Natural Enrichment Patterns and Mechanisms of Heavy Metals in Mid-Holocene Soils of the Southern Loess Plateau

Our purpose is to reveal the natural enrichment patterns of metals in the Holocene soils of the Southern Loess Plateau. Element and mineral contents and particle size were measured using X-ray fluorescence spectrometry, X-ray diffractometry, and laser diffraction, respectively. The study area has a subtropical climate with average annual precipitation and temperature of 800 mm and 15.3 °C during the mid-Holocene. At this time the summer monsoon and non-summer monsoon supplied 440 mm and 360 mm of precipitation, respectively. Soil moisture was in a positive balance and persistent gravity water occurred with a moisture content > 20