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

这是一个为期两年的工作计划，使用一个三维模型来模拟对流层中222Rn和210Pb的全球分布。氡-222(半衰期3.8天)由土壤释放到大气中；它衰减到210Pb(半衰期22.3年)，并迅速结合到气溶胶颗粒中，通过沉积去除。222Rn/210Pb系统是垂直混合、海洋和极地地区的大陆空气平流以及气溶胶长距离输送的极佳示踪剂。从世界各地的大量地点都可以获得测量到的浓度的长期时间序列。用三维模式成功地解释观测结果将极大地促进我们对污染物在对流层中的远程传输的理解。这项研究中使用的3-d模型以前已经被证明能够很好地模拟长线示踪剂(氟氯化碳的8.5Kr)的分布。第一项工作将是模拟北美地区的222Rn分布。模型结果将通过与美国222Rn浓度的观测时间序列进行比较来评估。将研究污染物从边界层到自由对流层的传输。222Rn的全球模拟将被用来研究南半球的远距离传输，其基础是在亚南极和南极地点测量的广泛的浓度时间序列。该项目的后半部分将涉及对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，而来自210Pb研究的南极结果将支持对海洋和极地地区大陆气溶胶远程输送的调查。

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.