Dissolved organic matter and estrogen interactions regulate estrogen removal in the aqueous environment: a review

Authors: MA, LI - University Of California - Cooperative Extension Service; Yates, Scott

Submitted to: Science of the Total Environment
Publication Type: Review Article
Publication Acceptance Date: 5/24/2018
Publication Date: 6/3/2018
Citation: Ma, L., Yates, S.R. 2018. Dissolved organic matter and estrogen interactions regulate estrogen removal in the aqueous environment: a review. Science of the Total Environment. 640-641:529-542. https://doi.org/10.1016/j.scitotenv.2018.05.301.
DOI: https://doi.org/10.1016/j.scitotenv.2018.05.301

Interpretive Summary: Endocrine disrupting compounds (EDCs) can adversely affect endocrine systems in humans and wildlife. EDCs include pharmaceuticals, pesticides and hormones, natural or synthetic, etc. Estrogens are important due to their potentially harmful effects on aquatic organisms at very low concentrations (i.e., ng L-1). Estrogens, are naturally produced in living creatures or as medicines administrated to humans and livestock. They are excreted either in free form or as conjugated constituents, primarily through urine, but also in the feces. Excreted estrogens enter aquatic environments through discharges from wastewater treatment plants (WWTPs), animal waste disposal and runoff of field applied hormone-bearing materials (manure, sewage sludge and biosolid, etc.). Natural surface water contains dissolved organic matter (DOM). Due to its high surface area and organic carbon content, DOM exhibits high capacity to bind with organic contaminants, including EDCs. There have been several studies probing the interactions of estrogens and DOM, and the impact of DOM on degradation and transformation. However, these studies were not systematically conducted so few generalizations have been made. In this paper, methodologies to characterize and quantify the interactions between estrogens and water-borne DOM and the resulting removal efficacies were reviewed. The development of a more fundamental understanding of current information will provide insights which could assist in effective regulatory controls. This information should be of interest to researchers, regulators, commodity groups, farmers, and the public.

Technical Abstract: This review summarizes the characterization and quantification of interactions between dissolved organic matter (DOM) and estrogens as well as the effects of DOM on aquatic estrogen removal. DOM interacts with estrogens via binding or sorption mechanisms like p-p electron donor-acceptor interaction and hydrogen bonding. The binding affinity is evaluated in terms of organic-carbon-normalized sorption coefficient (Log KOC) which varies with types and composition of DOM. DOM has been suggested to be a more efficient sorbent compared with other matrices, such as suspended particulate matter, sediment and soil; likely associated with its large surface area and concentrated carbon content. As a photosensitizer, DOM enhanced estrogen photodegradation when the concentration of DOM was below a threshold value, and when above, the acceleration effect was not observed. DOM played a dual role in affecting biodegradation of estrogens depending on the recalcitrance of the DOM and the nutrition status of the degraders. It is suggested that addition of biodegradable DOM into the aqueous media under substrate-limited conditions accelerated the biodegradation rate. DOM hindered enzyme-catalyzed removal of estrogens via competition for active sites on enzyme surfaces and inhibited the formation of metabolites via coupling of DOM radicals with estrogen radicals, or itself, to form cross-coupling species. Membrane rejection of estrogens was pronounced for hydrophobic DOM with high aromaticity and phenolic moiety content. Elimination of estrogens via photolysis, biodegradation, enzymolysis and membrane rejection in the presence of DOM is initiated by sorption, accentuating the role of DOM as a mediator in regulating aquatic estrogen removal.