Healthy food production is imperative for human health. However, many wetland soils are polluted with toxic elements such as arsenic, cadmium, mercury, antimony and others. In particular, paddy soil are very vulnerable since they serve as producer of food, including rice. Paddy soils are regularly flooded and thus, they underlie large fluctuations of redox conditions. Those changes of redox conditions have considerable impacts on the biogeochemical behavior of toxic elements as well as on pH, carbonate, and carbon solubility, chemistry of iron, manganese, and sulfur as well as on microbial community, which control the mobilization of toxic elements. Doubtless, the redox potential and pH are master variables in governing those mobilization processes. We are able to conduct experiment in the laboratory to study mechanistically the release dynamics of toxic elements. Also, we are seek for suitable amendments to stabilize those toxic metals in the soil which should be stabile even under dynamic redox conditions. Biochar is considered as one option to fulfill this purpose. Various results gained at several scales (microscale, laboratory and field scale) will be presented.