Characteristics of X-ray fluorescence scanning element of modern flood sediments in northern Shandong Province and its geological indicative significance

In August 2018, a typhoon-storm–induced flood disaster occurred in the Mihe River Basin in the northern Shandong Province of China. By investigating the flood inundated area, the sites were selected where fresh flood deposits in the lower reaches of the Mihe River and its tributary Danhe River were well preserved, and two sediment shallow drills MH1 and DH2 (with the length of 21.5 cm and 21 cm, respectively, including the lower section of modern soil) were obtained. The Avaatech X-ray fluorescence (XRF) spectroscopy core scanner made in the Netherlands was applied for element analysis, and the characteristics of modern flood sediment elements and its significance in paleoflood layers were discussed in combination with grain size index and other research results. Results show that Al, Ti, Si, Ca, and Fe elements presented similar fluctuation characteristics, and there was a significant positive correlation between them, and the signal intensity of these chemical elements peaked in fine-grained flood sediments sections. The signal intensity of Rb element was weakly correlated with particle size, and the change through the borehole was relatively stable but decreased at sedimentary interface, which might be related to the experimental deviation caused by cracks. The two elements of Sr and Zr were significantly positively correlated, and the signal intensity of them was low in the flood sediment layer. In addition, the Zr/Rb and Rb/Sr ratios were heavily correlated with grain size properties, and the influence of weathering and leaching on them is yet to be studied further. The Zr/Rb ratio was strongly positively correlated with the grain size, while the Rb/Sr ratio was significantly negatively correlated with the grain size, which is consistent with the conclusions obtained from the studies on other regional flood formations. The maximum Zr/Rb and minimum Rb/Sr values occurred in the clayey part of flood deposits, while the minimum Zr/Rb and maximum Rb/Sr values in the silty part of flood deposits with more coarser-grain composition. Therefore, Rb/Sr and Zr/Rb ratios can be used to indicate paleoflood deposits. This study provided a good reference for the identification of paleoflood deposit by using XRF technology.