The Relationship between Physical and Chemical Characteristics and the Loss of Pisha Sandstones

Pisha Sandstones are widely distributed in the wind-water erosion intersection zone of northwestern China. In this region, serious soil and water loss has caused the riverbed of the lower Yellow River to become higher than the adjacent ground. Fifty-two samples of four types of Pisha Sandstones (purple, white, pink and gray) from different depths (0 m, 2 m and 10 m) were examined in laboratory experiments to gain a better understanding of the relationship between erosion and the loss of Pisha Sandstones as well as the mechanisms of erosion. All of the samples were analyzed using chemical methods, X-ray diffraction and scanning electron microscopy. The mineral and chemical compositions of Pisha Sandstones were found to be very different from those of ordinary soil and varies greatly during the whole erosion process (sampling depth). Wind-water erosion also affected the microstructure between the deep and surface Pisha Sandstones, ultimately causing gravitational erosion and the loss of Pisha Sandstones. Although not all of the observations could be explained, it was apparent that wind erosion, water erosion and gravitational erosion had both direct and indirect effects on the loss of Pisha Sandstones.