Sorption of Selected Endocrine Disrupting Chemicals to Different Aquatic Colloids J. L. ZHOU,* R. LIU, A. WILDING, AND A. HIBBERD Department of Biology and Environmental Science, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QJ, United Kingdom The sorption of seven endocrine disrupting chemicals (EDCs) to aquatic colloids was determined by cross-flow ultrafiltration (CFUF) followed by gas chromatography-mass spectrometry (GC-MS). Results show that the colloidal organic carbon normalized sorption coefficient (K coc ) of EDCs to different aquatic colloids varies by a factor of 6-12 because such colloids are of different origin. Through characterization of colloidal samples, a significant relationship was established between K coc values and the molar extinction coefficient of colloids at 280 nm, whereas no other colloidal properties such as elemental ratios were correlated with K coc values. The results are consistent with other reports of the importance of the quality of sorbents such as their aromatic carbon content in sorbing various organic pollutants. The presence of a surfactant was found to increase K coc values for estrone (E1) and 17R- ethynylestradiol (EE2). The method was subsequently applied for determining EDC concentrations in field samples, where both conventional and truly dissolved EDCs showed higher concentrations close to sewage outfalls than either upstream or downstream, confirming the source- concentration relationship. In addition, the truly dissolved EDC concentrations were lower than the conventional dissolved concentrations, confirming that there were interactions between aquatic colloids and EDCs. It is estimated that between 10 and 29% of EDCs are associated with aquatic colloids. As colloids are highly abundant in rivers and ocean, they will therefore play a significant role in the environmental behavior and fate of EDCs. Introduction Colloids, generally defined as nanoparticles or macromol- ecules with a size between 1 nm and 1 µm, are ubiquitous in natural environmental systems. Because of weathering reactions and microbiological processes, colloids are pro- duced and transported into natural waters such as lakes, rivers, and sea. It has been widely recognized that colloid concentration is approximately 10 6 -10 8 particles per liter (1-3), and 10-40% of marine total organic carbon is colloidal in nature (4, 5). Although colloids constitute a relatively small fraction (10%) of total waterborne particle mass (6), the speciation, bioavailability, transport, and ultimate fate of trace pollutants are controlled by their sorption onto colloids (7, 8) because of their large surface area and a great number of sorption sites. There is potentially, therefore, a variety of mechanisms, for example, covalent, electrostatic, and specific sorption through which colloidal particles can interact with solutes in the aqueous phase. Colloidal material has further been implicated to play a crucial role as an intermediary in environmental and biogeochemical processes, for example, N and P cycling, aggregation, sedimentation, as well as trace metal behavior (9, 10). Thus, to understand the role of colloids in the fate and behavior of trace pollutants in the aquatic environment, it is essential to obtain and characterize colloids of different origins for determining their key physicochemical properties. Endocrine disrupting chemicals (EDCs) are pollutants that alter functions of the endocrine system and consequently cause adverse health effects in an intact organism or its progeny. The main evidence leading to disruption of endocrine function comes from changes observed in several wildlife species as well as humans, for example, feminization and hermaphroditism in wildlife and the development of testicular and prostate cancer and decreased sperm repro- duction in humans (11-13). These chemicals (e.g., hormones) may originate from natural processes in animals and plants which exert hormonal actions on other animals or plants. In addition, many industrial activities (e.g., agrochemicals, medicines) have produced chemicals such as dichlorodiphe- nyl trichloroethane, polychlorinated biphenyls, and certain pharmaceuticals being identified as potential EDCs. Such EDCs may be released directly or indirectly to the aquatic environment where interactions with colloidal materials are likely. As a result, the concentration, speciation, bioaccu- mulation, and toxicity of EDCs are all co-regulated by the presence of colloids (14-16). Direct measurement of the distribution of trace organic pollutants such as EDCs between colloids and dissolved phase has always been a challenge. Currently, fluorescence quench- ing, solubility enhancement, and radioisotopes have been used in such experimentation (17-21). In our previous study, crossflow ultrafiltration (CFUF) combined with gas chro- matography-mass spectrometry (GC-MS) has been suc- cessfully developed for determining the partition coefficients of selected EDCs between natural colloids and dissolved phase (22). It has been shown that the partition of selected EDCs onto colloids is relatively independent of the physi- cochemical properties of EDCs, in particular, their octanol- water partition coefficient values (Kow), and the sorption of relatively polar EDCs by colloids may be attributed to the physical-chemical properties of colloidal materials, for example, a great number of sorption sites with a variety of interaction mechanisms, for example, covalent, electrostatic, and specific binding. The purpose of this study was to extend the application of CFUF-GC-MS technique for determining sorption coef- ficients of EDCs to various types of natural colloids, to evaluate the key chemical characteristics of those different colloids, and to differentiate between truly dissolved and colloid- bound EDCs in field samples close to sewage outfalls. Experimental Section Materials. The solvents used including methanol and ethyl acetate were of distilled-in-glass grade (Rathburns). EDCs including 17-estradiol (E2), estrone (E1), 17R-ethynylestra- diol (EE2), 16R-hydroxyestrone, E2-d2, and 4-nonylphenol were purchased from Sigma United Kingdom, and bisphenol A, bisphenol A-d16, 4-tert-octylphenol, and bis(trimethylsilyl)- trifluoroacetamide (BSTFA) containing 1% of trimethylchlo- rosilane were supplied by Aldrich (Dorset, United Kingdom). * Corresponding author phone: 44 1273 877318; fax: 44 1273 677196; e-mail: j.zhou@sussex.ac.uk. 10.1021/es0619298 CCC: $37.00  xxxx American Chemical Society VOL. xx, NO. xx, xxxx / ENVIRON. SCI. & TECHNOL. 9 A PAGE EST: 7.6 Published on Web 11/29/2006