Sources and historical records of metal(loid)s in river sediments from an agricultural tributary of Tuojiang river: Evidence from geochemical analyses and Pb isotope

Clarifying the sources and historical variation of metal(loid)s in agricultural river sediments is vital for watershed contamination control and environmental improvements. In this study, a systematical geochemical investigation of Pb isotopic characteristics and the spatial-temporal distribution of metal(loid)s abundances was conducted to delineate the origins of metal(loid)s (Cd, Zn, Cu, Pb, Cr, and As) in sediments from an agricultural river, Sichuan Province, Southwest China. The results showed significant enrichment of Cd and Zn in the whole watershed, with substantial anthropogenic contributions of 86.1% and 63.1% for the surface sediments, and 79.1% and 67.9% for the core sediments, respectively. As was mainly derived from natural sources. Cu, Cr, and Pb were originated from the mixing sources of natural and anthropogenic processes. The anthropogenic origin of Cd, Zn, and Cu in the watershed was closely correlated with agricultural activities. The profile of EF-Cd and EF-Zn displayed an increasing trend from the 1960s-1990s, and then kept a high value, which was consistent with the development of national agricultural activities. Pb isotopic signatures suggested multiple sources of the anthropogenic Pb contamination, including industrial/sewage discharge, coal combustion, and vehicle exhaust. The average anthropogenic 206Pb/207Pb ratio (1.1585) approximated that of local aerosols (1.1660), suggesting aerosol deposition was a crucial pathway of anthropogenic Pb input to sediment. Furthermore, the anthropogenic Pb percentages (mean of 52.3 +/- 10.3%) from the EF approach were in line with that from the Pb isotopic method (mean of 45.5 +/- 13.3%) for sediments under intense anthropogenic impacts.