资源环境科技发展态势分析平台

Many studies use sedimentary biogenic silica (bSiO₂) stable isotopes (e.g. δ³⁰Si) as paleoproxies but neglect signals from other sedimentary reactive SiO₂ phases. We quantified δ³⁰Si for multiple reactive Si pools in coastal river‐plume sediments, revealing up to ‐5 ‰ difference between acid‐leachable vs. alkaline‐digestible amorphous SiO₂. Thus, previous studies have missed valuable information on early diagenetic products and, in cases where sediments were not cleaned, potentially biased bSiO₂ δ³⁰Si values. Acid‐leachable δ³⁰Si, i.e. from authigenic products, are either the result of multi‐step fractionation from a bSiO₂ source, or a ~2 ‰ fractionation (consistent with metal hydroxide formation) from slowly‐dissolving lithogenic SiO₂. This analysis also suggests that sedimentary diatom bSiO₂, which has increased regionally in the last half‐century, is the critical substrate of early authigenic Si precipitates. Regional eutrophication, which has stimulated sedimentary bSiO₂ accumulation, may have facilitated additional sequestration of both sedimentary Si and cations from early diagenetic products.