Estimation of Biogenic Silica Concentrations Using Scanning XRF: Insights from Studies of Lake Malawi Sediments
Estimation of Biogenic Silica Concentrations Using Scanning XRF: Insights from Studies of Lake Malawi Sediments
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DOI：
10.1007/978-94-017-9849-5_9
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发表时间：
2015-01-01
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影响因子：
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通讯作者：
Brown, Erik T.
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文献类型：
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作者：
Brown, Erik T.
通过对马拉维湖沉积岩心在一系列环境条件下的25KYR沉积数据集的比较，评估了使用硅和钛的XRF测量来估计湖泊沉积物中生物成因二氧化硅含量的情况。这种方法特别有吸引力，因为它将这些分析所需的劳动力减少了数百倍。硅既可以存在于碎屑相中，也可以存在于生物相中，而且这些相相互稀释，因此建立了一个简单的关系来校准XRF结果以估计生物硅的百分比。这需要选择合适的一个或多个元素作为碎屑沉积相的代表。使用来自短岩心(类似于35厘米)的成对的%BSI和XRF硅和钛数据来开发校准标尺。这种校准被应用于25,000年来的记录，以从XRF结果中估计%BSI。计算的BSI记录与测量的%BSI的比较表明，由于化学和物理特性的变化，校准参数可能会随着沉积物深度的变化而变化。对硅的XRF扫描计数时间进行评估；通常应将这些时间设置为允许>；500计数。
The use of XRF measurements of Si and Ti to estimate biogenic silica contents of lake sediment is evaluated by comparison of datasets from Lake Malawi sediment cores spanning 25 kyr of deposition under a range of environmental conditions. This approach is particularly attractive as it offers a several hundred-fold reduction in labor required for these analyses. Silicon can be present in both clastic and biogenic phases, and these phases dilute one another, so a simple relationship to calibrate XRF results to estimate percent biogenic silica was developed. This requires selection of an appropriate element (or elements) to use as a proxy for clastic sedimentary phases. Paired %BSi and XRF Si and Ti data from a short core (similar to 35 cm) were used to develop a calibration scale. This calibration was applied to a 25,000-year record to estimate % BSi from XRF results. Comparison of this calculated BSi record with measured %BSi indicates that calibration parameters can vary with depth in sediment due to changes in chemical and physical characteristics. XRF scanning counting times for Si are evaluated; typically these should be set to allow > 500 counts.