Abstract We report a statistical analysis of surface ozone (O3) measurements over the UK, 1999–2019. Data are from the Automatic Urban and Rural Network (AURN) that forms the basis of checking nationwide compliance with ambient air quality directives. We determine the mean O3 trend across all AURN sites to be 0.41 ± 0.07 μg m−3yr−1, composed of larger trends in suburban and urban environments (0.36 ± 0.11 μg m−3yr−1–0.75 ± 0.16 μg m−3yr−1) than in the rural environment (0.16 ± 0.07 μg m−3yr−1); consequently the gap between urban and rural surface O3 across the UK has steadily declined from 20 μg m−3 to 12 μg m−3 until 2012 when it has since stalled. These trends in urban surface O3 are coincident with and likely caused by a pronounced decline in surface concentrations of NO2 (proxy for NOx), which we link to reduced emissions from the transport sector. Using a gamma probability distribution to describe changes in surface O3, we find an increase in the probability of high mean O3 and an associated decrease in the probability of extreme (elevated) O3 events. We find no discernible trend in the number of days per year that exceed the 8-h mean O3 value of 100 μg m−3 set by the UK Department for Environment, Food and Rural Affairs (Defra) or a similar metric of 120 μg m−3 set by the EU. These exceedances, typically occurring during summer months across the network, range from 499 exceedances in 2010 to in excess of 2300 exceedances in 2003 and 2006. We find that 50% of these exceedances occur at temperatures greater than 18∘C (21∘C) in rural (urban) environments. With 50% (95%) of the 66 million UK inhabitants living and working within 12 km (50 km) of an AURN site, our analysis is relevant to a large fraction of the UK population. Consequently, we may need to re-prioritize epidemiological studies to understand the impact of chronic exposure to elevated mean O3 concentrations on human health.

中文翻译：

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英国环境地表臭氧水平增加，极端事件减少

摘要 我们报告了 1999-2019 年英国地表臭氧 (O3) 测量的统计分析。数据来自自动城乡网络 (AURN)，该网络构成了检查全国环境空气质量指令合规性的基础。我们确定所有 AURN 站点的平均 O3 趋势为 0.41 ± 0.07 μg m−3yr−1，由郊区和城市环境中的较大趋势组成（0.36 ± 0.11 μg m−3yr−1–0.75 ± 0.16 μg m−3yr− 1) 比在农村环境中 (0.16 ± 0.07 μg m−3yr−1)；因此，英国城乡表面 O3 之间的差距从 20 μg m-3 稳步下降到 12 μg m-3，直到 2012 年停滞不前。城市地表 O3 的这些趋势与 NO2（NOx 的替代物）地表浓度的显着下降一致并可能由其引起，我们将其与减少运输部门的排放联系起来。使用伽马概率分布来描述表面 O3 的变化，我们发现高平均 O3 的概率增加，而极端（升高）O3 事件的概率相应降低。我们没有发现每年超过英国环境、食品和农村事务部 (Defra) 设定的 8 小时平均 O3 值 100 μg m−3 或类似指标 120 μg m-3 的天数没有明显趋势−3 由欧盟设定。这些超标通常发生在整个网络的夏季月份，从 2010 年的 499 次超标到 2003 年和 2006 年的 2300 多个超标不等。我们发现这些超标中有 50% 发生在温度高于 18∘C (21∘C) 的情况下在农村（城市）环境中。由于 6600 万英国居民中有 50% (95%) 在 AURN 站点 12 公里（50 公里）范围内生活和工作，因此我们的分析与大部分英国人口相关。因此，我们可能需要重新确定流行病学研究的优先级，以了解长期暴露于升高的平均 O3 浓度对人类健康的影响。