Institute for Data, Systems, and Society, Massachusetts Institute of Technology, Cambridge, MA, USA.
Extreme Environments Research Laboratory, École Polytechnique Fédérale de Lausanne (EPFL) Valais, Wallis, Sion, Switzerland.
Environ Sci Process Impacts. 2021 Dec 15;23(12):1914-1929. doi: 10.1039/d1em00253h.
Mercury (Hg) is an environmental toxicant dangerous to human health and the environment. Its anthropogenic emissions are regulated by global, regional, and local policies. Here, we investigate Hg sources in the coastal city of Boston, the third largest metropolitan area in the Northeastern United States. With a median of 1.37 ng m, atmospheric Hg concentrations measured from August 2017 to April 2019 were at the low end of the range reported in the Northern Hemisphere and in the range reported at North American rural sites. Despite relatively low ambient Hg concentrations, we estimate anthropogenic emissions to be 3-7 times higher than in current emission inventories using a measurement-model framework, suggesting an underestimation of small point and/or nonpoint emissions. We also test the hypothesis that a legacy Hg source from the ocean contributes to atmospheric Hg concentrations in the study area; legacy emissions (recycling of previously deposited Hg) account for ∼60% of Hg emitted annually worldwide (and much of this recycling takes place through the oceans). We find that elevated concentrations observed during easterly oceanic winds can be fully explained by low wind speeds and recirculating air allowing for accumulation of land-based emissions. This study suggests that the influence of nonpoint land-based emissions may be comparable in size to point sources in some regions and highlights the benefits of further top-down studies in other areas.
汞（Hg）是一种对人类健康和环境都具有危害性的环境毒物。其人为排放受到全球、区域和地方政策的管控。在这里，我们调查了美国东北部第三大城市波士顿的沿海城市的汞来源。从 2017 年 8 月到 2019 年 4 月，大气汞浓度的中位数为 1.37ng m，处于北半球和北美农村站点报告的范围内的低值。尽管环境汞浓度相对较低，但我们使用测量-模型框架估计人为排放量比当前排放清单高 3-7 倍，这表明对小型点源和/或非点源排放的低估。我们还测试了一个假设，即海洋中的汞历史遗留源会导致研究区域的大气汞浓度升高；海洋每年全球汞排放量的 60%左右（其中大部分通过海洋发生再循环）来自于历史遗留排放（以前沉积的汞的再循环）。我们发现，在东风期间观察到的浓度升高可以完全由低风速和空气再循环解释，这允许陆基排放的积累。本研究表明，在某些地区，非点源陆基排放的影响可能与点状源相当，并强调了在其他地区进行进一步自上而下研究的好处。
