Distribution, sources, contamination, and risks of toxic metals in Zijiang River, a typical tributary of the midstream of the Yangtze River in China

•Five toxic metal concentrations in surface waters and sediments were studied.•There were high concentrations of Zn and a low concentration of Cd in ZR.•The main chemical fractions of Cd and Pb were different from the other three metals.•Cd was the typical contamination element in ZR sediments.•Cd came from different sources than Cr, Cu, Pb, and Zn.