Air Quality Research Division, Environment Canada , 2121 TransCanada Highway, Dorval, Quebec H9P 1J3, Canada.
Environ Sci Technol. 2014;48(3):1707-17. doi: 10.1021/es404473e. Epub 2014 Jan 14.
High levels of mercury in marine mammals threaten the health of Arctic inhabitants. Whether the Arctic Ocean (AO) is a sink or a source of atmospheric mercury is unknown. Given the paucity of observations in the Arctic, models are useful in addressing this question. GEOS-Chem and GRAHM, two complex numerical mercury models, present contrasting pictures of atmospheric mercury input to AO at 45 and 108 Mg yr(-1), respectively, and ocean evasion at 90 and 33 Mg yr(-1), respectively. We provide a comprehensive evaluation of GRAHM simulated atmospheric mercury input to AO using mercury observations in air, precipitation and snowpacks, and an analysis of the discrepancy between the two modeling estimates using observations. We discover two peaks in high-latitude summertime concentrations of atmospheric mercury. We show that the first is caused mainly by snowmelt revolatilization and the second by AO evasion of mercury. Riverine mercury export to AO is estimated at 50 Mg yr(-1) based on measured DOC export and at 15.5-31 Mg yr(-1) based on simulated mercury in meltwater. The range of simulated mercury fluxes to and from AO reflects uncertainties in modeling mercury in the Arctic; comprehensive observations in all compartments of the Arctic ecosystem are needed to close the gap.
海洋哺乳动物体内的汞含量过高会威胁北极居民的健康。目前还不清楚北极海洋是大气汞的汇还是源。鉴于北极地区的观测数据较少，模型在解决这个问题上很有用。GEOS-Chem 和 GRAHM 这两个复杂的汞数值模型，分别预测了大气汞向北极输入的情况，输入量分别为 45 和 108 Mg yr(-1)，以及海洋逃逸的情况，逃逸量分别为 90 和 33 Mg yr(-1)。我们利用大气汞在空气、降水和积雪中的观测值，对 GRAHM 模拟的大气汞向北极输入进行了全面评估，并利用观测数据对两种模型估算值之间的差异进行了分析。我们发现北极地区夏季大气汞浓度有两个高峰。我们表明，第一个高峰主要是由融雪再挥发引起的，第二个高峰是由北极海洋逃逸的汞引起的。基于测量的 DOC 输出，我们估计向北极海洋输送的河流汞量为 50 Mg yr(-1)，基于模拟的融水中的汞量，输送量为 15.5-31 Mg yr(-1)。模拟的北极海洋汞通量的范围反映了北极地区汞模型的不确定性；需要在北极生态系统的所有组份中进行全面的观测，以填补这一空白。
