Difference in attenuation among Mn, As, and Fe in riverbed sediments.

•First report of geochemical interactions in sediments of Chianan plain rivers.•No notable enrichment of As in bulk sediments or leachable fractions.•Mn accumulation is observed within top 1m in river sediments.•Iron and arsenic are attenuated earlier than manganese in the river sediments.•Arrest of arsenic depends on redox conditions along the entire flow pathway.