Fate and Transport of Free and Conjugate Natural Estrogens in Soil Monoliths.

Steroidal estrogenic hormones are potent endocrine disruptors, and animal agriculture is the greatest potential contributor to the environment. Urine from farm animals contain free and conjugated estrogens that can contribute to the entire estrogenic pool in the environment. Conjugated estrogens are important to consider, because they are more water soluble than free estrogens and can be readily transported with water. The objective of this study was to observe the mobility of free and conjugated estrogens borne in animal urine using replicated, undisturbed lysimeters constructed of soil monoliths from fields grazed by dairy cows (Bos taurus). Four lysimeters had dairy cow urine applied (Urine), and four had nothing applied (Control). Water transfer for all lysimeters was similar, and all lysimeters were near field capacity for the duration of the experiment. Physical solute transport was dominated by preferential flow, resulting in the rapid movement of a conservative anionic tracer (Bromide). Only free estrogens (17β-estradiol (E2), estrone (E1), estriol (E3)) were detected in the source urine (E3=771 ng/L, E2=121 ng/L, E1=104 ng/L). However, both free and conjugated (17β-estradiol-17-sulfate (E2-S), 17β-estradiol-3-glucuronide (E2-G), estrone-sulfate (E1-S)) estrogens were detected frequently in Control and Urine lysimeters (detection concentration ranks = E3 > E2-S > E2 > E2-G > E1-S > E1), indicating large amounts of antecedent steroidal estrogens. 17β-estradiol was the only estrogen significantly affected by the urine application, where a distinct early peak arrived before the first pore volume of effluent had been collected from the lysimeters. This early arrival of E2 was similar to the Bromide breakthrough curves, indicating E2 was preferentially transported through mobile regions of the soil. Additionally, the frequent detection of conjugates in the lysimeter effluent was important, because it indicated conjugates were stabile in soil, but had greater potential mobility than free estrogens.