<p>Heavy metals and Metalloid concentrations in urban lake sediments serve as critical indicators for assessing anthropogenic pollution. This study presented a comprehensive assessment of sediment contamination and applied a PCA-APCS-MLR receptor model to quantitatively apportion the sources of heavy metals and metalloid in the sediments of Qianhu Lake, a typical urban lake under significant anthropogenic pressure. The results showed that the mean concentrations of all target heavy metals and metalloid exceeded their background values, with spatial distributions reflecting pronounced anthropogenic influence. The Geo-accumulation Index (<i>I</i>_geo) revealed moderate Cd contamination, uncontaminated to moderate Zn and As contamination, and no contamination for the other heavy metals. The comprehensive potential ecological risk (<i>RI</i>) assessment of heavy metals and metalloid demonstrated a considerable ecological risk level. Multivariate statistical and APCS-MLR analyses indicated that Cr, Cu, Zn, As, and Pb were likely associated with traffic-related sources, Ni was primarily linked to natural sources but with high model uncertainty, and Cd was potentially associated with agricultural activities. These findings highlighted the significant ecological impact of traffic emissions and confirmed the APCS-MLR model as an effective tool for informing pollution control strategies in urban aquatic environments.</p>