Methodology of Tracking Source of Cadmium Anomalies and Their Quantitative Estimation in the Yangtze River Basin

Cd anomalies are spreading along almost the whole of the Yangtze River Basin, discovered by the multi-purpose geochemical investigation being carried out in China, have been one of the major ecological environmental issues. By taking the Anhui section of the Yangtze River Basin as its object, a systematical study on the methodology of the source tracking and quantitative estimation of the Cd anomalies has been carried out in the article. By determining the contents of elements in suspended matters in the Anhui section of the trunk stream and main tributaries of Yangtze River, it is shown that the suspended matters are the main carriers of heavy metals for long distance migrations; the concentration of Cd in the suspended matters is considerably higher than those of other heavy metals, and this may be the main reason for forming the Cd anomalies spreading along the whole Yangtze River Basin. Also, the tributaries of Yangtze River have significant influences on the variations of heavy metal contents in the suspended matters in its trunk stream. The quantitative computation of output flow of heavy metals for the trunk stream and main tributaries for the Anhui section of Yangtze River shows that the largest output flow of heavy metals is from Qiupu River, with roughly 4.45 t of Cd deposited in soils along either bank of the Anhui section of Yangtze River. Results of source tracking of Cd anomalies along Shun'an River by detailed survey of suspended matters, soil survey on a scale of 1:50,000, and rock survey indicate that endogenetic mineral deposits, especially Pb-Zn deposits, are the largest suppliers of Cd in the suspended matters. With techniques of layer sampling of sediments on alluvial beds and isotopic age-determination, the geochemical history of the sedimentation of Cd and other heavy metals and thus resulting pollutions have been primarily reconstructed, with prediction and early warning of the evolution of anomalies of Cd and other heavy metals.