Chemical characteristics of inorganic ammonium salts in PM2.5 in the atmosphere of Beijing (China)
Chemical characteristics of inorganic ammonium salts in PM2.5 in the atmosphere of Beijing (China)
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DOI：
10.5194/acp-11-10803-2011
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发表时间：
2011-01-01
影响因子：
6.3
通讯作者：
Zhu, T.
中科院分区：
文献类型：
--
作者：
Ianniello, A.;Spataro, F.;Zhu, T.
作为CAREBEIJING(北京及周边地区空气质量研究活动)的一部分，2007年冬季和夏季在北京(中国)进行了两次野外活动，测量了大气中HNO3、HCl和NH3及其相对盐分的浓度。在本研究中，环管技术采用2次和24小时的积分次数，在不受气体-颗粒和颗粒-颗粒相互作用干扰的情况下收集无机和可溶PM2.5。从时间和日变化以及气象影响的角度对结果进行了讨论。细颗粒物中的Cl-、NH4+和SO42-具有明显的季节变化，而细颗粒物NO3-的季节变化不大。细颗粒物NH4+和SO42-的日平均浓度夏季分别为12.30微克m(-3)和18.24微克米(-3)，冬季分别为6.51微克米(-3)和7.50微克米(-3)。细颗粒物氯离子的日平均浓度冬季(2.94微克m(-3))高于夏季(0.79微克m(-3))，而细颗粒物NO3-在冬季(8.38微克米(-3))和夏季(9.62微克米(-3))的日平均浓度相似。即使在夏季也有大量细颗粒物NO3的存在，这是因为大气中可用于中和H_2SO_4和HNO_3的局部和区域NH3浓度较高，这与所测量的颗粒物被中和的观察结果一致。细颗粒物的组成表明冬季和夏季以(NH4)(2)SO4为主。此外，夏季的高相对湿度条件似乎溶解了大量的HNO3和NH3，从而增加了大气中的细颗粒物NO3-和NH4+。在冬季和夏季，所有测量到的颗粒物物种的日变化规律相似，峰值在清晨较高，特别是在夏季，此时大气条件潮湿而稳定。这些日变化受风向的影响，暗示了区域和局部来源的影响。细颗粒物种类与NOx和PM2.5相关，支持了交通可能也是二次颗粒物的重要来源的假设。
The atmospheric concentrations of gaseous HNO3, HCl and NH3 and their relative salts have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China), as part of CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region). In this study, annular denuder technique used with integration times of 2 and 24h to collect inorganic and soluble PM2.5 without interferences from gas-particle and particle-particle interactions. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. Fine particulate Cl-, NH4+ and SO42- exhibited distinct temporal variations, while fine particulate NO3- did not show much variation with respect to season. Daily mean concentrations of fine particulate NH4+ and SO42- were higher during summer (12.30 mu g m(-3) and 18.24 mu g m(-3), respectively) than during winter (6.51 mu g m(-3) and 7.50 mu g m(-3), respectively). Daily mean concentrations of fine particulate Cl- were higher during winter (2.94 mu g m(-3)) than during summer (0.79 mu g m(-3)), while fine particulate NO3- showed similar both in winter (8.38 mu g m(-3)) and in summer (9.62 mu g m(-3)) periods. The presence of large amounts of fine particulate NO3- even in summer are due to higher local and regional concentrations of NH3 in the atmosphere available to neutralize H2SO4 and HNO3, which is consistent with the observation that the measured particulate species were neutralized. The composition of fine particulate matter indicated the domination of (NH4)(2)SO4 during winter and summer periods. In addition, the high relative humidity conditions in summer period seemed to dissolve a significant fraction of HNO3 and NH3 enhancing fine particulate NO3- and NH4+ in the atmosphere. All measured particulate species showed diurnal similar patterns during the winter and summer periods with higher peaks in the early morning, especially in summer, when humid and stable atmospheric conditions occurred. These diurnal variations were affected by wind direction suggesting regional and local source influences. The fine particulate species were correlated with NOx and PM2.5, supporting the hypothesis that traffic may be also an important source of secondary particles.