Quantitative Structure-Activity Relationships For Predicting The Joint Toxicity Of Substituted Phenols And Anilines To Algae

With the development of the industry and agriculture, a large number of poisonous substanceshave come into the natural water body, and caused water pollution. Expecially, when manypollutants coexist in the waters, the results may be more serious. In order to reveal toxic effects ofcoexisting pollutants to the organisms, not only the monotoxicity of pollutants but also joint toxicityshould be studied.By using Scenedesmus obliquus as a indicator, joint toxicity were determined with the methodof the algae inhibition test.The toxicities of binary mixtures of 2,4-dichloraniline or2,4-dichlorophenol with another phenol or aniline were carded out according to an equitoxicratio(1:1), while the binary toxicities of phenols or anilines with different toxical ratios and the jointtoxicities of three kinds of phenols or anilines with an equitoxic ratio (1:1) were determined. Themedian effective inhibition concentrations after 48h of exposure,expressed as EC₅₀ (mol/L), weregained through one variable linear regression analysis of the sum of toxicity units and the inhibitionrates as the relative toxic potency for the mixtures.Toxic Unit, Additive Index and Mixture Toxic Index were used to evaluate the joint toxicity.The results evaluated with Toxic Unit and Mixture Toxic Index indicated that joint effect of2,4-dichloraniline or 2,4-dichlorophenol with another phenols or anilines were additive or almostadditive when they coexisted with an equitoxic ratio.For the three kinds of ternary mixtures such as 2,4-dichlorophenol,diphenylamine andα-na-phthylamine, 2,4-dichlorophenol, m-chloroaniline and aniline, benzenol, aniline and 2-naphthol,benzenol,α-naphthylamine and 2,4-cichlorophenol, their joint toxicity effects are partial additionevaluated with toxicity unit method and mixture toxicity index method. The results evaluated by theabove methods all indicated that the joint toxicity effect ofα-naphthylamine, 2-naphthol and1-naphthol is antagonism.The quantitative structure-activity relationship (QSAR) models were developed for the jointtoxicity of binary and ternary mixture of phenols and anilines to algae by using octanol/waterpartition coefficient method, the molecular connectivity index method and the quantum chemistrymethod, and a seres of QSAR models were obtained by using SPSS10.0 software. The detainedQSAR model with the molecular connectivity index method is the most successful, as its square ofcorrelation coefficient is 0.890. The good relationships of joint toxicity of monocyclic aromatic hydrocarbons (37 series)likephenols and anilines or polycyclic aromatic hydrocarbons(24 series)such as naphthols,naphthylamines and resorcinols with another one of phenols or anilines was separately developedusing octanol/water partition coefficient method and square of their correlation coefficients wererespectively 0.838 and 0.852.The addition of octanol/water partition coefficient 1gP enormouslyimproved the prediction ofâ–³E-dependent models. Two models of equitoxicity of 2,4-dichloranilineor 2,4-dichlorophenol with another one of phenols or anilines to algae were respectively developedusing the frontier orbital energy gap and octanol/water partition coefficient.As regard to the binarymixtures with different toxical ratios and ternary equitoxieal mixtures, a good equationcharacterized with the same parameters above was also developed.