Suburban lakes, under the dual influence of agricultural expansion and accelerated urbanization, are facing increasingly severe heavy metal pollution, posing threats to aquatic ecosystems and surrounding human health. This study focuses on Shitang Lake, a typical suburban lake in the middle and lower reaches of the Yangtze River. Through sediment core sampling and chronological reconstruction, combined with grain size and elemental concentration analysis, the enrichment factor method and potential ecological risk index were employed to assess and reconstruct the pollution history of Cd, As, Pb, Co, Cu, Ni, Cr, and Zn over the past two centuries. Additionally, correlation analysis, cluster analysis, and positive matrix factorization were used to determine the sources of heavy metals and their relative contributions. The results show that most heavy metals (e.g., As, Pb, Co, Cu, Ni, Cr, and Zn) exhibited low pollution levels and slight ecological risks. However, Cd had significantly higher pollution levels and potential ecological risks, increasing from no pollution to moderate pollution starting in 1981, with strong ecological risk levels reached in 2004. Furthermore, since the mid-1970s, the comprehensive potential ecological risk index of the sed-iment has risen significantly, although the overall risk remains at a slight level. Source analysis revealed that before 1930, heavy metals in Shitang Lake sediments primarily originated from natural weathering (average contribution rate of 63.63%), while industrial and agricultural sources contributed 25.22% and 11.15%, respectively. From 1930 to 1974, the contribution of agricultural sources increased to 23.44%, while natural and industrial sources accounted for 51.72% and 24.84%, respectively. After 1975, the contributions of agricultural and industrial sources rose to 46.74% and 41.19%, becoming the main sources of pollution. This study provides a scientific basis for the prevention and control of heavy metal pollution in the Shitang Lake basin, offers a long-term perspective for the ecological protection of lakes in the middle and lower reaches of the Yangtze River, and serves as a theoretical reference and technical support for managing suburban lake pollution in other developing countries and regions under rapid urbanization.