Keywords: 
• copper /
• barley /
• terrestrial biotic ligand model /
• toxicity prediction

Abstract: The terrestrial biotic Ugand model(TBLM) is a newly developed method for evaluating bioavailability of heavy metal ion in soils.Seventeen soil samples covering China were selected in this study by adding a series of Cu concentrations.The soil solutions were extracted according to the method of maximum water holding capacity.The cation and anion concentrations as well as dissolved organic carbon(DOC) in soil solutions were measured for the predictions of Cu(Cu²⁺ and CuOH⁺ especially at high-pH conditions) and Mg ion activities.The WHAM 6 model was used to predict free Cu²⁺,CuOH⁺ and Mg²⁺ activities using 65% DOM as active fluvic acid(FA) and adjusted binding constant logK_CuFA=1.5.The predicted ion activities and measured barley relative root elongation as variables were input into TBLM equation,and binding constants and parameters were fitted out as logK_CuBL=4.87,logK_CuOH+=7.62,logK β=1.09 by DPS statistic software according the best agreement between measured and predicted barley relative root lengths.The results showed that predicted and measured barley root elongation can match quite well with an R²=0.90,RMSE=11.4 and almost all predicted values lied within 2-fold of measured values.In order to ensure accuracy of TBLM in our study,some parameters from relative studies were compared with the values in this study,which showed that our TBLM was better than others and more suitable for Cu prediction of bioavailability in Chinese soils because a series of high-pH soils samples were included.The study will help a lot on formulating guidance of soil environment risk assessments not only for China but for the other areas around world.