A process of the removal of dissolved elements in the ocean by adsorption onto settling particulate matters (scavenging) is studied analytically and using the Lagrangian and Eulerian numerical methods. The generalized model of scavenging in a multicomponent reactive medium with first-order kinetics consisting of water and multifraction suspended particulate matter was developed. Two novel numerical schemes were used to solve the transport–diffusion–reaction equations for transport dominated flows. The particle tracking algorithm based on the method of moments was developed. The modified flux-corrected transport method for the Eulerian transport–diffusion–reaction equations is a flux-limiter method based on a convex combination of low-order and high-order schemes. The flux limiters in the developed approach are obtained as an approximate solution of a corresponding optimization problem with a linear objective function. This approach allows the construction of the flux limiters with desired properties. The similarity solutions of the model equations for an idealized case of instantaneous release of reactive radionuclide on the ocean surface were obtained. It was found analytically that the dispersion of reactive contamination caused by reversible phase transition with increase of settling velocity, concentration of particulate matter and distribution coefficient can be much greater than that caused by diffusion, whereas an increase in the desorption rate results in a decrease of the dispersion caused by the phase transfer. The solutions using both numerical schemes are consistent with the analytical similarity solution even at zero diffusivity. The scavenging of the \(^{239,240}\)Pu that was introduced to the ocean surface due to the fallout from past nuclear weapon testing was simulated. The simulation results were in agreement with the observations in the northern Pacific. It was shown that even if the concentration of the \(^{239,240}\)Pu on the particulate matter does not exceed 2% of the total concentration, settling of particulate matter plays a crucial role in the vertical transport and dispersion of the reactive radionuclide. The importance of the scavenging by both the large fast-settling particles and small particles slowly settling and dissolving with depth due to the biochemical processes was demonstrated. For large particles, the “pseudodiffusivity” caused by phase transfer was 60 times greater than the diffusivity.

使用拉格朗日和欧拉数值方法分析研究了通过吸附到沉降颗粒物质上（清除）去除海洋中溶解元素的过程。建立了具有一级动力学的多组分反应介质中清除的广义模型，该动力学由水和多级悬浮颗粒物组成。两种新的数值方案用于求解输运主导流的输运-扩散-反应方程。开发了基于矩量法的粒子跟踪算法。欧拉输运-扩散-反应方程的修正通量校正输运方法是一种基于低阶和高阶方案的凸组合的通量限制器方法。所开发方法中的通量限制器是作为具有线性目标函数的相应优化问题的近似解而获得的。这种方法允许构建具有所需特性的通量限制器。获得了反应性放射性核素在海面瞬时释放的理想情况下模型方程的相似解。分析发现，随着沉降速度、颗粒物浓度和分配系数的增加，可逆相变引起的反应性污染物的分散可远大于扩散引起的分散，而解吸速率的增加导致相转移引起的色散。即使在零扩散率下，使用这两种数值方案的解也与解析相似解一致。的清扫\(^{239,240}\)模拟了由于过去核武器试验的影响而被引入海洋表面的 Pu。模拟结果与北太平洋的观测结果一致。结果表明，即使\(^{239,240}\) Pu在颗粒物上的浓度不超过总浓度的2%，颗粒物的沉降对反应物的垂直输送和分散也起着至关重要的作用。放射性核素。由于生化过程，大的快速沉降颗粒和小颗粒随着深度缓慢沉降和溶解，证明了清除的重要性。对于大颗粒，相转移引起的“伪扩散率”是扩散率的 60 倍。