About The Project

In September 2002, a group of UMass faculty received a grant of around $1.6 Million from the National Science Foundation to investigate the natural attenuation of highly acidic mine drainage from an old sulfur mine, the Davis Mine in Rowe, Midwestern Massachusetts. This project is an interdisciplinary collaboration among experts in microbiology, geology, environmental engineering and science education. The mine collapsed in 1910 and filled with groundwater. The overflowing groundwater drains out of the old mine shafts. The drainage mine waters are of an acidity lower than vinegar (pH values around 2) and carry large loads of heavy metals. Therefore we look for those bacteria that are key players in attenuation of acidity and heavy metal contamination.

The principal goals are to carefully examine the microbiological, geological and hydrological processes involved through field studies, modeling, and laboratory experiments, and to quantify the roles of extreme acid loving and acid-tolerant microorganisms. These organisms may have global significance for processes related to iron and sulfate in other near-surface environments.

The speed of acid attenuation will be estimated and integrated into a predictive model. International collaboration with the University of Manchester will enable comparisons with a similar sulfide mine in the U.K.

This research will also provide new information that will be applicable to developing remediation strategies at a range of acidic, heavy metal contaminated waste streams, including coal mining drainage and other aggressive industrial wastewaters. However, the implications of this research go beyond our understanding of local environmental problems. We will be able to provide the first really quantitative estimate of the importance of microbes in this aspect of global iron and sulfur cycling.

WHY DAVIS MINE?

The Davis Mine was once the largest operating pyrite mine in Massachusetts. It is located in the Heath quadrangle about four miles north of the town of Charlemont in the Berkshire Mountains of western Massachusetts. The geologic characterization of this mine is a Fe-(Zn-Cu-Pb) sulfide ore deposit formed by hydrothermal sulfide activity in the lower part of the Hawley Formation, which formed in the middle Ordovician at about 450 Ma. Pyrite is the most abundant sulfide present, comprising 60 to 70 volume percent of the ore. A weak Cu-Zn zonation, which is a common feature of many volcanogenic massive sulfides, is present in the deposit. The mine operated from 1882 until 1910 when it collapsed due to poor mining techniques. Tailings piles were distributed over an area of approximately 3 ha downstream from the mine shafts. The stream that drains the tailings piles, Davis Mine Creek, runs over a bed coated with yellow, ochre and red pigments, suggesting a complex community of microbes flourishing in the acidic environment. Except for the immediate vicinity of the mine, which is largely devoid of plant life, the area around the site is forested with a mixed hardwood community typically developed on glacial till in the upland areas in New England. The glacial till has a thickness of 5 to 20m, as estimated from seismic refraction profiles. Soils in the area are generally Inceptisols (ochrepts) or Spodosols (orthods). These soils usually have organic horizons ~5-10 cm thick, with a layer of decomposing organic matter above the "A" horizon.

We have accumulated data on water quality and mineralogy at the mine site from undergraduate class field visits over the past 20 years, and a recent Ph.D. dissertation (44) studied the envi-ronmental geochemistry of the mine tailings. Preliminary data show the extremely acidic condition of the stream, together with elevated concentrations of heavy metals, which are cha-racteristic of AMD sites. Similar data were collected by Vear and Curtis (1981) for an AMD site at Wales.

During our visits to the Davis Mine site, we often noted a pronounced odor of H2S in the vicinity of shallow wells installed between the stream and the forest perimeter, indicating sulfate reduction. Furthermore, Zn/Cu ratios in the water are high in the wells where the sulfurous odors were noted. The low pH of the water should inhibit the adsorption of either metal on the surface of oxyhydroxide or oxysulfate minerals, so preferential scavenging of dissolved Cu by sulfides may be causing the ratio to change, since CuS is several orders of magnitude less soluble than ZnS. SO4/Cl ratios are more variable, but also tend to be lower at the "anoxic" sites. Measurements of dissolved O2 also support the anoxic status of these locations. It is reasonable to presume that these reducing zones exist downstream of the mine in areas where AMD intersects organic layers in the forest soils and stream. The site is small (approximately 3 ha) and discharges via a single stream, so we will be able to gauge the intensity and extent of attenuation zones in down-gradient parts of the watershed using a manageable number of monitoring wells and sampling sites.

Davis Mine can serve as an excellent field site to document the extent and intensity of AMD attenuation by Fe(III) and sulfate reduction, and the role of microorganisms in these processes.

 

Biocomplexity in the Environment (BE) for Integrated Research and Education in Environmental Systems


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