The purpose of this study is to describe the impact of mine effluent on its environment, and to determine the processes, which influence the geochemistry of the spoil and of surface and groundwater in the Davis Mine Valley. The Davis Pyrite Mine is one of the small abandoned mines in the Berkshire Mts., in Massachusetts. Since the collapse of the mine, in 1911, forest has reclaimed its surroundings, yet the acid mine effluent still affects nearby streams. The spoil and the Davis Mine Creek watershed is a small area enclosed by rocks having minimal carbonate content. It has been untouched by humans for 80 years so the place is ideal for the study of the natural geochemical processes that control such environments. The surface and shallow ground-water in the Davis Mine Valley have low pH (3.28) and high total dissolved solid content. The upper 30–35 cm of the spoil pile is depleted in sulfide and silicate minerals, while it is enriched in iron-oxyhydroxide minerals. The amount of silicate minerals increases with depth. Three main processes determine the mineralogy, geochemistry, and hydrochemistry of the spoil in such a low buffer-capacity environment: (1) The bacterially catalyzed oxidation of pyrite is continuous, so it constantly produces low-pH water and high iron content. The acid water further dissolves minerals hence elevating metal-ion concentrations. (2) The water inflow with a relatively higher pH (rain, snowmelt, unaffected surface and subsurface water) flushes the freshly precipitated soluble constituents, and it dilute the element concentrations in the mixed water meanwhile increasing its pH. This process then enhances adsorption and precipitation. (3) The dynamic dissolution and precipitation of various iron-oxyhydroxides control the iron content of water and buffer the pH between 2.5 and 3.5. This low pH inhibits metal ion adsorption on mineral surfaces. Local formation of a surface hardpan layer modified chemical processes in the groundwater. This layer is built up from a crust of goethite and jarosite with low permeability that inhibits O2 diffusion and surface water infiltration.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-3409 |
| Date | 01 January 2000 |
| Creators | Ga'l, Nora Edit |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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