大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9...大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9月至翌年2月和2021年9-11月分别对上海及厦门地区近地表大气气溶胶中^(210)Po、^(210)Pb和^(210)Bi的活度浓度进行了连续观测;基于^(210)Po-^(210)Pb活度比(^(210)Po/^(210)Pb)和^(210)Bi-^(210)Pb活度比(^(210)Bi/^(210)Pb)两种示踪法计算了气溶胶颗粒物的滞留时间,并利用一维简单气溶胶沉降速率模型估算了3种核素以大气沉降方式输入东海的通量。结果显示,2016年上海秋、冬两季^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.11~1.27 m Bq/m^(3)、0.45~1.83 m Bq/m^(3)和1.12~6.10 m Bq/m^(3);2021年秋季厦门^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.05~0.85 m Bq/m^(3)、0.83~2.52 m Bq/m^(3)和0.17~1.32 m Bq/m^(3),上海近地表气溶胶中3种核素的活度浓度秋季平均值比厦门地区高。利用^(210)Po/^(210)Pb和^(210)Bi/^(210)Pb计算得到上海和厦门近地面大气的气溶胶滞留时间存在显著差异,基于^(210)Po/^(210)Pb计算上海气溶胶滞留时间均值为(94±54)d,基于^(210)Bi/^(210)Pb计算上海气溶胶滞留时间均值为(6.4±4.8)d,造成这种差异的原因很可能是两种示踪法本身具有的系统性差异。本文基于一维简易气溶胶沉降速率模型估算了上海地区的^(210)Pb、^(210)Bi和^(210)Po的大气沉降入东海的通量,其在秋季期间的变化范围分别为0.1~26.35 Bq/(m^(2)·d)、0.04~7.91 Bq/(m^(2)·d)和0.01~5.49 Bq/(m^(2)·d)。基于模型估算的^(210)Po、^(210)Bi和^(210)Pb沉降通量与研究区域的实际观测值接近一致,表明利用一维简易气溶胶沉降速率模型间接估算法在替代观测站直测核素的沉降入海通量方面具有一定可行性。展开更多
Beryllium-7 (^7Be) and lead-210 (^210pb) activities were measured from October 2002 to January 2004 at Waliguan Observatory (WO: 36.287°N, 100.898°E, 3816 m a.s.l (above sea level) in northwest China...Beryllium-7 (^7Be) and lead-210 (^210pb) activities were measured from October 2002 to January 2004 at Waliguan Observatory (WO: 36.287°N, 100.898°E, 3816 m a.s.l (above sea level) in northwest China. ^7Be and ^210pb activities are high with overall averages of 14.74-3.5 mBq m^-3 and 1.8±0.8 mBq m^-3 respectively. For both 7Be and ^210pb, there are significant short-term and seasonal variations with a commonly low value in summer (May-September) and a monthly maximum in April (for ^7Be) and in December (for ^210pb). The ratio of ^7Be/^210pb showed a broad maximum extending from April to July, coinciding with a seasonal peak in surface ozone (O3). The seasonal cycles of ^7Be and ^210pb activities were greatly influenced by precipitation and thermal dynamical conditions over the boundary layer, especially for ^210Pb. The vertical mixing process between the boundary layer and the aloft air modulates the variations of ^7Be and ^210pb at WO in summer. It is indicated that air mass had longer residence time and originated from higher altitudes at WO in the spring-summer time and the winter in 2003. During an event with extremely high weeklyaveraged ^7Be concentration (24.8 mBq m^-3) together with high O3 levels and low water mixing ratio, we found that air masses had been convectively transported a long distance to WO from high latitude source regions in central Asia, where significant subsiding motions were observed. In another case with the extreme ^210pb activity of 5.7 mBq m^-3 high CO2 level and specific humidity (in winter), air masses had come from south China and north Indian regions where 222Rn activities were high. This study, using ^7Be and ^210pb as atmospheric tracers, has revealed that complex interactions of convective mixing from the upper troposphere and long-range transports exist at WO.展开更多
