Study On The Applicability Of Biotic Ligand Model To Different Types Of Metals

Currently,the biotic ligand model?BLM?has been widely used to predict the biological toxicity of different types of metals,the species of tested organisms are becoming more and more extensive,the prediction results are mostly in good relationship with the experimental values.In this paper,biological toxicity among different types of metals were analyzed based on essential/non-essential metals,different metal valences respectively.The results are as follows:?1?The biological toxicity of essential metals is weaker than that of non-essential metals.Specifically,in terrestrial animals and plants,the toxicity order of metals is:Cu>Cd?Ni>Zn.In aquatic organisms,the toxicity order of metals is:Cd>Cu>Zn.?2?The biological toxicity of trivalent metals is stronger than that of divalent metals.Specifically,the affinity constants?log K?of trivalent metals are generally higher than 7.0 M^-1(even reach 8.0 M^-1?9.0 M^-1),mostly of which are higher than that of divalent metals.The maximum absorption flux rate(J_max)of trivalent metals is generally 10^-14 mol·cm^-2·s^-1,while the J_max of divalent metals is generally in the range of 10^-12-10^-14 mol·cm^-2·s^-1,the difference is basically between two orders of magnitude.In other words,compared with bivalent metals,the binding ability of trivalent metals to sensitive sites on biofilm is stronger,while the saturated absorption flux rate is relatively smaller.Three different methods of quantitative prediction for metal biological toxicity have been established based on the previous experimental data and methods of metal biological toxicity,the quantitative prediction for metal biological toxicity was carried out in different application scopes by analyzing the predicted values and the experimental values.The applicability of different methods for different types of metals or organisms was evaluated.The results are as follows:?1?The ratios of the predicted values obtained by using three quantitative prediction methods and the experimental values are mostly in the range of 0.9-1.1,which indicates that these three methods could predict metal biological toxicity well.?2?Piecewise function quantitative prediction method:it can be used to predict the toxicity of metals to terrestrial animals and plants with a wide range of p H values.In the prediction,the concentration of competing cations needs to be adjusted appropriately,when Ca²⁺accounts for 70%to 90%of the total Ca concentration,Mg²⁺accounts for 50%to 70%of the total Mg concentration,and the segmented critical value of water p H m=6.5,n=7.0,the prediction effect is better.?3?Single factor control quantitative prediction method:it is mainly applicable to the toxicity prediction of metals to terrestrial animals and plants and some aquatic organisms.In the prediction,the concentration of competing cations needs to be adjusted appropriately,when Ca²⁺accounts for 70%to 90%of the total Ca concentration,Mg²⁺accounts for 50%to 70%of the total Mg concentration,and Na⁺and K⁺account for about 90%of the total concentration,the prediction effect is better.?4?Michaelis-Menten equation quantitative prediction method:it can be used to predict the toxicity of different valence metals to single celled organisms or microorganisms in soil and water.In the prediction,the concentration of competing cations needs to be adjusted appropriately,when Ca²⁺accounts for 70%to 90%of the total Ca concentration,Mg²⁺accounts for 50%to 70%of the total Mg concentration,and Na⁺and K⁺account for about 90%of the total concentration,the prediction effect is better.