Abstract:

To establish a database of radionuclides, sampling began in 2022, with one aerosol sample collected weekly, with a sampling volume greater than 10000 m³, resulting in a total of 118 samples. By analysis, the activity ranges of ⁷Be and ²¹⁰ Pb were 0.89-16.0 mBq·m⁻³ and 0.55-5.60 mBq·m⁻³, respectively, and the mean activity concentrations of ⁷Be and ²¹⁰Pb were (7.02±3.15) mBq·m⁻³ and (1.66±1.07) mBq·m⁻³, respectively. These two radionuclides have distinct seasonal. The activity concentration of ⁷Be throughout the year exhibited two peaks in spring and winter, and the highest value of ²¹⁰Pb appeared in winter, with the lowest activity concentration occurring in summer. Correlation analysis revealed that high humidity reduced the activity concentration of ⁷Be, whereas temperature had a greater impact on the activity concentration of ²¹⁰Pb. The activity concentrations of ⁷Be and ²¹⁰Pb were negatively correlated with rainfall, indicating that their removal mechanisms were the same. Although ⁷Be and ²¹⁰Pb sources differ, there is a significant positive correlation in the activity concentration owing to the same transport and clearance mechanisms between the two. Two radioactive nuclides initially accumulated on particulate matter and subsequently reached the ground via dry and wet deposition processes. The analysis found that ²¹⁰Pb tended to bind to PM_2.5 with a larger surface area, whereas ⁷Be was more easily attached to the larger particle size PM₁₀. For the backward trajectory clustering analysis of radionuclide sources, the high-activity-concentration ⁷Be aerosol in spring was derived from the southward trajectory, and ⁷Be and ²¹⁰Pb in winter were due to the enrichment of local particulate matter. These results provide a better understanding of the spatial and temporal changes in ⁷Be and ²¹⁰ Pb activity concentrations in Shijiazhuang.

Key words: ⁷Be, ²¹⁰Pb, meteorological parameters, back trajectory, Shijiazhuang

摘要：

为了建立放射性核素数据库，从2022年开始连续采样，每周采集1个气溶胶样品，采样体积大于10000 m³，共计采集了118个样品。分析得到⁷Be和²¹⁰Pb的活度浓度范围分别为0.89－16.0 mBq·m⁻³和0.55－5.60 mBq·m⁻³，平均值分别为 (7.02±3.15) mBq·m⁻³和 (1.66±1.07) mBq·m⁻³。这两种放射性核素具有明显的季节分布特征，全年⁷Be的活度浓度在春季和冬季出现两个峰值，而²¹⁰Pb的最高值出现在冬季，在夏季两者的活度浓度最低。相关性分析结果表明，湿度高时⁷Be的活度浓度降低，而温度对²¹⁰Pb的活度浓度影响更大，⁷Be、²¹⁰Pb活度浓度均与降雨量呈负相关性，说明两者去除机制相同。虽然⁷Be和²¹⁰Pb来源不同，但由于两者之间存在相同的传输和清除机制，其活度浓度存在显著的正相关。两种放射性核素首先在颗粒物上富集，然后通过干湿沉降作用到地面，分析发现²¹⁰Pb倾向于与比表面积更大的PM_2.5结合，而⁷Be更易附着在较大粒径的PM₁₀上。对放射性核素的来源进行后向轨迹聚类分析，春季高活度浓度⁷Be气溶胶来源于偏南轨迹，冬季高活度浓度的⁷Be和²¹⁰Pb则由于局地颗粒物的富集作用。研究结果有助于较好地了解石家庄市气溶胶中⁷Be和²¹⁰Pb活度浓度的时空变化及其相关性。

关键词: ⁷Be, ²¹⁰Pb, 气象参数, 后向轨迹, 石家庄