低密度地球化学填图的重现性是开展全球尺度地球化学填图的核心科学问题之一,长期以来备受地球化学填图界的密切关注。但缺乏对低密度地球化学填图重现性定量评价的有效手段,对重现性的定量化认识一直相当薄弱。本研究利用中国地球化学基准计划(CGB)和区域化探扫面计划(RGNR)两种尺度钴元素数据,基于1 546个典型汇水域局部空间相关系数分析,对低密度地球化学填图重现性进行定量评价,探讨其空间分布特征与影响因素。研究结果表明,全国尺度上,相关性受到钴含量和地球化学景观条件的共同影响。局部尺度上,受到差异剥蚀影响。贫钴背景下(沉积物钴含量<13 μg/g),填图重现性指数R在0.4附近浮动,而富钴背景下(沉积物钴含量>13 μg/g),填图重现性指数R从0.4增加至0.6以上。岩溶区、热带雨林区和半干旱中低山丘陵景观区重现性指数R高达0.58~0.74。冲积平原和森林沼泽景观区重现性指数R小于0.32。本研究为低密度地球化学填图方法研究提供了定量评价指标,总体而言,低密度地球化学填图采样方法能较好地重现元素分布特征,在全球尺度地球化学填图中具有良好的应用前景。

Robustness is a fundamental scientific concern in low-density geochemical mapping, which has long garnered close attention from mapping researchers. However, quantitative understanding of robustness has been lacking due to the lack of effective quantitative assessment methods. In this study, using cobalt element data from two low-density mapping sources—the China Geochemical Baselines project (CGB) and the Regional Geochemical National Reconnaissance project (RGNR)—robustness is quantitatively assessed based on 1546 representative catchments through the utilization of local spatial correlation coefficients; the spatial distribution features and influencing factors are also discussed. On a national scale, robustness was influenced by sediment cobalt (Co) content and geochemical landscape conditions; on a local scale, it was affected by differential erosion in cobalt-rich and Co-poor source areas. In Co-poor environments (sediment Co<13 μg/g) the robustness index (R) value fluctuated around 0.4, while in Co-rich environments (sediment Co>13 μg/g) it increased from 0.4 to above 0.6 with rising Co content. Regions such as karst terrains, tropical rainforests, and semi-arid low hills had R values as high as 0.58 to 0.74, whereas alluvial plains and forested swamp regions had R values below 0.32. This study provides a reference for quantitative evaluaton of low-density mapping, deomonstrating that low-density geochemical mapping has good robustness and promising prospect in the global-scale geochemical mapping.