NOAA/WDS Paleoclimatology - South China Sea Isotope and Trace Metal Data Derived from Corals from 1877 to 1996 CE

Human activities have liberated substantial amounts of biologically active metals into oceans. However, identifying the sources and migration processes of these metals is challenging. Here we present first century-long records of concentrations and isotope compositions of Zn and Cu (d66Zn and d65Cu) in two corals from the northern South China Sea. The results show dramatic enrichment in coral Zn and Cu concentrations since the 1980s, which coincide with d66Zn and d65Cu increases. Coupled with concurrent land use/cover changes, we suggest that the enrichment trends of Cu and Zn in corals are best explained by human-induced rock weathering and soil erosion, which transferred isotopically heavy Zn and Cu fluxes into the coastal ocean. The metal releases due to land use/cover changes relative to direct anthropogenic sources could be even more significant in the future given that anthropogenic releases have been legally controlled and started to decline in recent decades.

人类活动已向海洋中释放了大量具有生物活性的金属元素。然而，甄别这类金属的来源与迁移过程仍颇具挑战。本研究报道了南海北部两处珊瑚中锌（Zn）与铜（Cu）浓度及其同位素组成（δ66Zn和δ65Cu）的首份长达一个世纪的记录。结果显示，自20世纪80年代以来，珊瑚体内的锌与铜浓度出现显著富集，且这一变化与δ66Zn和δ65Cu的升高同步。结合同期发生的土地利用/覆被变化，我们认为珊瑚体内铜与锌的富集趋势，最合理的解释是人类活动驱动的岩石风化与土壤侵蚀过程——该过程将同位素较重的锌与铜通量输送至近岸海域。鉴于近几十年来人为直接排放已通过法律管控并呈下降趋势，未来由土地利用/覆被变化引发的金属释放，其影响或较直接人为排放更为显著。