确定大气颗粒物平均滞留时间的新方法

从低层大气的基本属性出发,利用大气颗粒物中放射性核素的衰变特性与转移速率等相关信息, 建立了单位体积大气颗粒物中被吸附的放射性粒子数、衰变粒子数和转移粒子数的数学模型, 获得了确定低层大气颗粒物平均滞留时间的新方法.该方法解决了当前相关研究中出现的困惑, 说明了大气具有有限的自净功能,给出了大气颗粒物中同一衰变链上各核素达到活度平衡的条件 及降低平均滞留时间的途径,为大气环境的监测与治理提供了科学依据. 关键词： 大气颗粒物 平均滞留时间 氡子体 监测

A new method for monitoring the average residence time of atmospheric particulate matter

The long life decay products ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po of ²²²Rn are adsorbed in atmospheric particulate matters, thus making it possible to estimate the average residence time by measuring the specific activity or activity ratio of radon daughters. However, the existing research results are rather bad in consistency and the contradictory phenomena cannot be reasonably explained, which makes it inapplicable to atmospheric environmental monitoring. For this reason, starting with the basic attributes of lower atmosphere, based on the decay characteristics, transfer rates and other related information of radioactive nuclides in atmospheric particulates, a mathematical model is built to reflect the relationship among the particle numbers of the absorbed, decayed and transferred. Then, a new method is presented to estimate the average residence time of atmospheric aerosol. The method can solve the confusion that have appeared in the current research, reveal that the atmosphere has limited self-purification function, and provide the condition for nuclides in the same decaying chain to decay to the activity balance and the way to reduce the average residence time. All these conclusions will provide a scientific basis for further study and exploitation in atmospheric environment monitoring.
Keywords： atmospheric aerosol the average residence time radon and its decay products monitoring