The redox-sensitive elements,such as iron,manganese,sulfur,phosphorus,and arsenic,shift their speciation every millimeter(mm)across the soil-water interface in the flooded soil environments.Monitoring of element speciation at this high-resolution(HR)within the SWI is still difficult.The key challenge lies in obtaining sufficient porewater samples at spe-cific locations along the soil gradient for downstream analysis.Here with an optimized in-ductively coupled plasma mass spectrometry(ICP-MS)method and a HR porewater sampler,we demonstrate mm-scale element profiles mapping across the SWI in paddy soils.High-concentrations of iron and manganese(＞10 mg/L)were measured by ICP-MS in an extended dynamic range mode to avoid signal overflow.The iron profile along the SWI generated by the ICP-MS method showed no significant difference(p＜0.05)compared to that measured independently using a colorimetric method.Furthermore,four arsenic(arsenite,arsenate,monomethylarsonic and dimethylarsinic acid),two phosphorus(phosphite and phosphate)and two sulfur(sulfide and sulfate)species were separated in 10 min by ion chromatogra-phy-ICP-MS with the NH4HCO3 mobile phase.We verified the technique using paddy soils collected from the field,and present the mm-scale profiles of iron,manganese,and arsenic,phosphorus,sulfur species(relative standard deviation＜8％).The technique developed in this study will significantly promote the measurement throughput in limited samples(e.g.100 μL)collected by HR samplers,which would greatly facilitate redox-sensitive elements biogeochemical cycling in saturated soils.