Effects of halogens on European air-quality.
Effects of halogens on European air-quality.
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DOI：
10.1039/c7fd00026j
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发表时间：
2017-08
影响因子：
3.4
通讯作者：
T. Sherwen;M. Evans;R. Sommariva;L. Hollis;S. Ball;P. Monks;C. Reed;L. Carpenter;James D. Lee;G. Forster;B. Bandy;C. Reeves;W. Bloss
中科院分区：
文献类型：
--
作者：
T. Sherwen;M. Evans;R. Sommariva;L. Hollis;S. Ball;P. Monks;C. Reed;L. Carpenter;James D. Lee;G. Forster;B. Bandy;C. Reeves;W. Bloss
卤素（Cl、Br）对平流层臭氧（O3）有着深刻的影响。它们（Cl，Br和I）最近也被证明会影响对流层，特别是通过降低O3和OH的混合比例。它们影响区域空气质量的潜力还不太清楚。利用GEOS-Chem模式的欧洲网格（0.25° × 0.3125°），探讨了卤素对区域污染物（重点是O3）的影响。它最近已更新，包括卤素化学的代表。我们关注的是2015年夏天在英国北海海岸的Weybourne大气观测站举行的ICOZA活动。这些观测结果与英国空气质量网络的观测结果之间的比较表明，该模型在代表这一时期污染物的混合比/浓度方面具有一定的技巧。虽然该模型在模拟Weybourne ClNO 2观测结果方面取得了一定的成功，但它大大低估了内陆地区报告的ClNO 2观测结果。它也低估了IO，OIO，I2和BrO的混合比，但这可能反映了这些观测的沿海性质。模型模拟，有和没有卤素，突出卤素可以影响O3的过程。在整个领域O3的混合比减少卤素。在北方，这是由于平流进入该地区的背景O3的变化，而在南欧，这是由于当地的化学驱动的地中海排放。在欧洲，每小时超过50 nmol mol-1的O3的比例通过卤素从46%降低到18%。ClNO 2从N2 O 5吸收到海盐导致O3混合比的增加，但这些都小于由溴和碘引起的减少。边界层内12%的乙烷和16%的丙酮被Cl氧化。气溶胶对卤素的反应是复杂的，在大多数地方，PM2.5的减少幅度很小（约10%）。由于缺乏观测限制，再加上卤素的排放和化学处理存在很大的不确定性，这些结论充其量只能是试探性的。然而，这里的结果指出了卤素化学影响欧洲和世界其他地区空气质量政策的潜力。
Halogens (Cl, Br) have a profound influence on stratospheric ozone (O3). They (Cl, Br and I) have recently also been shown to impact the troposphere, notably by reducing the mixing ratios of O3 and OH. Their potential for impacting regional air-quality is less well understood. We explore the impact of halogens on regional pollutants (focussing on O3) with the European grid of the GEOS-Chem model (0.25° × 0.3125°). It has recently been updated to include a representation of halogen chemistry. We focus on the summer of 2015 during the ICOZA campaign at the Weybourne Atmospheric Observatory on the North Sea coast of the UK. Comparisons between these observations together with those from the UK air-quality network show that the model has some skill in representing the mixing ratios/concentration of pollutants during this period. Although the model has some success in simulating the Weybourne ClNO2 observations, it significantly underestimates ClNO2 observations reported at inland locations. It also underestimates mixing ratios of IO, OIO, I2 and BrO, but this may reflect the coastal nature of these observations. Model simulations, with and without halogens, highlight the processes by which halogens can impact O3. Throughout the domain O3 mixing ratios are reduced by halogens. In northern Europe this is due to a change in the background O3 advected into the region, whereas in southern Europe this is due to local chemistry driven by Mediterranean emissions. The proportion of hourly O3 above 50 nmol mol-1 in Europe is reduced from 46% to 18% by halogens. ClNO2 from N2O5 uptake onto sea-salt leads to increases in O3 mixing ratio, but these are smaller than the decreases caused by the bromine and iodine. 12% of ethane and 16% of acetone within the boundary layer is oxidised by Cl. Aerosol response to halogens is complex with small (∼10%) reductions in PM2.5 in most locations. A lack of observational constraints coupled to large uncertainties in emissions and chemical processing of halogens make these conclusions tentative at best. However, the results here point to the potential for halogen chemistry to influence air quality policy in Europe and other parts of the world.