Swine Manure: A Geochemical Perspective

Abstract

Highlights Geochemistry of swine manure has not been previously characterized as a point source for groundwater contamination. Earthen manure storages contain a solution composed of mainly ammonium and bicarbonate. Earthen manure storages have a low redox potential resulting in ammonium as the main form of nitrogen. Abstract. This study characterized the solution chemistry of seven swine manure storages in Saskatchewan, Canada. Manure storages are considered a point source for potential contaminant transport studies and modeling. A variety of earthen manure storages at hog production facilities in Saskatchewan were sampled, including two earthen manure storages servicing farrow to finish operations, two servicing farrows to wean operations, and three servicing finishing operations. In terms of manure seepage, the species of most common concern is nitrogen. Ammonium nitrogen is one of the most abundant ions studied in the earthen manure storage effluent. Potassium and sodium may be cations of concern as they will likely compete with ammonium for soil exchange sites, which will affect ammonium’s attenuation. Bicarbonate and chloride are the most abundant anions (bicarbonate >> chloride). High bicarbonate concentrations will likely affect the precipitation of carbonaceous minerals and may affect solution pH within seepage plumes. Earthen manure storages contain a solution composed of, as a percentage of total molal concentration, 36% ammonium, 36% bicarbonate, 8% potassium, 6% chloride, 5% sodium plus sulfate, calcium, magnesium, and other nutrients. The solution also contains approximately 6,000 mg/L organic carbon and 9,000 mg/L inorganic carbon and has a near neutral pH. As a result, the solution has low redox (Eh), resulting in nitrogen remaining in the ammonium-N form. Keywords: Geochemistry, Nutrient content, Swine manure.