Geochemical Evolution and Leachate Transport Beneath Two Carcass Burial Sites: A Field Investigation

Abstract

Abstract. This study presents the first complete investigation using soil coring to evaluate the geochemical evolution of leachate plumes beneath existing livestock burial sites. The objective of the study was to broaden our understanding and provide evidence-based resources for minimizing the environmental impacts of mass-mortality carcass burial. Pre-existing livestock burial sites were selected for a detailed analysis of contaminant transport beneath and surrounding the sites in an attempt to determine the risk to soil and groundwater. This analysis entailed soil coring at the site along with specific ion and solution extraction analyses on the soil cores to provide detailed 2-D images of leachate movement around and below the burial sites. The first site, near Pierceland, Saskatchewan, was used in 2001 to bury euthanized elk potentially suffering from chronic wasting disease (CWD). The soil cores were taken seven years post-burial, and the extent of leachate transport, upon analysis of the soil cores, was 1 to 1.5 m of vertical transport of anions (Cl, alkalinity), as well as some cations arising from ion exchange reactions (Ca and Mg). Ammonium ions were attenuated near the bottom and in the first meter beneath the bottom of the trench. There was no indication of lateral movement of ions at this site. The second site, near McLean, Saskatchewan, was used in 1952 to bury carcasses of culled livestock during an emergency depopulation effort for disease control measures during Canada’s only outbreak of foot and mouth disease. This site was cored nearly 60 years post-burial and demonstrated that vertical leachate movement was relatively slow over the 60 years, with movement of up to 1 to 2 m. Due to the presence of sand lenses in and around the burial pit, horizontal movement of up to 10 m of anions, such as Cl and bicarbonate, was discovered. Ammonium ions were indicated within the confines of the burial pit and in the soil immediately surrounding the pit. Both sites demonstrated plume characteristics consistent with previous geochemical models, and both showed little impact to the immediate surrounding environment. This would appear to indicate that the burial site selection characteristics were appropriately determined and that many parts of Saskatchewan are suitable for mass quantities of livestock carcass burial in the event of catastrophic events such as disease outbreaks or natural disasters. Keywords: Carcass leachate, Contaminant transport, Groundwater, Livestock burial, Mortality, Site investigation, Soil.