Potentially toxic elements contamination, risk and source analysis in sediments of Beiyun River supplied with reclaimed water, China

•Quantitatively identify the contribution of reclaimed water to toxic pollution.•The reclaimed water was as high as 67%, followed by agricultural and atmospheric.•The interactions of nutrients and cations influence the speciation of toxic elements.•The cations prevail in the exchangeable fraction, and communities in the reducible.•The synergistic effect dominate the oxidizable fraction, and the residual was stable.