上海市大气降水中~(210)Pb、~7Be的变化特征

7Be、210Pb等放射性核素已被广泛应用于区域及全球物质传输途径示踪的研究中。2009年8月到2010年10月在上海市普陀区华东师范大学校园设采样点采集了51场大气降水样品,分析了单次降水事件中7Be和210Pb的含量以及湿沉降通量的变化特征,并对比不同季节的变化特征。结果表明:1)单次降水事件中7Be的浓度变化范围为0.21~5.99 Bq/L,210Pb浓度的变化范围为0.01~0.90 Bq/L。7Be和210Pb的月均浓度具有明显的季节变化特征:7Be的浓度高值出现在冬季,夏季浓度最低;210Pb浓度高值出现在秋、冬季节,夏季浓度最低;7Be/210Pb高值主要出现在春、秋季节。2)7Be、210Pb沉降通量与降水量有一定相关性,但单次降水事件7Be和210Pb浓度与降水量并没有很好的相关性。7Be和210Pb沉降通量存在着较好的相关性,指示7Be、210Pb沉降路径有着较好的一致性。

Variation Characteristics of 210Pb and 7Be in Precipitation in Shanghai

Radioactive nuclides 7Be and 21~pb are widely used in the studies of atmospheric mass transmission. Rainwater samples were collected from August 2009 to October 2010 at the North Zhongshan Road campus, East China Normal University, Shanghai to study the variation of specific concentrations and integrated activity of 7Be and 210pb in individual rain events and the monthly variations of both particles. The results showed that the specific concentration range of 7 Be in 51 individual precipitation events was 0.21 -5.99 Bq/L, and the specific concentration range of 210pb was 0.01 -0.90 Bq/L. Meanwhile, the monthly average concentrations of 7Be and 210Pb had similar seasonal variation： i. e. , higher concentrations in winter and lower concentrations in summer for 7 Be, but higher concentrations in autumn and winter, and lower concentrations in summer for 210Pb. The higher ratio of 7Be/210pb was in spring and autumn. The concentrations of 7Be and 210pb for individual rain events were not well related to the precipitations due to the dilution effect of large precipitation.