Influence of submarine hydrothermalism on sulfur and metal accumulation in surface sediments in the Kueishantao venting field off northeastern Taiwan

Abstract

The distribution and accumulation of sulfur and trace metals in surface sediments in the submarine hydrothermal field of Kueishantao islet off northeastern Taiwan were investigated. The discharge of fluid from yellow vents and certain white vents had high concentrations of dissolved hydrogen sulfide (280–3742 μM) and trace metals (i.e. Al: 4.40–210 μM; Fe: 0.024–17.6 mM; Mn: 0.0002–12.8 mM; Ni: 4.82–54.9 nM; Zn: 0.002–2.32 μM) which resulted in sediments with varying sulfur and metal contents, and might have an impact on the benthic ecosystem of the venting field. The total concentration of trace metals in surface sediments was lower at stations close to vents (Fe: 440–1233 mg kg− 1; Mn: 2.31–35.7 mg kg− 1; Zn: 1.69–12.3 mg kg− 1) than at those located more distantly (Fe:9.30–49.29 g kg− 1; Mn: 318–1489 mg kg− 1; Zn: 43.6–226 mg kg− 1) largely because of the effects of coarse particles, high total sulfur (TS), and low total organic carbon. The Al/(Al + Fe + Mn) ratio, which is an indicator of hydrothermalism, increased with distance from the hydrothermal vents and was inversely related to the variations in TS content and the Fe/Al ratio. Additionally, the Fe/Mn ratio decreased significantly with distance from the hydrothermal vents, as a result of the preferential deposition of Fe over Mn in sediments with distance. Such distribution patterns and the close relationships between Fe and other trace metals clearly reflect the natural processes as well as fates of sulfur and trace metals after discharge from hydrothermal vents. Enrichment factors of the trace metals were elevated (> 1) at those stations influenced significantly by hydrothermal activity. Factor analyses for geochemical parameters and sampling locations strongly indicate the influence of hydrothermal activity on sulfur and metal distribution and accumulation in the study area.