Thallium(Tl)is a non-essential and toxic trace metal found in many plants,but it can accumulate at particularly high concentration in certain species such as green cabbage(Brassica oleracea L.var.capitata L.),and knowledge for the biogeochemical processes of Tl in the soil-plant system is underreported.The aim of this study is to explore the transfer and accumulation of Tl in the rhizospheric soil-green cabbage system from a long-term Tl contaminated site in southwestern Guizhou Province,China.Influencing factors such as Tl distribution in various soil fractions and physical–chemical characteristics of rhizospheric soil were investigated.Our results demonstrated that green cabbage had high accumulation of Tl,with most bioconcentration factor(BF)values exceeding 1,and up to a maximum level of 11.The enrichment of Tl in the green cabbage tissues followed a descending order,i.e.old leaves>fresh leaves>stems≈roots.The stems functioned as a channel for Tl transportation to the leaves,where most of the Tl(greater than 80%)was found to accumulate.In the rhizospheric soils,62–95%of Tl existed in the residual fraction,while lower concentrations of Tl(on average,1.7%of total T1 in rhizospheric soil)were found in the water and acid soluble fractions.The major fraction of labile Tl was located in the reducible fraction(9%).Our results also suggested that the uptake and enrichment of Tl in green cabbage was affected by Tl concentrations,soil water content,soil pH,soil organic material and cation exchange capacity in rhizospheric soil.The Tl isotope analysis results showed for the first time that the biogeochemical processes in the soil-plant system induced significant Tl isotopic fractionations,i.e.the ?205/203Tl in the root soil was +0.5,but greatly negative to –2.51 in the root,-3.05 in the stem and –5.13 in the leaf of green cabbage.