Seasonal features of brown carbon in northern China: Implications for BrC emission control
Seasonal features of brown carbon in northern China: Implications for BrC emission control
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DOI：
10.1016/j.atmosres.2021.105610
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发表时间：
2021-08
影响因子：
5.5
通讯作者：
Lei Wang;Wenjing Jin;Jianzhong Sun;Guorui Zhi;Zhengying Li;Yuzhe Zhang;Sicong Guo;Jian-Li He-
中科院分区：
文献类型：
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作者：
Lei Wang;Wenjing Jin;Jianzhong Sun;Guorui Zhi;Zhengying Li;Yuzhe Zhang;Sicong Guo;Jian-Li He-
由于棕色碳（BrC）由一系列吸收光的有机化合物组成，因此不太可能有一种单独的物质可以用作所有BrC成分的代表。因此，用于区分BrC和黑碳（BC）的现有方法通常是有缺陷的。此外，在中国北方，冬季农村取暖时使用家用固体燃料是一种常见的做法，这对空气污染有显著的贡献;然而，目前还不清楚在取暖季节期间固体燃料的密集消耗是否会影响北方中国每年的BrC排放量和环境BrC的季节特征，这是未来BrC控制的一个问题。因此，一个可靠的方法是必要的，以确定在不同的季节环境中的BrC的浓度和光学性质。在这项研究中，选择了四个典型的月份来代表北京一年中的四季。每天的大气样品收集使用石英过滤器的BrC和BC的分析。积分球（IS）的方法是第一次用来分离的光吸收的BrC从BC在环境PM2.5。我们发现BrC的年平均丰度为0.82 ± 0.44 μg m−3，在冬季达到峰值2.31 ± 0.44 μg m− 3，然后是秋季、春季和夏季。在350-850 nm范围内，BrC对太阳能的吸收量（FBrC）以冬季最高（21.78 ± 3.56%），其次为秋季（11.53 ± 5.29%）、春季（6.38 ± 4.06%）和夏季（4.26 ± 2.57%）。溴化碳丰度和吸收份额的季节性变化与家庭取暖做法的使用一致（冬季最高，晚秋和早春使用较少），生物质和/或煤炭是主要的能源类型。由于固体生物质燃料和化石燃料的低效燃烧被认为是BrC的重要来源，上述相关性表明，农村居民供暖在控制BrC的季节性特征中起主导作用，因此应成为北方中国BrC控制的主要重点。因此，在中国北方持续追求清洁供暖（从煤炭转向天然气或电力）将有助于缓解BrC和BC的气候变暖效应，并抵消清洁空气对气候的一些不利影响。我们的研究结果对全球其他使用固体燃料的地区的污染缓解也有更广泛的影响。
As brown carbon (BrC) consists of a collection of light-absorbing organic compounds, there is unlikely an individual substance that can be used as a proxy of all BrC constituents. Hence, available methods for distinguishing BrC from black carbon (BC) are often flawed. Moreover, the use of household solid fuels for winter rural heating is a common practice in northern China that significantly contributes to air pollution; however, it is unclear whether the intensive consumption of solid fuels during the heating season influences the yearly BrC emissions and the seasonal features of ambient BrC in northern China, which is a concern for future BrC control. Thus, a reliable method is necessary for determining the concentrations and optical properties of ambient BrC in different seasons. In this study, four typical months were selected to represent the four seasons of the year in Beijing. Daily atmospheric samples were collected using quartz filters for the analysis of BrC and BC. The integrating sphere (IS) approach was used for the first time to separate the light absorption of BrC from that of BC in ambient PM2.5. We found that the yearly average abundance of BrC was 0.82 ± 0.44 μg m−3, peaking at 2.31 ± 0.44 μg m−3in winter, followed by autumn, spring, and summer. Meanwhile, the solar energy absorption by BrC relative to that by BrC + BC across 350–850 nm (FBrC) was the highest in winter (21.78 ± 3.56%), followed by autumn (11.53 ± 5.29%), spring (6.38 ± 4.06%), and summer (4.26 ± 2.57%). The seasonal variations in BrC abundance and absorption share were consistent with the use of household heating practices (highest in winter and minor uses in late autumn and early spring), with biomass and/or coal being the dominant energy types. As low-efficiency burning of solid biomass fuels and fossil fuels is considered an important source of BrC, the aforementioned correlation suggests that rural residential heating plays a dominant role in controlling the seasonal features of BrC and should therefore be a main focus for BrC control in northern China. Hence, the ongoing pursuit of clean heating (switching from coal to gas or electricity) in northern China will help to mitigate the climate-warming effects of both BrC and BC and offset some of the adverse impacts of clean air efforts on climate. Our findings also have wider implications for pollution mitigation in other global regions that use solid fuels.