Measurements of 210Pb and 7Be in China and their analysis accompanied with global model calculations of 210Pb
Measurements of 210Pb and 7Be in China and their analysis accompanied with global model calculations of 210Pb
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DOI：
10.1029/2004jd005061
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发表时间：
2004-11
影响因子：
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通讯作者：
H. Lee;G. Wan;Xiangdong Zheng;C. Sanderson;B. Josse;Shilu Wang;Wei Yang;Jie Tang;Changsheng Wang
中科院分区：
文献类型：
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作者：
H. Lee;G. Wan;Xiangdong Zheng;C. Sanderson;B. Josse;Shilu Wang;Wei Yang;Jie Tang;Changsheng Wang
[1]以前的全球模式一般模拟中国地面空气高浓度的210Pb。为了检验模型的准确性和性能，需要210Pb的实测数据。本文首次在贵州贵阳（26.57°N, 106.72°E，海拔1080 m）和华里官山（36.29°N，海拔100 m）采集了地面大气放射性核素210Pb和7Be的测量数据。这些测量经过仔细分析，以保证数据和质量控制，并用于验证模型。结果表明，贵阳地区测得的210Pb和7Be的变化规律是一致的。在这种情况下，7Be浓度的增加是高压系统外围形成的空气的弱下沉的结果。由于边界层沉降较弱，边界层湍流会混合210Pb的向上运移，从而使210Pb浓度升高。7Be/210Pb的比值具有季节变化特征，且具有月波动特征。比值高峰出现在对流活动显著的春季和夏季。位于峰顶的Waliguan山测得的210Pb水平可归因于222Rn的长距离输送，并衰变成210Pb，而7Be浓度则与经过该站点的局部气流直接变化。研究发现，由于210Pb在高海拔的华里关山遗址发生了长距离的输运，因此不适合用7Be/210Pb的比值来分析该遗址的垂直输运交换过程。为了验证模式，我们利用法国气象公司开发的综合多尺度三维全球化学输运模式模拟了2002年210Pb的全球输运。将模型结果与实测数据进行比较发现，该模型对中国地区210Pb浓度的计算结果普遍较差。模式结果的低估可能是中国上空不明高氡源的结果。然而，该模型能够再现210Pb浓度的变化。
[1] Previous global models generally simulated high concentrations of 210Pb in the surface air over China. Measured data of 210Pb are needed in order to examine the accuracy and performance of the models. We collected the first-ever set of surface air radionuclide measurements of 210Pb and 7Be at Guiyang (26.57°N, 106.72°E, 1080 m above sea level) on the east of the Himalayas in Guizhou Province and at Mt. Waliguan (36.29°N, 100.90°E, 3816 m above sea level), a Global Atmosphere Watch station for the World Meteorological Organization, on the Qinghai-Tibetan plateau extending from the Himalayas in Qinghai Province, China. These measurements were carefully analyzed for data assurance and quality control and were used for validating models. The patterns for the variations in both measured 210Pb and 7Be at the Guiyang site have been shown to be consistent. In this case the increase of 7Be concentration was the result of the weak subsidence of air developed at the periphery of the high-pressure system. Because of the weak subsidence the boundary layer turbulence could mix the upward transport of 210Pb, thus increasing 210Pb concentration. The ratio of 7Be/210Pb indicated a seasonal variability with rough monthly oscillation. The ratio peaks were in spring and summer when the convective activities were significant. The 210Pb levels measured at Mt. Waliguan, located at the peak of the mountain, could be attributed to the long-range transport of 222Rn that decays to 210Pb, whereas the 7Be concentration varied directly with the local airflow passing over the site. We found that it was not appropriate to use the ratio of 7Be/210Pb for analysis of vertical transport exchange processes at the high-altitude Mt. Waliguan site because of the long-range transport of 210Pb that occurred at the site. For the purpose of model validation we have simulated the global transport of 210Pb for the year 2002 by using a comprehensive multiscale three-dimensional global chemical transport model developed by Meteo France. It was found by comparing model results with measurements that the model generally performed poorly for the calculations of 210Pb concentrations in China. The underestimates of model results could be the result of the unidentified high radon sources over China. However, the model was able to reproduce the variations of the 210Pb concentrations.