Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem
Global impacts of tropospheric halogens (Cl, Br, I) on oxidants and composition in GEOS-Chem
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DOI：
10.5194/acp-16-12239-2016
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发表时间：
2016-09
影响因子：
6.3
通讯作者：
T. Sherwen;J. Schmidt;M. Evans;L. Carpenter;K. Grossmann;S. Eastham;D. Jacob;B. Dix;T. Koenig;R. Sinreich;I. Ortega;R. Volkamer;A. Saiz‐Lopez;C. Prados-Román;A. Mahajan;C. Ordóñez
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作者：
T. Sherwen;J. Schmidt;M. Evans;L. Carpenter;K. Grossmann;S. Eastham;D. Jacob;B. Dix;T. Koenig;R. Sinreich;I. Ortega;R. Volkamer;A. Saiz‐Lopez;C. Prados-Román;A. Mahajan;C. Ordóñez
抽象。我们提出了一个模拟的全球现今对流层的组成，其中包括卤素（Cl，Br，I）的化学。在GEOS-Chem模型的基础上，我们包括海洋无机碘的排放，卤化气体的人为和生物来源，气相化学和非均质卤素化学的参数化方法。与施密特等人（2016年）一致，我们不包括海盐脱溴。卤素自由基（BrO，IO）的观察是稀疏的，但该模型在再现这些有一定的技巧。与不同的数据集相比，模拟IO显示出高和低的偏差，但BrO浓度似乎模拟得很低。活性氯物种的非常稀疏的观测数据集的比较表明，该模型代表了这些物种的影响的下限，可能是由于低估了排放量，因此负担。Cl，Br和I的列入结果在臭氧（O3）浓度的模拟中的一般改善，除了在极地地区，该模型现在低估了O3浓度。卤素化学减少了全球对流层O3的负担18.6%，O3的寿命从26天减少到22天。全球平均OH浓度为1.28 × 106个分子cm−3，比没有卤素的模拟低8.2%，导致CH 4的寿命增加（10.8%），因为OH氧化从7.47年增加到8.28年。Cl对CH 4的氧化很小（约2%），但对其他VOC（乙烷、丙酮和丙烷）的Cl氧化可能很大（约15- 27%）。Br对VOC的氧化较小，占乙醛损失的3.9%和甲醛损失的0.9%。
Abstract. We present a simulation of the global present-day composition of the troposphere which includes the chemistry of halogens (Cl, Br, I). Building on previous work within the GEOS-Chem model we include emissions of inorganic iodine from the oceans, anthropogenic and biogenic sources of halogenated gases, gas phase chemistry, and a parameterised approach to heterogeneous halogen chemistry. Consistent with Schmidt et al. (2016) we do not include sea-salt debromination. Observations of halogen radicals (BrO, IO) are sparse but the model has some skill in reproducing these. Modelled IO shows both high and low biases when compared to different datasets, but BrO concentrations appear to be modelled low. Comparisons to the very sparse observations dataset of reactive Cl species suggest the model represents a lower limit of the impacts of these species, likely due to underestimates in emissions and therefore burdens. Inclusion of Cl, Br, and I results in a general improvement in simulation of ozone (O3) concentrations, except in polar regions where the model now underestimates O3 concentrations. Halogen chemistry reduces the global tropospheric O3 burden by 18.6 %, with the O3 lifetime reducing from 26 to 22 days. Global mean OH concentrations of 1.28 × 106 molecules cm−3 are 8.2 % lower than in a simulation without halogens, leading to an increase in the CH4 lifetime (10.8 %) due to OH oxidation from 7.47 to 8.28 years. Oxidation of CH4 by Cl is small (∼ 2 %) but Cl oxidation of other VOCs (ethane, acetone, and propane) can be significant (∼ 15–27 %). Oxidation of VOCs by Br is smaller, representing 3.9 % of the loss of acetaldehyde and 0.9 % of the loss of formaldehyde.