International Congress on Engineering, Sciences and Innovative Technologies (ICESIT 2020) - Kuala Lumpur - Malaysia (2020-02-13)

Investigation of binding constants of nonylphenol and bisphenol A with aqueous dissolved organic matter and alkaline-extracted suspended organic matter.
Phenolic xenoestrogen compounds (PXEC) cause endocrine system disruption, which is a serious concern worldwide. Nonylphenol (NP) and Bisphenol A (BPA) are the main PXEC compounds that have received the attention of endocrine disruption research in the aquatic environment. The organic matter plays an important role in the binding capacity of hydrophobic organic compounds. Dissolved organic matter (DOM) and suspended particulate matter (SPM) affect PXEC distribution, transport, and biotoxicity in the aquatic environment. When PXEC binds to dissolved organic matter, the biotoxicity of PXEC can be decreased. A high binding constant has low toxicity; hence, the binding constants are important when trying to understand PXEC biotoxicity. Moreover, previous studies have assumed that low molecular weight DOM had insignificant binding capacity to hydrophobic organic compounds. The fluorescence quenching (FQ) method has been used to investigate binding constants between DOM and hydrophobic organic compounds. It is a sensitive and accepted method that can determine the binding capacity between DOM and PXEC. This study measured the binding constants (log KDOC) of PXEC on size-fractioned dissolved organic matter with an FQ method. Three size-fractioned DOM and alkaline-extracted SPM solution (designated AEOM) samples were studied and identified as SF-A (10 kDa-0.45 μm), SF-B (1-10 kDa), and SF-C (<1 kDa). The DOM and AEOM samples were measured with DOC concentration, UV-Vis, and fluorescence spectra. Four optical indicators were selected to examine the chemical structure and composition of DOM and AEOM. The optical indicators showed that the DOM and AEOM samples had significantly different qualities. The studied PXEC had a significant binding capacity on both the DOM and AEOMsize-fractioned samples. However, the NP compound (n= 102) had more validated tests than the BPA (n=69). The log KDOC of sized DOM were 5.57±0.55, and 5.26±0.43 L/kg-C, for NP and BPA, respectively. The log KDOC of NP was significantly higher than BPA (p=0.008). The log KDOC of sized AEOM was 4.05±0.31, and 3.88±0.29 L/kg-C, for NP, and BPA, respectively. The log KDOC of NP was significantly higher than BPA (p <0.001). The log KDOC of DOM was significantly higher than AEOM for individual PXEC (p<0.001). The log KDOC of size-fractioned DOM and AEOM was insignificantly different for both NP and BPA. The log KDOC values of NP had significantly higher log KDOC values of BPA, both sized DOM and AEOM. that possible that the PXEC hydrophobicity that octanol-water partition coefficient (log KOW) NP 4.48 is higher than the value of BPA 3.32. Moreover, the size-fractioned DOM and AEOM were equally important to bind NP and BPA. Keywords: Binding constant; Bisphenol A (BPA); Fluorescence quenching; Nonylphenol (NP); Optical indicators; Size-fractioned DOM and AEOM.
Miss Yung Yu Liu, Mr. Bo-Yu Dai, Mr. Chih-Hung Hsu, Mr. Chao-Pin Huang, Professor Ting-Chien Chen