Quantitative structure-activity relationship models for the reaction rate coefficients between dissolved organic...

Area of Science:

• Environmental Chemistry
• Photochemistry
• Water Quality Analysis

Background:

• Predicting the photolysis rate of pharmaceuticals and personal care products (PPCPs) in aquatic environments is essential for understanding their environmental fate.
• Accurate reaction rate data between dissolved organic matter (DOM) and PPCPs are scarce, and no predictive models currently exist for this critical photochemical parameter.
• The photoreaction rates of PPCPs are significantly influenced by interactions with DOM in natural waters.

Purpose of the Study:

• To develop a predictive model for the photolysis rates of PPCPs in natural aquatic environments.
• To define and measure a reaction rate coefficient (αDOM) that describes DOM-involved photoreactions of PPCPs.
• To establish quantitative structure-activity relationship (QSAR) models for predicting αDOM values.

Main Methods:

• Defined a reaction rate coefficient (αDOM) for DOM-involved photoreactions of PPCPs.
• Measured αDOM values for 40 PPCPs across 9 different DOM samples.
• Developed QSAR models using chemical and water quality descriptors via the random forest method, including a classifier for positive/negative values and separate regression models.

Main Results:

• Measured αDOM values exhibited significant variation, ranging from (-2.1 ± 0.1)×10^10 to (2.2 ± 0.1)×10^11 M⁻¹ s⁻¹.
• QSAR models demonstrated strong predictive performance: positive models achieved R²adj=0.92 and Q²ext=0.86, while negative models showed acceptable performance with R²adj=0.71 and Q²ext=0.70.
• A comprehensive photolysis model incorporating QSAR predictions for αDOM was established, highlighting the importance of water quality parameters through sensitivity analysis.

Conclusions:

• The developed QSAR models provide a robust tool for predicting PPCPs' photolysis rates in diverse aquatic matrices.
• The comprehensive photolysis model enables more accurate environmental fate assessments of PPCPs.
• This research offers valuable assistance for forecasting PPCPs' behavior and persistence in natural waters.