Irrigation with reclaimed water is a key method of alleviating agricultural water shortages (FAO, 2012). Recycled water can save water resources and promote the circulation of nutrients, but pollutants in reclaimed water and soil have potential to cause harm to humans, especially the endocrine disrupter chemicals (EDCs), which has attracted wide attention recently. EDCs can lead to endocrine disorders in aquatic organisms, affecting reproductive development and immune system (Lee et al., 2016; Tabassum et al., 2017).
Reclaimed water from the wastewater treatment plants (WWTPs) is regarded as the main source of EDCs of the agricultural environment. In addition to reclaimed water or effluent, treated sewage sludge is also normally used all over the world in agriculture soil (Hamid et al., 2012; Ömeroğlua et al., 2015; Belhaj et al., 2016; Biel-Maeso et al., 2019). Municipal landfills may also contain leachate with significant amounts of EDCs which could migrate into groundwater or uptaken by plants (Kalmykova et al., 2013; Zhang et al., 2015; Lu et al., 2015; Wang et al., 2019). In recent years, the fate of EDCs in soil-plant ecological system has given much attention (Card et al., 2013; Goeppert et al., 2015; Sidhu et al., 2015; Adeel M. et al., 2017, 2018).
Nonylphenol (NP) and bisphenol A (BPA) are two typical EDCs with high detection frequencies and concentrations in soils irrigated with reclaimed water (Careghini et al., 2015; Wang et al., 2018). The concentrations of NP in reclaimed water and agricultural soils were 0.05-63 µg. L− 1 and14.2-60.3 mg. kg− 1 (Liao et al., 2014; Sidhu et al., 2015; Wang et al., 2015, 2018; Kwak et al., 2017; Bruin et al., 2019). The concentrations of BPA in reclaimed water and agricultural soil were ND-101.6 µg. L− 1 and ND-147 µg. kg− 1, respectively (Gibson et al., 2010; USEPA 2010a; Luo, et al., 2014; Careghini et al., 2015; Yacoumas et al., 2020). The Danish Institute of Safety and Toxicology (DIST) derived a preliminary tolerable daily intake (TDI) value for NP of 5 µg. (day. kg)−1 body weight (Danish EPA 2000). USEPA estimated a reference dose for BPA of 50 µg. (day. kg)−1 body weight (USEPA-IRIS 2014). NP is composed of varieties of isomers. The estrogenic activity and the environmental fate were heavily dependent on the isomers structures, such as the side-chain length, the degree of branching, α-substituent type, steric index (Gabriel et al., 2008; Lu and Gan 2014; Schick and Oellig, 2019). The most toxic isomer among these isomers is 4-(3-ethyl-2-methylhexan-2-yl) phenol, which is noted as NP7 (Kim et al., 2005; Wang et al., 2015) (Supplementary Material 1). Adsorption, migration, and degradation are the main processes that NP and BPA in soil. Adsorption is vital and determines the rate of migration and transformation (Pollard and Morra, 2017). Adsorption of NP and BPA on soils are affected by a variety of factors, including dissolved organic matter (DOM), temperature, pH and ionic content (Bautista-Toledo et al., 2005; Stumpe et al., 2010; Yang et al., 2011; Soni and Padmaja, 2014; Ding et al., 2019), among which dissolved DOM plays a significant role (Sharma et al., 2009; Wang et al., 2019; Ding et al., 2019).
Daxing irrigation district, in the southeastern part of China, was one of typical sewage irrigation districts for more than 40 years. Previous studies of this district focused on the inorganic pollution or the total NP isomers (Wu et al., 2009; Bao 2014). The study of individual isomer is quite few because of the difficulty in the separation of NP isomers. While the risks of the different isomers to the local ecological environment were various. Especially the most toxic isomer 4-NP7, have much estrogenic activity to the environment, so the study on adsorption and desorption of NP isomer on field soil is imperative. The aim of this work is to investigate: (1) Comparison of the adsorption of NP, NP7, and BPA on field soil irrigated with reclaimed water. (2) The effect of different environmental factors of pH, temperature and different polyvalent metal ions (Na+, Ca2+, As (Ⅲ)) on the adsorption of NP, NP7 and BPA. (3) The mechanism of sorption of NP and BPA on soil by Fourier Transform Infrared Spectrometer (FTIR) analysis.