Rapid sulfate formation from synergetic oxidation of SO2 by O3 and NO2 under ammonia-rich conditions: Implications for the explosive growth of atmospheric PM2.5 during haze events in China.
Rapid sulfate formation from synergetic oxidation of SO2 by O3 and NO2 under ammonia-rich conditions: Implications for the explosive growth of atmospheric PM2.5 during haze events in China.
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DOI：
10.1016/j.scitotenv.2020.144897
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Si Zhang;Dapeng Li;Shuangshuang Ge;Shijie Liu;Can Wu;Yiqian Wang;Yubao Chen;Shaojun Lv
中科院分区：
文献类型：
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作者：
Si Zhang;Dapeng Li;Shuangshuang Ge;Shijie Liu;Can Wu;Yiqian Wang;Yubao Chen;Shaojun Lv
我国大气硫酸盐气溶胶浓度极高的现象仍时有发生，尤其是在冬季灰霾期间，由于缺少一些形成机制，模式往往低估了硫酸盐气溶胶浓度。本文利用烟雾箱模拟技术研究了我国城市大气中O3和NO2共存时SO2氧化的非均相反应动力学。结果表明，随着NH_3浓度从0.05 ppm增加到1.5 ppm，O_3对SO_2的氧化作用得到了显著的促进，并使反应室内颗粒的直径增长因子（GF）从1.29增加到1.98，从1.20增加到1.60。NaCl种子和（NH 4）2SO 4种子对SO2的吸收系数（γ）分别从4.47 × 10− 5和2.32 × 10− 5增加到1.52 × 10− 4和5.74 × 10− 5。在富NH3条件下，O3和NO2混合氧化SO2产生的硫酸盐是O3和NO2氧化SO2产生的硫酸盐之和的2.0-3.5倍，表明混合氧化剂对SO2的非均相氧化有很强的协同作用，在我国冬季灰霾期间，大气中的（NH 4）2SO 4和NH 4 NO3是导致PM2.5爆炸性增长的主要原因。结果进一步表明，这种协同作用仅在富NH3条件下才有效，这表明对O3、NOx和NH3的联合控制是进一步缓解我国PM2. 5污染的必要措施。
Extremely high levels of atmospheric sulfate aerosols have still frequently occurred in China especially in winter haze periods and often been underestimated by models due to some missing formation mechanisms. Here we investigated the heterogeneous reaction dynamics of SO2oxidation by the abundantly co-existing O3and NO2in the urban atmosphere of China by using a laboratory smog chamber simulation technique. Our results showed that with an increase of NH3concentrations from 0.05 ppm to 1.5 ppm, SO2oxidation by O3can be greatly promoted and lead to an exponential increase of diameter growth factor (GF) of particles in the chamber from 1.29 to 1.98 for NaCl seeds and from 1.20 to 1.60 for (NH4)2SO4seeds, along with an increasing uptake coefficient (γ) of SO2from 4.47 × 10−5to 1.52 × 10−4on NaCl seeds and from 2.32 × 10−5to 5.74 × 10−5on (NH4)2SO4seeds, respectively. The heterogeneous production of sulfate from oxidation of SO2under NH3-rich conditions by O3and NO2mixture in the chamber was 2.0–3.5 times the sum of sulfate from SO2oxidations by O3and NO2, suggesting a strongly synergetic effect of the mixed oxidants on the heterogeneous oxidation of SO2, which can cause rapid formation of (NH4)2SO4and NH4NO3and is responsible for the explosive growth of PM2.5in the winter haze period of China. Our chamber results further showed that such synergetic process is only efficient under NH3-rich conditions, clearly indicating that the combined controls on O3, NOx and NH3are necessary for further mitigating the PM2.5pollution in China.