Malcolm Elizabeth G, Keeler Gerald J, Lawson Sean T, Sherbatskoy Timothy D
University of Michigan Air Quality, Laboratory, Ann Arbor, MI, USA.
J Environ Monit. 2003 Aug;5(4):584-90. doi: 10.1039/b210124f.
The lack of high quality measurements of Hg and trace elements in cloud and fog water led to the design of a new collector for clean sequential sampling of cloud and fog water. Cloud water was collected during nine non-precipitating cloud events on Mt. Mansfield, VT in the northeastern USA between August 1 and October 31, 1998. Sequential samples were collected during six of these events. Mercury cloud water concentrations ranged from 7.5 to 71.8 ng l(-1), with a mean of 24.8 ng l(-1). Liquid water content explained about 60% of the variability in Hg cloud concentrations. Highest Hg cloud water concentrations were found to be associated with transport from the Mid-Atlantic and Ohio River Valley, and lowest concentrations with transport from the north of Mt. Mansfield out of Canada. Twenty-nine event precipitation samples were collected during the ten-week cloud sampling period near the base of Mt. Mansfield as part of a long-term deposition study. The Hg concentrations of cloud water were similar to, but higher on average (median of 12.5 ng l(-1)) than Hg precipitation concentrations (median of 10.5 ng l(-1)). Cloud and precipitation samples were analyzed for fifteen trace elements including Mg, Cu, Zn, As, Cd and Pb by ICP-MS. Mean concentrations were higher in cloud water than precipitation for elements with predominately anthropogenic, but not crustal origin in samples from the same source region. One possible explanation is greater in-cloud scavenging of crustal elements in precipitating than non-precipitating clouds, and greater below-cloud scavenging of crustal than anthropogenic aerosols.
由于缺乏对云水和雾水中汞及微量元素的高质量测量，因此设计了一种新的收集器，用于对云水和雾水进行清洁的连续采样。1998年8月1日至10月31日期间，在美国东北部佛蒙特州曼斯菲尔德山的9次非降水云事件中收集了云水。在其中6次事件中收集了连续样本。汞在云水中的浓度范围为7.5至71.8 ng l(-1)，平均为24.8 ng l(-1)。液态水含量解释了汞云浓度变化的约60%。发现汞云水中的最高浓度与来自大西洋中部和俄亥俄河谷的传输有关，而最低浓度与来自曼斯菲尔德山以北加拿大地区的传输有关。作为一项长期沉积研究的一部分，在曼斯菲尔德山山脚下为期十周的云采样期间收集了29个事件降水样本。云水的汞浓度与降水的汞浓度相似，但平均而言（中位数为12.5 ng l(-1)）高于降水的汞浓度（中位数为10.5 ng l(-1)）。通过电感耦合等离子体质谱法（ICP-MS）对云水和降水样本中的15种微量元素进行了分析，包括镁、铜、锌、砷、镉和铅。对于来自同一源区的样本中主要源自人为而非地壳的元素，其在云水中的平均浓度高于降水中的平均浓度。一种可能的解释是，与非降水云相比，降水云中地壳元素的云内清除作用更强，并且与人为气溶胶相比，地壳气溶胶的云下清除作用更强。
