Urban photochemistry in central Tokyo:: 1.: Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004
Urban photochemistry in central Tokyo:: 1.: Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004
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DOI：
10.1029/2007jd008670
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发表时间：
2007-11-15
影响因子：
4.4
通讯作者：
Kondo, Yutaka
中科院分区：
文献类型：
--
作者：
Kanaya, Yugo;Cao, Renqiu;Kondo, Yutaka
[1] 我们在2004年1月至2月和7月至8月的两次密集活动（IMPACT IV和IMPACT L）期间使用激光诱导荧光测量了东京市中心的OH和HO2自由基浓度。10分钟数据的估计检测限为夜间1.3 x 10(5) cm(-3)，白天5.2 x 10(5) cm(-3)。冬季和夏季HO2日间峰值浓度中值分别为1.1和5.7 pptv，而OH值分别为1.5 x 10(6)和6.3 x 10(6) cm(-3)。在夏季的某一天，当 O-3 混合比超过 100 ppbv 时，观察到高 HO2 混合比 (> 50 pptv)。冬季和夏季HO2 夜间平均浓度分别为0.7 和2.6 pptv，而OH 值分别为1.8 x 10(5) 和3.7 x 10(5) cm(-3)。尽管白天 HO2 浓度在冬季被低估，在夏季被高估，但受辅助观测限制的光化学盒模型能够很好地再现这两个时期的白天 OH 浓度。模型中冬季碳氢化合物浓度的增加导致白天 HO2 浓度的增加，从而与观测结果显示出更好的一致性；然而，该模型继续低估高 NO 混合比下的 HO2 浓度。这种低估在这两个时期的早晨和冬季的白天最为明显。我们研究了能够解释这种差异的过程，包括 HNO4 的未知反应或可线性缩放至 NO 混合比的未识别的 HOx 源。产生自由基的重要过程是两个时期夜间和冬季白天的烯烃+O-3反应，两个时期白天羰基的光解，以及冬季白天（使用测量的HONO浓度）和夏季早晨（使用估计的HONO浓度）HONO的光解。
[1] We used laser-induced fluorescence to measure the concentrations of OH and HO2 radicals in central Tokyo during two intensive campaigns (IMPACT IV and IMPACT L) in January-February and July-August 2004. The estimated detection limit for the 10-min data was 1.3 x 10(5) cm(-3) for the nighttime and 5.2 x 10(5) cm(-3) for the daytime. The median values of the daytime peak concentrations of HO2 were 1.1 and 5.7 pptv for the winter and summer periods, respectively, while the values for OH were 1.5 x 10(6) and 6.3 x 10(6) cm(-3). High HO2 mixing ratios (> 50 pptv) were observed on a day in summer when O-3 mixing ratios exceeded 100 ppbv. The average nighttime concentrations of HO2 were 0.7 and 2.6 pptv for the winter and summer periods, respectively, while the values for OH were 1.8 x 10(5) and 3.7 x 10(5) cm(-3). A photochemical box model constrained by ancillary observations was able to reproduce daytime OH concentrations reasonably well for both periods, although daytime HO2 concentrations were underestimated in winter and overestimated in summer. Increasing the wintertime hydrocarbon concentrations in the model led to an increase in daytime HO2 concentrations, thereby showing better agreement with observations; however, the model continued to underestimate HO2 concentrations at high NO mixing ratios. This underestimate was most pronounced in the mornings of both periods and during the daytime in winter. We studied processes that are capable of explaining this discrepancy, including unknown reactions of HNO4 or an unidentified HOx source that is linearly scalable to the NO mixing ratio. The important processes in terms of producing radicals were the olefin + O-3 reactions in the nighttime of both periods and during the daytime in winter, the photolysis of carbonyls in the daytime for both periods, and the photolysis of HONO during the daytime in winter (using measured HONO concentrations) and during mornings in summer (using estimated HONO concentrations).