Radical chemistry and ozone production at a UK coastal receptor site
Radical chemistry and ozone production at a UK coastal receptor site
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DOI：
10.5194/acp-23-14393-2023
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发表时间：
2023-11
影响因子：
6.3
通讯作者：
Robert Woodward-Massey;R. Sommariva;L. Whalley;D. Cryer;T. Ingham;W. Bloss;S. M. Ball;S. Cox;James D. Lee;C. Reed;L. Crilley;L. Kramer;B. Bandy;G. Forster;C. Reeves;P. Monks;D. Heard
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文献类型：
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作者：
Robert Woodward-Massey;R. Sommariva;L. Whalley;D. Cryer;T. Ingham;W. Bloss;S. M. Ball;S. Cox;James D. Lee;C. Reed;L. Crilley;L. Kramer;B. Bandy;G. Forster;C. Reeves;P. Monks;D. Heard
摘要。2015年7月在英国诺福克北部沿海地区进行的ICOZA（大气中臭氧综合化学）项目测量了OH、HO2、总RO2和部分形成的RO2以及OH反应性（kOH '）。最大日测定OH、HO2和总RO2自由基浓度分别为2.6 ~ 17 × 106、0.75 ~ 4.2 × 108和2.3 ~ 8.0 × 108 mol。厘米−3,分别。kOH '的变化范围为1.7 ~ 17.6 s−1，中位数为4.7 s−1。ICOZA的数据按风向划分，以评估经过北海（西北-东南方向）和伦敦等主要城市（西南方向）的空气之间的基本化学成分差异。使用主化学机制（MCMv3.3.1）的箱型模型与OH测量值基本一致，但它对下午西北偏南空气中HO2观测值的预测过高了约2-3倍，而对西南偏南空气中HO2观测值的预测稍好一些（低估系数约1.4-2.0）。箱形模式严重低估了NW-SE和SW空气的总RO2观测值，平均因子为~ 8-9。测量到的自由基和kOH '水平以及测量模型比显示出对NO混合比的强烈依赖，结果表明，在高nox条件下，过氧自由基化学尚未得到很好的理解。同时测量OH、HO2、总RO2和kOH '，得出所有自由基的实验（即观测确定的）预算以及总ROx（即OH + HO2 + RO2）。在NW-SE空气中，在实验不确定度范围内，ROx收支可以在白天关闭，但OH破坏速率超过OH生成速率，HO2生成速率大大超过HO2破坏速率，而RO2则相反。在西南偏南空气中，ROx预算分析显示白天ROx源缺失，但OH预算是平衡的，HO2和RO2预算的不平衡与西北偏南空气中相同。对于HO2和RO2，高NO混合比时预算失衡最严重，当RO2 + NO速率系数降低1 / 5时，HO2和RO2的产出率和破坏率之间的一致性最好。光稳态（PSS）计算在西北偏南空气中对白天OH的预测低估了~ 35%，而在西南偏南空气中，在仪器不确定度范围内（在2σ时为~ 26%）发现了一致性（~ 15%）。根据ROx、NO和NO2的观测值计算了原位臭氧生成速率（P(Ox)），并与mcm模型的自由基浓度计算结果进行了比较。mcm计算的P（Ox）显著低估了早晨测量计算的P(Ox)，低估程度与NO成正比。
Abstract. OH, HO2, total and partially speciated RO2, and OH reactivity (kOH′) were measured during the July 2015 ICOZA (Integrated Chemistry of OZone in the Atmosphere) project that took place at a coastal site in north Norfolk, UK. Maximum measured daily OH, HO2 and total RO2 radical concentrations were in the range 2.6–17 × 106, 0.75–4.2 × 108 and 2.3–8.0 × 108 molec. cm−3, respectively. kOH′ ranged from 1.7 to 17.6 s−1, with a median value of 4.7 s−1. ICOZA data were split by wind direction to assess differences in the radical chemistry between air that had passed over the North Sea (NW–SE sectors) and that over major urban conurbations such as London (SW sector). A box model using the Master Chemical Mechanism (MCMv3.3.1) was in reasonable agreement with the OH measurements, but it overpredicted HO2 observations in NW–SE air in the afternoon by a factor of ∼ 2–3, although slightly better agreement was found for HO2 in SW air (factor of ∼ 1.4–2.0 underprediction). The box model severely underpredicted total RO2 observations in both NW–SE and SW air by factors of ∼ 8–9 on average. Measured radical and kOH′ levels and measurement–model ratios displayed strong dependences on NO mixing ratios, with the results suggesting that peroxy radical chemistry is not well understood under high-NOx conditions. The simultaneous measurement of OH, HO2, total RO2 and kOH′ was used to derive experimental (i.e. observationally determined) budgets for all radical species as well as total ROx (i.e. OH + HO2 + RO2). In NW–SE air, the ROx budget could be closed during the daytime within experimental uncertainty, but the rate of OH destruction exceeded the rate of OH production, and the rate of HO2 production greatly exceeded the rate of HO2 destruction, while the opposite was true for RO2. In SW air, the ROx budget analysis indicated missing daytime ROx sources, but the OH budget was balanced, and the same imbalances were found with the HO2 and RO2 budgets as in NW–SE air. For HO2 and RO2, the budget imbalances were most severe at high-NO mixing ratios, and the best agreement between HO2 and RO2 rates of production and destruction rates was found when the RO2 + NO rate coefficient was reduced by a factor of 5. A photostationary-steady-state (PSS) calculation underpredicted daytime OH in NW–SE air by ∼ 35 %, whereas agreement (∼ 15 %) was found within instrumental uncertainty (∼ 26 % at 2σ) in SW air. The rate of in situ ozone production (P(Ox)) was calculated from observations of ROx, NO and NO2 and compared to that calculated from MCM-modelled radical concentrations. The MCM-calculated P(Ox) significantly underpredicted the measurement-calculated P(Ox) in the morning, and the degree of underprediction was found to scale with NO.