Sulfur isotopic fractionation and its implication: Sulfate formation in PM2.5 and coal combustion under different conditions
Sulfur isotopic fractionation and its implication: Sulfate formation in PM2.5 and coal combustion under different conditions
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硫同位素分馏及其意义：不同条件下PM2.5和煤燃烧中硫酸盐的形成
DOI：
10.1016/j.atmosres.2017.04.034
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发表时间：
2017-09-15
影响因子：
5.5
通讯作者：
Zhang, Haixiao
中科院分区：
文献类型：
--
作者：
Chen, Shanli;Guo, Ziyan;Zhang, Haixiao
为了准确探索高污染大气下的硫源和硫酸盐形成，我们于2014年1月1日至23日测定了南京地区PM2.5和大气SO2中硫酸盐的δ S-34值。基于硫同位素分馏，探讨了二氧化硫氧化过程中二次硫酸盐的形成机理。同时，我们同步研究了当地使用的原煤在燃煤和阴燃燃烧过程中的δ S-34值以及硫同位素分馏。结果表明，PM2.5中SO2和硫酸盐的δ S-34平均值分别为1.5和5.1 ppm。PM2.5中硫酸盐δ S-34值与南京及华北地区广泛使用的煤的S-34值一致，表明燃煤是PM2.5的重要硫源。硫同位素分馏因子范围在1.0014 ~ 1.0075之间，表明次生硫酸盐形成过程中存在SO2非均相氧化和SO2非均相氧化共存的现象。观测期内，SO2非均相氧化对硫酸盐的贡献在40.7% ~ 64.8%之间。煤的δ S-34值呈现中等正硫同位素特征，低硫煤中的有机硫主要由植物同化形成。此外，煤的et值与总硫含量呈负相关。此外，煤在燃烧过程中还存在显著的硫同位素分馏效应。烟气中PM2.5中的硫酸盐富集S-34，烟气中SO2富集S-32。燃煤与阴燃烟气中PM2.5和SO2 δ S-34值存在差异，这与煤的性质和燃烧温度有关。
In order to exactly explore sulfur source and sulfate formation under highly polluted atmosphere, we determined delta S-34 values of sulfate in PM2.5 and atmospheric SO2 in Nanjing region from 1 to 23 Jan. 2014. The secondary sulfate formation mechanism was discussed based on sulfur isotopic fractionation in the process of SO2 oxidation. Meanwhile, we synchronously studied delta S-34 values of raw coals used locally as well as sulfur isotopic fractionation during the combustion under coal burning and smoldering. The results show that delta S-34 average values of SO2 and sulfate in PM2.5 were 1.5 parts per thousand and 5.1 parts per thousand, respectively. delta S-34 values of sulfate in PM2.5 were consistent with those of coals widely used in Nanjing region and Northern China, indicating coal combustion was an important sulfur source for PM2.5. Sulfur isotopic fractionation factors ranged from 1.0014 to 1.0075, implying that SO2 heterogeneous and homogeneous oxidation were coexisting during the formation of the secondary sulfate. The contribution of SO2 heterogeneous oxidation to sulfate varied from 40.7% to 64.8% during the observation period. delta S-34 values of coals presented moderately positive sulfur isotopic signatures due to organic sulfur in low sulfur coals were mainly formed by plant assimilation. Besides, the negative relationship between et values of coals and total sulfur contents was also found. In addition, there existed a significant sulfur isotopic fractionation effect during coal combustion. Sulfate in PM2.5 in flue gas enriched S-34, while SO2 in flue gas enriched S-32. There was presence of the difference of delta S-34 values in PM2.5 and SO2 in flue gas between coal burning and smoldering, which was related to coal property and combustion temperature.