摘要
大气210Po、210Bi和210Pb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210Po、210Bi和210Pb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210Po、210Pb和210Bi的活度浓度进行了连续观测;基于210Po-210Pb活度比(210Po/210Pb)和210Bi-210Pb活度比(210Bi/210Pb)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210Po、210Bi、210Pb3种核素活度浓度的变化范围分别为0.11～1.27 mBq/m3、0.45～1.83 mBq/m3和1.12～6.10 mBq/m3;2021年秋季厦门210Po、210Bi、210Pb3种核素活度浓度的变化范围分别为0.05～0.85 mBq/m3、0.83～2.52mBq/m3和0.17～1.32 mBq/m3,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210Po/210Pb和210Bi/210Pb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210Po/210Pb计算上海气溶胶滞留时间均值为(94±54)d,基于210Bi/210Pb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210Pb、210Bi和210Po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/(m2·d)、0.04～7.91 Bq/(m2·d)和 0.01～5.49 Bq/(m2·d).基于模型估算的210Po、210Bi和210Pb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.
Abstract
The deposition fluxes of 210Po,210Bi and 210Pb in atmosphere are the basis for the application of radionuc-lide tracing in the ocean.In order to reveal the spatio-temporal variation of the activity of 210Po,210Bi and 210Pb in nearshore areas and estimate their deposition fluxes into the sea,in this paper,sampling observation and analysis of two typical areas near the East China Sea in Shanghai and Xiamen in different periods are carried out.A time series study was conducted on the the aerosol activities of 210Po,210Pb and 210Bi in Shanghai and Xiamen from September 2016 to February 2017 and from September to November 2021,respectively.The residence time of aerosol particle was calculated based on 210Po/210Pb and 210Bi/210Pb.Deposition fluxes of three nuclides were also estimated.This pa-per reported the activity of 210Po,210Bi and 210Pb in Shanghai in autumn and winter of 2016.The activity ranges of 210Po,210Pb and210Bi were 0.11-1.27 mBq/m3,0.45-1.83 mBq/m3 and 1.12-6.10 mBq/m3,respectively.In the fall of 2021,the activity ranges of 210Po,210Bi and 210Pb in Xiamen were 0.05-0.85 mBq/m3,0.83-2.52 mBq/m3 and 0.17-1.32 mBq/m3,respectively.The aerosol activity of each nuclide in Shanghai was higher than that in Xiamen.The estimated residence time based on 210Po-210Pb and 210Bi-210Pb methods are significantly different,for example,in Shanghai area,the averaged aerosol residence time based on 210Po-210Pb method was calculated to be(94±54)d,which is much higher than the result from 210Bi-210Pb method.The main reason for this difference is most likely due to the difference in the properties of the tracing isotopes we used.In this paper,based on a one-dimensional simple aerosol deposition rate model,the atmospheric deposition fluxes of 210Pb,210Bi and210Po over Shanghai area into the East China Sea are estimated,and their variation ranges are 0.1-26.35 Bq/(m2·d),0.04-7.91 Bq/(m2·d)and 0.01-5.49 Bq/(m2·d),respectively.The deposition fluxes of 210Po,210Bi and 210Pb estimated based on the model are close to the actual observed values in the study area during the same period in winter within a certain range.The feasibil-ity of estimating the deposition flux of nuclide into the sea with a simple one dimensional aerosol deposition rate model is verified.
基金项目
国家自然科学基金(42206166)
国家自然科学基金(42107251)
南海海洋资源利用国家重点实验室(海南大学)开放基金(MRUKF2021015)
万方数据