Behaviors of trace elements associated with dissolved organic matter in waters of Lake Shihwa, Korea

The behavior of dissolved trace elements in coastal seawater is influenced by various biogeochemical processes, including particle adsorption, decomposition of organic matter, and organic complexation. In this study, we measured the concentrations of dissolved trace elements (Al, V, Ni, Fe, Mn, Cu, Pb, Co, and Zn), together with dissolved organic matter (DOM), including organic carbon (DOC) and humic DOM (DOM_H), and ²³⁴Th in the artificial and saline Lake Shihwa, Korea. The concentrations of DOC (117–311 μM) and trace elements were significantly higher than those in other coastal waters, with average Al, Fe, and Mn concentrations of 709 ± 613 nM, 491 ± 452 nM, and 957 ± 657 nM, respectively. The large deficiencies of ²³⁴Th relative to ²³⁸U suggest an effective removal of ²³⁴Th via scavenging, with residence times of 1.4 ± 1.3 days. However, the concentrations of all measured trace elements against salinities showed conservative mixing patterns with significant positive correlations with DOM_H (r² > 0.72). These results suggest that all these trace elements are tightly combined with DOM_H, resulting in their conservative behaviors in the dissolved organic-rich coastal waters.