Sedimentary record of silver in recent times from Chaohu Lake, East China, and its implications

High-resolution record of silver (Ag) in lakes is indispensable for examining human impact on its deposition, and for understanding its geochemical cycling in the environment. However, such studies are extremely insufficient. In this study, a piston core (CHY) collected from the Chaohu Lake, east China, was analyzed to examine sedimentary history of Ag. A record of this metal in recent times was further reconstructed. The record displays significant changes. Prior to the 1960s, Ag concentrations stabilized at a relatively low level (0.06 ppm), but they increased rapidly (0.26 ppm) afterward. The average concentration of Ag in the profile is 0.13 ppm, higher than its crustal abundance. Enrichment factor (EF) analysis further reveals that Chaohu Lake was not polluted with Ag until the 1960s, but the pollution level increases rapidly since then, and now shows a moderate pollution. Sedimentary record of Ag closely follows population changes within the watershed, suggesting that human activity is possibly the ultimate driving factor for its distribution. Intensified industrial activities associated with population expansion may release silver to inflow rivers and Chaohu Lake, resulting in its ultimate settling down to the sediments. Sedimentary flux of Ag varies significantly between 42.9 and 392.0 μg/(m²·year), with an average of 236.8 μg/(m²·year). This is so far as we know the first high-resolution record of Ag and its flux in east China, providing new perspective for better understanding the distribution and transport of Ag in lake environment.