GEOCHEMICAL ASSESSMENT OF SOILS AROUND COBALT LEGACY MINE SHAFT IN EAST HAMPTON CT

The discovery and mining of cobalt, nickel, and gold at the Cobalt Legacy Mine site in East Hampton, CT began in the late 1700s and went to the mid-1800s, which at the time was a boom to the socio-economic discovery of the local society. After mining activities ceased, the site was abandoned and has been to date. The leftover mine piles have thus been exposed to various geochemical processes such as physical remobilization, chemical weathering of the abandoned gangue materials, possible dissolution, and transport to shallow groundwater systems as well as nearby streams. This study examined the concentrations and spatial distribution of Co, Na, Mg, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Al, P, S, Cd, Pb, and As, within the downgradient soils surrounding the mine shaft, with the overall goal of determining their fate and transport to the hydrologic system. A total of 19 soil samples were collected from the mine entrance ~25 meter away to the Mine Brook stream in ~5 meter intervals. Similarly, 14 water samples were collected from the adjacent streams to the mine site. Soil samples were later digested based on EPA 3052 method and analyzed using ICP-OES. In addition, soil samples were analyzed for basic soil parameters such as particle size distribution using the hydrometer method, organic matter contents, and soluble salts. Results showed the average order of abundance of elements as: Fe > Al > K> Mg > S > Ca > Mn > P > As > Pb > Zn > Cu >Cr; a range of 7,981.35-61,161.4; 6,329.09-25,125.74; 937.71- 11,959.87; 1,562.89-9,342.56; 0-3,925.31; 237.92- 1,616.48; 75.92- 863.42; 109.28- 599.12; 23.51-178.07; 0-106.83; 14.65- 45.46 mg/kg, respectively. Spatial trends have been analyzed, such as Cr and Zn levels, which are of the most concern to the environment. These are seen to be more concentrated in soil samples around the mine shaft, bringing concern to legacy elements leaching into the nearby soil and stream. In addition, the soil samples around the mine are seen to have the most concentrated levels of Mg, K, Mn, S, Cu, Fe. Using JMP statistical software, the geochemical data and soil constituent materials were evaluated. Further, calculation of the soil enrichment Factors (EF) and Geacumulation Indices (GI) provide useful information about the degree of soil enrichments as well as overall fate and transport of elements released from the mine shaft.