Nuclear activities that relate to waste disposal and storage, dismantling or new processes may produce toxic chemicals and radionuclides. Transfer into the geosphere and biosphere is a key issue of research that addresses the mobility, toxicity and risk of trace elements in natural systems. Knowledge of trace element speciation is essential for a better understanding of their environmental retention, transport and bioavailability [1-4]. As water is a most important vector for trace element dissemination, and particularly for radionuclides, the impact of humic substances (HSs), which are ubiquitous in all environments, is important to study, since HSs react strongly with trace elements [4-7]. The questions to be addressed are whether HSs increase or decrease trace element solubility, how trace element speciation is changed by HSs and how trace metal bioavailability and toxicity are affected.