2,2-Bis(4-hydroxyphenyl) propane (BPA) is a derivative of phenol and acetone (Rochester, 2013; Staples et al., 1998). It is widely used in the manufacture of important chemical raw materials such as polycarbonate and epoxy resin (Catenza et al., 2021; Huang et al., 2012; Ma et al., 2019). It is worth noting that in the manufacturing process of plastic products, the addition of bisphenol A can make it colorless and transparent, durable, lightweight and outstanding impact resistance, so bisphenol A has been widely used in plastic products, milk bottles, canned food coating and so on (Vilarinho et al., 2019). Due to the practicability of BPA, the annual output of BPA reached 5 million tons in 2015. However, studies have found that BPA is an endocrine disruptor (EDC) which disrupts the balance of the endocrine system in animals and humans (Akash et al., 2020; vom Saal et al., 2012). Many countries have started to restrict the use of BPA and there is an urgent need to develop and use alternatives to BPA (Catenza et al., 2021; Chen et al., 2016; Rochester, 2013). 4-hydroxyphenylsulfone (BPS) and 4-methylene-4-methylenediphenol (4,4’-BPF) are the main substitutes for BPA. BPS is mainly used in the production of color-fixing agents, resin flame retardants and so on, as well as the intermediate of pesticides and dyes (Liu et al., 2021). BPF is commonly used in the synthesis of flame retardants, antioxidants and indicative active agents (Qian et al., 2021). BPF used in industry usually refers to 4,4’-BPF, but in the production of BPF, it is inevitable to produce two kinds of isomers: 2,2’-BPF and 2,4’-BPF. However, few people pay attention to 2,2’-BPF and 2,4’-BPF (Guo et al., 2019; Sun et al., 2017). Due to the structural similarity between 4,4’-BPF and BPS and BPA, BPS and 4,4’-BPF were found to have the same potency in inhibitory hormone signaling as BPA (Gogola−Mruk et al., 2023; Le Fol et al., 2017; Wang et al., 2021). The high use of bisphenol analogs has led to their high detection frequency in various environmental media (Gao et al., 2023; Maturi et al., 2023; Qian et al., 2021; Xue et al., 2016). Among these, the soil environment has been found to be an important sink for bisphenol analogs (Xu et al., 2021). Bisphenol analogs in the soil can enter the aqueous environment through a variety of pathways, such as surface runoff, drainage flow and groundwater flow (Dueñas−Moreno et al., 2022). Due to unfavorable redox and degradation conditions in the groundwater, contaminants degrade very slowly (Yamazaki et al., 2015; Zhi et al., 2019). Once the contaminants reach the groundwater, the risk to human health is high. Therefore, understanding the mechanisms that control the transport of BPA and its substitutes through soil is essential for developing management practices to protect groundwater.
Several studies have shown that BPA, as a polar contaminant, is highly mobile and is likely to be able to cross the soil profile and enter groundwater. For example, (Dai et al., 2020) reported that BPA is highly mobile in porous media in both saturated and unsaturated conditions, and almost all of it flows out of the soil column in soils with low SOM content. The transport capacity of BPA in soil seems to be closely related to the rate of pore water in the soil, soil pH and SOM content (Guo et al., 2022; Zakari et al., 2016). Notably, as an alternative, BPS seems to have higher mobility than BPA (Shi et al., 2019; Shi et al., 2018). Adsorption is a key process to control the transport and fate of organic pollutants in various environments. BPA seems to have a stronger affinity for soil adsorption when in a non-dissociated state (pH < pKa) due to its greater hydrophobicity than BPS (Choi &Lee, 2017). This makes BPA more inclined to deposit in the soil and more BPS inclined to flow into the groundwater. However, the survey shows that the concentration of BPF seems to be one to two orders of magnitude higher than BPA in Japanese, Korean and Chinese waters (Qian et al., 2021; Yamazaki et al., 2015). Current research in BPF seems to be limited to the development of new acid catalysts and optimization of BPF isomer product distribution (Sun et al., 2017; Wang et al., 2016). The only few studies on BPF retention and distribution have focused on 4,4’- BPF (Liu et al., 2018; Wu et al., 2019). There is a gap in studies on the adsorption and transport of 2,2’-BPF, 2,4’-BPF in soils. Moreover, the transport of bisphenol analogs in different types of soils thus might be differ, this has not been tested.
The overarching goal of this study is to advance the current understanding of the fate and transport of bisphenol analogs in soil. Five bisphenol analogs including BPA, BPS, 4,4’-BPF, 2,2’-BPF, 2,4’-BPF uses 14C-labeled for column experiments and batch adsorption experiments. Four standard soils from Germany were used as media. The standard soils are available in large quantities and are representative and ecologically relevant for generating reproducible and comparable data (Bastos et al., 2014; Hofman et al., 2009). The use of 14C-labeled bisphenol analogs and standard soils for column experiments and batch adsorption experiments can effectively improve the accuracy and reproducibility of experimental data (Schaefer, 1991). Mathematical models are used to simulate and interpret experimental data. The objectives are as follows: 1) To compare the transport capacity of BPA and its substitutes, BPS and 4,4’-BPF in different soils, and to reveal the mechanism of interaction with soil. 2) The transport capacity of 4,4’-BPF and its isomers 2,2’-BPF and 2,4’-BPF in different soils was compared, and the interaction mechanism with soil was revealed. 3) To establish and test mathematical models for fate and transport of bisphenol analogizes in porous media.