Abstract
The Earth’s surface is a complex system involving mutual interactions of its many components, including mountains, rivers, forests, farmlands, lakes and grasses. The interaction and mutual feedback of chemical elements in Earth's surface layer can drive changes in chemical elemental distribution patterns. In this study, we evaluated the mechanisms and interactions driving the distribution patterns of macroelements, probiotics, halogens and heavy metals in soils in Southwest China, based on a systematic geochemical land-quality survey at a scale of 1:250000. The results showed that the parent material determines the natural state of chemical elements in land resources. Epigenetic geochemical dynamics reshapes the distribution patterns of chemical elements in top soil; biogeochemical processes drive the evolutionary trends of land quality; and human activities, such as mining, disrupt the natural evolution of chemical elemental distribution patterns. The establishment of an epigenetic geochemical dynamics theory allows the construction of a framework for understanding the Earth's surface layer and promoting technological innovations for the comprehensive geochemical investigation of land resources.
Highlights
The Earth’s surface is a complex system involving mutual interactions of its many components, including mountains, rivers, forests, farmlands, lakes and grasses
The Cl distribution pattern showed that it had significantly enriched the top soils on both sides of the Yangtze River and in the Pd-Zn-Ag deposit in the Leshan – Yibin – Luzhou area (Fig. 16), consistent with extensive distribution of Cl rich carbonate rocks in the study area
This indicates that the spatial distributions of Cu, Ni, Co, Cr, Ti and V are mainly controlled by the Emeishan basalt and carbonate rock parent materials (Figs. 26–31)
Summary
During complex physical and chemical weathering processes, soil parent materials can form in-situ residual soil. Emeishan basalt and carbonate rocks are the two most common soil parent materials in the study area. Main weathering and soil formation processes of basalt and carbonate rocks. During weathering and soil formation, especially under the action of carbonic acid, Ca2+, Mg2+ and Fe2+ ions are first separated to form bicarbonates during decomposition, dissolved in water and carried away. During soil formation from carbonate parent materials, approximately 96 % of Ca and 52 % of Mg were lost, whereas Fe, Al, Si, K and Na were enriched by 164, 5.5, 4, 16 and 2.9 times, respectively (Table 2). The deep and top soils above the basalt and limestone parent materials were considerably enriched in Fe and Al, indicating significant control by soil parent materials over the distributions
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