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Contaminated legacy sediments contribute to modern pollution loadings, particularly trace metals. These contributions are challenging to quantify as metal histories reconstructed from sediment records cannot be easily divided into legacy and concurrent contamination. In particular, the contribution from re-mobilization and delivery of legacy metals stored in catchment soil, colluvial, and fluvial environments are rarely considered or quantified when interpreting sediment records. Here, extended records of metals accumulation for a set of three lakes in Yunnan, China are compared with endmember chemistries using Monte Carlo-Markov Chain mixing models to help identify source contributions to the sediments. This approach allows attribution of metals transported by atmospheric and fluvial mechanisms in a region with a history of mining and metallurgy spanning millennia. These analyses reveal distinct source mixtures and demonstrate the sensitivity of lake records to basin sediment dynamics. In particular, substantial proportions of elevated metal concentrations in these lake systems seem to arise from soil contributions more than from atmospheric deposition of smelting emissions. The largest soil contributions seem to be in Erhai, a lake with erosion prone soils closely "connected" to the lake. Moreover, these invesigations illustrate the potential for mixing approaches to accommodate and clarify uncertainties in metal source and extraction as differences in extraction efficiency can be incorporated into source uncertainty estimates. Ultimately, these approaches emphasize the need to account for fluvial metal transport in interpretation of sediment histories., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Geochemical measurements on well-dated sediment cores from Lake Er (Erhai) are used to determine the timing of changes in metal concentrations over 4500 years in Yunnan, a borderland region in southwestern China noted for rich mineral deposits but with inadequately documented metallurgical history. Our findings add new insight into the impacts and environmental legacy of human exploitation of metal resources in Yunnan history. We observe an increase in copper at 1500 BC resulting from atmospheric emissions associated with metallurgy. These data clarify the chronological issues related to links between the onset of Yunnan metallurgy and the advent of bronze technology in adjacent Southeast Asia, subjects that have been debated for nearly half a century. We also observe an increase from 1100 to 1300 AD in a number of heavy metals including lead, silver, zinc, and cadmium from atmospheric emissions associated with silver smelting. Culminating during the rule of the Mongols, known as the Yuan Dynasty (1271-1368 AD), these metal concentrations approach levels three to four times higher than those from industrialized mining activity occurring within the catchment today. Notably, the concentrations of lead approach levels at which harmful effects may be observed in aquatic organisms. The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern day sediment quality. We demonstrate that historic metallurgical production in Yunnan can cause substantial impacts on the sediment quality of lake systems, similar to other paleolimnological findings around the globe.