Integration of historic groundwater data into the Continent Scale Geochemistry initiative

The groundwater dataset developed by Angela Giblin comprises over 5000 samples across much of Australia and is a useful contribution to the mapping of groundwater chemistry across Australia (the ‘Continental Scale Hydrogeochemistry’ initiative). Sampling and analytical methodology used by Giblin differed from many other protocols. In particular, water samples were not filtered in the field, or indeed prior to analysis. However, given the number of samples and their potential utility, it would be advantageous to modify data from these samples so that they can be readily integrated with other studies. The combined data were initially sorted to ensure consistent detection limits. Data that did not pass a thorough QA/QC assessment were rejected. Correction, and where necessary removal, of data (owing to the analytical artefacts from solids contamination during analysis) was applied. The degree of contamination in bailed samples, and what data therefore to reject, is calculated using an algorithm developed and tested for Western Australian groundwaters. Geochemical changes between sampling and delayed analysis (days or weeks later) cannot be directly quantified. Other research predicted which elements should be most affected by this. This was further tested by comparing overlapping results from Giblin with more recent data from the same sites in Western Australia and Queensland. Results showed good agreement for salinities and major ions, and for the ratio indices (K:Na, etc.) determined from such data. Saturation Index calculations for sulfates gypsum, celestine and barite also closely matched between differing datasets. There was good agreement between datasets for F, HCO₃, Si, V, As, Mo, Ba and U, and moderate agreement for Li, Cr and Au. Weak agreement for pH meant that saturation indices for carbonate minerals such as calcite, dolomite, magnesite, siderite and rhodochrosite did not align, and there was very poor agreement for P, Co, Ni, Cu, Zn, Pb, Mn and Fe. However, in general, these comparisons indicate groundwater to be a robust geochemical medium. Based on this study, this modified data should now be readily usable and ‘seamlessly’ comparable with other datasets. Combining data, across varying sources if necessary, allows hydrogeochemistry to be used to map geology, alteration, prospectivity and geomorphological factors from mine scale to the size of Australia.

由安吉拉·吉布林（Angela Giblin）构建的地下水数据集覆盖澳大利亚绝大多数区域，包含逾5000个水样样本，为澳大利亚全域地下水化学填图工作（‘大陆尺度水文地球化学’（Continental Scale Hydrogeochemistry）计划）作出了宝贵贡献。吉布林采用的采样与分析流程与多数现有标准方案存在显著差异，具体表现为采集的水样未在野外或分析前进行过滤处理。不过，鉴于该数据集的样本规模与潜在应用价值，对其数据进行标准化处理以实现与其他研究数据集的便捷整合，将具备显著优势。整合后的数据集首先经过排序处理，以确保检测限保持统一；未通过严格质量保证与质量控制（Quality Assurance/Quality Control, QA/QC）评估的数据均被剔除。针对分析过程中固体污染引发的分析伪影，研究团队对相关数据开展了校正工作，必要时直接剔除异常数据。吊桶采集水样的污染程度以及需剔除的数据阈值，均采用针对西澳大利亚州地下水开发并验证的算法进行计算。采样与延迟分析（间隔数日乃至数周）之间的地球化学变化无法直接量化，已有相关研究预先推测了受此影响最为显著的元素类别。为验证上述推测，研究团队将吉布林数据集的重叠采样点结果，与西澳大利亚州及昆士兰州同点位的最新采样分析数据进行了比对。比对结果显示，在盐度、主要离子以及由此计算得到的比值指数（如K:Na等）方面，两组数据具有良好的一致性；硫酸盐类矿物（石膏（gypsum）、天青石（celestine）、重晶石（barite））的饱和指数（Saturation Index）计算结果在不同数据集间也表现出高度一致性。氟（F）、碳酸氢根（HCO₃⁻）、硅（Si）、钒（V）、砷（As）、钼（Mo）、钡（Ba）及铀（U）的检测结果在数据集间一致性良好；锂（Li）、铬（Cr）与金（Au）则表现出中等程度的一致性。pH值的一致性较弱，导致方解石（calcite）、白云石（dolomite）、菱镁矿（magnesite）、菱铁矿（siderite）及菱锰矿（rhodochrosite）等碳酸盐矿物的饱和指数无法匹配；磷（P）、钴（Co）、镍（Ni）、铜（Cu）、锌（Zn）、铅（Pb）、锰（Mn）及铁（Fe）的检测结果一致性则极差。但总体而言，上述比对结果表明地下水是一种稳定性较强的地球化学介质。基于本研究，经标准化处理后的数据集现已可便捷使用，并能与其他数据集实现‘无缝’比对。若有需要，整合多源数据后，水文地球化学方法可用于从矿山尺度直至澳大利亚全境的地质、蚀变、成矿潜力及地貌因子填图。