Interference Adsorption Mechanisms of Dimethoate, Metalaxyl, Atrazine, Malathion and Prometryn in a Sediment System Containing Coexisting Pesticides/Heavy Metals Based on Fractional Factor Design(Resolution V) Assisted by 2D-QSAR

Abstract

The mechanisms of adsorption of pesticides(dimethoate, metalaxyl, atrazine, malathion and prometryn) and heavy metals(Cu, Cd, Pb, Zn and Ni) coexisting in sediments, with pesticides as target pollutants, and the influence of their main effects and double-order interaction effects were studied using the experimental design module in the Minitab software package with a 210‒3 fractional factorial design method at resolution V. The main, double-order interaction, synergistic and antagonistic effect values of pollutant concentrations influencing the adsorption of pesticides were set as dependent variables, while various quantum chemical parameters of pesticides were set as independent variables, and two-dimensional quantitative structure activity relationship(2D-QSAR) models were established by stepwise regression to reveal the adsorption mechanisms of pesticides in a composite contamination system. The main effects of pollutants concentration played the primary role in the adsorption of dimethoate and malathion(the rates of contributions were 53.54% and 56.46%, respectively), while double-order interaction effects were primarily responsible for metalaxyl, atrazine and prometryn adsorption(the rates of contributions were 79.05%, 60.21% and 57.89%, respectively) in the pesticide/heavy metals coexisting sediment system. The synergistic effects of the main effects and double-order interaction effects of pollutants concentration(synergistic effects) played a leading role in adsorption of malathion and prometryn(the rates of contributions were 70.61% and 69.61%, respectively), while antagonistic effects of the main effects and double-order interaction effects of pollutants(antagonistic effects) played a dominant role in the adsorption of dimethoate, metalaxyl and atrazine(the rates of contributions were 58.82%, 56.89% and 58.24%, respectively). Moreover, the correlation coefficient value(R2) ranged from 0.986 to 0.999(>0.8783) in the 2D-QSAR model, while the standard deviation(SD) ranged from 0.006 to 0.066 and the F test values were 22.684―199.544, indicating the model has good predictive ability and fit. The 2D-QSAR model revealed a significant correlation(P=0.05) between the main effects of pollutants concentrations on pesticides adsorption(main effect values) and the most positive hydrogen atomic charge( $$q_{H^+}$$ ), the highest occupied molecular orbital energy(EHOMO) and the dipole moment(μ). Furthermore, double-order interaction effect values of pollutant concentrations influenced the adsorption of pesticides(double-order interaction effect values), and the most positive atomic charge(q+), $$q_{H^+}$$ , and the lowest occupied molecular orbital energy(ELUMO) were significantly correlated. The qH+, ELUMO and μ of pesticides were found to be significant factors promoting pesticides adsorption, while the q+ and ELUMO of pesticides were significant inhibiting factors(P=0.05). Overall, this study provides a theoretical basis for further realization of combined pollution control of pesticide pollutants in complex environmental systems.