Modelling the coupled mercury-halogen-ozone cycle in the central Arctic during spring
Modelling the coupled mercury-halogen-ozone cycle in the central Arctic during spring
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DOI：
10.1525/elementa.2022.00129
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发表时间：
2023-05-11
影响因子：
3.9
通讯作者：
Zilker, Bianca
中科院分区：
文献类型：
--
作者：
Ahmed, Shaddy;Thomas, Jennie L.;Zilker, Bianca
北极春季期间，近地表汞和臭氧消耗事件发生在大气最低层。汞消耗是将北极内长寿命的元素汞转化为更具活性的形式的过程的第一步，这些形式沉积到冰冻圈、海洋和其他表面，最终融入北极食物网。由于雪、冰和气溶胶释放的活性卤素自由基的存在，导致汞和臭氧的消耗。在这项工作中，我们在最近发布的天气研究和预报模型以及化学 (WRF-Chem 4.3.3) 版本中添加了对北极大气汞循环的详细描述，其中包括北极溴和氯化学以及雪和气溶胶的活化/回收。我们的建模方法的主要优点是在线计算溴浓度和排放/回收，这是模拟北极汞消耗的每小时和每日变化所需的。我们使用该模型研究了北极气候研究多学科漂流观测站 (MOSAiC) 2020 年春季期间汞、臭氧和溴的反应循环之间的耦合，并与陆基、船基和遥感观测结果进行了比较。该模型预测元素汞氧化主要由溴化学驱动，颗粒汞是氧化汞的主要形式。该模型预测，沉积到陆地雪上的氧化汞的大部分（74%）会以气态元素汞的形式重新排放到大气中，而沉积到海冰上的氧化汞的一小部分（4%）会在春季重新排放到大气中。我们的工作表明，必须考虑大气中溴/臭氧化学的每小时差异，以捕获春季北极汞循环，包括其与冰冻圈和海洋的融合。
Near-surface mercury and ozone depletion events occur in the lowest part of the atmosphere during Arctic spring. Mercury depletion is the first step in a process that transforms long-lived elemental mercury to more reactive forms within the Arctic that are deposited to the cryosphere, ocean, and other surfaces, which can ultimately get integrated into the Arctic food web. Depletion of both mercury and ozone occur due to the presence of reactive halogen radicals that are released from snow, ice, and aerosols. In this work, we added a detailed description of the Arctic atmospheric mercury cycle to our recently published version of the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem 4.3.3) that includes Arctic bromine and chlorine chemistry and activation/recycling on snow and aerosols. The major advantage of our modelling approach is the online calculation of bromine concentrations and emission/recycling that is required to simulate the hourly and daily variability of Arctic mercury depletion. We used this model to study coupling between reactive cycling of mercury, ozone, and bromine during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) spring season in 2020 and evaluated results compared to land -based, ship-based, and remote sensing observations. The model predicts that elemental mercury oxidation is driven largely by bromine chemistry and that particulate mercury is the major form of oxidized mercury. The model predicts that the majority (74%) of oxidized mercury deposited to land-based snow is re-emitted to the atmosphere as gaseous elemental mercury, while a minor fraction (4%) of oxidized mercury that is deposited to sea ice is re-emitted during spring. Our work demonstrates that hourly differences in bromine/ozone chemistry in the atmosphere must be considered to capture the springtime Arctic mercury cycle, including its integration into the cryosphere and ocean.