Severe metal pollution due to industrial effluent releases has been documented in Jiulong River estuary which locates in Fujian Province, southern China. In the present study, time-series based water samplings were conducted during effluent discharge events to reveal the metal partitioning in the dissolved, particulate and colloidal phases. Different behaviors of metals in the dissolved fraction against salinity indicated different sources. Enhanced adsorption as well as formation of particulates resulted in elevated partitioning for Cu and Zn during the mixing process. Colloidal metals displayed positive correlations with dissolved or colloidal organic carbon, while constant colloidal partitioning suggested the excess binding capacity. Diffusive gradient in thin films (DGT) tec...[ Read more ]

Severe metal pollution due to industrial effluent releases has been documented in Jiulong River estuary which locates in Fujian Province, southern China. In the present study, time-series based water samplings were conducted during effluent discharge events to reveal the metal partitioning in the dissolved, particulate and colloidal phases. Different behaviors of metals in the dissolved fraction against salinity indicated different sources. Enhanced adsorption as well as formation of particulates resulted in elevated partitioning for Cu and Zn during the mixing process. Colloidal metals displayed positive correlations with dissolved or colloidal organic carbon, while constant colloidal partitioning suggested the excess binding capacity. Diffusive gradient in thin films (DGT) technique was then employed together with sediment cores to study the porewater dynamics of trace metals as well as benthic exchange fluxes. With the redox condition showing spatial and temporal variations, precipitation as sulfides and adsorption onto Mn/Fe (hydr)oxides were important in scavenging metals from porewaters in this estuarine area. Estimated fluxes at sediment-water interface indicated the overlying water as a major source for trace metals, whereas sediment could also be the source if surface remobilization dominated. In addition, taking advantage of flow field-flow fractionation (FlFFF) technique, colloidal size distribution of organic matter and metals was quantified. A dominance of dissolved metals in the 1-10 kDa fraction was demonstrated, which was regulated by terrestrial fulvic acid input. The small sized colloidal organic complexes were responsible for stabilizing trace metals. And variations in particle size fractions indicated different sources, fates and geochemical controls of the metals. Our results highlighted the impacts of both natural and anthropogenic processes on trace metal behaviors in the dynamic system. Results from these studies will further provide information on metal toxicity prediction, environmental impact assessment and pollution mitigation.