Migration and Enrichment of Heavy Metals During the Weathering Pedogenesis of Rocks in the Ningzhen ore cluster area

Weathering pedogenesis of rocks can release heavy metals to soil, and further accumulation of heavy metals in soil may exceed the national standard for safety soils. To understand the source, release, transport, and enrichment of heavy metals in the process of weathering pedogenesis, we systematically studied the migration and enrichment of heavy metals during rock weathering in the representative weathering pedogenesis profiles (carbonate rock, magmatic rock, and clastic rock) of the Ningzhen ore cluster area using a combination of field survey, rock and mineral identification, geochemical analysis and statistical analysis. The results showed that the soil of each profile has a provenance inheritance relationship with its underlying parent rock. The heavy metals in the soil of magmatic rock and clastic rock profiles showed similar chemical composition and content characteristics to the inherited parent rock. In contrast, the carbonate rock profile showed the geochemical characteristics of a low content of heavy metals in rocks and a high content in soil. In particular, the contents of Cd and As even exceeded the risk intervention values for soil contamination of agricultural land. It was revealed that the migration of heavy metals in weathering profiles of rocks under the same climatic conditions is controlled by multiple factors, such as rock lithology, the degree of chemical weathering of the profiles, and the occurrence state of heavy metals in rocks. The migration ability of heavy metals in magmatic rock and clastic rock profiles is proportional to the degree of chemical weathering, while the migration ability of heavy metals in carbonate rock profiles is inversely proportional to the degree of chemical weathering, leading to a higher potential for enrichment of heavy metals. Based on the above research, the release and migration pattern of heavy metals in the processes of rock weathering and soil formation was established.