Adsorption of three selected endocrine disrupting chemicals by aquatic colloids and sediments in single and binary systems

Abstract

Aquatic colloids are ubiquitous in natural river water, but their effects on the adsorption of pollutants by sediments are not fully understood. This study investigated the adsorption of three endocrine disrupting chemicals (EDCs) by aquatic colloids and sediments in single and binary systems. The role of aquatic colloids in the adsorption of EDCs by sediments in the binary system was evaluated. Water and sediment samples were collected from Huanyuankou (HS) and Lijin (LS) stations in the middle-low reaches of the Yellow River (China), and the aquatic colloids were separated using cross-flow filtration. The properties of aquatic colloids were characterized using an inductively coupled plasma–optical emission spectrometer, a TOC/TN analyzer, and a fluorescence spectrophotometer. Batch experiments were conducted to investigate the adsorption of three selected EDCs (bisphenol A (BPA), 17β-estradiol (E2), and 17α-ethynylestradiol (EE2)) by aquatic colloids and sediments. BPA, E2, and EE2 were quantified using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The adsorption data were described by the linear, Freundlich, and Langmuir adsorption isotherms. The contributions of aquatic colloids to the total adsorption of EDCs were evaluated in the context of the binary system of aquatic colloids and sediments. In a single system of colloids, the adsorption parameters of linear, Freundlich, and Langmuir isotherms (K f, K d, and K L Q max) follow the order of BPA > EE2 > E2, indicating the important role of inorganic minerals in the adsorption of EDCs. In a single system of sediments and binary system of colloids and sediments, the K f, K d, and K L Q max values follow the order of E2 > EE2 > BPA, suggesting that the main adsorption mechanism is hydrophobic interaction. Moreover, the colloids promote adsorption of EDCs by sediments in a binary system. Although the colloidal contents are much lower than the contents of the sediments, the contributions of colloids to the total EDCs adsorption are up to 35–60 % for LS and 10–28 % for HS. In a single system of colloids, both organic and inorganic components of colloids enhance the adsorption of EDCs. In a single system of sediments and a binary system of colloids and sediments, the adsorption of EDCs is mainly induced by the nonspecific hydrophobic interaction between EDCs and organic matters in the sediments and colloids. The colloids enhance the adsorption of EDCs; the more the EDCs are adsorbed by colloids, the greater are the contributions of colloids to the total adsorption of EDCs.