AUTHOR=Luan Feng , Yang Tingting , Lu Yuxi , Wang Ning 

TITLE=Molecular size-fraction and seasonal characteristics of dissolved trace metals in river and estuarine waters of the Yellow River, China

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1074829

DOI=10.3389/fmars.2022.1074829

ISSN=2296-7745

ABSTRACT=Spatial variations, sources and correlations with seawater environmental factors of the dissolved Fe, Mn, Cu, Zn, Cd and Pb in the surface water of the Yellow River Estuary in China were investigated. The clean sampling system, centrifugal ultrafiltration technique in conjunction with acid extraction, and ICP-MS were combined and used for the determination of the colloidal distribution of six metals in this region. Dissolved target metal was divided into five fractions, i.e. <1 kDa, 1-3 kDa, 3-10 kDa, 10-100 kDa and 100 kDa-0.45 μm, while the average concentrations of each fraction were 60.17, 46.54, 47.73, 251.03, 1.44 and 1.08 nmol L-1 in spring and 62.30, 48.18, 15.35, 203.05, 1.20 and 1.70 nmol L-1 in autumn, respectively. The results showed that colloidal Mn, Cu, Zn, Cd and Pb might be dominated by high-molecular-weight fraction (100 kDa-0.45 μm). Additionally, the contribution of low-molecular-weight colloidal Fe (1-10 kDa)  in this aquatic system was obvious. The addition in the colloidal and total dissolved fraction might be mainly related to particle-desorbed ligand, which was usually occurred in the middle salinity area. Dissolved organic carbon (DOC) and colloidal organic carbon (COC) concentration could not correlate with the behavior of Mn, Zn and Cd, which proved that the influence of inorganic ligands was higher than that of organic ligands or biological contributions, but the influence of salinity, dissolved oxygen (DO), pH and temperature should not be ignored. Two stations of Zn in autumn had contamination factor values >1, which indicates lower contaminant levels of Cu, Zn, Cd and Pb. Overall, the results herein should enrich existing research on the colloids, and on the other hand, enhance the understanding of the colloidal heterogeneity in kinetics, fate and geochemical features of Fe, Mn, Cu, Zn, Cd and Pb in the aquatic continuum, especially the river-sea mixing area.