X-ray Fluorescence (XRF) core scanning from sediment core of Lake Alchichica in Mexico@en

The geochemical data were measured from a 57-cm-long sediment core retrieved from Lake Alchichica (19° 24' 38 N, 97° 24' 14 W, 2322 masl) at a water depth of ~ 60 m using a Uwitec® coring device equipped with a 9-cm coring tube. Geochemical compositions of the sediment core were analyzed using an ITRAX X-ray fluorescence core scanner (CS-XRF) at the INRS Centre Eau Terre Environnement in Canada. The analysis produced the ratio of Compton (incoherent) to Rayleigh (coherent) scattering (Inc/Coh), which can serve as an indicator of sediment organic content. The scans were measured at 2 mm intervals using 20 kV with a current of 10 mA and a dwell time of 20 seconds. To reduce matrix effects and address the closed-sum issue, elemental intensities (measured in counts per second) were transformed using the centered log-ratio (clr) method. For better visualization, all elemental data were subjected to min-max normalization.本数据集的地球化学数据采自阿尔奇奇卡湖（Lake Alchichica，北纬19°24′38″、西经97°24′14″，海拔2322米）水深约60米的点位所钻取的57厘米长沉积物岩芯，该岩芯通过配备9厘米取芯管的Uwitec®取芯装置获取。沉积物岩芯的地球化学组成在加拿大INRS水-土-环境研究中心（Centre Eau Terre Environnement）采用ITRAX X射线荧光岩芯扫描仪（CS-XRF）完成分析。本次分析得到康普顿散射（Compton incoherent scattering）与瑞利散射（Rayleigh coherent scattering）的比值（Inc/Coh），该比值可作为沉积物有机质含量的指示指标。扫描测试以2毫米的间隔开展，测试参数设置为20千伏、10毫安电流，驻留时长20秒。为降低基体效应并解决封闭求和问题，以每秒计数（counts per second）为单位的元素强度采用中心化对数比（centered log-ratio, clr）方法进行转换。为获得更优的可视化效果，所有元素数据均经过最小-最大归一化（min-max normalization）处理。