Chemostratigraphy and source of mercury in the Tropical Western Pacific over the past 600 kyr

Abstract

To characterize the geochemical records of mercury (Hg) in the western tropical Pacific in the last 600 ka, the total concentration of Hg, and its isotopic compositions in Hole B at Site U1486 from the Western Pacific Warm Pool (WPWP) were determined. Some marked positive values of Δ199Hg in this core, and some Δ200Hg also exhibit significant positive, which resultes from the photoreduction of the volcanic Hg deposits through the long-range atmospheric transportation. In addition, dual odd-even Hg isotopes (Δ199Hg and Δ200Hg) database was also compiled to account for quantitative contributions to potential Hg sources, including marine Hg source, atmospheric Hg deposition, volcanic Hg source, and terrigenous Hg inputs. This study presents that sedimentary Hg in the core Hole B at Site U1486 originates mainly from the marine Hg source with a mean of 64.13%, which is similar to the changes of paleo-productivity in the WPWP with a character of the glacial-interglacial variation. The contributions of atmospheric Hg deposition, volcanic Hg source, and terrigenous Hg inputs represented approximately 17.88%, 10.37%, and 7.87% of the total Hg burden in this core, respectively. During the last 100 ka, the contribution of volcanic Hg source has increased overall, suggesting the increase of volcanic activity. And the amount of atmospheric Hg deposition in this core also generally increased during this period, which was in resonance with the eolian dust in the western Pacific. Furthermore, terrigenous Hg inputs in this study could be related to intensity of monsoon precipitation with an overall increasing trend. In this study, volcanic activities in sediment cores from the western Pacific can provide an additional and independent tool for the precise dating and synchronization of paleoenvironmental changes in these climatically significant regions.