Comparative Evaluation Of Bioavailability Of Tl In Soil-plant System Using DGT Technology And Conventional Extraction Technology

Tl is a typical trace element and highly toxic heavy metal.The study on the migration and transformation of thallium（Tl）in soil and the bioavailability of Tl in the soil-plant system is of great significance to the prevention and control of Tl pollution in soil.Traditional evaluation methods of Tl bioavailability include biological test methods,chemical speciation methods,etc.,but these methods are time-consuming,poor in reproducibility,and have large errors.Therefore,it is of great significance to find a more accurate,time-saving,and efficient method to evaluate the biological effectiveness of T1.The diffusive gradients in thin films（DGT）technique can be used for passive sampling of trace metals.DGT technology can simulate the absorption of Tl in the soil by plants,and is suitable for exploring the bioavailability of Tl in the soil-plant system.This paper used a new type of DGT equipped with titanium peroxide（TP-DGT）and combined chemical extraction and biological methods（Chinese cabbage）to evaluate the bioavailability of Tl in the soil.The results show that this experiment proves that the C_DGT extracted by the TP-DGT device using titanium peroxide（TP）as the adsorbent is compared with other conventional methods.In most soils,whether it is the aboveground part of Chinese cabbage or the underground part of Chinese cabbage,the biological effectiveness.Among the 10 tested soils,the correlation coefficient between the C_DGT extracted by the TP-DGT and the Tl content in the underground part of Chinese cabbage was greater than 0.9.The correlation coefficient of Tl content in the aboveground part of Chinese cabbage is greater than 0.8,and the fit of soil sample S8 is the best.The correlation coefficient R² between the effective state Tl extracted by DGT and the content of Tl in the underground part of Chinese cabbage reaches the value of 0.999 indicates that DGT technology can be used as a new technology to predict and evaluate the Tl of pakchoi in the tested soil.Therefore,TP-DGT can be used as a method to evaluate the bioavailability of the soil-pakchoi system.Combined with the DGT-DIFS model,it is better to explore the desorption kinetics of Tl in the soil-plant system.It is even possible to explore the absorption mechanism of pakchoi to Tl through DGT technology.One is to limit the concentration of Tl in the soil,and the other is to limit the growth and absorption of pakchoi itself.The DGT technology can be used to explore which of these two limiting processes is the main limitation.DGT technology can be more convenient and time-saving to evaluate and study the bioavailability of Tl contaminated soil,and has a better application prospect.