Factors controlling temporal and spatial variations of atmospheric deposition of 7Be and 210Pb in northern Taiwan
Factors controlling temporal and spatial variations of atmospheric deposition of 7Be and 210Pb in northern Taiwan
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DOI：
10.1029/2006jd007180
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发表时间：
2006-08
影响因子：
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通讯作者：
C. Huh;C. Su;L. Shiau
中科院分区：
文献类型：
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作者：
C. Huh;C. Su;L. Shiau
(1)结合气象资料，对台湾北部2个监测点监测到的7 Be和210 Pb的通量进行分析，探讨其时空变化的控制因素。台北盆地南康两种核素的9年时间序列均与湿降水有关，并遵循受台风、季风和梅雨调节的年循环。叠加在年周期上的是厄尔尼诺-南方涛动引起的年际变化和锋面、冷潮、沙尘暴和太平洋高压系统通过或入侵引起的季内振荡。观测到的7个Be/ 210 Pb比值指示了沉降核素的来源区域，高海拔降雨的比值较高，干沉降和低海拔降雨的比值较低。阳敏山2年时间序列表明，山区站点的7 Be和210 Pb通量与南康站点相同。然而，阳敏山的核素通量是南康的4-5倍。结合本研究成果和其他辅助研究成果，我们认为(1)在应用沉降核素研究地表过程时，应根据所涉及的时间尺度，合理地作出恒定通量的假设；(2)应用沉降核素研究丘陵区土壤侵蚀不仅要考虑干湿降水的控制，还要考虑云与土壤的直接接触和相互作用，从而增强核素通量。
(1) Fluxes of 7 Be and 210 Pb monitored at two contrasting sites in northern Taiwan were studied along with meteorological data to elucidate factors controlling their temporal and spatial variations. The 9 year time series of both nuclides at Nankang in the Taipei Basin show dependence on wet precipitation and follow an annual cycle regulated by typhoons, monsoons, and mei-yu¨. Superimposed on the annual cycle are interannual variation caused by El Nino-Southern Oscillation and intraseasonal oscillations due to the passage or invasion of fronts, cold surges, dust storms, and the Pacific high-pressure system. The observed 7 Be/ 210 Pb ratios are indicative of the source regions of the fallout nuclides, with higher ratios from high-altitude rain and lower ratios from dry fallout and low-altitude rain. The 2 year time series at Yangminshan shows that 7 Be and 210 Pb fluxes at the mountainous site are in phase with those at Nankang. However, nuclide fluxes at Yangminshan are 4-5 times those at Nankang. After combining results from this and other ancillary studies at Yangminshan, we suggest that (1) in applying fallout nuclides to study the Earth's surface processes, the assumption of constant flux should be made judicially according to the timescales involved, and that (2) the application of fallout nuclides to study soil erosion in hilly areas must consider not only control by wet and dry precipitation but also by direct contact and interaction of clouds with soils enhancing nuclide fluxes.