UNEARTHING THE GEOCHEMICAL FINGERPRINT OF THE 1914 GREAT SALEM MA CONFLAGRATION: EVIDENCE FROM THE PALMER COVE PARK LANDFILL
An exploratory excavation was used to evaluate the thickness and composition of the landfill cap. To assess the potential for post-depositional mobility of metals, soils from various depths in the excavation site were sampled, along with surface soils near the community garden. Samples were dried, homogenized and analyzed using pED-XRF to measure bulk concentrations of arsenic, cadmium, lead, chromium, copper, nickel and zinc. XRF results of soil near the community garden were compared to safety standards maintained by Massachusetts Department of Environmental Affairs MCP S-1 (Massachusetts Contingency Plan) for soil contamination in areas of human activity such as residential, parks, playgrounds and schoolyards. The excavation revealed the landfill cap as approximately 76 cm in depth and composed of soil with pebble sized rocks to densely packed diamicton containing rocks sized up to 20cm. There is no evidence of bio remediating or impermeable layering. At 76 cm, notably dark soil was exposed with various items of debris, confirming the presence of the landfill material. Weathered and oxidized rock and soil suggests evidence of mobilization of metals in the subsurface. Within the excavation, the concentration of lead was 94 ppm at the surface and 4,940 ppm at the boundary with the top of the landfill, while chromium concentrations were 99 ppm at the surface and 144 ppm at 76 cm. Of the ten samples taken near the community garden, two were direct surface samples with chromium concentrations reaching or potentially exceeding MCP S-1 limits.