Abstract Large uncertainties exist in the current treatment of atmospheric dry deposition and air-surface exchange of atmospheric mercury in chemical transport models and monitoring networks. To quantitatively assess these uncertainties, two existing bidirectional air-surface flux exchange models for gaseous elemental mercury (Hg0), originally developed by Wang et al. (2014, Atmos. Chem. Phys., doi:10.5194/acp-14-6273-2014) and Wright and Zhang (2015, J. Adv. Model. Earth Syst., doi:10.1002/2014MS000367) were compared in detail. The two models were applied to two vegetated land covers, a deciduous broadleaf forest and crops, surrounding a monitoring site in Georgia, USA for calculating air-surface exchange fluxes of Hg0 in 2009. The model inputs include measured 2-h ambient Hg0 concentrations and archived surface meteorology data produced from a weather forecast model. The annual net fluxes differed significantly between the two models, i.e., −8.6 μg m−2yr−1 vs. −0.7 μg m−2yr−1 over the deciduous broadleaf forest and −10.7 μg m−2yr−1 vs. 8.4 μg m−2yr−1 over the crops. When considering dry deposition and emission fluxes separately, similar deposition fluxes were produced by the two models, regardless of season and land cover, due to the similar canopy resistance formulas used in the two models. Much higher soil and lower stomatal emission fluxes were produced by Wang et al.‘s model than Wright & Zhang's model (soil: 30 vs. 8.9 μg m−2yr−1 and stomata: 0.5 μg m−2yr−1 vs. 8.3 μg m−2yr−1, averaged over the two canopies) due to the very different emission potentials used in the two models. Cuticle emission fluxes contributed less than 0.1% to the total emission flux in Wang et al.‘s model, and were not considered in Wright & Zhang's model. The differences in soil emission flux, total emission flux, and net flux were more pronounced in winter than in the other seasons. The large differences in the net fluxes between the two models were primarily caused by their very different schemes of soil emission potential.

中文翻译：

---

植被表面气态元素汞的两种双向空气-表面交换模型的比较

摘要 目前在化学输运模型和监测网络中处理大气干沉降和大气汞的气-表交换存在很大的不确定性。为了定量评估这些不确定性，最初由 Wang 等人开发的两个现有的气态元素汞 (Hg0) 双向空气-表面通量交换模型。(2014, Atmos. Chem. Phys., doi:10.5194/acp-14-6273-2014) 和 Wright 和 Zhang (2015, J. Adv. Model. Earth Syst., doi:10.1002/2014MS000367) 进行了详细比较。这两个模型应用于美国乔治亚州一个监测点周围的两个植被地覆盖、落叶阔叶林和作物，用于计算 2009 年 Hg0 的空气-地表交换通量。模型输入包括测量的 2 小时环境 Hg0 浓度和从天气预报模型产生的存档地表气象数据。两个模型之间的年净通量显着不同，即-8.6 μg m-2yr-1 vs. -0.7 μg m-2yr-1 落叶阔叶林和-10.7 μg m-2yr-1 vs. 8.4 μg m −2yr−1 在作物上。当分别考虑干沉降和排放通量时，由于两个模型中使用的冠层阻力公式相似，无论季节和土地覆盖情况如何，这两个模型都产生了相似的沉积通量。Wang 等人的模型比 Wright 和 Zhang 的模型产生了更高的土壤和更低的气孔排放通量（土壤：30 对 8.9 μg m−2yr−1 和气孔：0.5 μg m−2yr−1 对 8.3 μg m−2yr−1, 由于两个模型中使用的发射潜力非常不同，因此在两个檐篷上取平均值。在 Wang 等人的模型中，角质层排放通量对总排放通量的贡献不到 0.1%，而在 Wright & Zhang 的模型中没有考虑。冬季土壤排放通量、总排放通量和净通量的差异比其他季节更为明显。两个模型之间净通量的巨大差异主要是由于它们非常不同的土壤排放潜力方案造成的。