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认识210Pb的空气浓度变化对湖泊沉积和流域侵蚀示踪,对污染物全球扩散模型的建立和验证,以及对生态系统受天然辐照的评价等多领域都是关键的环节.基于云贵高原特殊的环境背景、沉积作用和大气模拟研究的前期进展,自2001年12月20日起,利用500NE型气溶胶采样器,连续2年逐周在贵阳观风山采集近地面空气滤膜样品.通过中国和美国两个实验室对210Pb浓度的γ-能谱同步系统观测表明,月均浓度呈现出规则的“U”型年分布;冬季为高值期,春末和夏季为低值期;年均浓度2.77±0.63mBq·m?3,为全球若干站点中最高平均浓度值的近4倍.影响黔中地区空气210Pb物质来源的可能因素有:土壤中较高U-Ra系的222Rn释放;碳酸盐岩溶蚀作用;煤、磷资源开发、加工和利用的影响.制约黔中地区空气210Pb高浓度和U型年分布特征的重要因素在于222Rn的析出.210Pb月均浓度随降水量呈现良好的幂函数关系,并随气温呈现良好的分组线性关系.其中:No.1组(6~11月)反映了较高温度季节土壤222Rn的相对低释放;No.2组(12~5月)映射了较低温度季节土壤222Rn的相对高析出.以降水和气温均权影响模拟计算获得的210Pb月均浓度与实测值之间具有很好的一致性,反映出黔中地区近地面空气210Pb浓度呈现出规则的“U”型年分布特征主要由区域性的降水和气温制约;同时还说明其年内气温和降水的变幅制约着210Pb月均浓度的高值与低值之比.在月时间尺度下,降水量和气温作为影响土壤(岩石)中222Rn析出的主要因素,获得了很好的映证.
Understanding 210Pb air concentration changes in lake sedimentation and basin erosion tracing, establishment and verification of global diffusion model of pollutants, as well as the assessment of the ecosystem by natural radiation and other fields are the key link.According to the Yunnan-Guizhou Plateau special Environmental background, sedimentation and atmospheric simulation study of the early progress, since December 20, 2001, the use of 500NE-type aerosol sampler, for 2 consecutive years in Guiyang Gufeng Hill, near-surface air filtration membrane samples collected by China and Observations on the 210Pb γ-spectrometer synchronization system in two laboratories in the United States showed that the monthly mean concentration showed a regular “U” type annual distribution; the winter was high, the late spring and summer were low; the average annual concentration 2.77 ± 0.63mBq · m-3, which is nearly 4 times of the highest average concentration in some sites in the world.The possible factors influencing the sources of air 210Pb in central Guizhou are as follows: 222Rn release from higher U-Ra system in soil; Salt Rock Corrosion, Influence of Exploitation, Processing and Utilization of Coal and Phosphorus Resources An important factor restricting the distribution of 210Pb high concentration and U-shaped year in Central Guizhou lies in the precipitation of 222Rn.The monthly average concentration of 210Pb presents a good power with precipitation The results showed that group No.1 (June-November) reflected the relatively low release of 222Rn in the soil with higher temperature, and that in group No.2 (December-May) The relatively high precipitation of soil 222Rn occurred in the lower temperature season.The 210Pb monthly average concentration obtained by the simulation of the influence of precipitation and temperature had good consistency with the measured value, which indicated that the 210Pb concentration of near-surface air in central Guizhou showed a The “U” type annual distribution of the rules is mainly controlled by regional precipitation and temperature, and also shows that the variation of temperature and precipitation during the year restricts the ratio of high and low 210Pb monthly mean concentrations. On the monthly time scale , Precipitation and air temperature as the main factors affecting the precipitation of 222Rn in the soil (rock), and obtained a good mapping.