Department of Microbiology and Environmental Toxicology , University of California at Santa Cruz , Santa Cruz , California 95064 , United States.
Department of Chemical and Environmental Engineering , University of Arizona , Tucson , Arizona 85721 , United States.
Environ Sci Technol. 2018 Mar 6;52(5):2527-2537. doi: 10.1021/acs.est.7b05395. Epub 2018 Feb 19.
Water samples from marine stratus clouds were collected during 16 aircraft flights above the Pacific Ocean near the Central California coast during the summer of 2016. These samples were analyzed for total mercury (THg), monomethyl mercury (MMHg), and 32 other chemical species in addition to aerosol physical parameters. The mean concentrations of THg and MMHg in the cloudwater samples were 9.2 ± 6.0 ng L (2.3-33.8 ng L) ( N = 97) and 0.87 ± 0.66 ng L (0.17-2.9 ng L) ( N = 22), respectively. This corresponds to 9.5% (3-21%) MMHg as a fraction of THg. Low and high nonsea salt calcium ion (nss-Ca) concentrations in cloudwater were used to classify flights as "marine" and "continental", respectively. Mean [MMHg] was significantly higher ( p < 0.05) than [MMHg] consistent with an ocean source of dimethyl Hg (DMHg) to the atmosphere. Mean THg in cloudwater was not significantly different between the two categories, indicating multiple emissions sources. Mean [THg] was correlated with pH, CO, NO, NH, and other trace metals, whereas [THg] was correlated with MMHg and Na. THg concentrations were negatively correlated with altitude, consistent with ocean and land emissions, coupled with removal at the cloud-top due to drizzle formation.
在 2016 年夏季，于加利福尼亚中部海岸附近的太平洋上空进行了 16 次飞机飞行，采集了海洋平流层云的水样。除了气溶胶物理参数外，这些样品还分析了总汞（THg）、一甲基汞（MMHg）和其他 32 种化学物质的浓度。云水中 THg 和 MMHg 的平均浓度分别为 9.2 ± 6.0ng/L（97 个样本）和 0.87 ± 0.66ng/L（22 个样本）。这对应于 MMHg 作为 THg 的分数为 9.5%（3-21%）。云水中低和高的非海相钙离子（nss-Ca）浓度分别用于将飞行分类为“海洋”和“大陆”。[MMHg]显著高于（p<0.05），与大气中二甲基汞（DMHg）的海洋来源一致。两种类型的云水中的平均 THg 没有显著差异，表明存在多种排放源。平均[THg]与 pH、CO、NO、NH 和其他微量元素相关，而[THg]与 MMHg 和 Na 相关。THg 浓度与海拔呈负相关，这与海洋和陆地排放物一致，并且由于毛毛雨的形成，在云顶处被去除。
