Study on Migration and Enrichment Characteristics and Risk Assessment of Heavy Metals (Metalloids) in Rock - Parent Material - Soil——Taking typical rock-soil profiles in Three Gorges Reservoir area as examples

Four typical rock-soil profiles in the key ecological area of the Yangtze River (Chongqing section) were selected to explore the migration and enrichment characteristics of heavy metal elements ( Cu, Pb, Zn, Cr, Ni, Cd, As, Hg ) in the process of weathering and soil formation, and to explore the typical health risks in this area. The results show that the soil in the Jurassic clastic rock weathering profile in the study area is weakly alkaline, and the soil in the Permian carbonate rock weathering profile is acidic and weakly acidic. The content of various elements in the Permian carbonate rock parent material soil is basically higher than that in the Jurassic clastic rock parent material soil, and the average content of eight heavy metal elements does not exceed the control value; Various elements in the same soil profile have similar migration and enrichment characteristics. The migration and enrichment of various elements are affected by multiple factors such as the characteristics of the parent rock, leaching and deposition, clay mineral adsorption, atmospheric dustfall, elemental geochemical properties and pH.;The Nemero comprehensive pollution index shows that the TP0301 and TP0302 profiles in the study area are in good condition and pollution-free. The TP0501 and TP0502 profiles were slightly polluted due to the light exceeding of Cd and As ; Health risk assessment showed that children were more susceptible to heavy metal elements than adults. Hand-mouth ingestion was the main way of soil pollution elements causing non-carcinogenic health risks. The carcinogenic risk in the study area was low, but the carcinogenic health risk index CR of Cr was close to 1 × 10⁻⁶, which should be concerned. According to the comprehensive analysis and evaluation, the soil in the study area is in good condition as a whole, but there is slight pollution in the weathering soil profile of Permian carbonate rocks. Considering the life and health safety of residents in the study area, it is suggested to strengthen the monitoring of metalloid As and heavy metal Cr in the weathering profile of Permian carbonate rocks. However, the carcinogenic health risk index of Cr is close to 1 × 10⁻⁶, which should be concerned.