Distribution, Risk Assessment, and Sources of Trace Metals in Surface Sediments from the Sea Area of Macao, South China

Due to rapid economic development in the Pearl River Delta, South China, trace metals pose a significant threat to the coastal ecosystems. In this study, we investigated the spatial distribution, contamination status, ecological risk, and possible sources of trace metals in 150 surface sediment samples from the Macao sea area. The results showed that concentrations of Ag, Pb, Cu, Zn, and Cd were highest in the Inner Harbour, whereas Cr, Co, As, and Ni were mainly accumulated in the downstream area of the Maliuzhou Waterway and the eastern area of Macao International Airport. Sediment grain composition, organic matter, total phosphorus, and hydrological regime were key factors influencing the spatial distribution patterns of trace metals. According to the environmental contamination indices of the enrichment factor, geo-accumulation index, and contamination factor, moderate contamination of trace metals occurs in the study area, while Ag and Pb contribute significantly to the contamination. Based on the potential ecological risk index, trace metals in surface sediments pose a low ecological risk. Correlation analysis and principal component analysis indicated that Cr, Co, Ni, and As were mainly derived from natural sources, whereas Ag, Pb, Cu, Zn, and Cd were mainly associated with anthropogenic sources.