Characteristics of U-pattern distribution of highconcentration 210Pb in surface air at central Guizhou, China
Characteristics of U-pattern distribution of highconcentration 210Pb in surface air at central Guizhou, China
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DOI：
10.1360/04wd0073
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发表时间：
2005-08
影响因子：
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通讯作者：
G. Wan;Wei Yang;Wang Shilu;E. Wan;Fengchang Wu;S. N. Lee;Changsheng Wang;Ronggui Huang
中科院分区：
文献类型：
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作者：
G. Wan;Wei Yang;Wang Shilu;E. Wan;Fengchang Wu;S. N. Lee;Changsheng Wang;Ronggui Huang
更好地了解地表空气中210Pb浓度的变化是追踪湖泊沉积和流域侵蚀、建立和验证污染物全球扩散模型以及评估自然辐射对生态系统影响的关键。根据云贵高原沉降、大气模式和独特环境背景的研究进展，从2001年12月20日开始，我们使用500 NE型气溶胶采样器，连续两年每周一次对贵阳市冠峰山地表空气进行过滤采样。中美两国实验室对210Pb浓度的同步详细γ能谱观测表明，210Pb月均浓度年变化呈规则的U型分布，高值出现在冬季，低值出现在春末和夏季。年平均 210Pb 浓度估计为 2.77±0.63 mBq/m3，大约是世界各地许多监测站报告的平均最高浓度的 4 倍。影响贵州省中部地区地表空气中210Pb来源的可能因素有： 土壤中富集的U-Ra系列222Rn的释放；碳酸盐岩的化学风化；煤炭、磷资源的开发、加工和利用。控制黔中地区地表空气中210Pb高浓度及其年U型分布的主要因素是222Rn的释放。月平均210Pb浓度与降水量增加呈良好的负幂函数关系，与月份分组气温上升呈良好的负线性函数关系。第1组（6月至11月）反映了在相对高温季节土壤中222Rn的释放量相对较低；第 2 组（12 月至 5 月）反映了在温度相对较低的季节，土壤中 222Rn 的释放量相对较高。降水和气温模拟的月均210Pb浓度与实测值吻合较好，表明黔中地区地表空气中210Pb浓度呈U型规律分布特征主要受区域降水和气温控制。同时也表明，年内气温和降水量的变化幅度也制约着月均210Pb浓度高值与低值的比例。从月的时间尺度来看，降水量和气温是影响土壤（岩石）中222Rn释放的主要因素。在这方面已经获得了有力的证据。
A better understanding of the variation of 210Pb concentrations in the surface air is the key to trace lake sedimentation and catchment erosion, to establish and validate the global diffusion model of contaminants, and to assess the impact of natural radiation on the ecological system. Basing on the study progresses of the sedimentation, the atmospheric model and the unique environmental background in the Yunnan-Guizhou Plateau, and starting from December 20, 2001, we made use of a 500 NE Type aerosol sampler to collect filter samples, once a week in the past consecutive two years, in the surface air at Mt. Guanfeng, Guiyang City, China. Synchronous detailed γ-energy spectrometric observations of 210Pb concentrations at both Chinese and U.S. laboratories have shown that the average monthly 210Pb concentration displays a regular U-patterns distribution of annual variations, with high values appearing in winter and low values in late spring and summer. The average annual 210Pb concentrations are estimated to be 2.77±0.63 mBq/m3, about 4 times the average maximum concentrations reported from quite a number of monitoring stations throughout the world. The possible factors affecting the sources of 210Pb in the surface air in the central part of Guizhou Province are: Release of 222Rn from the U-Ra series enriched in the soils; chemical weathering of carbonate rocks; the exploitation, processing and utilization of coal and phosphorous resources. The principal factor controlling the high 210Pb concentrations in the surface air in the central Guizhou and their annual U-pattern distribution is the release of 222Rn. The average monthly 210Pb concentrations show a good negative powerfunction relationship with increasing precipitation and also show a good negative linear-function relationship with the rise of air temperature in month grouping. Group No.1 (June to November) reflects a relatively low release of 222Rn from soils in relatively high temperature seasons; Group No.2 (December to May) mirrors a relatively high release of 222Rn from soils in relatively low temperature seasons. The average monthly 210Pb concentrations simulated in terms of the precipitation and air temperature are in good consistency with the measured values, revealing that the regular U-pattern distribution characteristics of 210Pb concentrations in the surface air in the central Guizhou are controlled predominantly by regional precipitation and air temperature. Meanwhile, it is also indicated that the magnitude of variation of air temperature and precipitation within the same year also constrains the ratio of high values over low values of average monthly 210Pb concentrations. On a month time scale, precipitation and air temperature are a main factor affecting the release of 222Rn from soils (rocks). In this aspect strong evidence has been obtained.