Three-Dimensional Simulations of Long-Range Pollutant Transport Using 222Rn and 210Ph as Tracers

这是一项为期两年的工作计划，利用三维模型模拟对流层中222Rn和210Pb的全球分布。氡-222（半衰期3.8天）通过土壤释放到大气中；它衰变为210Pb（半衰期22.3年），可迅速并入气溶胶颗粒中，并通过沉积除去。222Rn/210Pb体系是垂直混合、海洋和极地上空大陆空气平流以及气溶胶远距离输送的优秀示踪剂。可以从世界各地的许多地点获得测量浓度的长期时间序列。成功地用三维模式解释观测结果将大大提高我们对对流层中污染物远距离输送的认识。在这项研究中使用的三维模型已经被证明可以很好地模拟长列示踪剂（CFC的8.5Kr）的分布。第一项工作将是模拟222Rn在北美的分布。将通过与美国观测到的222Rn浓度的时间序列进行比较来评估模型结果。将研究污染物从边界层向自由对流层的输送。222Rn的全球模拟将用于研究南半球的远距离输送，其基础是在亚南极和南极地点测量的浓度的广泛时间序列。该项目的后一部分将涉及210Pb的全球模拟，重点是对北美、太平洋、北极和南极的观测结果进行解释。210Pb研究的结果将支持对大陆气溶胶在海洋和极地地区的远程传输的调查。

This is a two-year program of work to simulate the global distributions of 222Rn and 210Pb in the troposphere, using a three-dimensional model. Radon-222 (half-life 3.8 days) is released to the atmosphere by soils; it decays to 210Pb (half- life 22.3 years), which is rapidly incorporated into aerosol particles and is removed by deposition. The 222Rn/210Pb system is an excellent tracer of vertical mixing, advection of continental air over oceans and polar regions, and long-rang transport of aerosols. Long-term time series of measured concentrations are available from a large number of sites around the world. Successful interpretation of the observations with a 3-d model will advance significantly our understanding of long-rang transport of pollutants in the troposphere. The 3-d model to be used in this study has been shown previously to provide excellent simulations of the distributions of long-lined tracers(CFC's 8.5Kr). The first effort will be to model 222Rn distributions over North America. Model results will be evaluated by comparison with observed time series of 222Rn concentrations in the United States. Transport of pollutants from the boundary layer to the free troposphere will be investigated. Global simulations of 222Rn will be used to study long-range transport in the southern hemisphere, on the basis of extensive time series of concentrations measured at subantarctic and antarctic sites. The latter part of the project will involve global simulations of 210Pb, with emphasis on interpreting observations over North America, the Pacific Ocean, the Arctic, and the Antarctic Results from the 210Pb study will support an investigation of long-range transport of continental aerosol over oceans and polar regions.