| 沉积物的粒度分布特征及砷的次生富集机制 |
| 投稿时间：2025-07-10 修订日期：2025-09-04 |
| 关键词:Borehole sediment, grain size, arsenic, enrichment, Baoding Plain |
| 基金项目:国家重点研发计划项目（2021YFA0715900），广东省基础与应用基础研究基金（2024A1515030174），河北省中央引导地方科技发展资金项目（246Z3601G），河北省自然科学基金杰青基金项目（D2023504030） |
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| 摘要: |
| Characteristics of sediment grain size distribution and mechanism of arsenic secondary enrichment |
| The differential distribution of sediment grain size is one of the key factors controlling the spatial heterogeneity of arsenic (As) distribution in sediments, and it is also the most sensitive indicator for reconstructing sedimentary environments and tracing the sources of As in sediments. Studying the particle size distribution of sediments and the distribution of As in different grain size fractions helps trace the source-sink relationships and release-migration processes of As. This study focused on 68 sediment samples from 7 boreholes in different sedimentary facies in the Baoding Plain. The grain size distribution and geochemical characteristics of the sediments were analyzed, and the controlling factors of the heterogeneous distribution of sediment chemical composition was clarified. The main carriers of As in the sediments were identified, and the sources of As in the sediments were elucidated by combining the As/Fe ratio. The results showed that the grain size distribution of the sediment samples was mainly controlled by lithology, with little difference in grain size distribution among sediments of the same lithology in different sedimentary facies. The heterogeneous distribution of sediment chemical composition was strongly controlled by hydrodynamic sorting. Fine fraction (grain size < 0.062 mm) in the fine-grained (clay to silty sand) and coarse-grained sediments (fine sand to gravel) accounted for 85±12% and 22±5%, respectively. The proportion of sediment fine fraction was significantly positively correlated with the contents of total organic carbon (TOC), total As, and the HCl-extractable As/Fe/Mn. The As content in the sediments ranged from 0.5 to 29.5 mg/kg, with an average of 7.6±4.7 mg/kg. The As in the sediments was primarily derived from the lithosphere, with the secondary formed Fe/Mn oxides as the main carriers. These mobilizable Fe/Mn oxides-loaded As pose a high risk of As release into groundwater. |
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