From a chemical perspective, no one really thought it dissolves, but it does,” Jaffé says. “It doesn’t accumulate like we had for a long time believed. Rather, it is transported into wetlands and rivers, eventually making its way to the oceans.
According to the authors, the results imply that greater consideration must be given to carbon sequestration techniques (the process of capture and long-term storage of atmospheric carbon dioxide). Biochar addition to soils is one such technique. ... Although promising in storing carbon, Jaffé points out that as more people implement biochar technology, they must take into consideration the potential dissolution of the charcoal to ensure these techniques are actually environmentally friendly.
I am not sure what this new line of research implies (factors like time, type of ecosystem etc are not yet investigated) but it's definitely a point that needs to be taken into consideration.
The stability of biochar, a form of charcoal intentionally made to be added to soil to sequester carbon (C) and improve its function, remains unclear. As it is not feasible to perform long-term (decades, centuries) laboratory experiments to assess biochar evolution after soil amendment, the study of ancient archaeological charcoals can help to identify characteristics (and possibly molecular markers) associated with the decomposition and preservation dynamics of biochar in specific pedoclimatic environments.