Fate of Estrogens in Soils From Alberta, Canada.

Estrogenic compounds in livestock manure are also present in soils because manure is land applied as an important nutrient source for agricultural production. This is the first study to compare the sorption of 17ß-estradiol, estrone, estriol and equol in a wide range of soils. Specifically, for each of these four estrogens, the soil sorption coefficient (Kd) and the sorption coefficient per unit organic carbon (Koc) were determined in 121 surface soil samples (0-15 cm) obtained from upper-slopes, mid-slopes, and lower-slopes in agricultural fields across seven ecoregions in the Province of Alberta, Canada. Soil microcosm studies of the mineralization of [4-14C] 17ß-estradiol were conducted on a subset of 36 samples. Both Kd and Koc values significantly increased in the order of Kd-estriol = Kd-17ß-estradiol < Kd-estrone < Kd-equol. Soil organic carbon content (SOC) and Kd values were significantly positively correlated (r ranging from 0.50 to 0.75, p<0.001) and particularly small Kd values were observed when SOC was below a threshold value of 0.1 g C kg-1. The Mixed Grassland ecoregion (Brown Chernozemic soils), as well as upper-slopes in general, demonstrated lesser Kd values because of reduced SOC. Equations to predict estrogen Kd or Koc values at the regional level were established using either soil properties (Partial Least Square regression) or one single estrogen (simple linear regression). The strength of the prediction models, as determined by the coefficient of determination (r2) and other factors, was always better for Kd than Koc values. Regardless of the regression used, the r2 of the prediction models exceeded 0.70 for Kd-17ß- estradiol and Kd-estriol, but r2 was below 0.63 for Kd-estrone and Kd-equol. Maximum mineralization of 17ß-estradiol averaged 11.32 % but was significantly less in the Mixed Grassland ecoregion. Maximum mineralization was significantly positively correlated with Kd- 17ß-estradiol (r=0.63, p<0.001) and SOC (r=0.69, p<0.001).