文摘大气^(210)Po、^(210)Bi和^(210)Pb的沉降通量是海洋中核素示踪颗粒物动力学过程(颗粒有机碳输出、颗粒物输运)的基础参数,为揭示我国近海地区^(210)Po、^(210)Bi和^(210)Pb活度浓度的时空变化规律并估算其沉降入海通量,本文于2016年9月至翌年2月和2021年9-11月分别对上海及厦门地区近地表大气气溶胶中^(210)Po、^(210)Pb和^(210)Bi的活度浓度进行了连续观测;基于^(210)Po-^(210)Pb活度比(^(210)Po/^(210)Pb)和^(210)Bi-^(210)Pb活度比(^(210)Bi/^(210)Pb)两种示踪法计算了气溶胶颗粒物的滞留时间,并利用一维简单气溶胶沉降速率模型估算了3种核素以大气沉降方式输入东海的通量。结果显示,2016年上海秋、冬两季^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.11~1.27 m Bq/m^(3)、0.45~1.83 m Bq/m^(3)和1.12~6.10 m Bq/m^(3);2021年秋季厦门^(210)Po、^(210)Bi、^(210)Pb 3种核素活度浓度的变化范围分别为0.05~0.85 m Bq/m^(3)、0.83~2.52 m Bq/m^(3)和0.17~1.32 m Bq/m^(3),上海近地表气溶胶中3种核素的活度浓度秋季平均值比厦门地区高。利用^(210)Po/^(210)Pb和^(210)Bi/^(210)Pb计算得到上海和厦门近地面大气的气溶胶滞留时间存在显著差异,基于^(210)Po/^(210)Pb计算上海气溶胶滞留时间均值为(94±54)d,基于^(210)Bi/^(210)Pb计算上海气溶胶滞留时间均值为(6.4±4.8)d,造成这种差异的原因很可能是两种示踪法本身具有的系统性差异。本文基于一维简易气溶胶沉降速率模型估算了上海地区的^(210)Pb、^(210)Bi和^(210)Po的大气沉降入东海的通量,其在秋季期间的变化范围分别为0.1~26.35 Bq/(m^(2)·d)、0.04~7.91 Bq/(m^(2)·d)和0.01~5.49 Bq/(m^(2)·d)。基于模型估算的^(210)Po、^(210)Bi和^(210)Pb沉降通量与研究区域的实际观测值接近一致,表明利用一维简易气溶胶沉降速率模型间接估算法在替代观测站直测核素的沉降入海通量方面具有一定可行性。
基金the National Science Foundation of China (Grant Nos. 40175032 , 40575013).
文摘Beryllium-7 (^7Be) and lead-210 (^210pb) activities were measured from October 2002 to January 2004 at Waliguan Observatory (WO: 36.287°N, 100.898°E, 3816 m a.s.l (above sea level) in northwest China. ^7Be and ^210pb activities are high with overall averages of 14.74-3.5 mBq m^-3 and 1.8±0.8 mBq m^-3 respectively. For both 7Be and ^210pb, there are significant short-term and seasonal variations with a commonly low value in summer (May-September) and a monthly maximum in April (for ^7Be) and in December (for ^210pb). The ratio of ^7Be/^210pb showed a broad maximum extending from April to July, coinciding with a seasonal peak in surface ozone (O3). The seasonal cycles of ^7Be and ^210pb activities were greatly influenced by precipitation and thermal dynamical conditions over the boundary layer, especially for ^210Pb. The vertical mixing process between the boundary layer and the aloft air modulates the variations of ^7Be and ^210pb at WO in summer. It is indicated that air mass had longer residence time and originated from higher altitudes at WO in the spring-summer time and the winter in 2003. During an event with extremely high weeklyaveraged ^7Be concentration (24.8 mBq m^-3) together with high O3 levels and low water mixing ratio, we found that air masses had been convectively transported a long distance to WO from high latitude source regions in central Asia, where significant subsiding motions were observed. In another case with the extreme ^210pb activity of 5.7 mBq m^-3 high CO2 level and specific humidity (in winter), air masses had come from south China and north Indian regions where 222Rn activities were high. This study, using ^7Be and ^210pb as atmospheric tracers, has revealed that complex interactions of convective mixing from the upper troposphere and long-range transports exist at WO.