广西北部湾北部近海水体中不同形态210Po的分布及地球化学行为

Distribution and geochemical behavior of different phases for 210Po in offshore water of the northern Beibu Gulf,Guangxi

^(210)Po是典型的颗粒活性核素,可作为大气气溶胶沉降动力学过程、海洋颗粒态物质输运过程研究的示踪剂。本文研究了北部湾近海水域6个离岸断面的水质参数和不同形态^(210)Po的比活度分布及行为特征。结果表明溶解态、颗粒态和总^(210)Po的比活度变化范围分别为0.16~2.78、0.14~2.43和0.51~3.94 mBq/L,溶解态^(210)Po的比活度与水质参数无明显相关性,但颗粒态^(210)Po的比活度与水温、盐度和TSM质量浓度之间以及总^(210)Po的比活度与水温和TSM质量浓度之间呈显著相关关系。^(210)Po比活度的分布趋势在不同断面表现并不一致,但整体上近海水体中^(210)Po以颗粒态为主要存在形式,离岸水体中则主要以溶解态为主。进一步分析发现^(210)Po在固液两相中的分配系数与悬浮颗粒物质量浓度呈负相关关系;一维稳态不可逆清除模型的计算结果表明溶解态^(210)Po比颗粒态^(210)Po的停留时间更长,说明大气或河流输入北部湾近海的^(210)Po进入海水后会部分进入溶解相,使其在水中的停留时间加长。

^(210)Po is a typical natural particle active radionuclide,which can be used as a tracer for the study of atmospheric aerosol deposition dynamics and particle dynamics in marine environment.In this study,the water quality parameters and the specific activities distributions and behavior of different phases for ^(210)Po in six offshore sections of the north coastal Beibu Gulf were investigated.Results showed that the specific activities of dissolved,particulate and total ^(210)Po were 0.16-2.78 mBq/L,0.14-2.43 mBq/L and 0.51-3.94 mBq/L,respectively.There was no significant correlation between the specific activities of dissolved ^(210)Po and the water quality parameters,but the specific activities of particulate ^(210)Po showed significant correlation with water temperature,salinity and mass concentrations of TSM,respectively.At the same time,the specific activities of total ^(210)Po were significantly correlated with water temperature and mass concentrations of TSM,respectively.The distribution trends of ^(210)Po in different sections were not consistent,but in general,the particulate phase was the main existence form of ^(210)Po in the nearshore water,and the offshore ^(210)Po was confirmed mainly in the form of dissolved phase.Further analysis showed a negative correlation between the distribution coefficients of ^(210)Po in the solid-liquid phase and the mass concentrations of total suspended particulate matter.Based on the one-dimensional steady-state irreversible removal model,a longer residence time of dissolved ^(210)Po relative to particulate ^(210)Po was obtained,indicating that the atmospheric deposition and riverine input of ^(210)Po into the coastal Beibu Gulf would partially enter the dissolved phase after entering the seawater,so that its residence time in the water was prolonged.