Zhao-Feng Yuan, Williamson Gustave, Raju Sekar, Jonathan Bridge, Jia-Yue Wang, Wei-Jia Feng, Bin Guo, Zheng CHEN

Soil-water interface (SWI) hosts versatile elements speciation and controls elements cycling in flooded lands. However, the study on the element’s interaction along SWI is limited by the sampling and analytical methods available. Here with an optimized ICP-MS method and an updated porewater sampler, we succeeded in simultaneously mapping the elements of environmental concerns in every 1.7 mm across SWI, including arsenic (As), iron (Fe), manganese (Mn), phosphorus (P), and sulfur (S) as well as As, P and S species. Among these elements, dissolved Fe and Mn in high concentrations (> 10 mg·L-1) were measured by ICP-MS in an extended dynamic range (EDR) mode to avoid signal overflow. The dissolved Fe profile along SWI generated by ICP-MS was slightly lower than that of colorimetric method, but of the same trend. Furthermore, four As, one P and two S species can be separated in 10 minutes by IC-ICP-MS with NH4HCO3 mobile phase. We verified the technique using paddy soils collected from the field, and present the high-resolution (mm) profiles of total elements (Fe, Mn, As, P and S) and element species (arsenite, arsenate, phosphate, sulfide and sulphate). The technique developed in this study will greatly facilitate the study of biogeochemical cycling of redox sensitive elements in flooded soils.