Radium desorption from riverine or suspended sediment is an important source term of Ra isotopes in estuarine water, which is one of the significant factors affecting the source/sink material balance for Ra applications, such as estimating submarine groundwater discharge flux in coastal zones. In this paper, a theoretical model is proposed to study Ra desorption considering several influencing factors, including salinity, particle size and size distribution, alpha recoil range of atoms in the sediment grains, and grain surface roughness. The results of the model parameter sensitivity analysis show that the alpha-decay recoil can improve the number of total exchangeable Ra on grain surfaces, but it is more significant for sediment of small grain size. Sediment with large mean grain size may contain a considerable number of smaller particles, which may facilitate the Ra desorption quantity. Due to the relatively low concentrations of Ra in natural mineral, the Ra desorption quantity is not sensitive to the roughness of the sediment grain surfaces. The model fits well with the indoor experimental data, by fitting the experimental data or quoting the literature values, the desorption parameters (A, B, α, β) in the model can be determined to estimate the total number of exchangeable Ra of a sediment and also predict the Ra desorption of sediments in different conditions.

河流或悬浮沉积物中的镭解吸是河口水中Ra同位素的重要来源，这是影响Ra应用的源/汇物质平衡的重要因素之一，例如估算沿海地区的海底地下水排放通量。本文提出了一个理论模型来研究Ra解吸，其中考虑了几个影响因素，包括盐度，粒度和粒度分布，沉积颗粒中原子的α反冲范围以及晶粒表面粗糙度。模型参数敏感性分析的结果表明，α衰变后坐力可以提高晶粒表面总可交换Ra的数量，但对于小晶粒尺寸的沉积物则更为重要。平均粒径较大的沉积物可能包含大量较小的颗粒，这可以促进镭的解吸量。由于天然矿物中镭的浓度相对较低，镭的解吸量对沉积物颗粒表面的粗糙度不敏感。该模型与室内实验数据非常吻合，通过拟合实验数据或引用文献值，可以确定模型中的解吸参数（A，B，α，β），以估算沉积物可交换Ra的总数。并预测不同条件下沉积物的镭解吸。