Transport and fate of estrogens from swine manure in a biochar amended sandy soil in a freeze-thaw environment

Abstract

Under growing concerns of their possible adverse effects on ecosystems, natural steroidal sex hormones, originating from liquid swine manure, have been detected at trace concentrations in a number of natural environments. Various studies have highlighted biochar’s potential in adsorbing such hormones, given its structural and physiochemical properties. The remaining hormone adsorption capacity of a 1% slow pyrolysis biochar topsoil amendment was tested after one year of its application to a sandy soil, housed in outdoor lysimeters irrigated with simulated rainfall. The fate and transport of estrogens, over a 46-day period following the incorporation of liquid swine manure (4 g N/L @ 16 L/m2) into the topsoil, was monitored in biochar-amended and non-amended lysimeters. While in the first year of biochar application, a significant spatial-temporal stratification of steroidal sex hormones had been observed in the biochar-amended soil (vs. non-amended soil), in the second year biochar absorbed hormones to a considerably lesser degree. Concurring with the findings of laboratory batch adsorption experiments on fresh and used biochar, the present study showed that 1% slow pyrolysis biochar`s capacity to absorb sex hormones (estrogens) released from liquid swine manure in sandy soil decreases during second year. This is presumably the freezing and thawing weather conditions of experimental site that resulted in biochar surface degradation leading to the release of soluble organic carbon, thereby facilitating a heightened mobility of hormones and their resultant leaching to lower depths in the soil profile.