EXPLORING THE MOBILITY OF FECAL BIOMARKERS IN SOIL

Fecal stanol biomarkers are increasingly used in archaeological studies as a proxy of human presence, land use, and demographic change. Some studies investigate biomarker changes in soil profiles whereas others use nearby depositional basins, such as wetlands and lakes. Insufficient research has been done to explore the mobility of stanols in such differing sedimentary environments, which impacts their usefulness and reliability as a proxy of human activity. To understand the rate of stanol movement in the soil environment, two test plots, one sloped and one flat were established in the San Dimas Experimental Forest in southern California. Control samples show that the plots are on heavily decomposed granite with a coarse grain size and ~1% organic carbon. Pig dung was applied in Spring 2022, and the plots were sampled at fixed depths and lateral distances from the dung every six months. Initial results show significant vertical but limited lateral movement in the flat plot and both vertical and lateral movement in the sloped plot. Our results suggest that even with minor amounts of precipitation, fecal stanols are mobile in inorganic soils and their movement is dependent on topographic and hydrologic factors.