Distribution of heavy metals and radionuclides in the sediments and their environmental impacts in Nansha Sea area, South China Sea.

Activity concentrations of radionuclides (U, Ra, Th, and K) in the sediments of eight sampling stations and heavy metal concentrations (Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) in the sediments of two long cores from Nansha Sea area were obtained by high-purity germanium spectroscopy and inductively coupled plasma atomic emission spectrometry. In a correlation analysis between the radionuclides and heavy metals, Th was positively correlated with As and Pb. U demonstrated a significant positive correlation with Co, Ni, Cu, Zn, and Cd. K was positively correlated with Co, Ni, and Cu. The geo-accumulation index, pollution load index, potential ecological risk index, and multivariate statistical techniques were used to evaluate the pollution degree and possible sources of heavy metals in the sediments. An ecological risk assessment suggested that Cr, Co, Ni, Cu, Zn, Cd, and Pb were primarily derived from natural processes, while the source of As may be related to natural processes and human activities.