Batch experiments were performed to study adsorption and desorption of 75Se and 113Sn radiotracers at environmentally representative concentrations of ~0.3 ng L-1 and ~3 ng L-1, respectively. The radiotracers were incubated with wet bulk sediments from the Gironde Estuary and the Rhône River, combining freshwater and coastal seawater salinity (S = 0, S = 32) and three different Suspended Particulate Matter (SPM) concentrations (10 mg L-1, 100 mg L-1, 1000 mg L-1) to simulate six hydrologically contrasting situations for each particle type. Results showed no measurable adsorption for 75Se under the experimental conditions, whereas >90% of 113Sn rapidly adsorbed onto the particles during the first hours of exposure. Adsorption efficiency increased with increasing SPM concentration and seemed to be slightly greater for the Rhône River sediments, potentially related to the intrinsic mineral composition. Desorption of spiked sediments exposed to filtered, unspiked freshwater and seawater only occurred for 113Sn (<15% of the previously adsorbed 113Sn) in the Garonne River sediments. This study provides insights to the potential environmental behaviour of hypothetical radionuclide releases of Se and Sn into highly dynamic and contrasting aquatic systems. Multiple accidental scenarios for the case of the Gironde Estuary and the Rhône River are discussed. These scenarios suggest that the environmental fate of soluble radionuclides like Se will be associated to water hydrodynamics and potentially more bioavailable whereas highly particle-active radionuclides like Sn will follow natural river/estuarine sedimentary regimes. Information on reactivity of radionuclides is important for improving the precision of current approaches aiming at modelling environmental radionuclide dispersion in continent-ocean transition systems.

中文翻译：

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在河口盐度和浊度条件下，锡113和硒75放射性示踪剂的吸附和解吸动力学。

进行批处理实验以研究在环境代表性的浓度分别为〜0.3 ng L-1和〜3 ng L-1时75Se和113Sn放射性示踪剂的吸附和解吸。将放射性示踪剂与吉伦特河口和罗纳河的湿散装沉积物温育，结合淡水和沿海海水盐度（S = 0，S = 32）和三种不同的悬浮颗粒物（SPM）浓度（10 mg L-1，100） mg L-1、1000 mg L-1）来模拟每种颗粒类型的六个水文对比情况。结果表明，在实验条件下对75 Se的吸附没有可测量的，而在暴露的最初几个小时内，> 90％的113Sn迅速吸附到了颗粒上。吸附效率随着SPM浓度的增加而增加，并且对于罗纳河沉积物来说似乎更高一些，可能与内在的矿物成分有关。在加龙河沉积物中，仅对113Sn（小于先前吸附的113Sn的15％）暴露了加标的沉积物在过滤，未加标的淡水和海水中的解吸。这项研究提供了对假设的放射性核素将硒和锡释放到高动态和高对比度水生系统中的潜在环境行为的见解。讨论了吉伦特河口和罗纳河的多种意外情况。这些场景表明，可溶性放射性核素（如Se）的环境命运将与水的流体动力学相关，并可能具有更高的生物利用度，而高颗粒活性放射性核素（如Sn）将遵循自然的河流/河口沉积体系。