Below-cloud wet scavenging of soluble inorganic ions by rain in Beijing during the summer of 2014
Below-cloud wet scavenging of soluble inorganic ions by rain in Beijing during the summer of 2014
复制标题
2014年夏季北京降雨对可溶性无机离子的云下湿清除
DOI：
10.1016/j.envpol.2017.07.033
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发表时间：
2017
影响因子：
8.9
通讯作者：
Yao Xuefeng
中科院分区：
文献类型：
--
作者：
Xu Danhui;Ge Baozhu;Wang Zifa;Sun Yele;Chen Yong;Ji Dongshen;Yang Ting;Ma Zhiqiang;Cheng Nianliang;Hao Jianqi;Yao Xuefeng
湿沉降是减少大气污染最重要、最有效的去除机制之一。湿清除系数(WSC)作为决定湿沉积的关键参数，在化学输运模型(CTMS)中得到了广泛的应用，已有的数值存在较大的不确定性。利用多次降水过程中大气和雨水中可溶无机气溶胶(SO42−、NO2−和NH4+)的高分辨率观测资料，对2014年夏季北京地区云下大气水分散失进行了估算。观测期间降水中SNA的平均浓度分别为7.9 mg/L、6.2 mg/L和4.6 mg/L，其中云下清除作用的贡献率分别为56%、61%和47%。SNA的清除率(即雨中浓度与空气中浓度的比率)与云底高度和降水强度一起被用来估计WSC。SO42−的估计WSC与其他地方报道的相当.对于SNA，云下WSC与降水强度之间的关系服从指数幂分布(K=a Pb)。与前人的研究不同，本研究考虑了SNA的化学组成的差异，其中NO3−的WSC最高，其次是SO42−和NH4+。因此，我们建议CTMS在未来包括离子特异性WSCs。
Wet deposition is one of the most important and efficient removal mechanisms in the reduction of air pollution. As a key parameter determining wet deposition, the wet scavenging coefficient (WSC) is widely used in chemical transport models (CTMs) and reported values have large uncertainties. In this study, a high-resolution observational dataset of the soluble inorganic aerosols (SO 4 2−, NO 3− and NH 4+, hereafter SNA) in the air and in rainwater during multiple precipitation events was collected using sequential sampling and used to estimate the below-cloud WSC in Beijing during the summer of 2014. The average concentrations of SNA in precipitation during the observational period were 7.9 mg/L, 6.2 mg/L and 4.6 mg/L, with the contributions from below-cloud scavenging constituting 56%, 61% and 47% of this, respectively. The scavenging ratios of SNA (ie, the ratio of the concentrations in rain to concentrations in the air) were used with the height of the cloud base and the precipitation intensity to estimate the WSC. The estimated WSC of SO 4 2− is comparable to that reported elsewhere. The relationship between the below-cloud WSC and the precipitation intensity followed an exponential power distribution (K= a P b) for SNA. In contrast to previous studies, this study considers the differences between the chemical compositions of the SNA, with the highest WSC for NO 3−, followed by those of SO 4 2− and NH 4+. Therefore, we recommend that CTMs include ion specific WSCs in the future.