Leaching of free and conjugate natural estrogens in soil monoliths

Authors: CASEY, FRANCIS - North Dakota State University; SELBIE, DIANA - Agresearch; Hakk, Heldur; RICHARDS, KARL - Teagasc (AGRICULTURE AND FOOD DEVELOPMENT AUTHORITY)

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 2/6/2019
Publication URL: http://handle.nal.usda.gov/10113/6303468
Citation: Casey, F.X., Selbie, D., Hakk, H., Richards, K.G. 2019. Leaching of free and conjugate natural estrogens in soil monoliths. Water, Air, and Soil Pollution. 230:49. https://doi.org/10.1007/s11270-019-4079-z.
DOI: https://doi.org/10.1007/s11270-019-4079-z

Interpretive Summary: Endocrine disrupting estrogens are constantly, and at high levels, being eliminated by production animals as non-toxic, water-soluble metabolites, known as conjugates. Unexpected is the widespread occurrence of non-water soluble, but biologically active, deconjugated estrogens in surface waters. We hypothesized that after application to agricultural soil, estrogen conjugates are transported by water through soil, and then deconjugated to parent estrogen by soil bacteria. If true, this would provide a mechanism for estrogen transport into surface and ground waters. The objective of this study was to observe the mobility of free and conjugated estrogens present in surface applied dairy urine into wells placed in fields grazed by dairy cows. Contrary to the literature, we observed that the total degradation of estrogen conjugates to free estrogens in raw dairy urine had occurred, therefore, we were unable to monitor conjugate movement from urine application. However, both free and conjugated estrogens were frequently detected in control and treated wells, indicating historical soil estrogens from prior applications. The frequent detection of conjugates in wells suggested their persistence in low microbially-active soils, and a latent potential for environmental movement.

Technical Abstract: Natural free estrogens found in animal manures are potent endocrine disrupting compounds. Environmental detections can be caused by such processes as physical and chemical non-equilibrium, and colloidal or conjugate facilitate transport. Antecedent or “legacy” concentrations of estrogens resident in soil may also contribute significantly to environmental detections. The objective of this study was to measure and understand the dominant causes contributing to estrogen detections in the environment from a grazed system. To achieve this objective, the effluent of undisturbed lysimeters constructed from soils of fields grazed by dairy cows (Bos taurus) were monitored for free and conjugated estrogens. Four lysimeters were dosed with urine (Urine) and four only received water (Control). Water transfer for all lysimeters were similar, and all lysimeters were near field capacity for the duration of the experiment. Rapid transport of a conservative bromide tracer suggested preferential flow was an important physical non-equilibrium transport process. Free estrogens and conjugated estrogens (17ß-estradiol (E2), estrone (E1), 17ß-estradiol-17-sulfate (E2-17S), 17ß-estradiol-3-glucuronide (E2-3G), estrone-sulfate (E1-S)) were detected in the source urine (E2=17,248 ng/L, E1=1,006 ng/L, E2-3G=967 ng/L, E2-17S=886,456 ng/L, E1-S=1,730 ng/L). These same free and conjugated estrogens, in addition to estriol (E3), were all detected frequently in both Control and Urine lysimeters (detection concentration ranks: E3 > E2-17S = E2 > E2-3G = E1 = E1-3S). Total potential estrogenicity in the effluent of the Control and Urine were also similar, indicating the presence of antecedent estrogens was the dominant contribution to estrogenic detections. Additionally, the frequent detection of conjugates in the lysimeter effluent was important, because it indicated conjugates were stable in soil, but had greater potential mobility than free estrogens.