Anthropogenic Versus Natural Controls on Metals in Surface Sediments from the Zhejiang Island Sea Area: Evidence from Historical Baseline and PMF Analysis

Rapid industrialization, shipping, and petrochemical development have increased metal concentrations in coastal island ecosystems of eastern China. However, historical baseline information prior to large-scale coastal development remains scarce. This study investigated the concentrations and ecological risks of metals (Sr, Ni, V, Cr, Cu, Zn, Cd, Ba, Pb) in surface sediments collected in 2008 from the Zhejiang island sea areas, and used principal component analysis (PCA) and positive matrix factorization (PMF) to identify potential sources and estimate their contributions. Results showed that metals posed low to moderate ecological risks, with elevated risk levels occurring in Liuheng, Zhoushan, Daxie Island sea areas. Ni, Sr, Cu, Zn and Cd showed a certain degree of enrichment, whereas Cd presented the highest ecological risk. Three possible sources were identified: industrial activities (29.92%), combustion–lithological source (36.51%), and natural weathering (33.57%). Pb, Zn, Cu, and Cd appear to be primarily derived from industrial inputs, whereas V, Ni, and Cr showed a closer association with combustion–lithological sources. These results provided a historical geochemical baseline for this rapidly industrializing island sea areas in China and a reference framework for evaluating long-term environmental changes associated with coastal development, port expansion, and maritime activities in the East China Sea.