Mineralization and incorporation into soil organic matter of 14C labeled 17-[beta] estradiol and testosterone mixed with broiler litter

Abstract

The presence of the hormones estradiol and testosterone in the environment is of concern because they adversely affect vertebrate sexual characteristics. Landspreading broiler litter introduces these hormones into the environment. To determine the fate of these hormones in the soil, two studies were conducted. The first study determined the mineralization of 14C-labeled estradiol and testosterone at three water potentials (-0.03, -0.75 (17 β-estradiol only), -0.075 (testosterone only), and -1.5 MPa) and temperatures (10, 20, and 30°C). Radiolabeled CO2 (from mineralization) was captured in 1 M KOH traps and measured by liquid scintillation. With a few exceptions, the mineralization of estradiol either stayed the same or increased (1.5 to 13.8%) with increasing temperature and increasing soil water content. With a few exceptions, the mineralization of testosterone either stayed the same or increased (19.5 to 48.0%) with decreasing temperature and increasing soil water content. For both hormones, mineralization was dependent on soil type. The second study determined the incorporation of 14C-labeled estradiol and testosterone into a) three soil organic matter (SOM) fractions (fulvic acid, humic acid, and humin) at two water potentials (-0.03 and -1.5 MPa), two temperatures (10 and 30°C), and one sampling time (168 days), and b) at one water potential (-0.03 MPa), one temperature (30°C), and seven sampling times (0, 1, 3, 7, 14, 28, and 56 days). Both incorporation studies were conducted in a Cecil sandy loam. After the hormones (mixed with broiler litter) were mineralized on the soil surface, SOM fractions were extracted and analyzed separately with liquid scintillation and biological oxidation. As time increased, higher temperature and water potential decreased percentages of 14C estradiol and testosterone in water- and acetone-soluble fractions and increased percentages in SOM fractions. However, the distribution of the two hormones in SOM fractions differed. For estradiol, higher temperature and water potential increased the percentage in all three SOM fractions. For testosterone, higher temperature and water potential increased the percentage of hormone in fulvic acid and humin. Because more and more estradiol and testosterone become incorporated into SOM over time, landspreading these hormones may be less of an environmental concern than previously considered.

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