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Efforts to study how human activities have influenced the environment since the end of the Roman period to present day are lacking for North Central Europe. Here, we present new lead (Pb) isotope data determined from two sediment cores collected from ancient lakes spanning the last 1500 years, located in the Kuyavian-Pomeranian Voivodeship, Poland. Study sites at Radzyn Chelminski and Rywald were used to differentiate Pb sources. Radzyn Chelminski is located in the vicinity of a late Medieval Teutonic Order castle and town, while Rywald is situated within a relatively pristine area until the 19th century when it became used for agricultural purpose. Core samples were analyzed for Pb concentration and isotopes (Pb-206, Pb-207, Pb-208). Bayesian modeling was used to isolate the anthropogenic signal at each site over time.

For both sites, Pb enrichment factors relative to titanium (Ti) and upper continental crust values range from 13 to 159. Lead isotopic ratios range from background, pre-anthropogenic local values (Pb-206/Pb-207 = 1.31 +/- 0.03 parts per thousand, Pb-208/Pb-206 = 1.97 +/- 0.04 parts per thousand) to anthropogenic values (SW Poland coal, ore, slag Pb-206/Pb-207 = 1.17 +/- 0.01 parts per thousand, Pb-208/Pb-206 = 2.09 +/- 0.01 parts per thousand). Modeled anthropogenic contribution varies greatly over time, ranging from 14 to 100%. At Radzyn Chelminski, modeled anthropogenic Pb contribution and measured Pb concentration follow similar trends. However, at Rywald, from around A.D. 1000 to 1400 CE these profiles diverge significantly. Our new insights highlight different sources of Pb from the 12th century to present day: (1) short range agricultural activities from the town, and (2) long range mining activities. Additionally, prior to the 12th century, our data suggest continental anthropogenic activity possibly favored by a warmer climate. (C) 2019 Elsevier B.V. All rights reserved.