Nitrate(NO3-)is known to be actively involved in the processes of mineralization and heavy metal transformation;however,it is unclear whether and how it affects the bioavailability of antimony(Sb)in paddy soils and subsequent Sb accumulation in rice.Here,the effects of NO3-on Sb transformation in soil-rice system were investigated with pot experiments over the entire growth period.Results demonstrated that NO3-reduced Sb accumulation in brown rice by 15.6％compared to that in the control.After amendment with NO3-,the Sb content in rice plants increased initially and then gradually decreased(in roots by 46.1％).During the first 15 days,the soil pH increased,the oxidation of Sb(III)and sulfides was pro-moted,but the reduction of iron oxide minerals was inhibited,resulting in the release of ad-sorbed and organic-bound Sb from soil.The microbial arsenite-oxidizing marker gene aoxB played an important role in Sb(III)oxidation.From days 15 to 45,after NO3-was partially consumed,the soil pH decreased,and the reductive dissolution of Fe(III)-bearing minerals was enhanced;consequently,iron oxide-bound Sb was transformed into adsorbed and dis-solved Sb species.After day 45,NO3-was completely reduced,Sb(V)was evidently reduced to Sb(III),and green rust was generated gradually.Thus,the available Sb decreased due to its enhanced affinity for iron oxides.Moreover,NO3-inhibited the reductive dissolution of iron minerals,which ultimately caused low Sb availability.Therefore,NO3-can chemically and biologically reduce the Sb availability in paddy soils and alleviate Sb accumulation in rice.This study provides a potential strategy for decreasing Sb accumulation in rice in the Sb-contaminated sites.