Risk control and assessment of sulfide-rich sediment remediation by controlled-release calcium nitrate

•The risk of nitrate escape was restricted by the controlled-release scheme.•The use of controlled-release pellets achieved the goal of sediment remediation.•Subsequent pollutants released along with the increase of sediment pores.•The application of the pellets at depth reduced the subsequent risks.•Increased plant germination reflected the recovery of sediment ecological functions.