GLACIAL AND ANTHROPOGENIC TALES TOLD BY A SEDIMENT CORE ON ITS WAY TO BECOMING A WETLAND

Foothills Preserve is a retired cranberry farm in Plymouth, Massachusetts. This work aims to measure success of wetland restoration sites. Collectively, we have gathered pre-restoration soil, vegetation, hydrology, water and soil chemistry data, and environmental conditions, which will all be re-assessed post-restoration. This portion of the study examines the subsurface and how elemental compositions of different soil types from the original wetland and subsequent cranberry farming impact water and soil chemistry of the restored wetland. Soil cores were taken from the pre-restoration site and scanned with an x-ray fluorescence machine. Elemental data were plotted versus depth and compared with core images to determine correlations between element abundance and soil type. Si, K and Os are abundant in the sand applied during farming over the last 200 years (~1 cm/ ~3 yr), Ti is abundant in peat (max age 9,100 yr). Ba was present in the (glacial outwash) sand and agricultural soil from farming, but not in pre-anthropogenic wetland peat, and was therefore used to demarcate the transition between them. Pb was present in higher amounts in the sand and agricultural soil but not in the peat, which may be an indicator of residual pesticides. From this analysis, it is possible to determine where the glacial history of the soil ceased at the termination of the native wetland peat, and where the anthropogenic period begins, denoted by agricultural soils intercalated with applied sand layers, using as clues the concentrations of Si, K, Os and Ti which serve as indicators of specific soil types. Demarcating different soil types allows us to image the thickness of the anthropogenic aquifer above the original peat, which is useful for the restoration process, as it allows decisions to be made about whether the agricultural soils and sand can be removed or if they need to be incorporated into the new wetland. The elemental composition of this anthropogenic aquifer is also important in determining whether these soils will produce troublesome chemical- or nutrient-laden runoff should water come into contact with these post-agricultural soils. Post-restoration wetting of the site could mobilize soil nutrients and impact wildlife, so a thorough characterization of the subsurface can help guide wetland restoration interventions.