source of Hulis-C. The investigation by backward trajectory analysis showed that the long-range transport from the Northwest brought large amounts of PM2.5 and enhanced Hulis-C and levoglucosan level, indicating biomass burning as a significant source of Hulis-C under this type of synoptic weather conditions. In comparison, Hulis formation associated with the NOx oxidation pathway was mainly associated with the short-range transport from the neighboring cities. Marine aerosol was relatively clean and had little effects on Hulis-C. The CWT (concentration weighted trajectory) model results suggested that the Yangtze River Delta (YRD) region was an important source region of Hulis-C, while the effect of some northwestern areas was not negligible.
腐殖质类似物质（Hulis）是水溶性有机化合物的疏水性部分，已被认为在大气 PM2.5 的环境行为中发挥重要作用。本研究分析了 2013 年 9 月至 2014 年 8 月在上海市区采集的 PM2.5 中的 Hulis 和其他成分。腐殖质碳（Hulis-C）的年平均浓度为（2.61±2.58）μg/m3，占水溶性有机碳（WSOC）的约 50%。Hulis-C 的月平均浓度在 12 月最高，而夏季最低，与左旋葡聚糖和二次无机气溶胶（SIA）的高低一致。生物质燃烧和二次形成都是 Hulis-C 的重要来源，它们的贡献表现出明显的季节性。在深秋和冬季，发现 Hulis-C 浓度、NO3(-)/SO4(2-)质量比和氮氧化比（NOR）之间存在强烈的相互关联，表明大气中 NOx 向硝酸盐的氧化和相关气相反应可能与 Hulis-C 的形成有关。在夏季，光化学反应显然是 Hulis-C 的主要来源。后向轨迹分析的结果表明，来自西北部的长距离传输带来了大量的 PM2.5，并增加了 Hulis-C 和左旋葡聚糖的水平，表明在这种天气条件下，生物质燃烧是 Hulis-C 的重要来源。相比之下，与 NOx 氧化途径相关的 Hulis 形成主要与来自邻近城市的短距离传输有关。海洋气溶胶相对清洁，对 Hulis-C 的影响较小。CWT（浓度加权轨迹）模型的结果表明，长三角（YRD）地区是 Hulis-C 的重要源区，而一些西北地区的影响也不容忽视。
