GEOCHEMICAL ASSESSMENT OF LEGACY LEAD MINING SITES

Historically, lead (Pb) had been mined in Middletown, Connecticut beginning in the 1700s and in Loudville, Massachusetts as early as 1680. Since the mining operations at these sites became unprofitable to both states, the mine entrance locations have been abandoned and filled in for over a century. The mine piles have been exposed to natural processes of chemical weathering, possible dissolution of lead ore, and other gangue minerals in rain water, which could have influenced possible transport to shallow groundwater and surface water system. This study examined the concentrations, and spatial distribution of Pb and twelve chemical elements (Fe, As, Ni, S, P, Zn, Mn, Cu, Al, Cd, Cr, Hg) at the two abandoned mine sites with the overall goal of determining their overall fate and transport to the hydrologic system. A total of 28 soil samples (Loudville, MA: 15, Middletown, CT: 13) were collected up to approximately 100 feet away from the mine entrances. Similarly, a total of 14 water samples were collected from the adjacent streams to the mine sites. During sampling, basic physicochemical parameters of the water column that include pH, temperature, total dissolved solids, electrical conductivity, and dissolved oxygen were determined. In the laboratory, water samples were analyzed for chemical components, while soil samples were analyzed for both acid and soluble extractable elements 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 > Pb > P > Mn > Zn > As > S > Cu > Ni > Cr; with a range of 6,590-13,085, 3,400-6,902, 33-1,835, 832-1,035, 5-677, 19-455, 22-297, 32-215, 70-163, 0.03-31, 0.01-6 mg/kg respectively. In addition, concentrations were observed to decrease with distance away from the mine site. Multivariate statistical analysis shows a positive correlation between trace elements and fine-grained soil, an indication of a possible partitioning to fine grained sediment sizes. Laboratory analysis of sediment samples shows a high affinity between the soil samples and chemical elements, which invariably influenced the overall fate and transport of these elements to the critical zone environments.