Sorption of 17β-estradiol to pig slurry separates and soil in the soil-slurry environment

Abstract

Contamination of freshwater by estrogens from manure applied to agricultural land is of grave concern because of the potentially harmful effects on aquatic life and human health. Recent developments in liquid manure (slurry) management include partial removal of particulate slurry dry matter (PSDM) by separation technologies, which may also remove parts of the estrogens and enhance infiltration of the slurry on field application and hence the interaction between estrogens and the soil matrix. This study investigated how 17β-estradiol (E2), a natural estrogen commonly found in pig manure, sorbs to agricultural soils, to different size fractions of pig slurry separates, and to soils amended with each size fraction to simulate conditions in the soil-slurry environment. A crude fiber fraction (SS1) was prepared by sieving (<500 μm) the solids removed by an on-farm separation process. Three other size fractions (SS2 > SS3 > SS4) were prepared from the liquid fraction of the separated slurry by sedimentation and centrifugation. Sorption experiments were conducted in 0.01 mol L(-1) CaCl(2) and in natural pig urine matrix. Sorption in 0.01 mol L(-1) CaCl(2) was higher than that in pig urine for all solids used. Sorption of E2 to soil increased with its organic carbon content for both liquid phases. The solid-liquid partition coefficients of slurry separates were 10 to 30 times higher than those of soils, but the organoic carbon normalized partition coefficient values, reflecting sorption per unit organic carbon, were lower for slurry separates. Mixing slurry separates with soil increased the sorption of E2 to the solid phase significantly in the order: SS1 < SS3 < SS2 for both liquid phases. In contrast, SS4 reduced the sorption of E2 to the solid phase by increasing the sorption to suspended or dissolved organic matter. The study suggested that potentially 50 to 75% of E2 in slurry can be removed from the liquid fraction of slurry by physical separation.