Hexagonal turbostratic bessite,with the characteristics of high contents of vacancies,varying amounts of structural and adsorbed Mn3+,and small particle size,undergoes strong adsorption reactions with trace metal (TM) contaminants.While the interactions of TM,i.e.,Zn2+,with bessite are well understood,the effect of bessite structural characteristics on the coordination and stability of Zn2+ on the mineral surfaces under proton attack is as yet unclear.In the present study,the effects of a series of synthesized hexagonal turbostratic bessites with different Mn average oxide states (AOSs) on the coordination geometry of adsorbed Zn2+ and its stability under acidic conditions were investigated.With decreasing Mn AOS,bimessite exhibits smaller particle sizes and thus larger specific surface area,higher amounts of layer Mn3+ and thus longer distances for the first Mn-O and Mn-Mn shells,but a low quantity of available vacancies and thus low adsorption capacity for Zn2+.Zn K-edge EXAFS spectroscopy demonstrates that bessite with low Mn AOS has smaller adsorption capacity but more tetrahedral Zn (ⅣZn) complexes on vacancies than octahedral (ⅥZn) complexes,and Zn2+ is more unstable under acidic conditions than that adsorbed on bimessite with high Mn AOS.High Zn2+ loading favors the formation of ⅥZn complexes over ⅣZn complexes,and the release of Zn2+ is faster than at low loading.These results will deepen our understanding of the interaction mechanisms of various TMs with natural bessites,and the stability and thus the potential toxicity of heavy metal pollutants sequestered by engineered nano-sized metal oxide materials.