# Application of Corrected Methods for High-Resolution XRF Core Scanning Elements in Lake Sediments
## Materials and Analytical Methods
### Sampling and Analyses  
The split sections of cores FXH-B2 and LGH2 were flattened and then covered by a thin (4 \(\upmu\)m) Ultralene film to avoid water film formation and contamination of the measurement prism of the core scanner. Geochemical measurements were undertaken at 5-mm intervals using the Avaatech XRF core scanner (Avaatech B.V., Nederland; [[http://www.avaatech.com/](http://www.avaatech.com/)]([http://www.avaatech.com/](http://www.avaatech.com/))), located at Yunnan Normal University, in which a rhodium anode X-ray tube was used as the X-ray source. Separate scans at three voltages were carried out: (i) at 0.75 mA for 10 s using no filter, and tube voltages set to 10 kV (for Al, Si, K, Ca, Ti, Mn, Fe); (ii) at 0.5 mA for 20 s using a Pd-thin filter, with the tube voltage set to 30 kV (for Cu, Zn, Rb, Sr, Zr, Pb); and (iii) at 0.75 mA for 30 s using a Cu filter, with the tube voltage set to 50 kV (for Ba). The X-ray illumination area was set at 0.5 cm in the down-core direction and 0.2 cm in the cross-core direction for core FXH-B2, and 0.2 cm in the down-core direction and 1.2 cm in the cross-core direction for core LGH2. All scans were run down the center of the split core.  
In order to calibrate the XRF-scan intensities, 74 samples at 4-cm increments in core FXH-B2 and 26 samples at 60-cm increments in core LGH2 were selected for elemental proportions measurements. Prior to the measurements, samples were freeze-dried and compressed into powder pellets. The element proportions were determined by conventional XRF methods using a PANalytical Axios Advanced PW4400 X-ray Fluorescence (WD-XRF; Malvern. Analytical Ltd., Malvern. Worcestershire, U.K.; [[https://www.malvern.analytical.com/en/products/product-range/axios-fast](https://www.malvern.analytical.com/en/products/product-range/axios-fast)]([https://www.malvern.analytical.com/en/products/product-range/axios-fast](https://www.malvern.analytical.com/en/products/product-range/axios-fast))) spectroscope at the Institute of Earth Environment, Chinese Academy of Sciences. The analytical uncertainties are estimated to be 1-2% for all major metals, and the relative standard deviation is \(<\)5% for the trace metals.  
Sediment samples from core LGH2 were obtained at 1-cm intervals for determination of water content and grain-size distributions. Water content was measured by weighting the samples prior to and after freeze-drying. Samples for grain-size analysis were pretreated with 10% H\({}_{2}\)O\({}_{2}\) to remove organic matter and then washed with 10% HCl to remove carbonates. Finally, they were rinsed with deionized water and dispersed with 10 mL of 0.05 mol L\({}^{-1}\) (NaPO\({}_{3}\))\({}_{6}\) in an ultrasonic vibrator for 10 min. Grain-size distributions between 0.02 \(\upmu\)m and 2000 \(\upmu\)m were measured using a Malvern Mastersizer  
Figure 1: Geological maps with the locations of the cores used in this study. (**a**) Core FXH-B2 was retrieved from Lake Fuxian, and (**b**) core LGH2 was retrieved from Lake Lugu. Source: the Bureau of Geology and Mineral Resources of Yunnan Province (1982).  
2000 laser grain-size analyzer (Malvern Panalytical Ltd., Malvern, Worcestershire, U.K.; [[https://www.malvernanalytical.com/en/products/product-range/mastersizer-range/mastersizer-2000](https://www.malvernanalytical.com/en/products/product-range/mastersizer-range/mastersizer-2000)]([https://www.malvernanalytical.com/en/products/product-range/mastersizer-range/mastersizer-2000](https://www.malvernanalytical.com/en/products/product-range/mastersizer-range/mastersizer-2000))) and assigned to 100 size classes.