Anthropogenic effects on sediment quality offshore southwestern Taiwan: Assessing the sediment core geochemical record

Slag material was dumped in two sites off southwestern Taiwan by the China Steel Corporation during 1984-1995. By geochemically analyzing four sediment cores, we investigated the impact of slag on the sediment chemistry. Elemental profiles from the dumping sites show a strong depletion in detrital elements and enrichment in alkaline and redox-sensitive elements, especially for the top ∼20 cm of sediments. The relative enrichment factor (EFrel) exhibits wider range for Ca (0.73-13.33), Fe (0.88-3.03), Mg (0.94-9.58) and Mn (1.22-33.30) due to contamination of sediments by slag. Sediment weathering indicators also show a distinct change with lower values in sediments influenced by dumping due to Ca and Sr addition. Higher EFrel for As, Cd and Pb in the top sections of the cores indicate an additional modern/industrial input of these elements since ∼1950. Our study suggests that slag dumping may have a localized effect on biogeochemical processes by inducing the diagenetic remobilization of certain elements.